Diversity of Architecture of Copper(I) Coordination Polymers

1529(vs), 1466(s), 1425(s), 1398(vs), 1346(vs), 1319(w), 1200(s), 1157(vs), 1063(m), 1005(m), ..... Cu4···Cu3, 2.5350(16), S1C−Cu8−I6, 110...
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DOI: 10.1021/cg101018b

Diversity of Architecture of Copper(I) Coordination Polymers Constructed of Copper(I) Halides and 4-Methyl-1,2,4-Triazole-3-Thiol (Hmptrz) Ligand: Syntheses, Structures, and Luminescent Properties

2011, Vol. 11 130–138

Yu-Ling Wang,† Na Zhang,† Qing-Yan Liu,*,†,§ Zeng-Mei Shan,† Rong Cao,*,‡ Ming-Sheng Wang,‡ Jun-Jian Luo,‡ and Er-Lei Yang† †

College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, P. R. China, ‡State Key Laboratory of Structural Chemistry, FuJian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China, and §State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, Jiangsu, 210093, P. R. China Received August 3, 2010; Revised Manuscript Received November 7, 2010

ABSTRACT: Solvo(hydro)thermal reactions of CuX (X = Cl, Br, I) with 4-methyl-1,2,4-triazole-3-thiol (Hmptrz) ligand afforded four new copper(I) coordination polymers, namely, [Cu(μ4-mptrz)]n (1), [Cu(μ2-Hmptrz)(μ2-I)]n (2), [Cu12(μ4-mptrz)4(μ4-I)3(μ3-I)4(μ2-I)]n (3), and [Cu(μ2-Hmptrz)(μ2-DmptrzSS)I]n (4) (DmptrzSS = 4,40 -dimethyl-3,30 -dithiodi-1,2,4-triazole), respectively. Single-crystal X-ray diffraction revealed that compound 1 has a two-dimensional (2D) layered structure with (44 3 62) topology and contains meso-helical (CuS)n chains. Compound 2 features a one-dimensional (1D) chain structure constructed from an unusual inorganic [Cu(μ2-S)2Cu(μ2-I)2Cu]n chain formed from two types of four-membered Cu2(μ2-S)2 and Cu2(μ2-I)2 rings. Compound 3 is a two-dimensional (2D) structure constructed from rugby-shaped Cu6I5 and planar Cu4I3 cluster units, and two types of Cu(mptrz)2 units. The I- ion in structure 3 displays its coordination versatility with μ4-, μ3-, and μ2- bridging coordination modes. Compound 4 has a double-stranded chain structure containing an Hmptrz ligand and DmptrzSS ligand formed from in situ reaction. The structural diversity of these materials is reflected in the variety of coordination polyhedra displayed by the metal sites: linear, trigonal, and tetrahedral. Compounds 1-3 exhibit photoluminescences with fluorescent emissions varying from green to red in the solid state. Some structure-related emission shifts compared to the free ligand are studied. The reaction mechanism of the formation of DmptrzSS ligand has been proposed. In addition, elemental analysis, infrared spectra, and thermogravimetric analysis of compounds 1-4 are also described.

Introduction The construction of coordination polymers (CPs) from metal ions or metal clusters with multifunctional organic ligands is one of the most active areas of materials research. The intense interest in these materials is driven by their intrinsic architectural beauty and aesthetically pleasing structures, as well as potential applications such as catalysis, molecular magnets, photoluminescence, ion exchange, adsorption, and phase separation.1 Over the past several decades, several classes of coordination polymers such as metal-caboxylates and metal-pyridyl have been synthesized and investigated.2 Among these types of polymeric compounds reported so far, copper(I) halides-based inorganic-organic hybrid coordination polymers have been widely investigated due to their intriguing topology and possible applications in solar energy conversion, luminescence-based sensors, display devices, and probes of biological systems.3 In general, the copper(I) halides act as inorganic components, which are further linked by organic ligands to form more complicated frameworks in the construction of hybrid coordination polymers. On the other hand, the organic ligands also play a crucial role in the control of hybrid compounds through tuning their structural dimensionalities and stereochemistry with different coordination sites. Among these organic ligands, nitrogen-containing heterocyclic *To whom correspondence should be addressed. (Q.-Y.L.) E-mail: [email protected]; Fax: þ86-791-8120380. (R.C.) E-mail: rcao@ fjirsm.ac.cn. pubs.acs.org/crystal

Published on Web 11/22/2010

ligands such as 1,2-bis(40 -pyridyl)ethane, 1,3,5-tris(imidazol1-ylmethyl)benzene, and 2,20 -biquinazolin have been extensively employed in the synthesis of these hybrid coordination polymers.4 In addition, heterocyclic thioamides, especially pyridine-2-thione and its substituted derivatives, and 1,3-imidazolidine-2-thione, are also used for the construction of these coordination polymers.5 The thione donor group was introduced into the nitrogen-containing heterocyclic ligands allowing the stabilization of metal ions in low oxidation states such as Cu(I) and Ag(I). The heterocyclic thioamides can present in solution a thione (-NH-C(=S)-) and thiol -NdC(-SH)- tautomerism, whereas in the solid state they are present only in the thione form.6 4-Methyl-1,2,4-triazole-3-thiol (Hmptrz), with three potential donor atoms, is a triazole-based heterocyclic thioamide. Its electron-donating thiol and methyl groups can obviously enhance the conjugation degree of the fivemembered aromatic heterocycle. The combination of the Hmptrz ligand with metal halides is expected to isolate different sorts of coordination polymers under variable synthetic conditions. However, the coordination chemistry of the Hmptrz ligand is seldom investigated. To the best of our knowledge, only two X-ray structures of its complexes (organotin(IV) complexes) have been reported previously.7 Herein, we report a comprehensive study of a new hybrid system of Cu(I) polymers with the Hmptrz ligand. Four coordination polymers, [Cu(μ 4 -mptrz)]n (1), [Cu(μ2 -Hmptrz)(μ 2 -I)]n (2), [Cu 12 (μ4-mptrz)4(μ4-I)3(μ3-I)4(μ2-I)]n (3), and [Cu(μ2-Hmptrz)(μ2DmptrzSS)I]n (4) (DmptrzSS = 4,40 -dimethyl-3,30 -dithiodi1,2,4-triazole), were successfully isolated. In this paper, we r 2010 American Chemical Society

