Novel copper(I) complexes with extended π⋯π interactions: Synthesis, structure, characterization and spectroscopic properties

Inorganica Chimica Acta 416 (2014) 28–34

Contents lists available at ScienceDirect

Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica

Novel copper(I) complexes with extended p  p interactions: Synthesis, structure, characterization and spectroscopic properties Ting-Hong Huang, Min-Hua Zhang ⇑ Key Laboratory for Green Chemical Technology (Ministry of Education of China), R&D Center for Petrochemical Technology, Tianjin University, Tianjin 300072, China

a r t i c l e

i n f o

Article history: Received 30 November 2013 Received in revised form 22 February 2014 Accepted 11 March 2014 Available online 25 March 2014 Keywords: Copper(I) complexes p–p Stacking Crystal structure Optical properties

a b s t r a c t Based on ligand N,N0 -bis(pyridin-2-ylmethylene)biphenyl-4,40 -diamine (pmbb), two compounds of [Cu2 (pmbb)(CH3CN)2(PPh3)2](ClO4)22DMF (1) and [Cu2(pmbb) (PPh3)2(Cl)2] (2) have been synthesized and structurally characterized by IR, 1H NMR, 31P NMR and X-ray crystal structure analysis. Structural analysis reveals that both of these complexes contain the 1D embrace arrays, with different variations in p-stacking patterns and intermolecular C–H  p interactions. Crystal structure of 1 contains 1D tape-like arrays constructed by C–H  p and p  p interactions, and the ordered-layer-lattice DMF and ClO 4 are located between one-dimensional arrays. For 2, p-stacking interactions lead to the construction of 1D arrays and 2D sheet. The UV–Vis absorption spectra of complexes 1 and 2 reveal that p-stacking types may play an important role in optical absorption. DFT studies indicate the stability may be 2 > 1. In addition, the emission spectrum of complex 1 in acetonitrile solvent and thermogravimetric analysis of 2 are also observed. Ó 2014 Elsevier B.V. All rights reserved.

1. Introduction The intriguing structures of metal-containing compounds by intra- and intermolecular interactions have been one of the most active research subjects [1–5], especially for the spectroscopic properties associated with this class of compounds [6–10]. To these complexes, predicting and designing supramolecular structures is difficult due to the weakness of the interactions involved [11]. In particular, intermolecular edge-face (C–H  p) and p  p stacking interactions have led to the observation of unusual structures [12–18] and the utilization of these observations in molecular recognition [19,20], light-emitting devices [21,22] and dyesensitized solar cells applications [23–28] has also been reported. p-Stacking interactions between the p-electron clouds of aromatic systems have been extensively observed in many fields such as chemistry [29–35] and biochemistry [36–39]. They play an important role in the structures of biological macromolecules [40,41] and are useful to study on the intercalation of drugs into DNA [42]. The nature of the p-electron is based on p–p stacking interactions by electron complementarity. The stability order of p–p stacking is p-electron-deficient-p-electron-deficient > p-electron-deficient-p-electron-rich > p-electron-rich-p-electron-rich [43]. So, the enlargement of p-conjugated systems or polarized perturbation to p-system could change the intermolecular ⇑ Corresponding author. Tel./fax: +86 022 27406119. E-mail address: [email protected] (M.-H. Zhang). http://dx.doi.org/10.1016/j.ica.2014.03.011 0020-1693/Ó 2014 Elsevier B.V. All rights reserved.

arrangement dramatically. In infinitely p-stacking complexes, solid-state properties such as electrical conductivity depend on the influence of infinite p  p forces [44–46]. But the design and syntheses of infinite p-stacking structures, especially supramolecular structures formed by different kinds of p-stacking interactions, are difficult. Herein, we wish to report the synthesis, structure, and properties of two complexes, [Cu2(pmbb)(CH3CN)2 (PPh3)2](ClO4)2 2DMF (1) and [Cu2(pmbb) (PPh3)2(Cl)2] (2) (pmbb = N,N0 -bis(pyridin-2-ylmethylene)biphenyl-4,40 -diamine). It is noteworthy that the biphenyl part of the pmbb ligand is completely planar, which is unusual [47,48], and in packing structure C–H  p and p–p stacking interactions lead to the construction of 1D tape-like arrays and 2D network. 2. Results and discussion 2.1. Syntheses Complex 1 was synthesized by direct reactions of [Cu(CH3CN)4] ClO4 with PPh3 in CH3CN solution with appropriate amount of pmbb. The dependence of the product on the ratio of starting materials was observed. It was shown that the reactions of copper(I) salt with PPh3 in the presence of pmbb gave 1 when their ratio was set at 2:2:1 or 2:4:1. This reveals that the formation of the product has little dependence on the ratio of [Cu(CH3CN)4] ClO4: PPh3. Complex 2 was obtained by the reactions of 1 and excessive amount of NH4Cl. At room temperature, compound 1 is soluble CH3CN, but

