Syntheses, crystal structures and luminescent properties of two silver complexes of N,N,N′,N′-tetra(diphenylphosphanylmethyl)ethylene diamine

Inorganica Chimica Acta 362 (2009) 3910–3914

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Syntheses, crystal structures and luminescent properties of two silver complexes of N,N,N0 ,N0 -tetra(diphenylphosphanylmethyl)ethylene diamine Li Li a,b,c, Zhi-Gang Ren a, Ni-Ya Li a, Yong Zhang a, Jian-Ping Lang a,b,* a

Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Suzhou University, Suzhou 215123, Jiangsu, People’s Republic of China b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of China c School of Chemistry and Biological Engineering, Suzhou University of Science and Technology, Suzhou 215011, Jiangsu, People’s Republic of China

a r t i c l e

i n f o

Article history: Received 25 March 2009 Received in revised form 6 May 2009 Accepted 7 May 2009 Available online 18 May 2009 Keywords: N,N,N’,N’-tetra(diphenylphosphanylmethyl)ethylene diamine Silver Structure Polymer Molecular basket

a b s t r a c t Treatment of a suspension of AgNO3 and AgCl in MeOH with a solution of N,N,N0 ,N0 -tetra(diphenylphosphanylmethyl)ethylene diamine (dppeda) in CHCl3 afforded a binuclear complex [Ag2(dppeda)Cl](NO3)2MeOH (1). The analogous reactions using AgSCN and dppeda in EtOH/CH2Cl2 gave rise to a polymeric complex [Ag2(dppeda)(SCN)2]n (2). Both compounds were fully characterized by elemental analyses, IR spectra, 1H(31P) NMR, and single-crystal X-ray crystallography. The cation of 1 shows an interesting molecular basket framework in which dppeda adopts a side-by-side coordination mode. Compound 2 possesses an unique 2D (6,3) layer network with 34-membered metallomacrocycles in which dppeda takes a end-to-end coordination mode. The 2D topological framework of 2 is rare in the chemistry of tetraphosphines. The photoluminescent properties of 1 and 2 in solid state at ambient temperature were investigated. Ó 2009 Elsevier B.V. All rights reserved.

1. Introduction Metal complexes with multidentate phosphine ligands have attracted much attention in the design and construction of new metal–organic frameworks [1–18], in stabilizing low oxidation state metal complexes [19–22], and in the search of new drug delivery systems [23,24], anticancer agents [25], optical materials [26– 28], and catalysts [29]. Since a large number of the structures of complexes of silver(I) with mono- or di-phosphines have been reported in recent years [1,30–39], those with tri- and tetra-phosphines are also deserved to be further investigated due to their richness of P-donors, the diversity of coordination modes and the modifiable molecular rigidness. A series of large multimetallic cages and rings were prepared by reactions of various Ag(I) salts with these ligands. The rigidness and the conformation of these ligands played an important role in the formation of different topological frameworks. For example, the reactions of silver(I) with rigid planar ligands such as tris(diphenylphosphino)triazine and tris(diphenylphosphino)benzene produced several molecular cages [2–4] and a non-interpenetrating polymer [Ag4L3(O3SCF3)4] (L = tris(diphenylphosphino)benzene) with remarkably wide chan-

nels [5], while in the cases of flexible ligands, the resulting products mainly were simple complexes and only a few cages with CH3C(CH2PPh2)3 were reported [6]. N,N,N0 ,N0 -tetra(diphenylphosphanylmethyl)ethylene diamine (dppeda) [40] is one of such flexible multidentate phosphine ligands. In contrary to the tetra(diphenylphosphanylmethyl)ethane analogue [41], the dppeda ligand and its related tetraphosphine ligands exhibit less coordination modes in which the four PPh2 groups connect one metal for each [26] or chelate two metals or clusters [18,42] by the two –NP2 [43] or –N(CH2P)2 ends [25,44,45]. Although these tetraphosphine ligands can have various coordination modes to bind metals to form coordination polymers, no example has been reported to date. We carried out the reactions of various silver(I) salts with dppeda and a binuclear complex [Ag2(dppeda)Cl](NO3)2MeOH (1) and a polymeric complex [Ag2(dppeda)(SCN)2]n (2) were isolated therefrom. Compound 1 has a cationic molecular basket structure while compound 2 is a first example showing a 2D structure with a tetraphosphine ligand (dppeda). Herein we report their syntheses, structures and the luminescent properties. 2. Experimental

