Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives

Coordination Chemistry Reviews xxx (2016) xxx–xxx

Contents lists available at ScienceDirect

Coordination Chemistry Reviews journal homepage: www.elsevier.com/locate/ccr

Review

Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives Hai-Ying Wang a, Long Cui a, Jia-Ze Xie a, Chanel F. Leong b, Deanna M. D’Alessandro b, Jing-Lin Zuo a,⇑ a State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, PR China b School of Chemistry, The University of Sydney, Sydney 2006, Australia

a r t i c l e

i n f o

Article history: Received 31 August 2016 Received in revised form 22 October 2016 Accepted 28 October 2016 Available online xxxx Keywords: Coordination polymers Redox-active Tetrathiafulvalenes Porous materials Molecular conductors

a b s t r a c t This review article focuses on the development of coordination polymers based on tetrathiafulvalene and its derivatives. We aim to demonstrate novel opportunities for these coordination polymers in terms of their architectures and potential applications. The review is presented in five general sections according to the type of coordinating functional group in the organic linkers. Synthetic approaches, structural analyses, as well as physical and chemical properties are presented for each example. Valuable potential applications and perspectives for these novel materials are also discussed. Ó 2016 Elsevier B.V. All rights reserved.

Contents 1. 2. 3.

4.

5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overview of TTF-based linkers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TTF-carboxylates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. TTF-dicarboxylates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. TTF-tetracarboxylates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N-donor ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. TTF-monopyridine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. TTF-bipyridine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. TTF-tetrapyridine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. TTF-triazole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TTF-chelating ligand. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

00 00 00 00 00 00 00 00 00 00 00

Abbreviations: CP, coordination polymer; MOFs, metal–organic frameworks; PCPs, porous coordination polymers; TTF, tetrathiafulvalene; IPCT, ion pair charge-transfer; MV, methyl viologen; DMF, N,N0 -dimethylformamide; H2trioTTF, 2-(5, 6,8,9,11,12,14,15-octahydro-[1,3]dithiolo[4,5-h][1,4,13,7,10]trioxadithiacyclopentadecin-2-ylidene)1,3-dithiole-4,5-dicarboxylic acid; H2DMDC-TTF, 40 ,50 -bis(methylthio)-[2,20 -bi(1,3-dithiolylidene)]-4,5-dicarboxylic acid; H4TTFTC, tetrathiafulvalene tetracarboxylic acid; H4TTFTB, tetrathiavulvalence tetrabenzoic acid; HT, high-throughput; SCSC, single-crystal-to-single-crystal; DPNI, N,N0 -di-(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydii mide; SEC, spectroelectrochemistry; EDT-TTFpy, 4-(40 -pyridylmethylsulfanyl)-40 ,50 -ethylenedithiotetrathiafulvalene; TTF(py)2, 2,9-bis(4-pyridyl)tetrathiafulvalene; tta, thenoyltrifluoroacetonate; TTF(py)4, tetra(4-pyridyl)-tetrathiafulvalene; LBT-TTF, bis(TTF-1,2,3-triazole)-lutidine; H2TTFbp, N-(2-(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)5-(picolinamido)benzo[d][1,3]dithiol-6-yl)picol inamide; TTF-salphen, 2,20 -(2-(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)-1,3benzodithiole-5,6-diyl)bis(nitrilomethylidyne) bis(phenolate); salen, N,N0 -ethylenebis(salicylideneimine) dianion; AF, antiferromagnetic; 2,20 -bpy, 2,20 -bipyridine; 4,40 -bpy, 4,40 -bipyridine; bpe, 1,2-bis(4-pyridine) ethylene; phen, 1,10-phenanthroline; bpa, 1,2-bis(4-pyridine)ethane; AC, 9-anthracenecarboxylate; salphen, N,N0 -1,2-diphenylethylene-bis(salicylideneiminato) dianion; TTC2-TTF, tetrakis(ethylthio)tetrathiafulvalene; TMT-TTF, tetrakis(methylthio)tetrathiafulvalene; TTC3-TTF, tetrakis(propylthiothio)tetrathiafulvalene; BEDT-TTF, bis(ethyle nedithio)tetrathiafulvalene; FP-TRMC, flash photolysis-time-resolved microwave conductivity; VCD, vibrational circular dichroism; SCM, single-chain magnets; SCO, spincrossover; tces-TTF, 2,3,6,7-tetra(cyanoethylsulfanyl); CM-TTF, 2-[4,5-bis(methylsulfanyl)-1,3-dithiol-2-ylidene]-4,5-bis(2-cyanoethylsulfanyl)-1,3-dithiole; MOS, metalorganic surface; LLCT, ligand-to-ligand charge-transfer. ⇑ Corresponding author. E-mail address: [email protected] (J.-L. Zuo). http://dx.doi.org/10.1016/j.ccr.2016.10.011 0010-8545/Ó 2016 Elsevier B.V. All rights reserved.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

2

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

6. 7.

8.

5.1. TTF as building block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2. TTF as node . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S donor ligands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CN donor ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1. TTF-dicyanogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2. TTF-tetracyanogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction Coordination polymers (CPs) are intriguing metal–organic hybrid materials. In CPs, metal ions or metal-containing clusters act as nodes, and organic ligands act as spacers, both of which are linked via coordination bonds to form one-, two- or threedimensional extended structures [1,2]. When (permanent) porosity is present, CPs are referred to as either metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) [3,4]. The design and study of multifunctional CPs possessing multiple accessible properties has attracted enormous attention owing to their potential applications in a plethora of areas, including sensing, solar energy harvesting, and energy storage, etc. [5–7]. One of the key advantages of CPs is their structural modularity which can be designed according to targeted physical and chemical properties by combining metal ions and organic ligands with appropriate geometries and functionalities [8–10]. Realizing the coexistence or cooperativity between the desired properties is still a major challenge for chemists working in this area. Functional CPs can be rationally designed by using organic ligands with certain desirable properties such as redox activity. A promising candidate is tetrathiafulvalene (TTF, C6H4S4, Scheme 1), which has been well studied as a critical component of conductive and optoelectronic materials [11–14]. TTF is a sulfur-rich conjugated molecule with two reversible and easily accessible oxidation processes to its radical cation (TTF+) and dication (TTF2+) states. With TTF derivatives as ligands, redox-active and redoxswitchable CPs may be realized [15,16]. Owing to the electronrich character of TTF, which renders it a good electron donor, numerous organic charge transfer compounds incorporating the TTF core have been investigated for their potential application in electrochromic materials, electrocatalysis and photoconductive switches [17–19]. In addition, TTF moieties can form p  p stacked columns with relatively short SS interactions, which have been shown to facilitate efficient pathways for charge transport [20– 23]. Recent studies have shown TTF-based CPs to exhibit high electrical conductivity or high charge mobility – properties which are highly desirable in new electronic materials towards applications in semiconductor and/or optoelectronic devices [9,14,24]. If conductivity is combined with the added virtue of porosity of MOFs, TTF-supported CPs could find uses in fields outside traditional areas such as gas storage and separation, including batteries, supercapacitors and electrochemical sensors [25,26]. Moreover, the incorporation of magnetic spins such as paramagnetic ions with electrochemically-active TTF units allows for the development of novel multifunctional materials such as magnetic semiconductors or magnetic conductors that have potential applications in spintronics [27–30]. Taken together, the two highly

S

S

S

S

Scheme 1. Structure of TTF.

00 00 00 00 00 00 00 00 00

reversible electron oxidation processes, and the well characterized electrochemical and spectral properties make TTF-based complexes attractive motifs for multifunctional materials. Herein, we provide an overview of TTF-based CPs constructed from the most recurrent transition metals – namely copper, manganese, zinc, cadmium, cobalt, calcium, magnesium silver and iron – that have been prepared and characterized in the past two decades. The review is presented in five sections according to the type of coordinating functional groups in the organic linkers. For each compound, the synthesis, major structural features, and, whenever investigated, its functional properties are presented. Valuable potential applications and perspectives on these novel materials are also discussed. For the sake of legibility, all of the materials described are collected in Table 1. 2. Overview of TTF-based linkers The important characteristics of TTF-based linkers are rigidity, the number and orientation of binding sites (coordination numbers and coordination geometries), the relative distance(s) between the coordinating functionalities, and the nature of the functionalities present (i.e., the presence of additional heteroatoms, aromatic rings, alkyl chains). In order to promote the construction of materials which have infinite expansion in three dimensional coordination space, the ligands must be multidentate with at least two coordination sites. Finally, the ligands can be symmetric, asymmetric and/or chiral, which give rise to a vast array of coordination modes and topologies. Common TTF-based organic molecules or building blocks which are discussed in this review are shown in Fig. 1, and the auxiliary ligands are shown in Fig. 2. 3. TTF-carboxylates 3.1. TTF-dicarboxylates Direct coordination of TTF carboxylates to paramagnetic metal ions has proven to be a favorable strategy for constructing new CPs with multiphysical properties. The cobalt coordination polymer containing a TTF-dicarboxylate ligand, {[Co2(trioTTF)2(H2O)6] 5H2O}n (1) (trioTTF = 2-(5,6,8,9,11,12,14,15-octahydro-[1,3]dithiol o[4,5-h][1,4,13,7,10]trioxadithiacyclopentadecin-2-ylidene)-1,3-di thiole-4,5-dicarboxylate) was reported and exhibits a 1D structure with interchain S  S interactions between trioTTF units at a distance of 3.565 Å (Fig. 3) [31]. The carboxylate groups bridge Co(1) and Co(2) via a g2-COO coordination mode which gives rise to the 1D chain structure. Due to the weak interchain S  S and p  p interactions between the trioTTF groups, as well as the neutral oxidation state of TTF moieties, the room temperature conductivity of the compound is 2.9  1010 Scm1 which is in the range for insulators. The magnetic properties of compound 1 were indicative of ferromagnetic interactions between the intrachain CoII centers below 16 K, likely facilitated by p-d interactions between the metal ions and trioTTF linkers. Due to limited magnetic ordering in 1 between 300 and 225 K, no appreciable magnetic effect on

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

3

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx Table 1 List of CPs based on carboxylate ligands reported in the present review. Ligand H2trioTTF H2DMDC-TTF