T.-H. Huang, M.-H. Zhang / Inorganica Chimica Acta 416 (2014) 28–34

compound 2 is hardly soluble in CH3CN. Compounds 1 and 2 are soluble in DMF and DMSO, and hardly soluble in toluene, methanol and ethanol. The IR spectra for the complexes 1 and 2 reveal the characteristic pair of bands near 1483 and 1435 cm1, respectively, in agreement with complexes containing PPh3. The IR spectrum of 1 also exhibits several weak bands in the range 2200–2400 cm1 attibuted to m(C„N), different from 2. 1H NMR spectra of the complexes 1 and 2 shows expected resonances typical for the coordinated PPh3 and pmbb. In the 31P NMR spectra of the complexes 1 and 2 one singlet at 1.46 and 25.57 ppm indicate their electronic environments are different. In 2, chemical shift of the 31 P has higher frequencies from the deshielding effect of the Cl coordinated to copper(I) than the corresponding values in 1, providing evidence for coordination environment of copper(I) as a CuN2PCl chromophore. 2.2. Crystal structures The single crystal X-ray diffraction analysis reveals that the asymmetric unit of complex 1 contains half a pmbb, one Cu+, one PPh3, one CH3CN, one ClO 4 counterion and one DMF molecule. Ligand pmbb adopts a trans coordination mode to link two copper atoms while each of Cu(I) ion is coordinated by three N atoms from pmbb and CH3CN, one P atom from Ligand PPh3, forming a distorted tetrahedral geometry (Fig. 1). The Cu–N and Cu–P bond lengths are 1.989(3)–2.105(2) Å and 2.2102(12) Å within the normal ranges [49], and the metal ions are separated by a Cu  Cu

Fig. 1.

ORTEP

29

distance of 12.832 Å. Corresponding N–Cu–N bond angle ranges from 79.53(8) to 111.28(12) Å, while the N–Cu–P bond angle ranges from 114.13(7) to 122.17(7) Å. Moreover, the intramolecular C–H  p interactions are also observed, respectively, with CH/p distances of 2.83 Å [C–H  C < 3.1 Å, C–H  centroid < 3.4 Å] and angles of 147° [13–15]. This weak interactions (C–H  p) would be a driving force for all atoms of pmbb being nearly in the same plane and play a stabilizing role for conformation. In the solid state, intermolecular pmbb planes adopt p  p and C–H  p stacking interactions to link the cations into 1D tape-like supramolecular arrays along the a axis. The planes of pmbb involved in p-stacking are approximately parallel with centroid distances of 3.77–3.87 Å and dihedral angles of 12.85–16.44°. The short contacts of atom  atom between rings are in the range from 3.467 to 3.962 Å, which are close to the sums of the van der Waals radii [50], displaying typical p  p stacking interactions (Fig. 2a). In tape-like supramolecular arrays, two neighboring cations contains intermolecular C–H  p interactions, respectively, with CH/p distances of 2.66–2.92 Å and angles of 150–162° (Fig. 2b). These reveal that p  p and C–H  p stacking interactions between pmbb may be the driving force for the construction of supramolecular arrays, and are important in determining the packing structure. In addition, the ordered-layer-lattic ClO 4 and DMF are located between 1D tape-like arrays (Fig. 3). The structure also involves C–H  O hydrogen bonds (H  O = 2.43 Å, C  O = 3.03 Å). For 2, single crystal X-ray diffraction analysis shows that the general structure is analogous to complex 1, having a S-shape conformation with centrosymmetry. The inversion center locates at

View of the structure of 1. Hydrogen atoms are deleted for clarity.

Fig. 2. (a) Intermolecular p  p interactions between one molecule and the neighboring molecule in complex 1. Ring-central distances = 3.869 and 3.786 Å, dihedral angles = 16.44 and 12.85°. (b) Intermolecular C-H  p interactions between one molecule and the neighboring molecule in complex 1. H  pcentroid = 2.92 and 2.66 Å.