* Corresponding author. Address: Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Suzhou University, Suzhou 215123, Jiangsu, People’s Republic of China. Tel./fax: +86 512 65882865. E-mail address: [email protected] (J.-P. Lang). 0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2009.05.018

2.1. General All manipulations were carried out in open air. The ligand dppeda was prepared by literature procedure [40]. All solvents

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were predried over activated molecular sieves and refluxed over the appropriate drying agents under argon. All other chemicals were obtained from commercial sources and used as received. 1H NMR and 31P{1H} NMR spectra were recorded at ambient temperature on a Varian UNITY plus-400 spectrometer. Chemical shifts were referenced to the solvent signal in DMSO-d6 (1H) or to H3PO4 (85%) (31P external). IR spectra were recorded on a Varian Scamiter-1000 spectrometer (4000–400 cm1). Elemental analyses for C, H and N were performed on a Carlo-Erba CHNO-S microanalyzer. The photoluminescent spectra were performed on a Hitachi F-2500 spectrofluorometer. 2.2. Synthesis 2.2.1. Preparation of [Ag2(dppeda)Cl](NO3)2MeOH (1) To a suspension of AgCl (15 mg, 0.1 mmol) and AgNO3 (17 mg, 0.1 mmol) in MeOH (5 mL) was added a solution of dppeda (83 mg, 0.1 mmol) in CHCl3 (5 mL). The mixture was stirred for 20 min and was then filtered. Diethyl ether (20 mL) was layered onto the filtrate to form colorless cubes of 12MeOH after one week, which were collected by filtration and dried in air. Yield: 81 mg (66% based on Ag). Anal. Calc. for C56H60Ag2ClN3O5P4: C, 54.68; H, 4.92; N, 3.42; Found: C, 54.57; H, 4.50; N, 3.32%. IR (KBr disk): 3050 (m), 2927 (w), 2873 (w), 2820 (w), 1966 (w), 1893 (w), 1817 (w), 1627 (w), 1482 (m), 1435 (s), 1335 (s), 1097 (m), 1052 (m), 1037 (w), 997 (w), 847 (m), 738 (s), 691 (s), 512 (s), 475 (m). 1H NMR (DMSO-d6, 300 MHz, ppm): d 2.36 (s, 4H, –CH2CH2–), 2.47 (s, 8H, –CH2–), 3.14 (s, 6H, –CH3), 4.05 (br, 2H, –OH), 7.197.46 (m, 40H, –Ph). 31P{1H} NMR (300 MHz, ppm): d 4.60 (d, 1JAgP = 401 Hz).

Table 1 Summary of the crystallographic data for 1 and 2.

Chemical formula Fw Crystal system Space group a (Å) b (Å) c (Å) b (°) V (Å3) Z Dcalc (g cm3) F(000) l (Mo Ka, cm1) Reflections collected Unique reflections Reflections [I > 2.00r(I)] Parameters Ra wRb Goodness of fitness (GoF)c Largest residual peaks and holes (e/Å3)

1

2

C56H60Ag2ClN3O5P4 1230.14 monoclinic P21/c 14.058(3) 15.899(3) 24.179(5) 91.82(3) 5401.5(19) 4 1.513 2512 0.943 25 517 12 290 10 259 642 0.0688 0.1344 1.218 0.898, 0.547

C56H52Ag2N4P4S2 1184.76 monoclinic C2/c 27.239(5) 11.072(2) 19.280(4) 115.96(3) 5228(2) 4 1.505 2408 0.993 15 365 5956 3822 307 0.0874 0.1591 1.152 0.783, 0.468