H4TTFTC

H4TTFTB

EDT-TTFpy TTF(py)2

TTF(py)4

LBT-TTF H2TTFbp H2(TTFsalphen) TTC2-TTF

TTC3-TTF TMT-TTF

BEDT-TTF CM-TTF tcesTTF

Compound

Dimensionality

{[Co2(trioTTF)2(H2O)6]5H2O}n (1) [Ca(DMDC-TTF)(DMF)2]n (2) {[Mg2(DMDC-TTF)2(H2O)7]EtOH4H2O}n (3) [Cu(DMDC-TTF)(2,20 -bpy)]n (4) [Mn(DMDC-TTF)(2,20 -bpy)]n (5) {[Zn(DMDC-TTF)(4,40 -bpy)(H2O)] CH3CN}n (6) {[Mn(DMDC-TTF)(4,40 -bpy)(H2O)]CN3CN}n (7) {[Mn(DMDC-TTF)(bpe)0.5(DMF)]2H2O}n (8) {[Mn(DMDC-TTF)(bpa)(H2O)]2H2O}n (9) [M2(TTFTC)H2]n (M = K (10, 11), Rb (12), Cs (13)), [K(TTFTC+)H2]n (14) {[Ni2(H2O)5(TTFTC)]H2O}n (15) {[Mn(TTFTC)0.5(2,20 -bpy)(CH3OH)]2H2O}n (16) [Mn(TTFTC)0.5(phen)(H2O)2]n (17) {[Mn(TTFTC)0.5(2,20 -bpy)]H2O}n (18) [Co(TTFTC)0.5(4,40 -bpy)(MeOH)]n (19) {[M(4,40 -bpy)2(H2O)4][M(TTFTC)(H2O)2]}n (M = Mn, Co, Fe, Cu, Zn and Cd) (20–25) {(MV)[Mn(TTFTC)(H2O)2]2H2O}n (26) {(MV)[Mn(TTFTC)(H2O)2]}n (27) [(Zn(DMF))2(TTFTC)(DPNI)]n (28) {[Zn2(TTFTB)(H2O)2]H2O2DMF}n (29) [Mn2(TTFTB)]n (30) [Co2(TTFTB)]n (31) [Cd2(TTFTB)]n (32) {[Cd(H2TTFTB)(bpa)(H2O)2]DMF3H2O}n (33) {[Ba(H2TTFTB)(H2O)2]DMFC2H5OH}n (34) [Mn(l-Cl)Cl(EDT-TTFpy)2(CH3OH)]n (35) [M(tta)2(TTF(py)2)]n (M = Cu for 36, and Mn for 37) [Cd(AC)2(TTF(py)2)]n (38) {[Pb(AC)2(TTF(py)2)0.5]CH3CN}n (39) {[Co(acac)2(TTF(py)4)0.5](CHCl3)}n (40) [Mn(hfac)2(TTF(py)4)]n (41) {[Cu2(OAc)4(TTF(py)4)0.5]1.5(CHCl3)0.5(H2O)CH3CN}n (42) {[Mn(SCN)2(TTF(py)4)]6(CH2Cl2)}n (43) {[Mn(SeCN)Cl(TTF(py)4)]n (44) [Cu2(TTF(py)4)2(ClO4)2]2.5(CH2Cl2)1.5(CH3CN)}n (45) [Cd5Cl10(LBT-TTF)2(CH3CN)2]n (46) [Mn((R,R)-salphen)Fe(TTFbp)(CN)2]n (47-(RR)) [Mn((S,S)-salphen)Fe(TTFbp)(CN)2]n (47-(SS)) [Ru(salen)(CN)2Mn(TTF-salphen)]n (48)

1D 1D 1D 1D 1D 2D 2D 2D 3D 2D 2D 1D 2D 3D 3D 1D 1D 2D 3D 3D 3D 3D 3D 3D 3D 1D 1D 1D 2D 1D 2D 2D 2D 2D 3D 1D 1D 1D 1D

[(CuI)2TTC2-TTF]n (49) [(CuBr)2TTC2-TTF]n (50) {[Cu(TTC2-TTF)]ClO4}n (51) {[Cu(TTC2-TTF)]BF4}n (52) {[Cu(TTC3-TTF)]ClO4}n (53) [(CuI)2TMT-TTF]n (54) [Ag(TMT-TTF)SO3CF3]n (55) [Ag(TMT-TTF)0.5NO3]n (56) {(BEDT-TTF)2[Cu4Br6(BEDT-TTF)]}n (57)

1D 1D 1D 1D 1D 1D 1D 3D 1D

[Ag(CM-TTF)(CF3SO3)]n (58) {[Ag4(tcesTTF)2(CF3SO3)2](CF3SO3)2}n (59)  {[M2(tcesTTF)2(H2O)4]X62H2O}n (M = Co(II), Mn(II), Zn(II), Cd(II); X = ClO 4 , BF4 ) (60–63)

1D 3D 2D

the conductivity of the material was observed within this temperature range. Towards the development of magnetically tunable conductive materials, the enhancement of magnetic interactions between spin centers within CPs is critical. An analogue of the TTF-dicarboxylate ligand trioTTF, 2,3-bis(car boxyl)-6,7-bimethylthiotetrathiafulvalene (DMDC-TTF) has also been utilized to assemble a series of CPs with alkaline-earth metals [32]. 1D coordination polymers, [Ca(DMDC-TTF)(DMF)2]n (2) and {[Mg2(DMDC-TTF)2(H2O)7]EtOH4H2O}n (3) were obtained under ambient conditions and exhibit an array of sandwiched structures (Fig. 4) which form hydrogen bonded 2D layers. In 2, short S  S contacts (3.488 and 3.530 Å) between the methylthio groups of neighboring 1D chains give rise to a chalcogen bonded 2D structure, whereas in 3, strong hydrogen bonding interactions between adjacent 1D chains similarly result in a 2D structure. The different ionic radii of Ca2+ and Mg2+ led to significant structural differences

Conductivity (Scm1) 10

2.9  10

1  103

3.95  106 8.64  105 1.49  105 2.86  104

2  103(doped) 3  107(doped) 6  104(doped) 2  105(doped) 4  105(doped) 101.7(doped) 2.8  104(doped) 4.5  103(doped) 2.4(a)/3.3(b)/ 2.5  102(c) 3.47  106(doped)

Reference [31] [32] [32] [16] [16] [16] [24] [24] [24] [33] [34] [35] [35] [35] [36] [37] [40] [40] [41] [26] [43] [43] [43] [44] [44] [49] [50] [51] [51] [53] [53] [53] [53] [53] [53] [61] [62] [62] [63] [76] [77] [78] [79] [79] [80] [81] [82] [89] [90] [91] [92]

between 2 and 3, demonstrating the diversity of structures afforded by TTF-dicarboxylate ligands. In a subsequent study, a series of coordination polymers based on the ligand DMDC-TTF and an array of transition metal ions were synthesized, with the aim of constructing new polymeric p-d systems with multiphysical properties [16]. The materials [Cu(DMDCTTF)(2,20 -bpy)]n (4) and [Mn(DMDC-TTF)(2,20 -bpy)]n (5) exhibit 1D polymeric structures afforded by unidirectional metal–carboxylate linkages by virtue of the 2,20 -bpy chelating ligand. A change in the ratio of metal ion and co-ligand to Zn(II) and 4,40 -bpy, respectively, gives rise to {[Zn(DMDC-TTF)(4,40 -bpy)(H2O)]nCH3CN}n (6) which possesses a rigid 2D network due to p  p stacking interactions between DMDC-TTF and 4,40 -bpy ligands (Fig. 5). Weak intrachain antiferromagnetic interactions were found in 4 and 5, while electrochemical measurements unveiled two reversible oxidation waves due to the formation of the TTF radical cation and dication

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

4

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

the TTF-based ligand to adjacent auxiliary ligands. Although 7–9 are closely related 2D coordination polymers, the intensity of the ligand-to-ligand charge-transfer (LLCT) interaction varies in the order 8 > 7 > 9, which is consistent with the increase in the relative extent of conjugation of the bipyridine co-ligands. The experimental data which shows low energy LLCT transitions was corroborated by DFT calculations. The photocurrent responses of these compounds were also in accordance with the variation in the charge transfer energy across the series (Fig. 6d). This serves as the first example of photoelectric investigations into the effect of charge transfer on the photocurrent response of a material, and highlights key design features in the development of stimuli responsive multifunctional CPs.

(a) carboxylate ligands S

S

O

COOH

S

O

S S COOH H2(DMDC-TTF)

S

O

S

S

S

COOH

S

S

S

COOH

H2trioTTF HOOC

HOOC

S

HOOC

S S H4TTFTC

COOH

COOH

S

COOH HOOC

S

S

S

S COOH

H 4TTFTB

(b) N donor ligands S

S

S

S

S

S

N N

S N

EDT-TTFpy

S

S

S

S

S

S

S

3.2. TTF-tetracarboxylates

N N N

N N N

S

S

N

S

TTF(py)2

N

N

S

S

S

S

S

S

N

N TTF(py)4

LBT-TTF

(c) TTF-schiff base and analogue O S

S

S

NH

S

S

S

NH

N

S

N

S

S

S

N

OH

S

S

N

OH

O

H2TTFbp

H2(TTF-salphen)

(d) S donor ligands

R R

S

S

S

S R

S

R S S S S TMT-TTF R = CH3 TTC2-TTF R= C2H 5 TTC3-TTF R= C3H7

S

S

S

S

S

S

S

BEDT-TTF

(e) CN donor ligands NC

S

S

S

S

CN

S

S

S

S

CN

NC

S

S

S

S

CN

S

S

S

S

CN

tcesTTF

CM-TTF

Fig. 1. The molecular structures and related abbreviations of the TTF-based linkers discussed in this review.

states, respectively. The potential for reversible oxidation to the radical form in the solid state suggested the application of these systems as switchable magnetic semiconductors with properties tunable by electrochemical or chemical modulation. The work on DMDC-TTF-based CPs was extended to include the electron acceptor auxiliary ligands, 4,40 -bpy, bpe and bpa, which yielded novel two-dimensional structures exhibiting interesting p  p interactions [16,24]. In these compounds, {[Mn(DMDC-TTF) (4,40 -bpy)(H2O)]CN3CN}n (7), {[Mn(DMDC-TTF)(bpe)0.5(DMF)] 2H2O}n (8), and {[Mn(DMDC-TTF)(bpa)(H2O)]2H2O}n (9), the octahedral Mn(II) ions are chelated by the two carboxylate groups of the DMDC-TTF ligand, forming infinite chains that are further linked by bipyridine ligands to generate 2D frameworks (Fig. 6). Theoretical calculations showed that charge transfer occurs from

