Molecular Cage and 1-D Coordination Architectures Assembled from

WGY-10 spectrofluorometer. Synthesis of Ligands. 9,10-Bis[(ethylthio)methyl]anthracene (L1). To the hot ethanol solution (30 mL, ∼50 °C) of ethylth...
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CRYSTAL GROWTH & DESIGN

Molecular Cage and 1-D Coordination Architectures Assembled from Silver(I) and Dithioether Ligands with Bulky Anthrene Spacers: Syntheses, Crystal Structures, and Emission Properties

2006 VOL. 6, NO. 3 648-655

Tong-Liang Hu, Jian-Rong Li, Ya-Bo Xie, and Xian-He Bu* Department of Chemistry, Nankai UniVersity, Tianjin 300071, China ReceiVed June 22, 2005; ReVised Manuscript ReceiVed December 20, 2005

ABSTRACT: A series of dithioether ligands with bulky anthrene spacers, 9,10-bis[(ethylthio)methyl]anthracene (L1), 9,10-bis[(npropylthio)methyl]anthracene (L2), 9,10-bis[(n-butylthio)methyl]anthracene (L3), and 9,10-bis[(tert-butylthio)methyl]anthracene (L4), have been designed and synthesized. The reactions of these ligands with AgX (X ) NO3-, ClO4-, PF6-) lead to the formation of six new metal-organic coordination architectures, [Ag4(L1)2(NO3)4](CHCl3)2 (1), [Ag4(L2)2(NO3)4](CHCl3)2 (2), [Ag4(L3)2(NO3)4] (3), {[AgL2(CH3CN)](ClO4)}∞ (4), {[AgL4(NO3)]2(CH3CN)}∞ (5), and {[AgL4](PF6)}∞ (6), which have been characterized by elemental analyses, IR spectroscopy, and X-ray crystallography. Single-crystal X-ray analyses show that complexes 1-3 possess novel tetranuclear molecular cage structures, while 4-6 have chain structures. In 1-3, the S atoms of the ligands take a µ2-S bridging coordination mode to link AgI ions; thus four S atoms of two ligands link four AgI ions to form a tetranuclear cage. The differences of ligand terminal groups in L1, L2, and L3 do not greatly influence the structures of their complexes. However, the changes of the terminal groups cause subtle differences in the coordination geometry of the AgI centers, the number of solvent molecules encapsulated in the space among adjacent tetranuclear moieties, and the packing mode of the tetranuclear units. Complex 5, whose ligand bears larger tert-butyl terminal groups, is a one-dimensional (1-D) structure instead of a tetranuclear cage. In addition, the structural differences of 2 and 4 (5 and 6) may contribute to the relatively stronger coordination ability of NO3- than that of ClO4- (or PF6-). These results indicate that the terminal groups of the ligands and the counteranions may play important roles in governing the structural topologies of such metal-organic coordination architectures. Furthermore, complexes 1-6 also display strong blue emissions in the solid state at room temperature. Introduction The rational design of functional coordination architectures using multitopic organic ligands and metal ions represents a rapidly developing field in current coordination chemistry owing to their interesting structures and potential as functional materials, as well as the challenge associated with their syntheses.1-3 Considerable progress has been made on the theoretical forecast and network-based approaches aimed at controlling the topology and geometry of the networks to produce prospective coordination architectures with desired structures and useful functions.3f,4 It has been considered that the coordination preference of metal ions and the shape and bonding modes of the ligand are generally the primary considerations in metal-mediated selfassembly reactions.5 However, the prediction of coordination frameworks is still subjective and cannot be generalized because many other factors such as solvents,6 templates,7 and counteranions8 may also play profound roles in the formation of products. Accordingly, to understand the intrinsic connection between complex structures and factors affecting the framework formation seems to be a long-range challenge. In our previous work, some well-designed dithioether ligands with flexible spacers were successfully used to construct various structures of complexes including discrete molecules, one-, two-, and three-dimensional (1-D, 2-D, and 3-D) networks.9 As a continuation of our research on AgI coordination compounds with dithioether ligands, four structurally related dithioether ligands consisting of different terminal groups linked via rigid bulk anthrene spacers, L1-L4 (Chart 1), and six new AgI complexes of these ligands, [Ag4(L1)2(NO3)4](CHCl3)2 (1), [Ag4(L2)2(NO3)4](CHCl3)2 (2), [Ag4(L3)2(NO3)4] (3), {[AgL2(CH3* Corresponding author. E-mail: [email protected]. Fax: +86-2223502458.