P P R = |Fo|  |Fc|/ |Fo|. P P wR = { w(Fo2  Fc2)2/ w(Fo2)2}1/2. P c GOF = { w(|Fo|  |Fc|)2/(n  p)}1/2, where n = number of reflections and p = total number of parameters refined. a

b

ent atoms with Uiso(H) = 1.2Ueq(C). A summary of the important crystallographic information are tabulated in Table 1. 3. Results and discussion 3.1. Synthesis and spectral characterization of 1 and 2

2.2.2. Preparation of [Ag2(dppeda)(SCN)2]n (2) To a suspension of AgSCN (33 mg, 0.2 mmol) in 5 mL of MeCN was added a CH2Cl2 solution (5 mL) of dppeda (83 mg, 0.1 mmol). The mixture was stirred for about 3 h and then filtered. Ethanol (15 mL) was layered onto the filtrate to produce colorless prisms of 2 after 2 months, which were collected by filtration and dried in air. Yield: 75 mg (63% based on Ag). Anal. Calc. for C56H52Ag2N4P4S2: C, 56.77; H, 4.42; N, 4.73; Found: C, 56.87; H, 4.30; N, 4.62%. IR (KBr disk): 3051 (w), 2962 (w), 2880 (w), 2841 (w), 2081 (s), 1661 (w), 1481 (m), 1434 (s), 1319 (w), 1181 (w), 1097 (m), 1026 (w), 999 (w), 856 (s), 741 (s), 692 (s), 517 (m), 478 (m). 2.3. X-ray crystallography All measurements were performed on a Rigaku Mercury CCD Xray diffractometer (3 kV, sealed tube) at 50 °C, using graphite monochromated Mo Ka (k = 0.71070 Å). Colorless cubes of 12MeOH with dimensions 0.40  0.30  0.17 mm and 2 with dimensions 0.30  0.20  0.12 mm were mounted on a glass fiber with grease. Diffraction data were collected at x mode with a detector distance of 35 mm to the crystal. The collected data were reduced by using the program CrystalClear (Rigaku and MSC, Ver. 1.4, 2008), and an absorption correction (multi-scan) was applied, which resulted in transmission factors ranging from 0.704–0.856 for 12MeOH and 0.755–0.890 for 2. The reflection data were also corrected for Lorentz and polarization effects. The crystal structures of 1 and 2 were solved by direct methods and refined on F2 by full-matrix least-squares methods with the SHELXTL-97 program [46,47]. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in geometrically idealized positions (C–H = 0.98 Å for methylene groups and C– H = 0.94 Å for phenyl groups) and constrained to ride on their par-

Treatment of AgCl and AgNO3 (molar ratio 1:1) with dppeda followed by a standard workup afforded 1 in 66% yield (Scheme 1). The reaction of AgCl with dppeda could result in a clear solution, from which no meaningful product was isolated. Intriguingly, the reaction of AgNO3 with bppeda in MeOH/CHCl3 produced 1 only in a very low yield. The chloride may be derived from the CHCl3 solvent used in the reaction. Changing the ratio of dppeda and AgCl into 1:1 or 1:3 always produced 1 in varied yields. On the other hand, analogous reaction of AgSCN with 1/2 equiv. of dppeda gave rise to 2 in 63% yield (Scheme 1). Compound 2 could also be obtained in relatively high yield from the reaction of 1 with 2 equiv. of NH4SCN in CH2Cl2 followed by the similar procedure to that used in the isolation of 1. Compound 1 is soluble in CHCl3, CH2Cl2 and DMSO, and insoluble in MeOH, MeCN and Et2O, while 2 is almost insoluble in common solvents. The elemental analyses were consistent with their formulas. In the IR spectrum of 1, the strong band at 1335 cm1 of 1 may be assigned to the stretching vibration of the uncoordinated nitrate anion while the strong band at 2081 cm1 in the IR spectrum of 2 has the stretching vibration of the bridging thiocyanate groups. The 1H NMR spectrum of 1 showed signals related to protons of the ethylene groups, the methylene groups and the phenyl groups at 2.36, 2.47 and 7.197.46 ppm, respectively. In addition, singlets at 3.14 and 4.05 ppm for the solvated MeOH molecules were also observed. A single broad doublet resonance at 4.60 ppm was observed for the phosphino groups of dppeda in the 31P{1H} NMR of 1, indicating that the complex has effective C2v symmetry in solution [7]. The chemical shifts from 33.1 ppm (1) to dppeda (28.5 ppm) may be due to the coupling between the 107Ag(109Ag) and 31P nuclei. The coupling (1JAgP = 401 Hz) is consistent with the presence of a AgP2Cl unit [48–53]. The identities of 1 and 2 were further confirmed by single crystal X-ray analysis.