30

T.-H. Huang, M.-H. Zhang / Inorganica Chimica Acta 416 (2014) 28–34

Fig. 3. The 1D tape-like arrays of [Cu2(pmbb)(CH3CN)2(PPh3)2]2+ (purple) complexes separated by the ordered-layer-lattice DMF(red) and ClO 4 (green) in 1. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

the centroid of the phenylene ring. Ligand pmbb also takes a trans coordination mode to bridge two copper atoms, while each Cu+ adopts a distorted tetrahedral geometry constructed by one P atom from PPh3 and two N atoms from ligand pmbb and one Cl (Fig. 4). The Cu–P and Cu–Cl bond lengths are 2.2102(7) and 2.3164(8) Å, comparable with those in similar complexes [51]. It is noteworthy that two atoms (N1 and N2) are found in the place left for the lone electron pair around the Cu(I) ion with the Cu(1)–N(1) and Cu(1)– N(2) bond lengths of 2.1187(18) and 2.1492(19) Å, which are longer than the corresponding values in complex 1, respectively. The Cu  Cu separation of 13.015 Å is also larger than the corresponding values in compound 1. All these show that all atoms of ligand pmbb are not in the same plane. Just as 1, intermolecular pmbb planes adopt offset displaced p  p stacking interactions to link the cations [Cu2(pmbb) (PPh3)2 (Cl)2] into 1D tape-like supramolecular arrays along the a axis in the complex 2 (Fig. 5). The centroid–centroid distance between the pyridyl rings is ca. 3.54 Å, with the dihedral angle of 0°, and the short distances between the atoms are 3.532 Å for C–C and 3.542 Å for C–N, revealing typical p  p stacking interactions. Moreover, 1D tape-like arrays extend to generate a 2D network by intermolecular C–H  p and p  p stacking interactions along ab plane, forming a supramolecular 2D sheet. The pyridyl ring from binuclear cations [Cu2(pmbb) (PPh3)2(Cl)2] in the adjacent 2D sheets parallel to phenyl rings attached to phosphorus with a centroid-to-centroid distance of 3.63 Å, the dihedral angle of 7.25° and the short contacts of atom  atom between rings ranging from 3.361 to 3.827 Å, displaying the existence of significant p  p stacking interactions (Fig. 5). In the 2D sheet, intermolecular C– H  p interactions are also observed, with CH/p distances of 2.87–2.94 Å and angles of 155–161°, respectively (Fig. 6) [52–55]. These C–H  p and p  p stacking interactions lead to the construction of a 2D supramolecular network by the stacking of the 1D supramolecular arrays along the a axis in a staggered style (Fig. 7). This kind of stacking manner in 2 is much different from the eclipsed stacking manner in 1. The packing structure also involves C–H  Cl hydrogen bonds (H  Cl = 2.74 and 2.66 Å, C  Cl = 3.63 and 3.54 Å) [56,57]. 2.3. Thermal analyses

Fig. 4.

ORTEP

View of the structure of 2. Hydrogen atoms are deleted for clarity.

Thermogravimetric analysis (TG-DTA) was carried out under 50 ml min1 flowing N2 gas for 2. The temperature was ramped at a rate of 10 °C min1 from 25 to 800 °C (Fig. 8). The TG-DTA analysis shows that complex 2 is ther-

a

3.54

3.63

3.63

Fig. 5. A view of p  p stacking interactions in complex 2. Hydrogen atoms are omitted for clarity.

T.-H. Huang, M.-H. Zhang / Inorganica Chimica Acta 416 (2014) 28–34

31

Fig. 6. A view of C-H  p stacking interactions in complex 2. Hydrogen atoms are deleted for clarity.

Fig. 9. The solid-state UV–Vis absorption spectra of complexes 1 (–) and 2 (  ).

Fig. 7. 2D supramolecular structure of 2 constructed by intermolecular C-H  p and p  p stacking interactions along ab plane. Hydrogen atoms are omitted for clarity.

Fig. 10. The UV–Vis absorption spectra of complexes 1 (–) in acetonitrile solution and 2 (  ) in DMF solution.

2.4. Spectroscopic properties Fig. 8. TGA curves of 2 (  ) in nitrogen atmosphere and at the heating rate of 10 °C/ min.

mally stable up to 260 °C and then the weight loss occurred with two defined intervals of weight loss, one beginning at 260 °C and ending at 450 °C (with 60% weight loss) and then 450–800 °C (with 6% weight loss), attributable to decomposition of ligand PPh3 and pmbb.

2.4.1. UV–Vis spectra The solid-state UV–Vis absorption spectra of complexes 1 and 2 were observed (Fig. 9). Complexes 1 and 2 exhibit the absorption peaks at 235 nm and near 350 nm, which was attributed to the p?p⁄ transition of ligand [58,59]. In 1, the absorption peaks of 450 nm can be tentatively assigned to a metal-to-ligand charge transfer (MLCT) [60,61]. However, the absorption peaks of 2 near

32

T.-H. Huang, M.-H. Zhang / Inorganica Chimica Acta 416 (2014) 28–34 Table 3 The HOMO, LUMO energy (eV) and energy gap (eV) of [Cu2(pmbb)(CH3CN)2(PPh3)2] (ClO4)2 (1a) and [Cu2(pmbb) (PPh3)2(Cl)2] (2).