Four crystalline three-dimensional CPs formulated as [M2(TTFTC)H2]n (M = K (10, 11), Rb (12), Cs (13); TTFTC = tetrathiafulvalene tetracarboxylate) and derived from the ligand H4TTFTC with alkaline cations have also been investigated (Fig. 7) [33]. The exploration of various experimental parameters (temperature, pH) that influence the synthesis led to different structures being obtained, all of which comprise parallel stacking interactions between TTFTC moieties. The performance of 10, 11, 12 and 13 as anode materials was probed via galvanostatic charge–discharge experiments where the materials were found to have moderate capacities and good cyclabilities. Despite the structural instability of the TTFTC ligand to oxidation to its dication state, the discovery of more robust TTF-based CPs may pave the way towards high performance batteries. In order to exploit the possibility of oxidation of the organic linker in TTF-based compounds, a combined electro-(sub)hydrothermal synthesis method was also employed to prepare a fifth 3D coordination polymer [K(TTFTC+)H2]n (14) in which the TTFTC ligand was oxidized in situ to its radical form, giving rise to a CP with high charge density and regularly stacked TTFTC+ radicals. As a result of the enhanced charge density, 14 exhibits an appreciable conductivity of about 1 mScm1 at room temperature, and is a semiconductor with an activation energy of 0.22 eV. The TTFTC/M(II) (M = Ni, Co) system was investigated using a high-throughput (HT) methodology for synthesis [34]. This study yielded a dinuclear complex, {[Ni(H2O)4]2(TTFTC)4H2O}n (MIL136(Ni)), which is comprised of octahedral Ni(II) centers coordinated to four water molecules and two oxygen atoms belonging to adjacent carboxylate groups of a TTFTC ligand; in the solid state, this complex packs to form a 3D hydrogen bonded network. Upon partial dehydration, MIL-136(Ni) evolves into a 2D coordination polymer {[Ni2(H2O)5(TTFTC)]H2O}n (MIL-1360 (Ni)) (15) via a single-crystal-to-single-crystal (SCSC) transformation (Fig. 8) to give a layered-structure along the 110 plane with slight bending of the TTF cores. This transformation demonstrates the flexibility of TTF-based materials to dynamic structural changes. By inserting auxiliary ligands into TTFTC-based frameworks, three Mn(II) CPs with different connectivities were obtained [35]. For instance, crystals of {[Mn(TTFTC)0.5(2,20 -bpy)(CH3OH)]2H2O}n (16) showed 1D extended chain structures whose secondary building unit (SBU) is a dinuclear Mn(II) cluster. Employing a different auxiliary ligand, 1,10-phenanthroline (phen), a 2D CP [Mn (TTFTC)0.5(phen)(H2O)2]n (17) was formed with infinite Mn(II)— carboxylate linkages. [Mn(TTFTC)0.5(2,20 -bpy)]nnH2O (18) possesses a 3D crystal structure where infinite -Mn-(O-C-O)2-Mnchains are each connected to four adjacent chains of two different orientations to form a higher dimensional material (Fig. 9). In each of the CPs (16, 17 and 18), p  p stacking interactions between auxiliary ligands assist in stabilizing the structures. Surfacemodified electrodes of these systems were used to study their

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

5

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

auxiliary ligands N

N

N

N N

N

4,4'-bpy

2,2'-bpy

phen

COOH N

N N

N

* N OH

AC

bpe

bpa

* N HO

N

O

O

N

N

O

O

(R,R)- or (S,S)-H 2Salphen

DPNI

N N

NC

N Ru

O

CN O

[Ru(salen)(CN)2]-

Fig. 2. The molecular structure and related abbreviation of auxiliary ligands mentioned in this review.

Fig. 3. (a) One-dimensional polymer chain of {[Co2(trioTTF)2(H2O)6]5H2O}n (1); (b) Temperature dependence of vMT for 1 recorded under a 2 kOe field. Reproduced from Ref. [31] with permission from Science in China Press and Springer, Berlin, Heidelberg.

Fig. 4. The 1D polymeric structure of (a) [Ca(DMDC-TTF)(DMF)2]n (2), and (b) {[Mg2(DMDC-TTF)2(H2O)7]EtOH4H2O}n (3), showing interchain S  S contacts and hydrogen bonds, respectively [32].

redox activity revealing that the redox properties of TTF are retained in the coordination polymers. Weak antiferromagnetic interactions between Mn(II) centers were found in 16 which suggested negligible long range magnetic communication through the TTFTC ligands. Towards the development of higher dimensional magnetic materials, TTF-based ligands with softer coordi-

nating groups may facilitate electronic delocalization across metal–ligand–metal bridges. A 3D cobalt coordination polymer, [Co(TTFTC)0.5(4,40 -bpy) (MeOH)]n (19), was achieved by employing the linear bidentate auxiliary ligand 4,40 -bpy (Fig. 10) [36]. The overall network in 19 consists of Co-TTFTC sheets which are pillared by 4,40 -bpy. Solid-

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

6

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

Fig. 5. The 1D polymeric structure of (a) [Cu(DMDC-TTF)(2,20 -bpy)]n (4) and (b) [Mn(DMDC-TTF)(2,20 -bpy)]n (5) demonstrating the TTF stacking interactions between adjacent chains (dotted lines); (c) 2D structure of {[Zn(DMDC-TTF)(4,40 -bpy)(H2O)]CH3CN}n showing D-A stacking interactions between DMDC-TTF and 4,40 -bpy ligands (black dotted) and between DMDC-TTF ligands from neighboring chains (red dotted) (6); (d) Solid state cyclic voltammogram of complexes 4, 5 and 6 demonstrating the two reversible oxidation processes (CH3CN, 0.1 molL1 n-Bu4NClO4, 100 mV s1). Reproduced from Ref. [16] with permission from the Royal Society of Chemistry.

Fig. 6. View of the 2D networks of (a) [Mn(DMDC-TTF)(4,40 -bpy)(H2O)]nnCN3CN (7); (b) [Mn(DMDC-TTF)(bpe)0.5(DMF)]n2nH2O (8); (c) [Mn(DMDC-TTF)(bpa)(H2O)]n2nH2O (9) showing organization of D and A ligands; (d) Photocurrent responses of 7–9 in the presence of a 0.1 molL1 Na2SO4 aqueous solution. Reproduced from Refs. [16] and [24] with permission from the Royal Society of Chemistry and the American Chemical Society, respectively.

state cyclic voltammetry experiments revealed that compared with the ligand, the redox potentials of the TTF core in 19 were shifted to higher potentials due to coordination-induced electron withdrawing effects of the metal centers. Interestingly, the auxiliary ligand 4,40 -bpy combined with TTFTC and an array of transition metal ions has also produced six

isostructural ionic 1D CPs, {[M(4,40 -bpy)2(H2O)4][M(TTFTC) (H2O)2]}n (M = Mn, Co, Fe, Cu, Zn and Cd) (20–25) [37]. In these systems, [M(H2O)2]2+ units are bridged by TTFTC4 to form a 1D polymer anionic chain {[M(TTFTC)(H2O)2]2}n (Fig. 11), whereas the 1D cationic chain {[M(4,40 -bpy)(H2O)4]2+}n is constructed from [M (H2O)2]2+ and 4,40 -bpy. The anionic and cationic chains, which

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

7

Fig. 7. (a) Crystal structure of [K(TTFTC+)H2]n (14); (b) View of the uniform 1D stack along the short axis of the TTF molecules; (c) Temperature dependence of the electronic conductivity of 14; (d) Fit of the data to a law of the type r = r0 exp(Ea/T). Reproduced from Ref. [33] with permission from the American Chemical Society.

Fig. 8. (a) MIL-136 (Ni); (b) the 2D network of (MIL-1360 (Ni)) (15) where i) and ii) denote the temperatures employed for the single-crystal-to-single-crystal transformation process [34].

are arranged in a parallel fashion, form 2D sheets via hydrogenbonding and p  p interactions between TTFTC and 4,40 -bpy units of adjacent chains. In a similar vein to system 16 described above, magnetic measurements on the Mn and Co analogues are consistent with two non-interacting metal ion sites. TTF and its derivatives (TTFs) have been widely used as building blocks for charge-transfer compounds due to the unique redox properties of the TTF moiety [19,38,39]. The new type of ion pair charge-transfer (IPCT) type salts, {(MV)[Mn(TTFTC)(H2O)2]2H2O}n (26) and {(MV)[Mn(TTFTC)(H2O)2]}n (27), exhibit 1 and 2D Mn (II)—TTFTC anionic coordination structures, respectively, held together by the photoactive organic cation methyl viologen (MV2+) [40]. In these materials the electron acceptor (A) MV2+ and the electron donor (D) TTF moiety are stacked in an alternating DADADA fashion (Fig. 12) at distances of 3.40 and 3.51 Å, which gives rise to CT from the TTF donor to MV2+ acceptor. Due to the special mixed-stack arrangement and D-A packing mode, 26 and 27 both exhibit pronounced and reversible photocurrent responses. Evidence also showed that the Mn(II) metal center possesses a catalytic effect in the photocurrent generation mechanism which was not observed for similar materials based on Li and Na. This work not only benefits the understanding of photocurrent generation mechanisms involving metal ions, but also provides inspiration for the design and synthesis of viable materials for optoelectronics applications.

A redox-active donor-acceptor (D-A) MOF, [(Zn(DMF))2(TTFTC) (DPNI)]n (DPNI = N,N0 -di-(4-pyridyl)-1,4,5,8-naphthalenetetracar boxydiimide) (28) has also been described which incorporates the donor and acceptor, TTFTC and DPNI, respectively (Fig. 13) [41]. Packing of both units results in a diamondoid topology with substantial p  p stacking of TTFTC and DPNI ligands in a herringbone arrangement in the order -DADADA- along the a-direction at distances of 3.561 Å. This CP exhibits CT due to D-A interactions within its crystalline structure. This through-space interaction is manifested by the formation of ligand-based radicals in the assynthesized material and leads to a partial degree of charge separation. Five distinct electronic states of the framework could be accessed using solid state electrochemical (Fig. 13c) and spectroelectrochemical techniques, including for the first time in application to metal–organic frameworks, EPR spectroelectrochemistry (SEC) (Fig. 13d). The degree of charge transfer could be controlled via electrochemical redox modulation and was quantified using complementary DFT modelling of the charge transfer state. The incorporation of bulkier benzoic acid pendant groups in the ligand tetrathiavulvalence tetrabenzoic acid (H4TTFTB) assisted in extending the length of the ligand to achieve larger pore CPs. The ligand itself was synthesized through a palladium-catalyzed cross-coupling between TTF and ethyl-4-bromobenzoate [42]. H4TTFTB was subsequently reacted with transition metals such as Zn(II) to achieve the coordination polymer {[Zn2(TTFTB)(H2O)2]

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

8

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

Fig. 9. (a) 1D polymer chain of {[Mn(TTFTC)0.5(2,20 -bpy)(CH3OH)]2H2O}n (16); (b) 2D network of [Mn(TTFTC)0.5(phen)(H2O)2]n (17) and (c) 3D network of {[Mn (TTFTC)0.5(2,20 -bpy)]H2O}n (18) [35].