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Scheme 1.

3.2. Crystal structure of [Ag2(dppeda)Cl](NO3)2MeOH (1) Compound 1 crystallizes in the monoclinic space group P21/c and the asymmetric unit consists of one independent [Ag2(dppeda)Cl]+ cation, one NO 3 anion and two MeOH solvent molecules. The structure of the cation was presented in Fig. 1, and its selected bond lengths and angles are listed in Table 2. Each Ag(I) atom in this cation adopts a trigonal planar coordination geometry, coordinated by one l-Cl and two P atoms from the dppeda ligand. The dppeda ligand shows a side-by-side coordination mode and each of the two pairs of P atoms from different ethylene diamino groups chelate one Ag(I) atom to form one 9-membered metallomacrocycles. One chloride further bridges the two Ag(I) atoms, thereby forming a molecular basket structure, where the ethylene diamino group serves its bottom while the l-Cl bridge acts its handle. Such a basket structure is uncommon and was only found in those related Ag(I) complexes with a larger tetraphosphine ligand (tetrakis(diphenylphosphinito)resorcinarene) [resorcinarene(O2CR)4(OPPh2)4Ag2(l-Cl)]CF3SO3 (R = C6H11, C4H3S, 4-C6H4Me, OCH2Ph) [7]. The torsion angle between the two [AgP2Cl] groups is 78.91(1)o. This kind of coordination nicely demonstrates that the coordination geometry of [AgL2X] groups depends on the length

of the chain between the two donor atoms (six atoms herein), which was proposed by Meijboom et al. recently [1]. The mean Ag–P bond length (2.4359(14) Å) in 1 is in between with those of tri-coordinated Ag(I) complexes [resorcinarene(O2CR)4(OPPh2)4Ag2(l-Cl)]CF3SO3 (R = C4H3S) (2.424(2) Å); and [Ag(P(C6H11)3)2Cl] (2.471(3) Å) [37]. The average Ag–Cl bond lengths (2.5417(14) Å) is longer with those observed in [resorcinarene(O2CR)4(OPPh2)4Ag2(l-Cl)]CF3SO3 (R = C4H3S) (2.509(2) Å) and [Ag(P(C6H11)3)2Cl] (2.489(3) Å). The Ag(1)  Ag(2) contact is 3.460 Å, which excludes any metal/metal interaction. Because of the formation of the Ag–l-Cl–Ag bridge, dppeda in 1 exists in the boat configuration. 3.3. Crystal structure of [Ag2(dppeda)(SCN)2]n (2) Compound 2 crystallizes in the monoclinic space group C2/c and the asymmetric unit consists of half a [Ag2(dppeda)(SCN)2] molecule. As shown in Fig. 2, there is a twofold axis running through the center of C(3) and C(3A). Each Ag(I) atom is coordinated by two P atoms from dppeda and one S and one N from two thiocyanate groups, forming a distorted tetrahedral geometry. Different from that in 1, dppeda in 2 presents a end-to-end coordination mode and each of the two pairs of P atoms from the same ethylene Table 2 Selected bond lengths (Å) and angles (°) for 1 and 2.