Crystal Growth & Design, Vol. 11, No. 1, 2011

Experimental Section Materials and Instruments. All chemicals were purchased commercially and used without further purification. Elemental analyses were carried out on an Elementar Vario EL III analyzer and IR spectra (KBr pellets) were recorded on PerkinElmer Spectrum One. Fluorescent spectra were measured at room temperature with a single-grating Edinburgh EI920 fluorescence spectrometer equipped with a 450-W Xe lamp, an nF900 lamp, and a R928P PMT detector. The thermogravimetric measurements were performed with a Netzsch STA449C apparatus under a nitrogen atmosphere with a heating rate of 15 °C/min from 25 to 900 °C. Powder X-ray diffraction patterns were performed on a Bruker Advance D8 ADVANCE diffractometer using Cu-KR radiation. Synthesis of [Cu(μ4-mptrz)]n (1). Method 1. A mixture of CuCl (0.0254 g, 0.25 mmol) and 4-methyl-1,2,4-triazole-3-thiol (0.0286 g, 0.25 mmol) in a 1:1 molar ratio in 9 mL of CH3CN/DMF (v/v = 1:2) solution was introduced into a Parr Teflon-lined stainless steel vessel (20 mL). The vessel was sealed and heated to 120 °C. The temperature was held for 3 days and then the mixture was cooled naturally to form colorless crystals of 1 (yield: 0.009 g, 22% based on Cu). Method 2. A mixture of CuBr (0.0717 g, 0.5 mmol) and 4-methyl1,2,4-triazole-3-thiol (0.0579 g, 0.5 mmol) in a 1:1 molar ratio in 15 mL of CH3CN/H2O (v/v = 1:2) solution was introduced into a Parr Teflon-lined stainless steel vessel (25 mL). The vessel was sealed and heated to 160 °C. The temperature was held for 2 days and then the mixture was cooled naturally to form colorless crystals of 1. Colorless crystalline product was filtered, washed with CH3CN/ H2O, and dried at ambient temperature (yield: 0.056 g, 64% based on Cu). Anal. Calcd for C3H4N3SCu (177.69): C, 20.28; H, 2.27; N, 23.65%. Found: C, 20.24; H, 2.21; N, 23.68%. IR spectrum (cm-1, KBr pellet): 3437(m), 3132(m), 3031(w), 2945(w), 2915(w), 1645(w), 1583(w), 1529(vs), 1466(s), 1425(s), 1398(vs), 1346(vs), 1319(w), 1200(s), 1157(vs), 1063(m), 1005(m), 978(w), 824(s), 704(m), 690(w), 647(s), 511(w). Synthesis of [Cu(μ 2-Hmptrz)(μ2 -I)]n (2). A mixture of CuI (0.0480 g, 0.25 mmol) and 4-methyl-1,2,4-triazole-3-thiol (0.0286 g, 0.25 mmol) in a 1:1 molar ratio in 9 mL of CH3CN was introduced into a Parr Teflon-lined stainless steel vessel (20 mL). The vessel was sealed and heated to 120 °C. The temperature was held for 3 days and then the mixture was cooled naturally to form pale brown crystals of 2. Pale brown crystalline product was filtered, washed with CH3CN, and dried at ambient temperature (yield: 0.054 g, 71% based on Cu). Anal. Calcd for C3H5N3SICu (305.60): C, 11.79; H, 1.65; N, 13.75%. Found: C, 11.77; H, 1.61; N, 13.73%. IR spectrum (cm-1, KBr pellet): 3453(w), 3276(s), 3136(m), 3022(w), 2933(w), 1631(w), 1553(vs), 1524(w), 1473(vs), 1424(s), 1390(m), 1360(m), 1240(w), 1219(s), 1152(m), 1047 (s), 951(s), 848(m), 746(m), 689(w), 665(m), 639(w), 514(w). Synthesis of [Cu12(μ4-mptrz)4(μ4-I)3(μ3-I)4(μ2-I)]n (3). A mixture of CuI (0.1431 g, 0.75 mmol) and 4-methyl-1,2,4-triazole-3-thiol (0.0288 g, 0.25 mmol) in a 3:1 molar ratio in 9 mL of CH3CN was introduced into a Parr Teflon-lined stainless steel vessel (20 mL). The vessel was sealed and heated to 120 °C. The temperature was held for 3 days, and then the mixture was cooled naturally to obtain brown crystals of 3 and some indefinite brown solid. Since the crystals have typical shapes, they could easily be manually separated from the powder. Brown crystalline washed with CH3CN and dried at ambient temperature (yield: 0.009 g, 9% based on Cu). Anal. Calcd for C6H8N6I4S2Cu6 (1117.14): C, 6.45; H, 0.72; N, 7.52%. Found: C, 6.41; H, 0.69; N, 7.46%. IR spectrum (cm-1, KBr pellet): 3448(m), 3111(w), 3021(w), 2930(w), 1641(w), 1524(s), 1468(s), 1429(s), 1420(s), 1354(s), 1215(m), 1204(m), 1176(m), 1064 (s), 850(m), 707(m), 642(w), 546(m), 516(w), 468(w). Synthesis of [Cu(μ2-Hmptrz)(μ2-DmptrzSS)I]n (4). A mixture of CuI (0.0477 g, 0.25 mmol), 4-methyl-1,2,4-triazole-3-thiol (0.0579 g, 0.5 mmol), and KI (0.0415 g, 0.25 mmol) in a 1:2:1 molar ratio in 9 mL of CH3CN/DMF (v/v = 2:1) solution was introduced into a