[Cu2(pmbb)(CH3CN)2(PPh3)2] (ClO4)2 (1a) [Cu2(pmbb) (PPh3)2(Cl)2] (2)

Fig. 11. The excitation (  ) and emission (_) spectra of complexes 1 in acetonitrile solution (5  104 M) at room temperature.

Table 1 Crystal data and structure refinement details of complexes 1–2. Complex

1

2

Empirical formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z qcalc (g cm3) l (mm1) F(0 0 0) h range (°) Reflections collected Independent reflections (Rint) Data/restraints/parame ters Goodness-of-fit (GOF) on F2 Final R indices [I > 2r(I)]

C70H68Cl2Cu2N8O10P2 1441.24 triclinic  P1

C60H48Cl2Cu2N4P2 1084.94 monoclinic P2(1)/c 17.080(2) 8.5366(11) 18.941(2) 90 109.710(6) 90 2599.9(6) 2 1.386 1.026 1116 2.21–27.56 23337 5954 (0.0220) 5954/0/316 1.037 R1 = 0.0380, wR2 = 0.0963 R1 = 0.0532, wR2 = 0.1057 0.409 and 0.343

R indices (all data) Largest difference peak and hole (e Å3)

8.533(5) 11.074(6) 19.610(11) 74.184(7) 89.835(7) 79.794(7) 1752.7(17) 1 1.365 0.791 746 1.94–27.49 40585 7986 (0.0185) 7986/0/427 1.016 R1 = 0.0525, wR2 = 0.1549 R1 = 0.0602, wR2 = 0.1651 1.057 and 0.613

HOMO/eV

LUMO/eV

Energy gap (eV)

5.15

4.19

0.96

4.50

3.44

1.06

520 nm are evidently red-shift compared to 1. The similarity in optical properties is not unprecedented [62–64], but the interpretation of this result is not known. The optical properties of complexes 1 in acetonitrile solution and 2 in DMF solution are shown in Fig. 10. All the complexes have intense absorption bands near 280 nm (e  35000 M1cm1) at room temperature, which are assigned to p?p⁄ transition. A broad absorption peak near 350 nm (e  28 000 M1 cm1) in 1 and 2 are attributed to dp–p⁄ MLCT absorption whose magnitude of the extinction coefficient is on the order expected for a dp–p⁄ transitions [65]. 2.4.2. DFT studied Molecular orbital theory reveals that the larger the difference between the energy values of 4E (DE = ELUMO  EHOMO), the more stable the molecular structure may be [66,67]. But the stability of compound 1 and 2 in the solid state is due to a complicated combination of several forces. Complex 1 contains one [Cu2 (pmbb)(CH3CN)2(PPh3)2](ClO4)2 (1a) molecule and two DMF(1b) molecules. So, only the quantum chemical calculations for 1a and 2 were carried out. The main compositions of the HOMO, LUMO energy and energy gap for 1a and 2 are shown in Table 3. The HOMO?LUMO excitation of 1a is calculated at 0.96 eV, decreasing the HOMO?LUMO energy gap (0.10 eV) in comparison to that of 2 (1.06 eV). As a result, the energy values show that the stability may be 2 > 1a. Due to DMF molecules located in the packing structure, the stability of 1 will decrease in comparison to that of 1a. Therefore, the stability may be 2 > 1. 2.4.3. Luminescent properties As shown in Fig. 11, complex 1 is photoluminescent in acetonitrile solvent at room temperature. Complex 1, upon excitation at 475 nm, displays a relatively emission with kmax at 552 nm in acetonitrile solution at room temperature, similarly to the previously report, which may be assigned to MLCT [56,68,69]. Moreover, the weak emission peak centered at 725 nm was attributed to transfer of Z to E conformation [70]. 3. Conclusion

Table 2 Selected bond lengths (Å) and angles (°) for complexes 1–2. 1 Cu(1)–N(3) Cu(1)–N(1) Cu(1)–N(2) Cu(1)–P(1)

1.989(3) 2.094(3) 2.105(2) 2.2102(12)

N(3)–Cu(1)–N(1) N(3)–Cu(1)–N(2) N(1)–Cu(1)–N(2) N(3)–Cu(1)–P(1) N(1)–Cu(1)–P(1) N(2)–Cu(1)–P(1)

111.28(12) 106.05(10) 79.53(8) 117.61(8) 114.13(7) 122.17(7)