Fig. 1. Perspective view of the cation structure of 1 with 30% thermal ellipsoids. All hydrogen atoms are omitted for clarity. The phenyl groups are plotted as hexagons.

Compound 1 Ag(1)–P(1) Ag(1)–P(3) Ag(1)–Cl(1) P(1)–Ag(1)–P(3) P(1)–Ag(1)–Cl(1) P(3)–Ag(1)–Cl(1)

2.4384(13) 2.4310(14) 2.5409(14) 127.05(5) 119.98(5) 112.35(5)

Ag(2)–P(2) Ag(2)–P(4) Ag(2)–Cl(1) P(2)–Ag(2)–P(4) P(2)–Ag(2)–Cl(1) P(4)–Ag(2)–Cl(1)

2.4360(14) 2.4381(14) 2.5424(14) 124.47(5) 110.90(5) 122.79(5)

Compound 2 Ag(1)–P(1) Ag(1)–P(2) P(1)–Ag(1)–P(2) P(1)–Ag(1)–N(2) P(2)–Ag(1)–N(2)

2.482(2) 2.5001(19) 100.26(6) 119.84(18) 114.64(16)

Ag(1)–N(2) Ag(1)–S(1B) P(1)–Ag(1)–S(1B) P(2)–Ag(1)–S(1B) N(2)–Ag(1)–S(1B)

2.240(6) 2.660(2) 105.28(7) 100.64(7) 113.69(16)

Symmetry code: B, 0.5  x, 0.5 + y, 0.5  z.

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Fig. 2. Perspective view of a repeating unit of 2 with 30% thermal ellipsoids. All hydrogen atoms are omitted for clarity. The phenyl groups are plotted as hexagons.

diamino group chelates one Ag(I) atom. The dppeda in 2 exists in the chair configuration and connects two Ag(I) atoms to form a [Ag2(dppeda)] fragment. Each thiocyanate binds one Ag(I) in one fragment through its N atom and further links the other Ag(I) in the neighboring fragment via its S atom. To this end, six Ag(I) atoms, two dppeda molecules and four SCN anions are alternatively interconnected to form a rare 34-membered macrocycle (Fig. 3a). Such a macrocycle is further fused via the NCS bridges and dppeda bridges to form a 2D (6,3) layer network expanded along the bc plane (Fig. 3b). Alternatively, this 2D structure may be viewed as the [Ag(SCN)]n chains connected by the bridging dppeda ligands. There are no evident intermolecular hydrogen interactions between the two layers in the crystal of 2. The mean Ag–P bond length (2.486(2) Å) in 2 is close to those in [Ag(dpph)(SCN)]2 (2.448(4) Å) [38] and [Ag2(dppn)2(l-SCN)2]n (2.488(5) Å) [39], while the Ag–N and Ag–S bond lengths (2.240(6) Å versus 2.336(5) Å) are evidently shorter than those of the corresponding ones of [Ag(dpph)(SCN)]2 (2.660(2) Å versus 2.677(4) Å) and [Ag2(dppn)2(l-SCN)2]n (2.32(2) Å versus 2.732(5) Å). As mentioned above in this paper, the reaction of 1 with 2 equiv. of NH4SCN could generate 2. According to the above analysis of the structures of 1 and 2, it is found that during the reaction, the framework of 1 was broken and the chloride was replaced by thiocyanate. The unsaturated Ag(I) centers in 1 were completed by one more thiocyanate while the coordination mode of dppeda was changed from the side-by-side mode in 1 to the end-to-end mode in 2.

Fig. 3. (a) The 34-membered macrocycle consisting of six Ag(I), four SCN and two dppeda; (b) the 2D (6,3) network extending along the bc plane. All hydrogen atoms and phenyl rings are omitted for clarity.