H2O2DMF}n (29) containing columnar stacks of TTF and benzoatelined infinite one-dimensional channels [26]. In this MOF, close intermolecular SS contacts of the neighboring TTF cores (3.7568 Å), enabled efficient through-space charge transport through the material (Fig. 14). This 3D MOF remains porous upon desolvation and exhibits a charge mobility of 0.2 cm2/Vs, as confirmed by flash-photolysis time-resolved microwave conductivity measurements. This work represents the first example of a perma-

nently porous MOF with high charge mobility, and has inspired further exploration of the electronic properties of these materials. The reaction of H4TTFTB with various transition metals afforded a series of isostructural MOFs with the formula [M2(TTFTB)(H2O)2]n (M = Mn, Co and Cd) (30–32) (Fig. 15) [43]. These MOFs exhibit a close relationship between their single-crystal electrical conductivities and the S  S distance of neighboring TTF cores, which inversely correlate with the ionic radius of the metal ion. Thus, larger cations and shorter S  S contacts favor better overlap between pz orbitals on neighboring S and C atoms. DFT calculations confirmed that the modulation of the S  S distance has an important effect on band dispersion and subsequently influences the electrical conductivity of the framework. For example, the Cd analogue, with the largest cation and shortest S  S contact, exhibited the highest electrical conductivity in the series, r = 2.86 (±0.53)  104 Scm1, which is also amongst the highest in 3D microporous MOFs. These results provide the first demonstration of tunable intrinsic electrical conductivity in this class of materials and serve as a blueprint for controlling charge transport in MOFs with pstacked motifs. The versatility of the TTFTB ligand in producing interesting CPs was further realized in a study on the structures and redox properties of the 3D CPs {[Cd(H2TTFTB)(bpa)(H2O)2]DMF3H2O}n (33), and {[Ba(H2TTFTB)(H2O)2]DMFC2H5OH}n (34) [44]. The structure of 33, described as a (3,8)-connected tfz-d net (Fig. 16a), is comprised of distorted octahedral Cd(II) ions linked by carboxylates to form a dinuclear cluster (-Cd-(O-C-O)2-Cd-). These dinuclear clusters are connected by H2TTFTB2 anions to form 2D sheet motifs and are further linked by bpa ligands along the a axis to give a 3D pillared layer-type network. In contrast, 34, which does not feature any auxiliary ligands, exhibits a new (4,8)-connected 3D topological network with a point symbol of (44.62)2(48.64.816) (Fig. 16b), and features 10-coordinate Ba(II) ions linked by carboxylates to form dinuclear (-Ba-(O-C-O)4-Ba-) units. Solid-state electrochemical measurements of 33 and 34 both showed two reversible oxidation processes corresponding to the TTF skeleton which were stable over multiple sweeps. Furthermore, sorption experiments of 33 revealed a typical type II N2 isotherm at 77 K, indicating a surface-adsorption phenomenon. In the case of CO2 adsorption, 33 exhibits a two-step uptake profile whereby the first step was attributed to the presence of intrinsic micropores and the second to the sliding of 3D pillared layer-type nets, to reveal additional void space for the diffusion of CO2 molecules (Fig. 16c). Meanwhile, 34 revealed adsorption selectivity for CO2 over N2 owing to the large p-electron clouds from the TTF ligand which favors strong CO2 physisorption due to dipole-induced-dipole interactions (Fig. 16d). Though not investigated, it is envisaged that

Fig. 10. Crystal structure of [Co(TTFTC)0.5(4,40 -bpy)(MeOH)]n (19) [36].

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

9

paramagnetic metal ions to organic radicals. In this context, the monohalogen-bridged Mn(II) polymer, [Mn(l-Cl)Cl(EDTTTFpy)2(CH3OH)]n (35) with a 1D chain structure has been reported, and is based on the TTF monopyridine ligand (EDTTTFpy) [49]. Two EDT-TTFpy ligands are bonded to Mn(II) through two N atoms in trans positions, and two bridging l-Cl anions along the axial direction link the Mn(II) ions into an infinite chain (Fig. 17). Magnetic measurements show that compound 35 exhibits moderate antiferromagnetic coupling between the Mn(II) centers. The chemical and electrochemical partial oxidation of this system has significant potential to unlock conducting and magnetic p-d systems. 4.2. TTF-bipyridine

Fig. 11. (a) The 1D anionic chain of {[M(TTFTC)(H2O)2]2}n; (b) Parallel packing of 1D anionic {[M(TTFTC)(H2O)2]2}n and cationic {[M(4,40 -bpy)(H2O)4]2+}n [37].

redox modulation of these porous CPs may demonstrate tunable uptake behaviors as a function of redox state. 4. N-donor ligands Ligands containing pyridyl functionalities are well-known to coordinate with metallic centers to yield interesting multifunctional materials [45–48]. 4.1. TTF-monopyridine In view of the significant interest in developing materials that possess dual functionalities such as magnetic and conducting properties, a popular strategy has been the direct coordination of

2,9-Bis(4-pyridyl)tetrathiafulvalene (TTF(py)2) is an analogue of 4,40 -bpy and could serve as a donor linker owing to its effective charge-transfer properties. 4,40 -Bpy has been widely used as a building block, especially for self-assembly of framework systems, but only a handful of compounds containing TTF(py)2 have been reported. Two isostructural 1D zigzag chain complexes based on the pyridyl ligand (TTF(py)2), {[M(tta)2][TTF(py)2]}n (M = Cu for 36, and Mn for 37; tta = thenoyltrifluoroacetonate) were prepared in 2011 [50]. In 36, Cu(tta)2 units are linked by the TTF(py)2 bridging ligands in a zigzag fashion forming an infinite chain structure (Fig. 18). The electrochemical properties of these complexes indicate that they undergo more facile oxidation than the ligand itself, revealing that the coordination of TTF units to the metal ions impacts the electron donating properties of the ligand. Magnetic measurements showed that there are only weak interactions between the paramagnetic ions due to their large separation. A 1D Cd(II) CP, [Cd(AC)2(TTF(py)2)]n (38) and a 2D coordination polymer, {[Pb(AC)2(TTF(py)2)0.5]CH3CN}n (AC = 9-anthracenecarboxylate) (39), based on the same pyridyl ligand were also

Fig. 12. (a) Donor-Acceptor (D–A) packing diagrams of the anionic 1D chain {(MV)[Mn(TTFTC)(H2O)2]2H2O}n (26); (b) The 2D anionic network of {(MV)[Mn(TTFTC)(H2O)2]}n (27) showing the D–A stacking interactions between TTFTC and MV units (dotted line); (c) Photocurrent responses of 26 without light filter (red line), with a 380 nm light filter (blue line), and with a 420 nm light filter (green line); (d) Photocurrent responses of 27 in the presence of a 0.1 molL1 Na2SO4 aqueous solution. Reproduced from Ref. [40] with permission from the American Chemical Society.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

10

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

Fig. 13. (a) Stacking of the TTFTC and DPNI ligands in [(Zn(DMF))2(TTFTC)(DPNI)]n in the order DADADA at distances of 3.561 A; (b) Crystal structure of 28 viewed down the caxis; (c) Solid state CV of 28 at 100 mV s1 in a 0.1 M n-Bu4NPF6/CH3CN electrolyte; (d) Solid state EPR SEC of 28 at 0 V (black) and -0.80 V (red) in 0.1 M n-Bu4NPF6/CH3CN. Grey lines show the spectral transition and the arrows show the direction of the spectral change. Reproduced from Ref. [41] with permission from the Royal Society of Chemistry.

Fig. 14. (a) View of a helical TTF stack in {[Zn2(TTFTB)(H2O)2]H2O2DMF}n with a depiction of the shortest intermolecular SS contact; (b) A view of the 1D channels; (c) Conductivity transients observed by FP-TRMC upon excitation at 355 nm with 6.5  1015 cm2 photons per pulse for 29 (black trace) and H4TTFTB (red trace); (d) Photocurrent transients observed for 20–26 lm thick solid films of materials in PMMA matrices sandwiched between Au-semitransparent and Al electrodes. Reproduced from Ref. [26] with permission from the American Chemical Society.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

11

Fig. 17. View of a chain of [Mn(l-Cl)Cl(EDT-TTFpy)2(CH3OH)]n (35) [49].

Fig. 15. Correlation between S  S distance and electrical conductivity in [M2(TTFTB)(H2O)2]n [43].

synthesized using a solvothermal technique [51]. In the latter case, relatively few studies have probed the coordination chemistry of TTF-based ligands to heavy p-block elements such as Pb(II), and this was the first study of the role of main-group Pb(II) ions (donor center) on the charge transfer properties of TTF using an anthracenyl ligand (acceptor moiety) as a fluorescent indicator. The Cd(II) compound offered a convenient point of comparison; in this system, one TTF(py)2 ligand adopts a monodentate and the other a bidentate coordination mode. The asymmetric units Cd(AC)2[TTF(py)2] are

bridged through the bis-monodentate TTF(py)2 into a 1D chain (Fig. 19a). In compound 39, the carboxylate groups link Pb(II) ions to form an 1D chain and TTF(py)2 ligands connect adjacent chains via two side pyridine groups to form a 2D network with a planar mesh-like structure (Fig. 19b). Measurements of the intensity of fluorescence quenching of the AC ligand showed that Pb(II) ions mediate a favorable ligand-to-ligand charge-transfer (LLCT) interaction, in comparison with the Cd(II) ion.