2 Cl(1)–Cu(1) Cu(1)–N(1) Cu(1)–N(2) Cu(1)–P(1)

2.3164(8) 2.1187(18) 2.1492(19) 2.2102(7)

N(1)–Cu(1)–N(2) N(1)–Cu(1)–P(1) N(2)–Cu(1)–P(1) N(1)–Cu(1)–Cl(1) N(2)–Cu(1)–Cl(1) P(1)–Cu(1)–Cl(1)

78.50(7) 124.28(5) 120.25(5) 105.87(5) 109.12(6) 113.61(3)

Two new metal complexes with N,N0 -bis(pyridin-2-ylmethylene)biphenyl-4,40 -diamine (pmbb) have been synthesized and characterized. Complexes 1 are organized into 1D tape-like arrays though C–H  p and p  p interactions, while the ordered-layerlattic ClO 4 and DMF are located between 1D supramolecular arrays. For 2, Crystal structure contains 1D supramolecular arrays and 2D sheet formed by C–H  p and p  p interactions. This structure variation may be related to the change of anions, which leads to the construction of different p-stacking types. The UV–Vis absorption spectra of 1 and 2 reveal that p-stacking types may be an important to optical absorption of complexes. DFT studied shows that the stability may be 2 > 1. Moreover, thermogravimetric analysis displays complex 2 is stable up to 260 °C and the emission spectra of complex 1 in acetonitrile exhibits the emission peak near 552 and 725 nm.

T.-H. Huang, M.-H. Zhang / Inorganica Chimica Acta 416 (2014) 28–34

4. Experimental 4.1. General methods and materials All chemicals were of A.R. grade and were used as received without further purification. N,N0 -Bis(pyridin-2-ylmethylene)biphenyl-4,40 -diamine (pmbb) was prepared according to Refs. [71,72]. IR spectra were recorded as KBr pellets on a Nicolet 6700 spectrometer in the range 4000–450 cm1. 1H and 31P[71] spectra were recorded on a Bruck 400 spectrometer at 400.15 and 161.98 MHz, respectively. Absorption spectra were measured with U-3010 (solid) and Varian CARY-50UV spectrophotometer. The luminescent spectra were measured at room temperature on Cary Eclipse fluorescence spectrophotometer. The absorption and luminescent spectroscopy of complexes were measured in CH3CN. Caution! Perchlorate salts are potentially explosive and should be synthesized in small quantities and handled with great care. 4.2. Synthesis of [Cu2(pmbb)(CH3CN)2(PPh3)2](ClO4)22DMF (1) A mixture of [Cu(CH3CN)4] ClO4 (0.0326 g, 0.1 mmol) and PPh3 (0.0262 g, 0.1 mmol) in5 ml CH3CN was stirred at room temperature for 0.5 h and then pmbb (0.0181 g, 0.05 mmol) was added. The reaction mixture was allowed to stir for 1 h at room temperature. The vapor diffusion of diethyl ether into the solution gave red block crystals. The complex was obtained by filtration, washed with diethyl ether and dried in vacuo. Yield: 0.0578 g (80%). IR (cm1): 3058 (w), 1680 (vs), 1479 (m), 1435 (s), 1384 (w), 1092 (vs), 832 (s), 749 (s), 697 (s), 621(m), 522(m). 1H NMR (400 MHz, CDCL3): d = 2.04 (6H, CH3–C„), 2.85–3.07 (12H, CH3– N–), 6.97–9.38 (50H, –CH@O + pmbb + PPh3). 31P[71] NMR (CD3SOCD3, 25 °C, TMS): 1.46 ppm. 4.3. Synthesis of [Cu2(pmbb) (PPh3)2(Cl)2] (2) A solution of 1 (36 mg, 0.10 mmol) in CH3CN (5 ml) was added solid NH4Cl to form the crude product (2) at room temperature. The material was separated by filtration, washed with CH3CN and CH3OH, and was dissolved in DMF–CH3CN (5:1). The vapor diffusion of diethyl ether into the solution gave red block crystals. The complex was obtained by filtration, washed with diethyl ether and dried in vacuo. Yield: 0.0324 g (60%). IR (cm1): 3419 (br), 1586 (w), 1483 (m), 1434 (s), 1364 (w), 1093 (m), 829 (m), 745 (s), 697 (s), 516(s). 1H NMR (CD3SOCD3, 25 °C, TMS): d = 7.01–9.33 (48H, pmbb + PPh3). 31P[71] NMR (CD3SOCD3, 25 °C, TMS): 25.57 ppm. 4.4. X-ray crystallography Crystals suitable for X-ray structure analysis obtained by vapor diffusion of diethyl ether into a solution of complexes 1 and 2. Reflection intensity data were collected on a Bruker APEX CCD diffractometer with graphite monochromated Mo Ka radiation (k = 0.71073 Å) using the x technique at room temperature. All structures were solved by direct methods and refined by fullmatrix least-squares on all F2 data using SHELXTL. All hydrogens were generated geometrically, assigned fixed isotropic thermal parameters, and included in structure factor calculations. Crystal and structure refinement data are summarized in Table 1. Selected bond lengths and bond angles are given in Table 2. 4.5. Computational details The quantum chemical calculations for 1 and 2 were carried out with LDA-DFT as implemented in the Dmol3 package provided by