3.4. Photoluminescent properties of 1 and 2 Both 1 and 2 in solid state emits fluorescence at room temperature when they are irradiated by UV light (Fig. 4). Upon excitation at 310 nm (1) and 342 (2) nm, they exhibit photoluminescence with emission maxima at ca. 390 nm and 413 nm, respectively. Considering the emission band of dppeda is at ca. 386 nm, the emissions of 1 may be assigned as the p–p* intraligand (IL) transitions of phenyl groups [54]. In contrary, both excitation and emission bands of 2 are red-shifted relative to that of 1, which may be due to the ligand-to-ligand (SCN ? dppeda) charge transfer (LLCT) [55].

Fig. 4. The emission spectra of 1 (kex = 310 nm) and 2 (kex = 342 nm) along with dppeda (kex = 316 nm) in the solid state.

4. Conclusions In the work reported here, we have demonstrated that reactions of Ag(I) with dppeda produced two unique Ag/dppeda complexes 1 and 2. Compound 1 possesses a cationic molecular basket structure

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in which dppeda adopts a side-by-side coordination mode. Compound 2 has a rare 2D (6,3) layer network with a 34-membered macrocycle in which dppeda takes a end-to-end coordination mode. Such a topological framework of 2 is unprecedented in the chemistry of tetraphosphines. Isolation of 1 and 2 suggested that dppeda would be an excellent ligand for the metal/tetraphosphine assemblies. However, dppeda exhibited as a doubly-bridging ligand in both products, which is similar to that found in the less complicated diphosphine ligands. We are currently extending this work by studies on the assembly of other novel dppeda-based arrays from its reactions of other metals such as Cu(I), Au(I) and Pd(II). Acknowledgements This work was supported by the National Natural Science Foundation of China (20525101 and 20871088), the State Key Laboratory of Organometallic Chemistry of Shanghai Institute of Organic Chemistry (08-25), the Qin-Lan Project of Jiangsu Province, and the ‘‘Soochow Scholar” Program and the Program for Innovative Research Team of Suzhou University. Appendix A. Supplementary material CCDC 715880 and 715881 contain the supplementary crystallographic data for 1 and 2. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2009.05.018. References [1] R. Meijboom, R.J. Bowen, S.J. Berners-Price, Coord. Chem. Rev. 253 (2009) 325. [2] J. Zhang, M. Nieuwenhuyzen, J.P.H. Charmant, S.L. James, Chem. Commun. (2004) 2808. [3] J. Zhang, P.W. Miller, M. Nieuwenhuyzen, S.L. James, Chem. Eur. J. 12 (2006) 2448. [4] J. Zhang, X.L. Xu, S.L. James, Chem. Commun. (2006) 4218. [5] X.L. Xu, M. Nieuwenhuyzen, S.L. James, Angew. Chem., Int. Ed. 41 (2002) 764. [6] S.L. James, D.M.P. Mingos, A.J.P. White, D.J. Williams, Chem. Commun. (1998) 2323. [7] D.J. Eisler, C.W. Kirby, R.J. Puddephatt, Inorg. Chem. 42 (2003) 7626. [8] P.M. Van Calcar, M.M. Olmstead, A.L. Balch, Chem. Commun. (1996) 2597. [9] M. Beaupérin, E. Fayad, R. Amardeil, H. Cattey, P. Richard, S. Brandès, P. Meunier, J.C. Hierso, Organometallics 27 (2008) 1506. [10] J.C. Hierso, A. Fihri, V.V. Ivanov, B. Hanquet, N. Pirio, B. Donnadieu, B. Rebiere, R. Amardeil, P. Meunier, J. Am. Chem. Soc. 126 (2004) 11077. [11] H.J. Kitto, A.D. Rae, R.D. Webster, A.C. Willis, S.B. Wild, Inorg. Chem. 46 (2007) 8059. [12] P. Nair, C.P. White, G.K. Anderson, N.P. Rath, J. Organomet. Chem. 691 (2006) 529. [13] L.D. Field, B.A. Messerle, R.J. Smernik, T.W. Hambley, P. Turner, Inorg. Chem. 36 (1997) 2884.

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