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Parr Teflon-lined stainless steel vessel (20 mL). The vessel was sealed and heated to 120 °C. The temperature was held for 3 days and then the mixture was cooled naturally to obtain red-brown solution containing a few brown solids. The brown solid was filtered off. Upon standing and evaporation of the resulting solution under ambient conditions for three weeks, yellow crystals of 4 were obtained. The yellow crystalline product was filtered, washed with CH3CN/DMF, and dried at ambient temperature (yield: 0.061 g, 61% based on Cu). Anal. Calcd for C9H13N9IS3Cu (533.91): C, 20.27; H, 2.46; N, 23.65%. Found: C, 20.21; H, 2.42; N, 23.57%. IR spectrum (cm-1, KBr pellet): 3442(m), 3102(m), 3016(w), 2943(w), 1641(w), 1568(m), 1507(vs), 1427(w), 1415(w), 1346(s), 1293(w), 1228(s), 1193(s), 1151(vs), 1077 (m), 1049(m), 943(s), 859(m), 695(m), 660(w), 637(w), 618(w), 545(w), 509(m). X-ray Crystallography. X-ray diffraction data of compounds 1-4 were collected on a Bruker Apex II CCD diffractometer equipped with a graphite-monochromated Mo-KR radiation (λ = 0.71073 A˚). Data reduction was performed using SAINT and corrected for Lorentz and polarization effects. Adsorption corrections were applied using the SADABS routine.8 The structures were solved by the direct methods and successive Fourier difference syntheses, and refined by the full-matrix least-squares method on F2 (SHELXTL Version 5.1).9 All non-hydrogen atoms are refined with anisotropic thermal parameters. Hydrogen atoms attached to carbon atoms were assigned to calculated positions with isotropic thermal parameters fixed at 1.2 times that of the attached carbon atom. The R1 values are defined as R1 = Σ Fo| - |Fc /Σ|Fo| and wR2 = {Σ[w(Fo2 - Fc2)2]/Σ[w(Fo2)2]}1/2. The final Fourier map showed residual peaks of 3.461 e 3 A˚-3 and holes of -3.382 e 3 A˚-3 for compound 2, and 2.151 and -1.952 e 3 A˚-3 for compound 3, respectively. The relatively higher residuals are due to the absorption correction problems with the heavy I ions. The details of the crystal parameters, data collection, and refinement are summarized in Table 1, and the selected bond lengths and bond angles are listed in Table 2. )

present their solvo(hydro)thermal reactions, crystal structures, solid-state photoluminescent properties, thermal stabilities, and infrared (IR) spectra.

)

Article

Results and Discussion Syntheses. 4-Methyl-1,2,4-triazole-3-thiol, which has three potential donor atoms (one S atom and two N atoms), is an effective ligand for coordinating to metal cations to generate diverse structural networks. However, as the methyl group in Hmptrz ligand takes up the linking site of the third N atom and thus terminates the propagation of Cu/mptrz/Cu linkages to a three-dimensional (3D) framework. As expected, all the present compounds display low-dimensional structures. The chemical equations for the preparation of compounds 1-4 are shown in Scheme 1. The reaction of copper(I) chloride with Hmptrz in a 1:1 molar ratio in CH3CN/DMF has formed two-dimensional (2D) layer of [Cu(μ4-mptrz)]n (1) in low yield. Replacing the copper(I) chloride with copper(I) bromide in a similar reaction also leads to compound 1 with high yield, which indicates that the final product is independent of the Cl- or Br- of the copper(I) salts. However, inorganic halides (Cl-, Br-, and I-) of the corresponding copper(I) salts are commonly incorporated into the final coordination polymers.3,10 Reactions of Hmptrz with 1 or 3 equiv of CuI in CH3CN solution afforded compounds 2 and 3, respectively, which successfully introduced the I- ion into the final products. Reaction of Hmptrz with CuI in a 2:1 molar ratio in the presence of KI in CH3CN/DMF solution resulted in a red-brown solution. Yellow crystals of 4 were obtained upon evaporation of the resulting solution for three weeks. It should be noted that compound 4 contains the Hmptrz ligand and the novel DmptrzSS ligand formed from in situ reaction. The formation of DmptrzSS ligand is rather interesting. As shown in Scheme 2, the DmptrzSS ligand is formed by oxidative coupling reaction. Similar reactions with other copper(I) halides or copper(I) iodide without KI

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Table 1. Crystallographic Data for Compounds 1-4a 1

2

3

4

C6H8N6I4S2Cu6 1117.14 296(2) orthorhombic Pnma 8 15.6513(15) 16.1222(15) 16.0671(15) 90 90 90 4054.3(7) 3.660 12.482 24727 4028 2955 4032 0.0667 0.0380 0.0899

C18H26N18I2S6Cu2 1067.81 296(2) triclinic P1 1 7.1138(7) 11.0894(11) 11.8195(12) 104.9670(10) 92.2620(10) 100.7640(10) 881.15(15) 2.012 3.358 5753 3178 2159 520 0.0322 0.0409 0.0901

)

)