33

Materials Studio. The local functional for the exchange correlation potential is LDA-PWC. The core electrons for metals were treated by Effective Core Potentials. Self consistent-field (SCF) density convergence was 104. The basis set is DND + 4.4. The convergence tolerances for energy change, maximum force, and maximum displacement between optimization cycles were set as 1.0  104 Ha, 0.02 Ha Å1, and 0.01 Å, respectively. Appendix A. Supplementary material CCDC 941588 and 942990 contain the supplementary crystallographic data for compounds 1 and 2, respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. References [1] R.E. Dawson, A. Hennig, D.P. Weimann, D. Emery, V. Ravikumar, J. Montenegro, T. Takeuchi, S. Gabutti, M. Mayor, J. Mareda, C.A. Schalley, S. Matile, Nat. Chem. 2 (2010) 533. [2] L.-C. Gui, X.-J. Wang, Q.-L. Ni, M. Wang, F.-P. Liang, H.-H. Zou, J. Am. Chem. Soc. 134 (2011) 852. [3] J. Jin, T. Iyoda, C. Cao, Y. Song, L. Jiang, T.J. Li, D.B. Zhu, Angew. Chem. Int. Ed. 40 (2001) 2135. [4] P. Martín-Gago, M. Gomez-Caminals, R. Ramón, X. Verdaguer, P. MartinMalpartida, E. Aragón, J. Fernández-Carneado, B. Ponsati, P. López-Ruiz, M.A. Cortes, B. Colás, M.J. Macias, A. Riera, Angew. Chem. Int. Ed. 51 (2012) 1820. [5] V.B. Zabolotnyy, D.S. Inosov, D.V. Evtushinsky, A. Koitzsch, A.A. Kordyuk, G.L. Sun, J.T. Park, D. Haug, V. Hinkov, A.V. Boris, C.T. Lin, M. Knupfer, A.N. Yaresko, B. Buchner, A. Varykhalov, R. Follath, S.V. Borisenko, Nature 457 (2009) 569. [6] H.V.R. Dias, H.V.K. Diyabalanage, M.G. Eldabaja, O. Elbjeirami, M.A. Rawashdeh-Omary, M.A. Omary, J. Am. Chem. Soc. 127 (2005) 7489. [7] M. Ruthkosky, C.A. Kelly, M.C. Zaros, G.J. Meyer, J. Am. Chem. Soc. 119 (1997) (2005) 12004. [8] C.S. Smith, K.R. Mann, J. Am. Chem. Soc. 134 (2012) 8786. [9] J.D. Wood, J.L. Jellison, A.D. Finke, L. Wang, K.N. Plunkett, J. Am. Chem. Soc. 134 (2012) 15783. [10] Z. Zhou, C.J. Fahrni, J. Am. Chem. Soc. 126 (2004) 8862. [11] C.B. Aakeroy, N.R. Champness, C. Janiak, CrystEngComm 12 (2010) 22. [12] C. Janiak, J. Chem. Soc., Dalton. Trans. (2000) 3885. [13] C. Janiak, S. Temizdemir, S. Dechert, W. Deck, F. Girgsdies, J. Heinze, Mario J. Kolm, Tobias G. Scharmann, Oliver M. Zipffel, Eur. J. Inorg. Chem. 2000 (2000) 1229. [14] M. Nishio, CrystEngComm 