4.3. TTF-tetrapyridine The tetra(4-pyridyl)-tetrathiafulvalene (TTF(py)4) [52] ligand was first reported in 2014 in relation to a series of discrete Ru(II) complexes, and has since been used to prepare a number of coordination polymers [53]. Five 2D networks and one 3D MOF have been prepared using diffusion techniques. As noted previously, a particular goal in the field has been the development of multifunc-

Fig. 16. 3D network of (a) {[Cd(H2TTFTB)(bpa)(H2O)2]DMF3H2O}n (33) and (b) {[Ba(H2TTFTB)(H2O)2]DMFC2H5OH}n (34); Gas sorption isotherms for (c) 33 and (d) 34 at low temperature. Reproduced from Ref. [44] with permission from the American Chemical Society.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

12

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

Fig. 18. The 1D chain structure of complex {[M(tta)2][TTF(py)2]}n [50].

tional materials wherein complementary magnetic and electronic functionalities can be accessed simultaneously. The complexes {[Co(acac)2TTF(py)4)0.5]CHCl3}n (40), [Mn (hfac)2(TTF(py)4)]n (41), and {[Cu2(OAc)4(TTF(py)4)0.5]1.5(CHCl3) 0.5(H2O)CH3CN}n (42) possess similar (4,2)-connected bimodal 2D networks, while {[Mn(SCN)2(TTF(py)4)]6(CH2Cl2)}n (43) and [Mn(SeCN)Cl(TTF(py)4)]n (44) have similar (4,4)-connected bimodal 2D structures with two different rings (Fig. 20). In complexes 40, 41 and 42, TTF(py)4 ligands are bound to four units of [Co(acac)2], [Mn(hfac)2] and [Cu2(OAc)4], respectively, to yield 2D networks consisting of a rhombus ring. In complexes 43 and 44, [Mn(SCN)2] and [Mn(SCN)Cl] units are coordinated by TTF(py)4 ligands, resulting in 2D networks which consist of two different individual rings. The magnetic susceptibility measurements for compounds 40, 43, and 44 revealed antiferromagnetic interactions between the magnetic centers. Furthermore, solid-state electrochemical studies on 40, 41, 43, and 44 showed that the redox activity of the TTF moiety was retained in the coordination polymers.

Unfortunately, these CPs showed poor electrical conductivity due to the absence of obvious intermolecular p  p and shorter S  S interactions within the structures. The 3D coordination polymer, {[Cu2(TTF(py)4)2(ClO4)2]2.5(CH2Cl2)1.5(CH3CN)}n (45), shows a 2-fold interpenetrated (4,4)connected binodal PtS-type 3D network (Fig. 21) [53]. The Cu(I) centers are coordinated by four N atoms from four different TTF (py)4 ligands resulting in a distorted tetrahedral coordination mode. Six TTF(py)4 ligands and four Cu(I) ions constitute a tetranuclear {Cu4[TTF(py)4]6} cage-like sub-building block. Further, through the bridging ligand TTF(py)4, the cages are linked together into a 3D structure. Due to interpenetration of the 3D nets the gas adsorption properties of this framework were not optimal. 4.4. TTF-triazole Triazole heterocycles have proven to be ideal ligands for spincrossover (SCO) Fe(II) complexes by virtue of their intermediate

Fig. 19. (a) The 1D chain structure of complex [Cd(AC)2(TTF(py)2)]n (38); (b) view of the 2D networks and 1D Pb(II)-carboxylate chain for {[Pb(AC)2(TTF(py)2)0.5]CH3CN}n (39) [51].

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

ligand-field strengths which are favorable for SCO [54,55]. In particular, Fe(II) one-dimensional triazole-based materials are promising candidates for applications in information technology platforms given their molecular bistability (i.e., the presence of two or more electronic states in a given system due to external perturbation). From a synthetic point of view, the 1,2,3-triazoles offer the possibility of several coordination sites and possess a rich variety of binding and bridging modes. Hence, they are expected to be versatile building blocks for the preparation of coordination materials [56–60]. Reaction of the chelating mixed pyridine1,2,3-triazole ligand, lutidine-bis(1,2,3-triazole-5-TTF) (LBT-TTF) and CdCl2 gave a one-dimensional coordination polymer, [Cd5Cl10(LBT-TTF)2(CH3CN)2]n (46) (Fig. 22) [61]. This polymer contains a repeating unit ‘‘Cd5Cl10”, which is coordinated by two TTF ligands through the triazole units. While the electrochemical, spectral and magnetic properties of the polymer were not investigated, further investigations of the TTF-triazole ligand in Fe(II) complexes may pave the way towards new spin-crossover, switchable materials with multi-stimuli responsive behavior. 5. TTF-chelating ligand Recently, the design and synthesis of new multifunctional molecular materials with an interplay or synergy between two or more properties has attracted increasing attention. As noted previously, the construction of molecular materials combining magnetic and conductive properties in the same crystal lattice has been one of the most important challenges in the field. One effective strategy in this regard is the assembly of tetrathiafulvalene with paramagnetic metal ions which may establish a coupling between mobile and localized electrons. On the one hand, TTFs may lead to molecular conductivity through interchalcogen-atom interactions, which

13

Fig. 22. The 1D chain structure of complex [Cd5Cl10(LBT-TTF)2(CH3CN)2]n (46) [61].

are often observed in molecule based conductors and superconductors. Electrochemically active TTF units can be used to link magnetic centers to form many interesting structures and multifunctional materials. The synthetic strategies to construct magnetic conductors/semiconductors include (i) the introduction of a TTF ligand into a cyanometalate building block or (ii) the use of a TTF-based complex as a node to react with cyanometalates. Both of these approaches are discussed further here. 5.1. TTF as building block Introduction of the p-conjugated tetrathiafulvalene annulated ligand into dicyanometallates resulted in the versatile redoxactive dicyanideferrite building block [n-Bu4N][Fe(TTFbp)(CN)2]

Fig. 20. The abridged view of 2D network (a) M = Co, Mn, Cu (40–42), (b) M = Mn (43, 44) [53].

Fig. 21. The 3D framework 45 (a) a single network showing the two types of channels marked as ‘A’ (pore dimensions 16.3  24.3 Å) and ‘B’ (pore dimensions 8.9  10 Å). (b) Illustration of the 2-fold interpenetration of these networks. Reproduced from Ref. [53] with permission from the American Chemical Society.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

14

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

(H2TTFbp = N-(2-(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)-5(picolinamido)benzo[d][1,3]dithiol-6-yl)picol inamide) [62]. Two enantiopure 1D complexes, [Mn((R,R)-salphen)Fe(TTFbp) (CN)2] n (47-(RR)) and [Mn((S,S)-salphen)Fe(TTFbp)(CN) 2] n (47(SS)) (salphen = N,N 0 -1,2-diphenylethylene-bis(salicylideneimi nato) dianion) were synthesized by incorporating a chiral Mn (III) Schiff-base complex with the building block. The two compounds are a pair of enantiomers, as confirmed by circular dichroism (CD) and vibrational circular dichroism (VCD) spectra, and crystallize in the chiral space group P1 (Fig. 23). The [Fe (TTFbp)(CN) 2]  anion and [Mn(salphen)]+ cation are coordinated to each other, forming neutral cyano-bridged double chains in 47-(RR) and 47-(SS) with the repeating units (-Mn-NC-Fe-

Fig. 25. Structures of bisdithiolene polymers where M indicates a transition metal ion.

Fig. 23. Perspective view of the infinite 1D zigzag chains of (a) 47-(RR) and (b) 47-(SS); (c) CD spectra of 47-(RR) and 47-(SS) in KBr pellets; (d) Temperature dependence of the 0 00 in-phase vM and out-of-phase vM at different frequencies with a zero applied dc field for 47-(SS). Reproduced from Ref. [62] with permission from The Royal Society of Chemistry.

Fig. 24. The chain structure of [Ru(salen)(CN)2Mn(TTF-salphen)]n (48) [63].

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

15

CN-)n . The electrochemical properties of the materials revealed that the redox activity of the TTF moiety was maintained in the complexes. Moreover, antiferromagnetic couplings were detected between the Fe(III) and Mn(III) centers within a chain, and a field-induced magnetic phase transition was observed (TN = 4.8 K). In these systems, the introduction of the redoxactive TTF unit, coupled with chirality into cyanide-bridged complexes with interesting magnetic properties introduces yet another degree of complexity to the design parameters for multifunctional materials. 5.2. TTF as node

Fig. 26. (a) Synthesis of the cobalt bisdithiolene polymer; (b) CPE studies of MOS (Si) (0.6(1)  106 molCo/cm2, red) and bare Si (black) at 0.12 V vs RHE in pH 1.3 H2SO4 solutions under chopped (light on/light off) 1 Sun illumination. Reproduced from Ref. [66] with permission from the American Chemical Society.

The tetrathiafulvalene-fused salphen ligand (H2TTF-salphen) represents an interesting system with combined O- and N-donor moieties [13]. Deprotonation of the phenol functionalities of H2TTF-salphen provides a tetradentate N2O2 coordination sphere for metal ions. The reaction of [Mn(TTF-salphen)][OAc] (TTFsalphen2 = 2,20 -((2-(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)-1, 3benzodithiole-5,6-diyl)bis(nitrilomethylidyne)bis(phenolate)dianion) and the cyanometalate building block (n-Bu4N)[Ru(salen) (CN)2] (salen2 = N,N0 -ethylenebis(salicylideneimine)dianion) salicylaldehyde leads to a one dimensional complex, [Ru(salen)(CN)2Mn(TTF-salphen)]n (48) [63]. The [Mn(TTF-salphen)]+ cation and the [Ru(salen)(CN)2] anion are connected to each other through the CN groups to form a 1D chain (Fig. 24). The magnetic properties indicate the presence of intra-chain antiferromagnetic coupling between neighboring Ru(III) and Mn(III) ions. While the related discrete dinuclear heterometallic complex [(Tp)Fe(CN)3Mn(TTFsalphen)CH3OH] (where Tp = Tris(pyrazolyl)hydroborate) exhibits single molecule magnetic behavior with an energy barrier of 13.8 K, the polymer was not found to exhibit single-chain magnetic behavior. 6. S donor ligands

Fig. 27. Chemical structures of the conductive coordination nanosheets based on TTFs/ M(dmit)2/M(dddt)2. The centers of the organic linkers are referred as metal nodes, the outer phenyl rings are denoted as coordination groups and the metal dithiolene complex can be regarded as an inorganic analogue of TTF and M(dmit)2 or M(dddt)2.

In addition to the aforementioned p-electron donor properties of TTF, metal bisdithioleneato complexes are well-known pelectron acceptors. The reaction of tetrathiafulvalene-tetrathiolate or dithiolene with transition metal salts led to the formation of metal bisdithiolene 1D chain polymers wherein the donor and acceptor functionalities were fused into a conjugated system (Fig. 25) [64,65]. While a range of transition metal ions were investigated (M = Cu, Fe, Pt, Pd, Ni and Au in Fig. 25), the nickel derivative displayed an unusually low energy electronic absorption band in the near-infrared region and a metal-like temperature depen-

Fig. 28. The representative 1D chains of (a) [(CuI)2TTC2-TTF]n (49) and (b) {[Cu(TTC2-TTF)]ClO4}n (51) [76,78].