C3H5N3ISCu formula C3H4N3SCu fw 177.69 305.60 temp (K) 296(2) 293(2) cryst syst monoclinic monoclinic space group P2(1)/n P2(1)/n Z 4 4 a (A˚) 8.8195(11) 5.871(3) b (A˚) 5.0838(6) 13.107(6) c (A˚) 11.7800(15) 10.051(5) R (deg) 90 90 β (deg) 109.4000(10) 96.792(8) γ (deg) 90 90 498.19(11) 768.0(6) V (A˚3) -3 2.369 2.643 Dcalcd (g 3 cm ) -1 4.663 7.051 μ (mm ) no. of reflns collected 3580 5500 independent reflns 1244 1685 obsd reflns (I>2σ(I)) 1151 1597 F(000) 352 568 R[int] 0.0241 0.0245 0.0330 0.0525 R1 (I>2σ(I)) 0.0930 0.1908 wR2 (all data) P P P a 2 2 2 P R1 = Fo| - |Fc / |Fo| and wR2 = { [w(Fo - Fc ) ]/ [w(Fo2)2]}1/2.

have not been observed with the formation of DmptrzSS ligand, which indicates I- of the KI could be involved in the hydro(solvo)thermal reaction. Thus, we propose that the oxidant in this reaction is I2 molecule, which is generated by the reaction of I- and O2 in water solvent. Crystal Structure of [Cu(μ4-mptrz)]n (1). Compound 1 has a 2D layered structure. As shown in Figure 1, the asymmetric unit of 1 consists of one copper(I) ion and one mptrzmonoanion. Cu(1) coordinates to two S atoms and two N atoms from four mptrz- ligands in a distorted tetrahedral coordination geometry, having Cu-S distances of 2.2833(7) and 2.4231(7) A˚, and Cu-N distances of 2.0420(19) and 2.122(2) A˚, respectively (Table 2). The bond dimensions involving copper are normal, and are comparable with the values in related copper(I) complexes.11 As shown in Figure 1, the mptrz- ligand acts as a tetradentate ligand (Chart 1a) with the μ2-S atom and two monodentate N atoms. The Cu(I) ions are interconnected by the S atoms of mptrzligands into a 1D 21 helical (CuS)n chain (Figure 2a), which is consistent with the compound crystallized in P21/n space group. The (CuS)n helical chains are further linked by the triazole rings to form a 2D layered structure, as depicted in Figure 2a. It is interesting that the neighboring (CuS)n helices have an opposite handedness (Figure S1, Supporting Information). Thus, the 2D layer has meso-helical (CuS)n chains. The 2D structure may be more clearly understandable on the basis of a topological approach. As depicted in Figure 2, each Cu atom is coordinated by four mptrzligands, and each mptrz- ligand links four Cu atoms together. In this way, the Cu atom and the mptrz- ligand both act as 4-connected nodes in a ratio of 1:1. The two 4-connected nodes are topologically equivalent nodes with the topology notation of (44 3 62), as shown in Figure 2b. Crystal structure of [Cu(μ2-Hmptrz)(μ2-I)]n (2). Compound 2 features a 1D chain structure constructed from an unusual inorganic [Cu(μ2-S)2Cu(μ2-I)2Cu]n looped chain formed from two types of four-membered Cu2(μ2-S)2 and Cu2(μ2-I)2 rings sharing the Cu atoms. As depicted in Figure 3, the asymmetric unit of 2 contains one copper(I) ion, one Hmptrz ligand, and one iodide ion. The copper atom is fourcoordinated by two μ2-S atoms and two μ2-I atoms in a

distorted tetrahedral geometry, with Cu-S bond lengths of 2.334(2) and 2.457(2) A˚, and Cu-I bond lengths of 2.5994(13) and 2.6611(13) A˚, respectively (Table 2). The copper atoms are bridged by the μ2-I and the μ2-S atoms of the Hmptrz ligands to give a 1D chain propagating along the a axis, as depicted in Figure 3. The chain features an uncommon inorganic [Cu(μ2-S)2Cu(μ2-I)2Cu]n looped chain containing two types of centrosymmetric four-membered Cu2(μ2-S)2 and Cu2(μ2-I)2 rings with the S(1)-Cu(1)-S(1B) and I(1)-Cu(1)-I(1A) angles of 101.28(7) and 114.16(5)°, respectively. Thus, the alternating Cu2(μ2-S)2 and Cu2(μ2-I)2 units sharing the Cu atoms to build this inorganic [Cu(μ2-S)2Cu(μ2-I)2Cu]n looped chain as shown in Figure 3. Many complexes based on the infinite Cu2(μ2-I)2 chains have been documented,12 but only one complex, [Cu(C8H9NS2)I]n (C8H9NS2 = N-phenyl-S-methyldithiocarbamato), containing heterobridged [Cu(μ2-S)2Cu(μ2-I)2Cu]n chain has been reported.13 The Cu2(μ2-S)2 plane and Cu2(μ2-I)2 plane intersect with each other with a dihedral angle of 85.3°, which is slightly larger than that in complex [Cu(C8H9NS2)I]n (83.4°). The Cu 3 3 3 Cu distances in the Cu2(μ2-S)2 and Cu2(μ2-I)2 units are 3.040(2) and 2.859(2) A˚, respectively, which are slightly longer than the corresponding values in complex [Cu(C8H9NS2)I]n (2.977 and 2.647 A˚), and the latter contact is close to the sum of the van der Waals radii of Cu atoms (2.80 A˚), implying the existence of weak Cu 3 3 3 Cu interactions. The Hmptrz ligand bridges two copper(I) ions through its S atom as shown in Chart 1b. As shown in Figure 4, the interchain N(2)-H(2) 3 3 3 N(1C) (symmetry code: C -x þ 1, -y þ 1, -z þ 1) hydrogen bonds (N 3 3 3 N = 2.978(10) A˚), linked the adjacent chains to generate a 2D layer in the ac plane. Crystal Structure of [Cu12(μ4-mptrz)4(μ4-I)3(μ3-I)4(μ2-I)]n (3). Compound 3 is a 2D structure constructed from unique rugby-shaped Cu6I5 and planar Cu4I3 secondary building units (SBUs) and two types of Cu(mptrz)2 SUBs. The 2D structure has a crystallographically imposed m symmetry (Figure S2, Supporting Information). As shown in Figure 5, the mirror plane passes through Cu(1), Cu(5), Cu(6), Cu(7), Cu(8), Cu(9), I(1), I(2), I(3), I(5), I(6), and I(7) atoms. Cu(1) atom is coordinated by two N atoms from two mptrz- ligands