Chart 1

CN)](ClO4)}∞ (4), {[AgL4(NO3)]2(CH3CN)}∞ (5), and {[AgL4](PF6)}∞ (6), have been synthesized and characterized. We report herein the syntheses, crystal structures, and emission properties of these AgI complexes. The influences of the terminal groups of ligands and anions on the resultant structures of their metal complexes are briefly discussed. In addition, the emission properties of these complexes were also studied in the solid state at room temperature. Experimental Section Materials and General Methods. All the reagents for synthesis were obtained commercially and purified by standard methods prior to use. 9,10-Bis(chloromethyl)anthracene was synthesized by the literature method.10 Elemental analyses of C, H, and N were performed on a Perkin-Elmer 240C analyzer. IR spectra were measured on a TENSOR 27 (Bruker) FT-IR spectrometer with KBr pellets. 1H NMR spectra were recorded on a Bruker AC-P500 spectrometer (300 MHz) in CDCl3 medium at 25 °C with tetramethylsilane as the internal reference. The X-ray powder diffraction (XRPD) was recorded on a Rigaku D/Max-2500 diffractometer at 40 kV, 100 mA for a Cu-target tube and a graphite monochromator. Emission spectra were taken on a WGY-10 spectrofluorometer. Synthesis of Ligands. 9,10-Bis[(ethylthio)methyl]anthracene (L1). To the hot ethanol solution (30 mL, ∼50 °C) of ethylthiol sodium salt (1.68 g, 0.02 mol), 9,10-bis(chloromethyl)anthracene (2.75 g, 0.01 mol)

10.1021/cg050286p CCC: $33.50 © 2006 American Chemical Society Published on Web 02/14/2006