6 (2004) 130. [15] M. Nishio, Phys. Chem. Chem. Phys. 13 (2011) 13873. [16] M. Nishio, M. Hirota, Y. Umezawa, The CH/p interaction (evidence, nature and consequences), Wiley-VCH, New York, 1998. [17] M. Nishio, Y. Umezawa, K. Honda, S. Tsuboyama, H. Suezawa, CrystEngComm 11 (2009) 1757. [18] Y. Umezawa, S. Tsuboyama, K. Honda, J. Uzawa, M. Nishio, Bull. Chem. Soc. Japan 71 (1998) 1207. [19] I.M. Sluch, A.J. Miranda, O. Elbjeirami, M.A. Omary, L.M. Slaughter, Inorg. Chem. 51 (2012) 10728. [20] V.W.-W. Yam, K.M.-C. Wong, N. Zhu, J. Am. Chem. Soc. 124 (2002) 6506. [21] C.-S. Liu, X.-S. Shi, J.-R. Li, J.-J. Wang, X.-H. Bu, Cryst. Growth Des. 6 (2006) 656. [22] V.W.-W. Yam, R.P.-L. Tang, K.M.-C. Wong, K.-K. Cheung, Organometallics 20 (2001) 4476. [23] A. Dualeh, F. De Angelis, S. Fantacci, T. Moehl, C. Yi, F. Kessler, E. Baranoff, M.K. Nazeeruddin, M. Grätzel, J. Phys. Chem. C 116 (2011) 1572. [24] M.K.R. Fischer, S. Wenger, M. Wang, A. Mishra, S.M. Zakeeruddin, M. Grätzel, P. Bäuerle, Chem. Mater. 22 (2010) 1836. [25] S. Franco, J. Garín, N. Martínez de Baroja, R. Pérez-Tejada, J. Orduna, Y. Yu, M. Lira-Cantú, Org. Lett. 14 (2012) 752. [26] M. Katono, T. Bessho, S. Meng, R. Humphry-Baker, G. Rothenberger, S.M. Zakeeruddin, E. Kaxiras, M. Grätzel, Langmuir 27 (2011) 14248. [27] A. Kira, Y. Matsubara, H. Iijima, T. Umeyama, Y. Matano, S. Ito, M. Niemi, N.V. Tkachenko, H. Lemmetyinen, H. Imahori, J. Phys. Chem. C 114 (2010) 11293. [28] L. Yu, J. Xi, H.T. Chan, T. Su, L.J. Antrobus, B. Tong, Y. Dong, W.K. Chan, D.L. Phillips, J. Phys. Chem. C 117 (2013) 2041. [29] E. Despagnet-Ayoub, S. Schigand, L. Vendier, M. Etienne, Organometallics 28 (2009) 2188. [30] N. Schultheiss, D.R. Powell, E. Bosch, Inorg. Chem. 42 (2003) 5304. [31] T.M. Swager, ACS Macro Letters 1 (2011) 3. [32] S. Tsuzuki, K. Honda, R. Azumi, J. Am. Chem. Soc. 124 (2002) 12200. [33] G. Zeni, R.C. Larock, Chem. Rev. 104 (2004) 2285. [34] T.-H. Huang, M.-H. Zhang, Inorg. Chim. Acta 410 (2014) 150. [35] T.-H. Huang, M.-H. Zhang, C.-Y. Gao, L.-T. Wang, Inorg. Chim. Acta 408 (2013) 91. [36] H. Baruah, M.W. Wright, U. Bierbach, Biochemistry 44 (2005) 6059. [37] A. Migliore, J. Chem. Theory Comput. 7 (2011) 1712. [38] W. Yan, L. Zhang, D. Xie, J. Zeng, J. Phys. Chem. B 111 (2007) 14055.