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Table 2. Selected Bond Lengths (A˚) and Bond Angles (deg) of 1-4a Compound 1 Cu1-S1 Cu1-N2A Cu1-S1B Cu1-N1C S1-C1

2.2833(7) 2.0420(19) 2.4231(7) 2.122(2) 1.733(2)

S1-Cu1-S1B N2A -Cu1-S1 N2A-Cu1-N1C N1C-Cu1-S1B

120.668(19) 113.79(6) 103.29(8) 98.98(6)

Compound 2 Cu1-S1 Cu1-I1A Cu1-I1 Cu1-S1B S1-C1 Cu1 3 3 3 Cu1A

2.457(2) 2.5994(13) 2.6611(13) 2.334(2) 1.708(7) 2.859(2)

Cu1-N1 Cu2-S1 Cu2-I1 Cu2-I2 Cu2-I4 Cu3-I1 Cu3-I3 Cu3-I4 Cu3-N2B Cu4-N4 Cu4-I2 Cu4-I3 Cu4-I4 Cu5-N5 Cu6-S2 Cu6-I5 Cu6-I6 Cu7-I5 Cu7-I6 Cu7-I7 Cu8-S1C Cu8-I6 Cu8-I7 Cu9-S2E Cu9-I7 Cu1 3 3 3 Cu8H Cu2 3 3 3 Cu3 Cu2 3 3 3 Cu4 Cu4 3 3 3 Cu3 Cu5 3 3 3 Cu9I Cu5 3 3 3 Cu6 Cu6 3 3 3 Cu9I Cu6 3 3 3 Cu7 Cu7 3 3 3 Cu8

1.884(7) 2.308(2) 2.6770(13) 2.7596(14) 2.7202(15) 2.7378(13) 2.7295(13) 2.6408(13) 1.993(7) 2.003(8) 2.6946(14) 2.8193(14) 2.6304(14) 1.835(8) 2.491(3) 2.604(3) 2.731(2) 2.537(2) 2.595(2) 2.560(2) 2.288(2) 2.7401(19) 2.9331(19) 2.297(3) 2.618(2) 2.882(2) 2.6526(16) 2.7258(17) 2.5350(16) 2.901(3) 3.033(3) 2.580(3) 2.968(3) 2.804(2)

S1B-Cu1-S1 S1-Cu1-I1 I1A -Cu1-I1 S1B-Cu1-I1A Cu1 3 3 3 Cu1B

101.28(7) 107.22(6) 114.16(5) 120.36(6) 3.040(2)

Compound 3 N1-Cu1-N1A S1-Cu2-I1 S1-Cu2-I2 S1-Cu2-I4 I2-Cu2-I1 I2-Cu2-I4 I1-Cu2-I4 N2B-Cu3-I1 N2B-Cu3-I3 N2B-Cu3-I4 I3-Cu3-I1 I3-Cu3-I4 I1-Cu3-I4 N4-Cu4-I2 N4-Cu4-I3 N4-Cu4-I4 I3-Cu4-I2 I3-Cu4-I4 I2-Cu4-I4 N5-Cu5-N5A S2-Cu6-S2A S2-Cu6-I5 S2-Cu6-I6 I5-Cu6-I6 I5-Cu7-I6 I5-Cu7-I7 I7-Cu7-I6 S1C-Cu8-S1D S1C-Cu8-I6 S1C-Cu8-I7 I7-Cu8-I6 S2E-Cu9-S2F S2E-Cu9-I7

173.9(4) 104.69(7) 114.82(7) 107.40(8) 102.38(5) 111.40(5) 116.21(5) 107.71(19) 111.5(2) 104.0(2) 92.04(4) 123.95(5) 116.84(5) 117.7(2) 104.8(2) 103.9(2) 93.28(4) 120.86(5) 116.44(5) 169.5(5) 107.20(16) 118.75(9) 100.68(8) 107.65(9) 114.14(8) 118.89(8) 126.97(8) 132.19(14) 110.04(7) 95.43(7) 108.75(6) 121.54(17) 117.72(8)

Figure 1. ORTEP drawing of 1 with 40% probability displacement ellipsoids.

Scheme 1. Synthesis of Compounds 1-4

Scheme 2. Formation of the DmptrzSS Ligand

Compound 4 Cu1-N2 Cu1-S3 Cu1-S3A Cu1-N4B S3-C7 S1-C1 S2-C4 S1-S2

2.019(4) 2.2289(15) 2.7364(17) 2.022(4) 1.695(5) 1.738(5) 1.758(5) 2.101(2)