Molecular Cage and 1-D Coordination Architectures was added. The mixture was further stirred at 50 °C for 4 h. After the sample was cooled, 30 mL of water was added and left to stand for 2 h. The yellow precipitate was filtered, washed with water and ethanol, and recrystallized from CHCl3/Et2O (1:1) to obtain a light yellow powder.11a Yield: 70%. m.p.: 181-183 °C. Anal. Calcd. for C20H22S2: C, 73.57; H, 6.79. Found: C, 73.22; H, 6.53. 1H NMR: δ 1.38 (t, J ) 7.2 Hz, 6H, CH2-CH3), 2.72 (q, J ) 7.2 Hz, 4H, S-CH2CH3), 4.75 (s, 4H, Ar-CH2-S), 7.54-7.58 (m, 4H, Ar), 8.36-8.41 (m, 4H, Ar). L2, L3, and L4 were synthesized by the similar procedure as described above. 9,10-Bis[(n-propylthio)methyl]anthracene (L2).11b Yield: 80%. m.p.: 174-176 °C. Anal. Calcd. for C22H26S2: C, 74.52; H, 7.39. Found: C, 74.36; H, 7.22. 1H NMR: δ 1.02 (t, J ) 7.2 Hz, 6H, CH2CH3), 1.75 (h, J ) 7.2 Hz, 4H, S-CH2-CH2-CH3), 2.67 (t, J ) 7.2 Hz, 4H, S-CH2-CH2-CH3), 4.72 (S, 4H, Ar-CH2-S), 7.54-7.57 (m, 4H, Ar), 8.35-8.38 (m, 4H, Ar). 9,10-Bis[(n-butylthio)methyl]anthracene (L3). Yield: 75%. m.p.: 131-133 °C. Anal. Calcd. for C24H30S2: C, 75.34; H, 7.90. Found: C, 75.13; H, 8.04. 1H NMR: δ 0.919 (t, J ) 7.5 Hz, 6H, CH2CH3), 1.43 (h, J ) 7.5 Hz, 4H, S-CH2-CH2-CH2-CH3), 1.67 (f, J ) 7.5 Hz, 4H, S-CH2-CH2-CH2-CH3), 2.69 (t, J ) 7.5 Hz, 4H, S-CH2CH2-CH2-CH3), 4.72 (S, 4H, Ar-CH2-S), 7.54-7.57 (m, 4H, Ar), 8.35-8.38 (m, 4H, Ar). 9,10-Bis[(tert-butylthio)methyl]anthracene (L4).11c Yield: 65%. m.p.: 252-254 °C. Anal. Calcd for C24H30S2: C, 75.34; H, 7.90. Found: C, 75.01; H, 7.67. 1H NMR: δ 1.57 (s, 18H, C(CH3)3), 4.71 (s, 4H, Ar-CH2-S), 7.53-7.57 (m, 4H, Ar), 8.34-8.37 (m, 4H, Ar). Preparations of Complexes 1-6. [Ag4(L1)2(NO3)4](CHCl3)2 (1). The solution of AgNO3 (17 mg, 0.1 mmol) in CH3OH (10 mL) was carefully layered on top of a CHCl3/CH3CN (10 mL/3 drops) solution of L1 (33 mg, 0.1 mmol) in a test tube. After ca. two weeks at room temperature, light yellow single crystals appeared at the boundary between CH3OH and CHCl3/CH3CN. Yield: 30%. Anal. Calcd. for C42H46Ag4Cl6N4O12S4: C, 32.11; H, 2.95; N, 3.57. Found: C, 31.90; H, 2.73; N, 3.75. IR (KBr pellet, cm-1): 2958w, 2921w, 2866w, 2427w, 1476w, 1446m, 1384Vs, 1265m, 1249m, 1225m, 1122w, 1028w, 927w, 839w, 798w, 775w, 758m, 715w, 626w, 602w, 576w. [Ag4(L2)2(NO3)4](CHCl3)2 (2). The solution of AgNO3 (17 mg, 0.1 mmol) in CH3OH (10 mL) was carefully layered on top of a CHCl3/ CH3CN (10 mL/3 drops) solution of L2 (35 mg, 0.1 mmol) in a test tube. After ca. one week at room temperature, light yellow single crystals appeared at the boundary between CH3OH and CHCl3/CH3CN. Yield: 30%. Anal. Calcd. for C46H54Ag4Cl6N4O12S4: C, 33.95; H, 3.34; N, 3.44. Found: C, 33.57; H, 3.48; N, 3.63. IR (KBr pellet, cm-1): 2957m, 2924w, 2865w, 2427w, 1764w, 1523w, 1474w, 1445m, 1384Vs, 1240m, 1228m, 1121w, 1032w, 926w, 900w, 839w, 825w, 789m, 776m, 737m, 630w, 602w, 575w. [Ag4(L3)2(NO3)4] (3). The solution of AgNO3 (17 mg, 0.1 mmol) in CH3OH (10 mL) was carefully layered on top of a CHCl3/CH3CN (10 mL/3 drops) solution of L3 (38 mg, 0.1 mmol) in a test tube. After ca. 20 days at room temperature, light yellow single crystals appeared at the boundary between CH3OH and CHCl3/CH3CN. Yield: 30%. Anal. Calcd. for C48H60Ag4N4O12S4: C, 39.91; H, 4.19; N, 3.88. Found: C, 39.64; H, 4.41; N, 3.65. IR (KBr pellet, cm-1): 2956m, 2933m, 2872w, 2360m, 2341w, 1618w, 1524w, 1428Vs, 1385s, 1294s, 1231m, 1178m, 1034m, 819w, 786m, 775m, 743w, 727w, 710w, 604m. {[AgL2(CH3CN)](ClO4)}∝ (4). The solution of AgClO4 (21 mg, 0.1 mmol) in CH3OH (10 mL) was carefully layered on top of a CHCl3/ CH3CN (10 mL/3 drops) solution of L2 (35 mg, 0.1 mmol) in a test tube. After ca. 3 weeks at room temperature, light yellow single crystals appeared at the boundary between CH3OH and CHCl3/CH3CN. Yield: 35%. Anal. Calcd. for C24H29AgClNO4S2: C, 47.81; H, 4.85; N, 2.32. Found: C, 47.57; H, 4.93; N, 2.14. IR (KBr pellet, cm-1): 2957m, 2926w, 2866w, 2298w, 2267w, 1695w, 1522w, 1473w, 1444m, 1416w, 1376m, 1296w, 1229m, 1144m, 1087Vs, 927w, 900w, 788m, 769m, 736m, 624s, 600w, 575w. {[AgL4(NO3)]2(CH3CN)}∞ 5. The solution of AgNO3 (17 mg, 0.1 mmol) in CH3OH (10 mL) was carefully layered on top of a CHCl3/ CH3CN (10 mL/3 drops) solution of L4 (38 mg, 0.1 mmol) in a test tube. After ca. four weeks at room temperature, light yellow single crystals appeared at the boundary between CH3OH and CHCl3/CH3CN. Yield: 40%. Anal. Calcd. for C50H63Ag2N3O6S4: C, 52.40; H, 5.54; N, 3.67. Found: C, 52.13; H, 5.32; N, 3.45. IR (KBr pellet, cm-1):