34 [39] [40] [41] [42] [43] [44] [45]

[46] [47] [48] [49] [50] [51] [52] [53] [54] [55]

T.-H. Huang, M.-H. Zhang / Inorganica Chimica Acta 416 (2014) 28–34 X. Zhang, I. Lee, A.J. Berdis, Biochemistry 44 (2005) 13101. W.T. Go´z´dz´, Langmuir 24 (2008) 12458. A.S. Mahadevi, G.N. Sastry, Chem. Rev. 113 (2012) 2100. Y. Shi, M.J. Steenbergen, E.A. Teunissen, L.S. Novo, S. Gradmann, M. Baldus, C.F. Nostrum, W.E. Hennink, Biomacromolecules 14 (2013) 1826–1837. Q.-L. Ni, X.-F. Jiang, L.-C. Gui, X.-J. Wang, K.-G. Yang, X.-S. Bi, New J. Chem. 35 (2011) 2471. P. Kar, R. Biswas, Y. Ida, T. Ishida, A. Ghosh, Cryst. Growth Des. 11 (2011) 5305. K.S. Kim, S.B. Suh, J.C. Kim, B.H. Hong, E.C. Lee, S. Yun, P. Tarakeshwar, J.Y. Lee, Y. Kim, H. Ihm, H.G. Kim, J.W. Lee, J.K. Kim, H.M. Lee, D. Kim, C. Cui, S.J. Youn, H.Y. Chung, H.S. Choi, C.-W. Lee, S.J. Cho, S. Jeong, J.-H. Cho, J. Am. Chem. Soc. 124 (2002) 14268. X.-J. Wang, L.-C. Gui, Q.-L. Ni, Y.-F. Liao, X.-F. Jiang, L.-H. Tang, Z. Zhang, Q. Wu, CrystEngComm 10 (2008) 1003. C. He, L.-Y. Wang, Z.-M. Wang, Y. Liu, C.-S. Liao, C.-H. Yan, J. Chem. Soc., Dalton Trans. (2002) 134. H.-C. Wu, P. Thanasekaran, C.-H. Tsai, J.-Y. Wu, S.-M. Huang, Y.-S. Wen, K.-L. Lu, Inorg. Chem. 45 (2005) 295. R.J. Less, B. Guan, N.M. Muresan, M. McPartlin, E. Reisner, T.C. Wilson, D.S. Wright, Dalton Trans. 41 (2012) 5919. M. Winter, WebElements periodic table (Professional Edition), http:// www.webelements.com. Y.-L. Xiao, Q.-H. Jin, Y.-H. Deng, Z.-F. Li, W. Yang, M.-H. Wu, C.-L. Zhang, Inorg. Chem. Commun. 15 (2012) 146. I. Dance, M. Scudder, Chem. Commun. (1995) 1039. I. Dance, M. Scudder, Chem.-Eur. J. 2 (1996) 481. I. Dance, M. Scudder, J. Chem. Soc., Dalton. Trans. (1996) 3755. B. Gil-Herna´ndez, P. Gili, J.K. Vieth, C. Janiak, J.N. Sanchiz, Inorg. Chem. 49 (2010) 7478.

[56] H.A. Habib, A. Hoffmann, H.A. Höppe, G. Steinfeld, C. Janiak, Inorg. Chem. 48 (2009) 2166. [57] B. Wisser, C. Janiak, Z. Anorg, Allg. Chem. 633 (2007) 1796. [58] M.G. Crestani, G.F. Manbeck, W.W. Brennessel, T.M. McCormick, R. Eisenberg, Inorg. Chem. 50 (2011) 7172. [59] S. Das, A. Nag, D. Goswami, P.K. Bharadwaj, J. Am. Chem. Soc. 128 (2005) 402. [60] J. Huang, O. Buyukcakir, M.W. Mara, A. Coskun, N.M. Dimitrijevic, G. Barin, O. Kokhan, A.B. Stickrath, R. Ruppert, D.M. Tiede, J.F. Stoddart, J.-P. Sauvage, L.X. Chen, Angew. Chem. Int. Ed. 51 (2012) 12711. [61] P.A. Papanikolaou, N.V. Tkachenko, Phys. Chem. Chem. Phys. 15 (2013) 13128. [62] M. Arca, G. Azimi, F. Demartin, F.A. Devillanova, L. Escriche, A. Garau, F. Isaia, R. Kivekas, V. Lippolis, V. Muns, A. Perra, M. Shamsipur, L. Sportelli, A. Yari, Inorg. Chim. Acta 358 (2005) 2403. [63] L.-H. He, J.-L. Chen, F. Zhang, X.-F. Cao, X.-Z. Tan, X.-X. Chen, G. Rong, P. Luo, H.R. Wen, Inorg. Chem. Commun. 21 (2012) 125. [64] T. Kern, U. Monkowius, M. Zabel, G. Knör, Eur. J. Inorg. Chem. 2010 (2010) 4148. [65] R. Hou, T.-H. Huang, X.-J. Wang, X.-F. Jiang, Q.-L. Ni, L.-C. Gui, Y.-J. Fan, Y.-L. Tan, Dalton Trans. 40 (2011) 7551. [66] J. Han, F. Bai, H. Zhao, Y. Xing, X. Zeng, M. Ge, Chin. Sci. Bull. 54 (2009) 3508. [67] J. Han, Y. Xing, C. Wang, P. Hou, F. Bai, X. Zeng, X. Zhang, M. Ge, J. Coord. Chem. 62 (2009) 745. [68] H.A. Habib, A. Hoffmann, H.A. Hoppe, C. Janiak, Dalton Trans. (2009) 1742. [69] H.A. Habib, J. Sanchiz, C. Janiak, Dalton Trans. (2008) 1734. [70] Z.-F. Yao, X. Gan, W.-F. Fu, J. Coord. Chem. 62 (2009) 1817. [71] P.J. Ball, T.R. Shtoyko, J.A. Krause Bauer, W.J. Oldham, W.B. Connick, Inorg. Chem. 43 (2003) 622. [72] S. Zarra, M.M.J. Smulders, Q. Lefebvre, J.K. Clegg, J.R. Nitschke, Angew. Chem. Int. Ed. 51 (2012) 6882.