Cu1 3 3 3 Cu1A N2-Cu1-N4B N2-Cu1-S3 N2-Cu1-S3A S3-Cu1-S3A S3-Cu1-N4B S3A-Cu1-N4B

2.8295(15) 106.69(18) 118.02(13) 91.01(13) 111.39(5) 125.74(13) 96.17(13)

a Compound 1, A: -x þ 3/2, y - 1/2, -z þ 3/2; B: -x þ 3/2, y þ 1/2, -z þ 3/2; C: x - 1/2, -y þ 1/2, z - 1/2. Compound 2, A: -x, -y þ 1, -z þ 2; B: -x þ 1, -y þ 1, -z þ 2. Compound 3, A: x, -y þ 3/2, z; B: x 1/2, y, -z þ 1/2; C: x, -y þ 3/2, z þ 1; D: x, y, z þ 1; A: x, -y þ 3/2, z; E: x - 1/2, -y þ 3/2, -z þ 3/2; F: x - 1/2, y, -z þ 3/2; G: x þ 1/2, y, -z þ 1/2; H: x, y, z - 1; I: x þ 1/2, y, -z þ 3/2. Compound 4, A: -x, -y, -z 1; B: -x þ 1, -y, -z - 1.

in a nearly linear fashion (N(1)-Cu(1)-N(1A) = 173.9(4)° and Cu-N = 1.884(7) A˚) to form a Cu(mptrz)2 SBU. The dihedral angle between the two triazole rings of the mptrzligands is 4.27°. Atom Cu(5) has a similar coordination

Chart 1. Coordination Modes of the mptrz Ligand

geometry to that of Cu(1) with a Cu-N bond distance of 1.835(8) A˚ and a slightly small N-Cu-N bond angle of 169.5(5)°. The two triazole rings linked by Cu(5) atom has a smaller dihedral angle between them (3.16°). The two Cu(mptrz)2 units display different coordination modes. The Cu(mptrz)2 unit of Cu(1) atom bridges five copper(I) atoms through its two monodentate N atoms and two μ2-S atoms,

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Figure 4. Hydrogen bonding in 2 between two adjacent chains giving rise to a 2D hydrogen-bonded layer in the ac plane.

Figure 2. (a) 2D structure of 1 highlighted with the helical (CuS)n chains. (b) Schematic view of the 4-connected (44 3 62) topology of 1 (The copper atom and the mptrz- ligand are represented by blue and red balls, respectively).

Figure 5. ORTEP drawing of 3 with 30% probability displacement ellipsoids (H atoms of the methyl groups are omitted for clarity).

Figure 3. 1D polymeric double-stranded chain of 2 running along the a axis.

while the other Cu(mptrz)2 unit acts as a tetradentate ligand with two monodentate N atoms and two μ2-S atoms as depicted in Figure S3, Supporting Information. Different from those of Cu(1) and Cu(5) atoms, the Cu(2), Cu(3), Cu(4), Cu(6), and Cu(8) atoms adopt distorted tetrahedral coordination geometries but have different coordination environments. The Cu(3) and Cu(4) have [CuI3N] coordination environments, and Cu(6) and Cu(8) display [CuI2S2] coordination environments, respectively, while Cu2 exhibits a [CuI3S] coordination environment. These Cu-I, Cu-N, and Cu-S distances are normal (Table 2) and comparable to those in related copper(I) complexes.11 Cu(7) atom is

three-coordinated by three μ2-I, where the four atoms are located at a plane with the Cu-I distances of 2.537(2), 2.560(2), and 2.595(2) A˚ and I-Cu-I bond angles of 118.89(8), 114.14(8), and 126.97(8)°, respectively. Cu(9) also has a planar coordination geometry and is three-coordinated by two S atoms and one μ3-I. The Cu-S and Cu-I distances are 2.297(3) and 2.618(2) A˚, respectively. It is worth noting that in this structure the copper(I) atoms has a coordination number varying from two to four and are accompanied by a variety of coordination geometries such as linear, trigonal, and tetrahedral. Therefore, this a rare example of copper(I) complex with diverse copper(I) coordination geometries. Of particular interest is that structure 3 contains two types of uncommon inorganic cationic Cu6I5 and Cu4I3 clusters. As shown in Figure 6a, Cu(2), Cu(3), and Cu(4) atoms are capped by a μ3-I(4) atom generating a Cu3I tetrahedron with Cu-I distances of 2.7202(15), 2.6408(13), and 2.6304(14) A˚, respectively, which are comparable to those in related μ3-I complexes.14 The Cu 3 3 3 Cu distances of 2.6526(16), 2.5350(16), and 2.7258(17) A˚, respectively, are significantly shorter than the sum of the van der Waals radii of copper atom, which provides supporting evidence for the significance of

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Figure 6. View of the (a) rugby-shaped Cu6I5 cluster and (b) planar Cu4I3 cluster in structure 3.