Crystal Growth & Design, Vol. 6, No. 3, 2006 649 2962m, 1571w, 1470s, 1417Vs, 1385s, 1292s, 1221w, 1161s, 1030w, 1001w, 946w, 881m, 822w, 787w, 771m, 715m, 631m, 601w, 579w. {[AgL4](PF6)}∞ 6. The solution of AgPF6 (25 mg, 0.1 mmol) in CH3OH (10 mL) was carefully layered on top of a CHCl3/CH3CN (10 mL/3 drops) solution of L4 (38 mg, 0.1 mmol) in a test tube. After ca. 20 days at room temperature, light yellow single crystals appeared at the boundary between CH3OH and CHCl3/CH3CN. Yield: 45%. Anal. Calcd. for C24H30AgF6PS2: C, 45.36; H, 4.76. Found: C, 45.11; H, 4.87. IR (KBr pellet, cm-1): 2958m, 2898w, 1567m, 1445Vs, 1364s, 1224w, 1160s, 1004m, 946w, 880s, 833Vs, 789m, 775m, 719m, 633m, 582w, 560m, 465w, 406w. Caution! Although we have met no problems in handling AgI perchlorate during this work, it should be treated with great caution owing to their potential explosive nature. X-ray Crystallography. Single-crystal X-ray diffraction measurements for complexes 1-6 were carried out on a Bruker Smart 1000 CCD diffractometer equipped with a graphite crystal monochromator situated in the incident beam for data collection at 293(2) K. The determinations of unit cell parameters and data collections were performed with Mo-KR radiation (λ ) 0.71073 Å) and unit cell dimensions were obtained with least-squares refinements. The program SAINT12 was used for integration of the diffraction profiles. All structures were solved by direct methods using the SHELXS program of the SHELXTL package and refined with SHELXL.13 Ag atoms were found from E-maps and other non-hydrogen atoms were located in successive difference Fourier syntheses. The final refinement was performed by full matrix least-squares methods with anisotropic thermal parameters for non-hydrogen atoms on F2. The hydrogen atoms were added theoretically, riding on the concerned atoms and refined with fixed thermal factors. Crystallographic data and experimental details for structural analyses are summarized in Table 1.

Results and Discussion Tetranuclear Molecular Cages [Ag4(L1)2(NO3)4](CHCl3)2 (1), [Ag4(L2)2(NO3)4](CHCl3)2 (2), and [Ag4(L3)2(NO3)4] (3). Complexes 1-3 are obtained by the reactions of AgNO3 with L1, L2, and L3, respectively, under the same experimental conditions. X-ray diffraction analyses revealed that complexes 1-3 have discrete Ag4L2 molecular cage structures, consisting of two ligands and four metal ions. The crystal structure of 1 consists of a tetranuclear [Ag4(L1)2(NO3)4] molecule and two chloroform molecules per formula unit. Two ligands are arranged in a crossed face-to-face syn conformation to coordinate to four AgI ions from opposite directions to form tetranuclear Ag4L2 molecular cages, in which two anthracene groups are parallel to each other with a separation of approximately 5.6 Å. The [Ag4(L1)2(NO3)4] unit has no crystallographic symmetry for the ligands or the metal ions, and four crystallographic independent AgI centers exist containing two kinds of coordination geometry. The first kind of AgI center (Ag1, Ag2) adopt a distorted tetrahedron geometry coordinated by two S atoms from distinct ligands and two O atoms from one NO3-, while the second ones (Ag3, Ag4) are three-coordinated by two S atoms of distinct ligands and an O atom from NO3- showing a slightly distorted trigonal planar coordination geometry with the AgI center deviating from the coordination plane by ca. 0.06(7) (Ag3) and 0.38(2) Å (Ag4), respectively. The bond angles around the first kind of AgI center (Ag1, Ag2) range from 43.5(5) to 139.8 (9)° and those of the second AgI centers (Ag3, Ag4) range from 99.3(2) to 136.3 (8)°. The Ag-S [ranging from 2.482(2) to 2.604(3) Å] and Ag-O [ranging from 2.345(1) to 2.591(1) Å] bond lengths in 1 are in the expected range for such complexes.9c,14 The NO3anions show two kinds of coordination modes: one acts as a terminal coordination to AgI centers (Ag3, Ag4), and another adopts a chelating mode to coordinate to AgI centers (Ag1, Ag2). It is clear that the chelating nitrate anion forms two unequal Ag-O bond lengths that are evidently longer than the Ag-O