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

16

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

dence of conductivity which was characteristic of donor–acceptor charge transfer salts. This high conductivity was attributed to the existence of a partial degree of charge transfer due to oxidation of the donor TTF moiety during polymer formation. These types of 1D polymers have recently been exploited for redox catalysis given the well-known efficiency of dithiolene species (particularly those of cobalt) for the hydrogen evolution reaction. A key strategy for the development of clean energy technologies is the replacement of noble metal catalysts such as Pt with lower cost and more earth abundant materials such as these polymeric systems. The cobalt(II) dithiolene polymer was synthesized by the reaction of cobalt and benzene-1,2,4,5tetrathiol in the presence of base (Fig. 26) [66]. The cobalt dithiolene catalysts were interfaced with glassy carbon or Si electrodes to generate MOS (metal–organic surface)-modified cathodes. MOS (Si) was an efficient photocathode material for solar-driven hydrogen production from water, with photocurrents of 3.8 mA/cm2 achieved at 0 V vs RHE under simulated 1 Sun illumination. The generated MOS displays current densities that are significantly higher than those of the analogous molecular complex, suggesting that immobilization provides a significant increase in efficiency and stability, thus paving the way towards the development of practical devices. 2D CP materials have attracted great attention due to their unique properties compared with the aforementioned 1D chainlike polymers and 3D framework systems. Recent research has involved the assembly of coordination nanosheets to form materials that have two significant advantages over single crystals. First, numerous combinations of metals and ligands can potentially be integrated into nanosheets, providing a plethora of chemical structures with unique electronic properties. Secondly, most coordination reactions to form nanosheets proceed under ambient conditions and at room temperature, making ‘‘bottom-up” processing easy and inexpensive. Coordination nanosheets with multi-sulfur 1,2-dithiolene ligands can be considered as an isolobal analogy to M(d8) in M (dmit)2 or M(dddt)2 (dmit = 1,3-dithio-2-thione-4,5-dithiolate, dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) and the central C@C group in the BEDT-TTF molecule (Fig. 27). Among them, NiDT (X = S, M = Ni), a p-conjugated 2D coordination nanosheet, exhibits high electrical conductivity, comparable in magnitude to, or higher than values reported for organic conductors and conducting MOFs [67–70]. The graphitic-type topologies of these materials are the subject of extensive computational modelling studies which aim to elucidate the electronic properties [71,72]. The relative disposition of the 2D sheets can be eclipsed, stepped-parallel or staggered, resulting in 1D pores through the material. A key outcome of computational studies has been the demonstration of continuous tuning of the bandgap as the 2D sheets are slid with respect to one another. A host of potential applications are envisaged for these materials in nanoelectromechanical and optoelectronics devices, amongst others. Sulfur-rich ligands can be obtained by introducing additional sulfur atoms at the periphery of the TTF skeleton [73–75]. Such ligands could act as bridges between different metal centers leading to polynuclear complexes with an increased potential for intermolecular stacking and orbital overlap which could enhance the conducting properties. The ligand TTC2-TTF has been employed to coordinate transition metals, yielding a series of coordination polymers [(CuI)2TTC2TTF]n (49), ([(CuBr)2TTC2-TTF]n (50), {[Cu(TTC2-TTF)]ClO4}n (51), {[Cu(TTC2-TTF)]BF4}n (52)), {[Cu(TTC2-TTF)]ClO4}n (53) and [(CuI)2TMT-TTF]n (54) [76–80]. All these CPs were synthesized under argon using Schlenk techniques. In 49, 50 and 54, the Cu(I) ions are linked by TTC2-TTF molecules and halogen anions to form 1D chains (Fig. 28a); in 51, 52 and 53, the Cu(I) ions are linked by

TTC2-TTF molecules only to form 1D chains (Fig. 28b). Electrical resistivity measurements show that CPs 50–54 are insulators, while the corresponding compounds doped with iodine behave as semiconductors at room temperature. In the latter case, iodine doping was proposed to induce a mixed-valence or partial oxidation state in the materials (corresponding to partial oxidation of some TTF-based moieties to their radical cation analogues). Infrared spectroscopy confirmed the presence of both the neutral and radical cation forms of TTF in the structure (based on the stretching frequency of the central C@C bond). The increase in the degree of conductivity upon doping was thus tentatively ascribed to charge transfer transitions between the neutral and radical cation TTF moieties which promotes electronic delocalization. Silver(I) coordination polymers based on TMT-TTF including [Ag (TMT-TTF)SO3CF3]n (55), have also been reported (Fig. 29) [81]. Two Ag(I) centers are involved in a distorted triangular prismatic geometry with two sulfur atoms and one oxygen atom on the top triangular plane. Each TMT-TTF ligand bridges two Ag(I) centers with four sulfur atoms into two independent sinusoidal shaped chains. Two such chains are interwoven and run along the b-axis (Fig. 29). While the compound is an insulator at room temperature, the corresponding iodine doped material behaves as a semiconductor with a conductivity of 2.8  104 Scml. As noted previously for the Cu(I) complexes, the origin of the increased conductivity was tentatively ascribed to the presence of TTF molecules in a mixed-valence (or partial oxidation) state which gives rise to conduction pathways.

Fig. 29. The chain structure of [Ag(TMT-TTF)SO3CF3]n (55) [81].

Fig. 30. 3D framework of complex [Ag(TMT-TTF)0.5NO3]n (56) [82].

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

A 3D silver(I) complex [Ag(TMT-TTF)0.5NO3]n (56) has also been prepared using TMT-TTF and shows an unprecedented 4.16-net porous inorganic layer of silver nitrate [82]. Each Ag(I) is coordinated by three oxygen atoms from three different nitrate ions, extending to form an infinite inorganic layer composed of silver and nitrate ions (Fig. 30). The nearest neighboring inorganic layers are linked by TMT-TTF molecules through the coordination of methylthio groups with silver ions to generate a threedimensional framework. Compound 56 is an insulator, however, after treatment with iodine vapor, the room temperature conductivity was determined to be 4.5  103 Scm1 which is consistent with semiconducting behavior, with an activation energy of approximately 0.08 eV. Measurements of the binding energy of the sulfur atoms from X-ray photoelectron spectroscopy, coupled with data from infrared spectroscopy for the central C@C stretching frequency of the TMT-TTF unit revealed a combination of neutral and radical cation ligand within the framework. The origins of the conductivity enhancement were thus ascribed to a mixedvalence interaction of the type mentioned above. Copper(II) halides have the potential to oxidize TTF and its derivatives leading to a variety of Cu(I) charge-transfer complexes with significantly different structural and physical properties, such as metallic conductivity and superconductivity [81,83–88]. With this goal in sight, several Cu(I) complexes were crystallised via diffusion procedures [89]. The 1D Cu(I) compound, {(BEDTTTF)2[Cu4Br6(BEDT-TTF)]}n (57) is a hybrid material in which conducting layers and one dimensional lattices coexist in the crystal structure (Fig. 31a). In these systems, the BEDT-TTF molecule directly coordinated to the copper ions is in its dication state. It is interesting to note that while compound 57 is diamagnetic, it shows anisotropic electrical conductivity and exhibits semiconducting behavior (Fig. 31b). The room temperature conductivities and activation energies are 2.4 Scm1 and 22 meV, 3.3 Scm1 and 22 meV, and 2.5  102 Scm1 and 17 meV along the a-, band c-axis, respectively. Above 270 K, the occurrence of a metallic

17

regime along the c-axes, the BEDT-TTF stacking direction, is probably due to the BEDT-TTF conducting layer. 7. CN donor ligands 7.1. TTF-dicyanogen The previous examples of chemically-modified TTF ligands shown in Section 6 demonstrate the significant efforts that have been placed in introducing additional functional groups such as sulfur atoms at the periphery of the TTF moiety in an attempt to enhance S  S interactions leading to conductive or superconductive molecular stacks. Flexible links have also been introduced to TTF to generate new functional ligands. The unsymmetrical TTF derivative 2-[4,5-bis(methylsulfanyl)-1,3-dithiol-2-ylidene]-4,5-bi s(2-cyanoethylsulfanyl)-1,3-dithiole (CM-TTF), has been prepared by attaching the methylsulfanyl group at one end of TTF and the cyanoethylsulfanyl group at the other, and displays unique coordination flexibility. In [Ag(CM-TTF)(CF3SO3)]n (58), each Ag(I) ion adopts a five coordinate square-pyramidal geometry comprising two S and two N atoms from two separate CM-TTF molecules, while the CM-TTF molecule chelates two metal ions with the terminal MeS and CN groups, forming an infinite chain structure (Fig. 32) [90]. While the complex and its air oxidized species are poorly conductive, ESR measurements showed that the signal at g = 2.007 for 58 was sensitive to oxidation by air. The decrease in intensity of the ESR signal and increase in its linewidth (at constant g) upon air exposure was ascribed to spin exchange between mobile electrons which are confined to a single chain. 7.2. TTF-tetracyanogen The formation of 3D coordination networks based on Ag(I) and the symmetric tetracyano ligand, such as {[Ag4(tcesTTF)2(CF3SO3)2] (CF3SO3)2}n (tcesTTF = 2,3,6,7-tetra(cyanoethylsulfanyl)) (59), have

Fig. 31. (a) Packing diagram of complex {(BEDT-TTF)2[Cu4Br6(BEDT-TTF)]}n (57); (b) Comparison of the temperature dependences of conductivities along the a-, b-, and c-axes (left) and temperature dependences of resistivity along the c-axis (right). Reproduced from Ref. [89] with permission from the American Chemical Society.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

18

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

Fig. 32. The chain structure of [Ag(CM-TTF)(CF3SO3)]n (58) [90].

Fig. 33. (a) 1D chains and (b) ‘‘8”-shaped channels and axially chiral motifs in 59 [91].