Cu 3 3 3 Cu contacts. Two Cu3I tetrahedron symmetry-related by a mirror plane are linked by three μ4-I (I(1), I(2), and I(3)) atoms that are located at the mirror plane, to give a rugbyshaped Cu6I5 cluster having the Cu-I distances range from 2.6770(13) to 2.8193(14) A˚ (Table 2). The rugby-shaped Cu6I5 cluster can be described as a triangular prism of copper atoms, where each tetragonal plane is capped by a μ4-I atom and each triangular plane is capped by a μ3-I atom (Figure 6a). Many copper(I)-iodide cluster-based frameworks have been documented.15 However, most of the reported copper(I)iodide cluster are neutral CunIn clusters, which are commonly based on Cu2I2 rhomboid dimers16 or Cu4I4 cubane tetramers.17 Coordination architectures constructed by discrete high-nuclear cationic CumIn clusters have rarely been observed previously. This type of rugby-shaped cationic Cu6I5 cluster, to the best of our knowledge, is unprecedented. In addition, a planar cationic Cu4I3 cluster are also observed, which is formed by two fused Cu2I2 four-membered rings and a dangling copper(I) atom (Figure 6b). Compared with the extensively investigated neutral and anionic copper(I) halide clusters,3 the formation and structures of cationic copper(I) halide aggregates remained unexplored. In addition, the inorganic-organic hybrid coordination polymers constructed from copper(I) halides inorganic components commonly contain only one kind of inorganic copper(I) halides cluster. The present compound containing two types of cationic copper(I) iodide clusters, therefore, is an unique example of CumIn cluster-based complex. It is also noteworthy that the iodine ion in this structure displays three bridging modes of μ4-I, μ3-I, and μ2-I, which exhibit its coordination versatility. As shown in Figure S4, Supporting Information, the Cu6I5 clusters are interconnected by the Cu(mptrz)2 units to generate a 1D chain-like structure. The Cu4I3 cluster are interconnected by the other type of Cu(mptrz)2 units to form another kind of 1D chain. The two kinds of chains are further linked by the Cu(4)N(4) and Cu(8)-S(1) coordination bonds to give a 2D structure as depicted in Figure 7. Crystal Structure of [Cu(μ2-Hmptrz)(μ2-DmptrzSS)I]n (4). Compound 4 has a double-stranded chain structure. As shown in Figure 8, the asymmetric unit of 4 consists of one Cu(I) ion, one Hmptrz ligand, one DmptrzSS ligand, and one iodide ion. It should be noted that under the present solvothermal conditions, the unusual dimerization of Hmptrz ligand occurs in situ to yield the novel organic ligand of 4,40 -dimethyl3,30 -dithiodi-1,2,4-triazole (DmptrzSS) (Scheme 2). This is the first report of the dimeric reaction of the Hmptrz ligand. As

Figure 7. 2D layered structure of 3.

Figure 8. ORTEP drawing of 4 with 40% probability displacement ellipsoids.

shown in Figure 8, Cu(1) is coordinated by two S atoms from two Hmptrz ligands and two N atoms from two DmptrzSS ligands in a distorted tetrahedral geometry with a long Cu(1)-S(3A) distance of 2.7364(17) A˚ (symmetry code: A - x, -y, -z - 1). The Cu(1)-S(3) and Cu-N distances are 2.2289(15), 2.019(4), and 2.022(4) A˚, respectively. A pair of μ2-S atoms (S(3) and S(3A)) from two Hmptrz ligands related by a inversion center, bridge two Cu atoms to form a centrosymmetric dinuclear [Cu2(Hmptrz)2] unit with a central homobridged Cu2(μ2-S)2 core. The Cu 3 3 3 Cu distance in the Cu2(μ2-S)2 units are 2.8295(15) A˚, which are slightly shorter than the corresponding values in complex 2 (3.040(2) A˚) and indicates direct interaction between the metal atoms. Similar to that in complex 2, the Hmptrz ligand only using its μ2-S atom bridges two Cu(I) atoms to form a [Cu2(Hmptrz)2] core. However, differing from that of complex 2, the

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Figure 9. 1D double-stranded chain structure of 4.

[Cu2 (Hmptrz)2 ] units in structure 4 are linked by the long flexible μ2-DmptrzSS ligands to generate a double-stranded chain structure running along the a axis, as illustrated in Figure 9. Differing from those of compounds 2 and 3, iodide anion in this structure is not involved in coordination but only acts as a charge-compensating agent. Photoluminescent Properties. The combination of organic linkers and metal centers in coordination polymers provides an efficient route to a new type of photoluminescent materials with potential applications because of their structure- and metal-dependent emission. In addition to the diverse structural characteristics of copper(I) complexes, the photoluminescent properties of the copper(I) complexes are also well studied. The photoluminescence properties of 1-4 as well as free ligand were examined in the solid state at room temperature. The free Hmptrz displays photoluminescent emission at 536 nm under 337 nm radiation (Figure 10).The main chromosphere of this ligand is the aromatic five-membered triazole ring, and its conjugation degree is further enhanced by the electron-donating thiol and methyl groups. This conjugation enhancement results in that the maximum emission wavelength of the Hmptrz ligand is red-shifted compared with those of 1,2,4-triazole ligand18 and 1H-1,2,4-triazole3-thiol ligand.19 The photoluminescence of Hmptrz ligand has been assigned as originating from intraligand (IL) π-π* transitions. After excitation at 372 nm, compound 1 exhibits photoluminescent emission with the maximum at 584 nm (Figure 10). The emission energy of 1 is much lower than that of the free ligand, which eliminates an intraligand IL excited state. The metal-to-ligand charge transfer (MLCT) excited states are important in the photophysical properties of the copper(I) complexes that constructed from easily reducible ligands.20 In compound [Cu(μ4-mptrz)]n (1), the anionic mptrzligand has a more electronically delocalizing or electronegative, which can provide a lower energy π* state. Therefore, the emission of compound 1 can be tentatively assigned to (MLCT) transition, which is consistent with those of other copper(I) complexes with aromatic heterocyclic ligands.21 In the case of 2, green photoluminescence with the maximum emission at 549 nm upon excitation at 369 nm was observed (Figure 10). Because the emission energy and profile of compound 2 is similar to that of the free ligand, the luminescence behavior of 2 may be assigned as the intraligand (IL) π-π* transitions. In contrast to the free ligand, compound 2 exhibits a red-shift of 13 nm for its emission band, probably as a result of decreased π-π stacking interactions. Upon excitation at 360 nm, compound 3 produced a broad red emission with the maximum at 644 nm (Figure 10). The emission of 3 occurs at a much low energy of 644 nm with a large Stokes shift (284 nm). As described above, the structure of 3 contains polynuclear copper(I) iodide clusters with

Figure 10. The solid-state excitation and emission spectra of the Hmptrz ligand and compounds 1-3 at room temperature.