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Table 1. Crystallographic Data and Structure Refinement Summary for Complexes 1-6

chemical formula formula weight space group a/Å b/Å c/Å R/deg β/deg γ/deg V/Å3 Dc/g cm-3 Z µ/mm-1 Ra/wRb

chemical formula formula weight space group a/Å b/Å c/Å R/deg β/deg γ/deg V/Å3 Dc/g cm-3 Z µ/mm-1 Ra/wRb a

1

2

3

C42H46Ag4Cl6N4O12S4 1571.25 P1h 12.391(3) 13.088(4) 18.254(5) 73.271(4) 71.073(4) 86.599(5) 2679.8(1) 1.947 2 1.957 0.0796/0.2339

C46H54Ag4Cl6N4O12S4 1627.35 P1h 12.996(5) 13.370(5) 18.274(6) 74.182(6) 70.752(6) 88.958(6) 2875.2(2) 1.880 2 1.827 0.0598/0.1272

C48H60Ag4N4O12S4 1444.72 P4(2)/n 17.221(3) 17.221(3) 9.070(3) 90 90 90 2689.7(1) 1.784 2 1.653 0.0442/0.0880

4

5

6

C24H29AgClNO4S2 602.92 C2/c 24.126(6) 8.357(2) 27.559(7) 90 112.233(4) 90 5143(2) 1.557 8 1.080 0.0890/0.2377

C50H63Ag2N3O6S4 1146.01 P2(1)/n 11.083(1) 28.652(3) 16.311(2) 90 92.770(2) 90 5173.4(8) 1.471 4 0.968 0.0363/0.0844

C24H30AgF6PS2 635.44 P1h 10.115(4) 11.274(4) 13.293(5) 99.634(6) 97.617(5) 114.820(5) 1321.2(8) 1.597 2 1.035 0.0551/0.1212

R ) ∑(||Fo| - |Fc||)/∑|Fo|. b wR ) [∑(|Fo|2 - |Fc|2)2/∑(Fo2)]1/2.

bonds formed by the mono-coordination nitrate anion. This kind of phenomena was also observed in other AgI complexes.15 In 1, each S atom of ligands adopts a µ2-S bridging coordination mode to link two AgI ions. Thus, four AgI centers are linked by four S atoms from two distinct L1 ligands to form an eight-membered macrometallocycle, which adopts a boat conformation. In the eight-membered ring, the four AgI centers are approximately coplanar and almost form a tetragonal with side lengths (the adjacent Ag‚‚‚Ag distances) of 4.514, 4.410, 4.595, and 4.499 Å, and diagonal lengths of 6.404 and 6.305 Å, respectively. Although the L1 ligand just contains two S donors, each ligand coordinates to four AgI centers due to the µ2 coordination of the S donor. In our previous investigation on dithioether ligands,9 the dithioether ligands generally adopt syn- or transbridging coordination modes to coordinate to two AgI centers (each S donor coordinates to one AgI center). While in 1, the dithioether ligand adopts the rare tetra-coordination mode. To date, various molecular cages were synthesized by the coordination of selected metal ions with carefully chosen ligands.8f,16 Among these cage structures, the molecular cages formed by bidentate bridging ligands and metal ions usually adopt M2L3 or M2L4 modes. To the best of our knowledge, complex 1 is the first M4L2 molecular cage formed by bidentate bridging ligands and metal ions. In the fast developing field of crystal engineering and coordination polymers, special attention is paid to the pores that are often created in framework materials. In contrast, the voids formed outside and between discrete molecular architectures have sometimes been overlooked. These voids, like potential pores or channels, can easily form between such molecular species, and it is also possible to think of using such discrete large molecules as the building blocks for multidimensional network structures.3f,17 The ability of gas storage or guest transport by such structures has been demonstrated.18 In 1, such