Fig. 34. The 2D network of compound {[M2(tcesTTF)2(H2O)4]X62H2O}n [92].

also been investigated [91]. The Ag(I) ion and C„N moiety on the one side of TTF skeleton are linked, forming a right-handed helix (Fig. 33a), and the Ag(I) ions can easily bridge the S atoms of the cyanoethylsulfanyl arms leading to a 2D layered structure. The CF3SO 3 anions subsequently bridge the 2D layers to form a 3D network (Fig. 33b). Due to the intramolecular SS contacts in 59, the

system exhibits semi-conductive behavior with an electrical conductivity of 3.47  106 Scm1 at room temperature. Four isostructural complexes, {[M2(tcesTTF)2(H2O)4]X62H2O}n  (M = Co(II), Mn(II), Zn(II), Cd(II); X = ClO 4 , BF4 ) (60–63), were obtained using electrocrystallization techniques, and were found to exist as extended 2D networks [92]. Each tcesTTF ligand links three metal ions to form a planar network (Fig. 34). Magnetic measurements indicate that the Zn(II) complex 62 is diamagnetic while the Mn(II) complex 61 is paramagnetic due to two uncoupled Mn (II) spins, with no contribution from tcesTTF+. IR and Raman vibrational spectra of these materials, coupled with UV–vis spectroscopic measurements showed however, that tcesTTF was indeed present in its fully oxidized radical cation state within the materials [93]. By assuming electron-molecular vibration coupling and performing related theoretical analysis, charge transfer was confirmed to take place between the tcesTTF+ molecules belonging to neighboring polymeric networks, leading to coupling of their C@C stretching modes. The origin of these interactions was short SS interactions between the TTF cores of tcesTTF+ in the neighboring networks.

8. Conclusions In this review, a brief summary of coordination polymers based on redox-active tetrathiafulvalene and its derivatives has been presented. Although a large number of TTF-based CPs have been reported, selected examples of CPs displaying common coordina-

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

tion motifs with multifunctional properties have been discussed. More than sixty TTF-based CPs (Table 1) have been highlighted in this review, and these materials have been synthesized by combining different metal ions (predominantly those of the d elements) and TTF-based ligands. Most linkers used for the construction of CPs are conjugated or rigid (Fig. 1 and 2). For all of the reported materials, the main structural features determined by single crystal X-ray diffraction have been detailed. Selected properties and synthetic methods for each example have also been summarised, in order to provide some guidelines for the design and synthesis of functional materials containing ligands. In view of the large number and structural variety of TTF-based systems described here, it is evident that a significant degree of predictive knowledge now exists to guide future synthetic efforts towards TTF-based coordination polymers with desired structural and physical properties. The key structure–function correlations that come to light include promoting interchalcogen SS interactions of the type often observed in molecule based conductors and superconductors. Although the control of dimensionality in the solid state stands as one of the global challenges for chemists, rational approaches to ‘crystal engineering’ in TTF-based systems are evident [3]. A major thrust of research efforts has been the development of multifunctional materials wherein dual magnetic and conducting behavior can be realized within a given system. In these socalled ‘‘p-d” systems, the mobile p electrons are provided by TTF, while the paramagnetic metal ions contribute the localized d electrons leading to conductive magnetic materials. While a number of systems described in this review have incorporated these highly useful synergistic functions, the majority of these materials is dense and lack permanent porosity. The advent of porous TTFbased systems, as described for some MOFs in Section 3.2, heralds a new era in advanced multifunctional materials, and future efforts should focus on surmounting the synthetic challenges in this area. While partial oxidative doping has been shown to improve the conductive properties of a number of the systems described herein, the advent of more robust and highly porous coordination polymers would significantly improve the prospects for exploiting host-guest interactions to further perturb the functional properties. At the fundamental level, electrochemical, UV–visible and infrared/Raman vibrational spectra of TTF-based coordination polymers, coupled with single crystal structural analyses have provided detailed insights into the charge transfer properties. In particular, the C@C stretch of TTF is known to be highly sensitive to the degree of ionization (i.e., the frequency of these modes strongly decreases as the average degree of ionization increases). Likewise, X-ray photoelectron spectroscopy provides a highly useful measure of the sulfur binding energies. Taken together, these techniques offer intimate insights into the charge state of TTF within a given material. One caveat to note here is the different timescales of the techniques, which must be taken into account (e.g., bond lengths from X-ray structural analyses offer an average measure compared with measurements of infrared/Raman spectra which report on the significantly faster timescale of molecular vibration). At the applied level, a plethora of industrially and technologically-important applications can be envisaged for multifunctional TTF-based systems. These range from electrochromic materials, to electrocatalysis relevant to clean energy technologies and photoconductive switches, as described for various examples throughout this review. When combined with permanent porosity, the range of potential applications extends beyond the traditional areas of gas storage and separations for MOFs, to include energy storage (e.g., batteries) and transformation. Given the rapid developments in synthetic, theoretical, and applied aspects of these sys-

19

tems over the past two decades, we are confident that the field of TTF-based CPs will continue to flourish. Acknowledgments This work was supported by the Major State Basic Research Development Program (2013CB922101), the National Natural Science Foundation of China (21631006), the Natural Science Foundation of Jiangsu Province (BK20130054) and the Australian Research Council. We also gratefully acknowledge Lei Sun, Yue Wu, Jing-yuan Ge and Fei Yu for their help on this paper. References [1] S.R. Batten, N.R. Champness, X.-M. Chen, J. Garcia-Martinez, S. Kitagawa, L. Öhrström, M. O’Keeffe, M. Paik Suh, J. Reedijk, Pure Appl. Chem. 85 (2013) 1715–1724. [2] S.R. Batten, N.R. Champness, X.-M. Chen, J. Garcia-Martinez, S. Kitagawa, L. Ohrstrom, M. O’Keeffe, M.P. Suh, J. Reedijk, CrystEngComm 14 (2012) 3001– 3004. [3] B.F. Hoskins, R. Robson, J. Am. Chem. Soc. 112 (1990) 1546–1554. [4] O.M. Yaghi, G. Li, H. Li, Nature 378 (1995) 703–706. [5] J.R. Long, O.M. Yaghi, Chem. Soc. Rev. 38 (2009) 1213–1214. [6] H.-C. Zhou, J.R. Long, O.M. Yaghi, Chem. Rev. 112 (2012) 673–674. [7] H.C. Zhou, S. Kitagawa, Chem. Soc. Rev. 43 (2014) 5415–5418. [8] K.M. Fromm, Angew. Chem., Int. Ed. 48 (2009) 4890–4891. [9] L. Sun, M.G. Campbell, M. Dinca˘, Angew. Chem., Int. Ed. 55 (2016) 3566–3579. [10] K. Terakura, S. Ishibashi, Phys. Rev. B 91 (2015). [11] H. Jiang, X. Yang, Z. Cui, Y. Liu, H. Li, W. Hu, C. Kloc, CrystEngComm 16 (2014) 5968–5983. [12] J.O. Jeppesen, J. Becher, Eur. J. Org. Chem. 2003 (2003) 3245–3266. [13] D. Lorcy, N. Bellec, M. Fourmigué, N. Avarvari, Coord. Chem. Rev. 253 (2009) 1398–1438. [14] D.M. D’Alessandro, J.R.R. Kanga, J.S. Caddy, Aust. J. Chem. 64 (2011) 718–722. [15] L. Ouahab, T. Enoki, Eur. J. Inorg. Chem. 2004 (2004), 919. [16] Q.Y. Zhu, J.P. Wang, Y.R. Qin, Z. Shi, Q.H. Han, G.Q. Bian, J. Dai, Dalton Trans. 40 (2011) 1977–1983. [17] C. Kwang-Fu Shen, H.M. Duong, G. Sonmez, F. Wudl, J. Am. Chem. Soc. 125 (2003) 16206–16207. [18] J. Guasch, L. Grisanti, M. Souto, V. Lloveras, J. Vidal-Gancedo, I. Ratera, A. Painelli, C. Rovira, J. Veciana, J. Am. Chem. Soc. 135 (2013) 6958–6967. [19] S. Kimura, H. Suzuki, T. Maejima, H. Mori, J.-I. Yamaura, T. Kakiuchi, H. Sawa, H. Moriyama, J. Am. Chem. Soc. 128 (2006) 1456–1457. [20] M.B. Nielsen, C. Lomholt, J. Becher, Chem. Soc. Rev. 29 (2000) 153–164. [21] A. Kobayashi, E. Fujiwara, H. Kobayashi, Chem. Rev. 104 (2004) 5243–5264. [22] T. Enoki, A. Miyazaki, Chem. Rev. 104 (2004) 5449–5478. [23] D.M. D’Alessandro, Chem. Commun. 52 (2016) 8957–8971. [24] P. Huo, T. Chen, J.L. Hou, L. Yu, Q.Y. Zhu, J. Dai, Inorg. Chem. 55 (2016) 6496– 6503. [25] L. Sun, C.H. Hendon, M.A. Minier, A. Walsh, M. Dinca˘, J. Am. Chem. Soc. 137 (2015) 6164–6167. [26] T.C. Narayan, T. Miyakai, S. Seki, M. Dinca, J. Am. Chem. Soc. 134 (2012) 12932– 12935. [27] N. Motokawa, H. Miyasaka, M. Yamashita, K.R. Dunbar, Angew. Chem., Int. Ed. Engl. 47 (2008) 7760–7763. [28] G. Cosquer, F. Pointillart, Y. Le Gal, S. Golhen, O. Cador, L. Ouahab, Chem. Eur. J. 17 (2011) 12502–12511. [29] Z.-P. Lv, Z.-Z. Luan, H.-Y. Wang, S. Liu, C.-H. Li, D. Wu, J.-L. Zuo, S. Sun, ACS Nano 9 (2015) 12205–12213. [30] Z.-P. Lv, Z.-Z. Luan, P.-Y. Cai, T. Wang, C.-H. Li, D. Wu, J.-L. Zuo, S. Sun, Nanoscale 8 (2016) 12128–12133. [31] Y. Chen, C. Li, C. Wang, D. Wu, J. Zuo, X. You, Sci. China, Ser. B: Chem. 52 (2009) 1596–1601. [32] J.-P. Wang, Z.-J. Lu, Q.-Y. Zhu, Y.-P. Zhang, Y.-R. Qin, G.-Q. Bian, J. Dai, Cryst. Growth Des. 10 (2010) 2090–2095. [33] A. Nguyen Tle, R. Demir-Cakan, T. Devic, M. Morcrette, T. Ahnfeldt, P. AubanSenzier, N. Stock, A.M. Goncalves, Y. Filinchuk, J.M. Tarascon, G. Ferey, Inorg. Chem. 49 (2010) 7135–7143. [34] A. Nguyen Tle, T. Devic, P. Mialane, E. Riviere, A. Sonnauer, N. Stock, R. DemirCakan, M. Morcrette, C. Livage, J. Marrot, J.M. Tarascon, G. Ferey, Inorg. Chem. 49 (2010) 10710–10717. [35] Y.R. Qin, Q.Y. Zhu, L.B. Huo, Z. Shi, G.Q. Bian, J. Dai, Inorg. Chem. 49 (2010) 7372–7381. [36] M.-Y. Shao, P. Huo, Y.-G. Sun, X.-Y. Li, Q.-Y. Zhu, J. Dai, CrystEngComm 15 (2013) 1086–1094. [37] Y. Han, Y. Song, Inorg. Chem. Commun. 55 (2015) 83–87. [38] T. Iimori, T. Naito, N. Ohta, J. Phys. Chem. C 114 (2010) 9070–9075. [39] J. Yamada, T. Sugimoto, T.T.F. Chemistry, Fundamentals and Application of Tetrathiafulvalene, Springer, Berlin, 2004. [40] Y.D. Huang, P. Huo, M.Y. Shao, J.X. Yin, W.C. Shen, Q.Y. Zhu, J. Dai, Inorg. Chem. 53 (2014) 3480–3487.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011