Cu 3 3 3 Cu interactions. The low-energy emissions associated with large Stokes shifts have been commonly observed for copper(I)-cluster based complexes, which can be assigned to a metal-cluster-centered transition involving the s and p metal orbital. The large Stokes shift is caused by the elimination of the ground-state distortion in the excited state. On the

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other hand, for copper(I) iodide cluster compounds, the highest occupied molecular orbital (HOMO) is presumably composed largely of iodide p orbitals. Thus, excited-state assignments must account for major components of iodide to metal charge transfer (XMCT) and iodide to ligand charge transfer (XLCT) character for the low-energy and highenergy emissions, respectively.22 With these concerns in mind, the emission band at 644 nm of 3 can be assigned to originate from an excited state of mixed halide-to-metal charge transfer (XMCT) and copper-cluster-centered d f s,p character. Compound 4 exhibits no observable photoluminescence. We speculate that there is apparently a strong change in the electronic structures of the ligands (from the keton (Hmptrz) to enol (DmptrzSS) form with formation of aromatic triazole π-system). Additionally, there is more vibrational coupling for structure 4 based on the flexible DmptrzSS ligand with a freely rotational S-S bond, which provides effective radiationless relaxation. The further lifetime measurements for each emission maximum of compounds 1-3 are also investigated. The results show that the lifetimes of the three compounds are out of the range (nanosecond) of the fluorescence spectrometer. The short lifetimes of the three compounds suggest that photoluminescences for compounds 1-3 should be assigned to fluorescence. FT-IR Spectra, Thermogravimetric Analysis, and Powder X-ray Diffraction. The infrared spectra of compounds 1-4 show similar main characteristic peaks. The IR spectra of compounds 1-4 show the C-H stretching vibrations of the methyl group at 2945, 2933, 2930, and 2943 cm-1, respectively. The weak absorption bands at 3031, 3022, 3021, and 3016 cm-1 for compounds 1 to 4, respectively, are due to the C-H stretching of triazole ring. The thioamide groups normally exhibit four different bands in the region of 1570-1395 (band I), 1420-1260 (band II), 1140-940 (band III), and 800-700 cm-1 (band IV).23 The four compounds show corresponding absorption bands at their IR spectra in I-IV regions, yet with somewhat slight fluctuation. Bands I and II are mainly originated from CdN stretching vibrations and/or N-H deformation vibrations, while bands III and IV are significantly influenced by CdS content. However, it is difficult to identify these bands unambiguously because each band contains some contribution from the strongly coupled CdS stretching mode, which arises because the carbon atom of the thiocarbonyl group (CdS) is directly linked to the nitrogen atom. To examine the thermal stability of these compounds and their structural variation as a function of the temperature, thermogravimetric analysis (TGA) was performed on singlephase polycrystalline samples of these materials (Figure S5, Supporting Information). The TGA trace for compound 1 displays a small gradual weight loss starting at 160 °C, and then a sharp continual weight loss occurred at 205 °C, which is attributed to the decomposition of the organic ligand. The total weight loss at 640 °C is 57.7%. Compound 2 is stable up to 210 °C, and then it exhibits two main steps of weight losses. The first step (215-357 °C) corresponds to the decomposition of the organic ligands. The second step (360-780 °C) is attributed to the decomposition of the copper halides inorganic portion of the compound. The total weight loss at 780 °C is 75.3%. For compound 3, the slow combustion of the organic ligands occurs at 205 °C. Upon further heating, the main building block of the compound starts to decompose. The total observed weight losses are 72.5% at 815 °C for 3.

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Compound 4 is not stable and displays a rapid mass loss of 5.5% between 45 and 185 °C, which is attributed to the incomplete decomposition of the organic ligands. Then a sharp continual weight loss occurs at 185 °C. The total observed weight losses are 88.3% at 820 °C. The purities and crystallinities of the bulk samples were checked by powder X-ray diffraction (PXRD). PXRD patterns of compounds 1-4 are illustrated in Figure S6 (Supporting Information). The different structures of compounds 1-4 also have been indicated by their different XRPD patterns. Their XRPD patterns are in good agreement with the ones simulated from single crystal structural data; thus all compounds were obtained as a single phase. Conclusions In conclusion, the self-assembly of copper(I) halide salts with Hmptrz afforded four novel copper(I) coordination polymers. The synergism of the potentially polydentate bridging Hmptrz ligand and the effectiveness of the halide ions in adopting bridging modes provide complex connectivity patterns and remarkable structural diversity. Compound 1 is a 2D layered structure with meso-heclical (CuS)n chains. Compound 2 has a 1D chain structure constructed from an unusual inorganic [Cu(μ2-S)2Cu(μ2-I)2Cu]n looped chain. Compound 3 is a 2D structure featuring unprecedented rugby-shaped cationic Cu6I5 and planar cationic Cu4I3 clusters. Compound 4 has a double-stranded chain structure containing Hmptrz and DmptrzSS formed from an oxidative coupling reaction. All the present compounds display low-dimensional structures. The methyl group in the Hmptrz ligand takes up the linking site of the third N atom and thus terminates the propagation of Cu/mptrz/Cu linkages to the 3D framework. In addition, compounds 1-3 display fluorescent emissions varying from green to red in the solid state, indicating structure-dependent photoluminescent properties of the coordination polymers, and revealing the potential for application in light-emitting diode (LED) technology. Acknowledgment. This work was supported by the National Natural Science Foundation of China (Grant 20901033), the Provincial Natural Science Foundation of Jiangxi (Grant 2009GZH0056), and the Key Project of Education Department of Jiangxi Province (Grant GJJ10016). Supporting Information Available: X-ray structure data for 1-4 in CIF format. Powder X-ray diffraction patterns of compounds, some structures of compounds 1 and 3, and TG curves. This material is available free of charge via the Internet at http://pubs.acs.org.

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