voids exist, which contains CHCl3 guest molecules. The intermolecular π-π contacts formed between parallel anthracene rings along the c-direction (d ) 3.482(2) Å τ ) 3.10°) connect the [Ag4(L1)2(NO3)4] molecular cages into a chain, and such chains are aligned side-by-side in the ab-plane, resulting in a 3D network containing such channels (Figure 1b,c). Compound 2 has a similar Ag4L2 molecular cage structure and packing mode to that of 1. However, in contrast to the structure of 1, there is only one AgI center (Ag3) adopting trigonal planar coordination geometry, and the other three have distorted tetrahedron geometry (Figure 2). The structure of 3 also contains a Ag4L2 molecular cage similar to those of 1 and 2 (Figure 3a), but it shows higher symmetry than those of 1 and 2. In the molecular cage of 3, a C2 symmetry axis exists passing through the two centers of anthracene rings, and the coordination modes of four AgI centers are selfsame, and all of the four nitrate anions adopt a chelating coordination geometry. In addition, compound 3 also shows a different packing mode from that of 1 and 2 (Figure 3b). In 1 and 2, the packing of molecular cages adopts a head-to-head mode through intermolecular π-π contacts, while in 3, the molecular cages pack in a head-to-tail mode with the neighboring anthracene rings adopting a crossed orientation. In the three compounds described above, the three bridging ligands have the same backbone but subtle differences of the terminal groups. Since the same silver salt (AgNO3) is used in all three cases, the overall shapes of the above structures are apparently dominated by the anthracene core of each ligand. The differences of ligand terminal groups in L1, L2, and L3 do not greatly influence the structures of their complexes, and only causes subtle differences in the coordination geometry of AgI centers, the number of solvent molecules encapsulated in the space among adjacent tetranuclear units, and the packing mode of such tetranuclear units.

Molecular Cage and 1-D Coordination Architectures

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Figure 2. Molecular cage structure of 2.

Figure 1. (a) Molecular cage structure of 1, (b) the quasi 1-D chain structure formed by intermolecular π-π interactions (nitrate anions were omitted for clarity), and (c) 3-D stacking of 1 containing channels.

One-Dimensional (1-D) Complex {[AgL2(CH3CN)](ClO4)}∞ 4. When AgClO4 was used instead of AgNO3 to react with L2, a new complex 4 was formed which is composed of an extended cation chain of [AgL2(CH3CN)+]∞ (Figure 4) and ClO4-. In the cation chain, there is one crystallographic independent AgI center that adopts a slightly distorted trigonal planar coordination geometry coordinated by two S donors from distinct L2 ligands and a N donor from acetonitrile. All Ag-donor bond distances (Table 2) are within the normal range for such coordination bonds.9c,14 The AgI center deviates from the coordination plane by ca. 0.23(5) Å, and the bond angles around the AgI center range from 95.8 (4) to 158.2 (1)°. Different from 1-3, in 4, L2 ligand adopts a bidentate bridging mode to coordinate to AgI centers using two S donors to form a 1-D chain polymer along the b-direction with the intramolecular Ag‚‚‚Ag and S‚‚‚S separations of 8.357 and 7.687 Å, respectively. The aromatic rings in the chain are all parallel to each other with the adjacent interplanar distance of 5.5 Å,

Figure 3. (a) Molecular cage structure of 3, and (b) the quasi 1-D structure formed by the intermolecular π-π interactions (nitrate anions were omitted for clarity).

and the dihedral angle between the anthracene ring and the coordination plane is 30.2°. In addition, the interplanar distance between two neighboring parallel aromatic rings of the adjacent chains is ca. 3.4 Å, indicating the presence of face-to-face π-π stacking interactions which pack the 1-D chains into a doublechain architecture. In 4, all ligands adopt a trans-configuration, and this kind of coordination mode of bidentate bridging ligands favors forming a polymeric chain rather than discrete molecular aggregates.19 The structural differences of 1-3 and 4 show the influences of anions on the structures of complexes. In general, the effect of anions on the frameworks of complexes can be explained as

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Figure 4. 1-D chain cation and the double-chain motif formed by the π-π interactions in 4. Table 2. Selected Bond Lengths [Å] and Angles [°] for Complexes 1-6 Ag(1)-S(1) Ag(2)-S(2) Ag(3)-S(3) Ag(4)-S(1) S(2)-Ag(1)-S(1) S(3)-Ag(3)-S(4)