20

H.-Y. Wang et al. / Coordination Chemistry Reviews xxx (2016) xxx–xxx

[41] C.F. Leong, B. Chan, T.B. Faust, D.M. D’Alessandro, Chem. Sci. 5 (2014) 4724– 4728. [42] Y. Mitamura, H. Yorimitsu, K. Oshima, A. Osuka, Chem. Sci. 2 (2011) 2017– 2021. [43] S.S. Park, E.R. Hontz, L. Sun, C.H. Hendon, A. Walsh, T. Van Voorhis, M. Dinca, J. Am. Chem. Soc. 137 (2015) 1774–1777. [44] B. Chen, Z.-P. Lv, C.F. Leong, Y. Zhao, D.M. D’Alessandro, J.-L. Zuo, Cryst. Growth Des. 15 (2015) 1861–1870. [45] K.S. Gavrilenko, Y.L. Gal, O. Cador, S. Golhen, L. Ouahab, Chem. Commun. (2007) 280–282. [46] E. Isomura, K.-I. Tokuyama, T. Nishinaga, M. Iyoda, Tetrahedron Lett. 48 (2007) 5895–5898. [47] N. Benbellat, K.S. Gavrilenko, Y. Le Gal, O. Cador, S. Golhen, A. Gouasmia, J.M. Fabre, L. Ouahab, Inorg. Chem. 45 (2006) 10440–10442. [48] L.K. Keniley Jr., L. Ray, K. Kovnir, L.A. Dellinger, J.M. Hoyt, M. Shatruk, Inorg. Chem. 49 (2010) 1307–1309. [49] C. Jia, S.X. Liu, C. Ambrus, A. Neels, G. Labat, S. Decurtins, Inorg. Chem. 45 (2006) 3152–3154. [50] R. Wang, L.C. Kang, J. Xiong, X.W. Dou, X.Y. Chen, J.L. Zuo, X.Z. You, Dalton Trans. 40 (2011) 919–926. [51] Y.-H. Li, Y.-G. Sun, P. Huo, Q.-Y. Zhu, J. Dai, Inorg. Chem. Commun. 68 (2016) 33–36. [52] V. Vajpayee, S. Bivaud, S. Goeb, V. Croué, M. Allain, B.V. Popp, A. Garci, B. Therrien, M. Sallé, Organometallics 33 (2014) 1651–1658. [53] H.Y. Wang, Y. Wu, C.F. Leong, D.M. D’Alessandro, J.L. Zuo, Inorg. Chem. 54 (2015) 10766–10775. [54] O. Kahn, C.J. Martinez, Science 279 (1998) 44–48. [55] J. Krober, E. Codjovi, O. Kahn, F. Groliere, C. Jay, J. Am. Chem. Soc. 115 (1993) 9810–9811. [56] T. Biet, N. Avarvari, Org. Biomol. Chem. 12 (2014) 3167–3174. [57] Y.H. Lau, P.J. Rutledge, M. Watkinson, M.H. Todd, Chem. Soc. Rev. 40 (2011) 2848–2866. [58] D.S. Pedersen, A. Abell, Eur. J. Org. Chem. 2011 (2011) 2399–2411. [59] M.L. Gower, J.D. Crowley, Dalton Trans. 39 (2010) 2371–2378. [60] J.D. Crowley, E.L. Gavey, Dalton Trans. 39 (2010) 4035–4037. [61] T. Biet, N. Avarvari, CrystEngComm 16 (2014) 6612–6620. [62] L. Cui, Z.P. Lv, C.F. Leong, J. Ru, D.M. D’Alessandro, Y. Song, J.L. Zuo, Dalton Trans. 45 (2016) 16575–16584, http://dx.doi.org/10.1039/C1036DT01756H. [63] L. Cui, F. Zhu, C.F. Leong, J. Ru, F. Gao, D.M. D’Alessandro, J. Zuo, Sci. China: Chem. 58 (2015) 650–657. [64] N.M. Rivera, E.M. Engler, R.R. Schumaker, J. Chem. Soc., Chem. Commun. (1979) 184–185. [65] R. Vicente, J. Ribas, P. Cassoux, L. Valade, Synth. Met. 13 (1986) 265–280. [66] C.A. Downes, S.C. Marinescu, J. Am. Chem. Soc. 137 (2015) 13740–13743. [67] H. Maeda, R. Sakamoto, H. Nishihara, Langmuir 32 (2016) 2527–2538. [68] T. Kambe, R. Sakamoto, K. Hoshiko, K. Takada, M. Miyachi, J.H. Ryu, S. Sasaki, J. Kim, K. Nakazato, M. Takata, H. Nishihara, J. Am. Chem. Soc. 135 (2013) 2462– 2465.

[69] T. Kambe, R. Sakamoto, T. Kusamoto, T. Pal, N. Fukui, K. Hoshiko, T. Shimojima, Z. Wang, T. Hirahara, K. Ishizaka, S. Hasegawa, F. Liu, H. Nishihara, J. Am. Chem. Soc. 136 (2014) 14357–14360. [70] M.G. Campbell, S.F. Liu, T.M. Swager, M. Dinca, J. Am. Chem. Soc. 137 (2015) 13780–13783. [71] F. Shojaei, H.S. Kang, J. Phys. Chem. C 118 (2014) 25626–25632. [72] F. Shojaei, J.R. Hahn, H.S. Kang, Chem. Mater. 26 (2014) 2967–2974. [73] M.R. Bryce, J. Mater. Chem. 5 (1995) 1481–1496. [74] T. Jorgensen, T.K. Hansen, J. Becher, Chem. Soc. Rev. 23 (1994) 41–51. [75] M.R. Bryce, Chem. Soc. Rev. 20 (1991) 355–390. [76] G. Xinmin, M. Megumu, K.-S. Takayoshi, M. Masahiko, Bull. Chem. Soc. Jpn. 67 (1994) 3009–3011. [77] X. Gan, M. Munakata, T. Kuroda-Sowa, M. Maekawa, Y. Misaki, Polyhedron 14 (1995) 1343–1350. [78] X. Gan, M. Munakata, T. Kuroda-Sowa, M. Maekawa, M. Yamamoto, Polyhedron 14 (1995) 1647–1651. [79] M. Yamamoto, X. Gan, T. Kuroda-Sowa, M. Maekawa, Y. Suenaga, M. Munakata, Inorg. Chim. Acta 261 (1997) 169–174. [80] M. Munakata, T. Kuroda-Sowa, M. Maekawa, A. Hirota, S. Kitagawa, Inorg. Chem. 34 (1995) 2705–2710. [81] M. Munakata, L.P. Wu, X. Gan, T. Kuroda-sowa, Y. Suenaga, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A 284 (1996) 319–327. [82] C. Jia, D. Zhang, C.-M. Liu, W. Xu, H. Hu, D. Zhu, New J. Chem. 26 (2002) 490– 494. [83] U. Geiser, M.A. Beno, A.M. Kini, H.H. Wang, A.J. Schultz, B.D. Gates, C.S. Cariss, K. Douglas Carlson, J.M. Williams, Synth. Met. 27 (1988) A235–A241. [84] A.M. Kini, U. Geiser, H.H. Wang, K.D. Carlson, J.M. Williams, W.K. Kwok, K.G. Vandervoort, J.E. Thompson, D.L. Stupka, Inorg. Chem. 29 (1990) 2555–2557. [85] J.M. Williams, A.M. Kini, H.H. Wang, K.D. Carlson, U. Geiser, L.K. Montgomery, G.J. Pyrka, D.M. Watkins, J.M. Kommers, Inorg. Chem. 29 (1990) 3272–3274. [86] M. Kurmoo, D.R. Talham, P. Day, J.A.K. Howard, A.M. Stringer, D.S. Obertelli, R. H. Friend, Synth. Met. 22 (1988) 415–418. [87] M.B. Inoue, Q. Fernando, M. Inoue, Synth. Met. 42 (1991) 2069–2072. [88] M.B. Inoue, C. Cruz-Vazquez, M. Inoue, G.J. Pyrka, K.W. Nebesny, Q. Fernando, Synth. Met. 22 (1988) 231–237. [89] R. Kanehama, M. Umemiya, F. Iwahori, H. Miyasaka, K. Sugiura, M. Yamashita, Y. Yokochi, H. Ito, S. Kuroda, H. Kishida, H. Okamoto, Inorg. Chem. 42 (2003) 7173–7181. [90] L.P. Wu, J. Dai, M. Munakata, M. Maekawa, Y. Suenaga, Y. Ohno, J. Chem. Soc., Dalton Trans. (1998) 3255–3262. [91] Y. Ding, Q. Chen, J.-C. Zhong, M. Munakata, H. Konaka, G.-L. Ning, H.-Z. Wang, Polyhedron 27 (2008) 1393–1400. [92] J. Olivier, S. Golhen, R. S´wietlik, O. Cador, F. Pointillart, L. Ouahab, Eur. J. Inorg. Chem. 2009 (2009) 3282–3290. [93] I. Olejniczak, A. Lapinski, R. Swietlik, J. Olivier, S. Golhen, L. Ouahab, ChemPhysChem 12 (2011) 2124–2130.

Please cite this article in press as: H.-Y. Wang et al., Functional coordination polymers based on redox-active tetrathiafulvalene and its derivatives, Coord. Chem. Rev. (2016), http://dx.doi.org/10.1016/j.ccr.2016.10.011