[Ag4(L1)2(NO3)4](CHCl3)2 (1) 2.554(3) Ag(1)-S(2) 2.604(3) Ag(2)-S(3) 2.482(2) Ag(3)-S(4) 2.558(2) Ag(4)-S(4) 135.3(8) S(3)-Ag(2)-S(2) 136.3(8) S(1)-Ag(4)-S(4)

2.536(3) 2.543(3) 2.563(2) 2.566(2) 139.8(9) 132.9(7)

Ag(1)-S(1) Ag(2)-S(2) Ag(3)-S(3) Ag(4)-S(1) S(1)-Ag(1)-S(2) S(3)-Ag(3)-S(4)

[Ag4(L2)2(NO3)4](CHCl3)2 (2) 2.500(2) Ag(1)-S(2) 2.537(2) Ag(2)-S(3) 2.553(2) Ag(3)-S(4) 2.578(2) Ag(4)-S(4) 143.9(6) S(2)-Ag(2)-S(3) 128.5(6) S(1)-Ag(4)-S(4)

2.532(2) 2.589(2) 2.569(2) 2.581(3) 133.1(6) 132.0(6)

Ag(1)-O(2) Ag(1)-S(1) O(2)-Ag(1)-O(1) O(1)-Ag(1)-S(1) O(1)-Ag(1)-S(1)*

[Ag4(L3)2(NO3)4] (3) 2.467(4) Ag(1)-O(1) 2.484(1) Ag(1)-S(1)a 50.3(1) O(2)-Ag(1)-S(1) 121.5(1) O(2)-Ag(1)-S(1)* 101.9(1) S(1)-Ag(1)-S(1)*

Ag(1)-N(1) Ag(1)-S(2) N(1)-Ag(1)-S(1)a S(1)a-Ag(1)-S(2)

{[AgL2(CH3CN)](ClO4)}∝ (4) 2.224(13) Ag(1)-S(1)a 2.471(3) 95.8(4) N(1)-Ag(1)-S(2) 158.2(1)

Ag(1)-O(2) Ag(1)-S(2) Ag(2)-O(4) Ag(2)-S(3) O(2)-Ag(1)-S(1) S(1)-Ag(1)-S(2) S(1)-Ag(1)-O(1) O(4)-Ag(2)-S(4) S(4)-Ag(2)-S(3)

{[AgL4(NO3)]2(CH3CN)}∞ (5) 2.450(3) Ag(1)-S(1) 2.481(8) Ag(1)-O(1) 2.381(3) Ag(2)-S(4) 2.576(8) 117.2(1) O(2)-Ag(1)-S(2) 131.6(2) O(2)-Ag(1)-O(1) 104.2(8) S(2)-Ag(1)-O(1) 136.2(7) O(4)-Ag(2)-S(3) 122.7(2)

Ag(1)-S(1) S(2)-Ag(1)-S(1) a

{[AgL4](PF6)}∞ (6) 2.416(1) Ag(1)-S(2) 154.5(5)

2.484(4) 2.569(1) 126.6(1) 87.9(1) 135.5(5) 2.445(3) 101.7(4)

2.457(8) 2.544(3) 2.508(8) 106.2(11) 49.8(6) 120.3(8) 101.0(7)

2.406(1)

Symmetry code: for 3, x - 1, y, z; for 4, x, y + 1, z.

their differences in sizes and coordination ability.8 In this contribution, NO3- anions coordinate to AgI centers in the formation of 1-3 due to its relatively strong coordination ability than that of ClO4-, while ClO4- only acts as counteranion in the formation of 4 due to its poor coordination ability. The differences of coordination abilities of anions greatly influence the coordination and linkage modes of the ligands to result in different structure complexes. It is obvious that the coordination of NO3- anions to AgI centers plays an important role in the formation of molecular cages of 1-3.

Figure 5. (a) Perspective view of 5 showing the coordination geometry of the AgI centers and (b) 1-D helical chain of 5 (nitrate anions and tertiary butyl groups were omitted for clarity).

One-Dimensional (1-D) Complex {[AgL4(NO3)]2(CH3CN)}∞ 5. The structure of complex 5 consists of neutral chains of {[AgL4(NO3)]2}∞ and acetonitrile molecules. In the neutral chain, there are two crystallographic independent AgI centers that adopt a different coordination geometry. The first kind of AgI center (Ag1) adopts a distorted tetrahedron geometry coordinated by two S atoms from distinct L4 ligands and two O atoms from one NO3-, while the second (Ag2) is threecoordinated by two S atoms of distinct L4 ligands and an O atom from NO3- showing a slightly distorted trigonal planar coordination geometry with the AgI center deviating from the coordination plane by ca. 0.04(7) Å. The bond angles around AgI centers range from 49.8(6) to 131.6(2) (Ag1) and 101.0(7) to 136.2(7)° (Ag2). All Ag-donor bond distances (Table 2) are within the range expected for such coordination bonds.9c,14 In 5, L4 ligand adopts a bidentate bridging mode (similar to that of 4) to coordinate to AgI centers using two S donors to form a spiral 1-D chain polymer extending along the c-direction with AgI atoms arranged in four parallel lines, instead of a linear motif as that in 4. Along the spiral chain, the intramolecular adjacent nonbonding Ag‚‚‚Ag distances are 10.297, 8.616, 8.106, and 8.616 Å, respectively, and all the ligands adopt a trans configuration with the two coordinated S atoms distances of 7.866, 8.101, 7.866, and 7.924 Å, respectively. In preparing 1-3 and 5, the same reaction conditions were used except for the different ligands. The structural differences of these complexes show the influences of terminal groups on the structures of complexes. In 1-3 and 5, when the terminal groups were changed from ethyl to n-propyl, then to n-butyl, only subtle differences in the coordination geometry of AgI center, the number of solvent molecules encapsulated in the space among adjacent tetranuclear units, and the packing mode of tetranuclear units resulted. When the terminal groups are changed to tert-butyl, complex 5 has a 1-D structure instead of a tetranuclear structure, probably due to the steric hindrance of the larger tert-butyl groups of L4, which prevents the formation of syn configuration when coordinating to AgI ions.

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Crystal Growth & Design, Vol. 6, No. 3, 2006 653

those found in other three or four coordination Ag-S complexes.9c,14

Figure 6. 1-D chain cation of 6.

One-Dimensional (1-D) Complex {[AgL4](PF6)}∞ 6. The reaction of L4 with AgPF6 instead of AgNO3 gave rise to a new complex 6 consisting of an extended cation chain of [(AgL4)+]∞ (Figure 6) and PF6- anions. In the cation chain, one crystallographic independent AgI center adopts approximately linear coordination geometry coordinated by two S donors from distinct L4 ligands. The Ag-S bond distances fall in the range of 2.406(1)-2.416(1) Å, which are shorter than

In 6, L4 ligand also adopts a bidentate bridging mode (similar to 4 and 5) to coordinate to AgI centers using two S donors to form a 1-D chain polymer extending along the c-direction with AgI atoms arranged in two parallel lines, which is different from that of 4 and 5. Along the cation chain, the intramolecular adjacent nonbonding Ag‚‚‚Ag distances are 7.709 and 8.515 Å, respectively. All ligands adopt a trans configuration with the two coordinated S atoms distances of 7.713 and 7.861 Å, respectively. The adjacent two aromatic rings in the chain are not parallel to each other with a dihedral angle of 41.1°. In 5 and 6, the differences in 1-D chains show the influences of anions on the structures of complexes. In the former, NO3anions coordinate to AgI centers in the formation of the complex

Figure 7. XRPD patterns of complexes 1-6: (a) for 1, (b) for 2, (c) for 3, (d) for 4, (e) for 5, and (f) for 6.

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Hu et al.

References

Figure 8. Emission spectra of 1-6 in the solid state at room temperature.

due to its relatively strong coordination ability compared to that of PF6-, while PF6- only acts as counteranion in the formation of 6. XRPD Results. To confirm the phase purity of the bulk materials, X-ray powder diffraction (XRPD) experiments have been carried out for complexes 1-6. The XRPD experimental and computer-simulated patterns of 1-6 are shown in Figure 7. Although the experimental patterns have a few un-indexed diffraction lines and some are slightly broadened in comparison with those simulated from the single-crystal models, it still can be well considered that the bulk synthesized materials and the crystals used for diffraction are homogeneous for complexes 1-6. Emission Properties. In the solid state, complexes 1-6 exhibit blue fluorescent emission at room temperature. As shown in Figure 8, the emission spectra of complexes 1-6 consist of similar broad emission bands in the visible light region that extend beyond 650 nm. The emission maxima (λmax) are 498 (1), 526 (2), 488 (3), 484 (4), 459 (5), and 449 nm (6) (λex ) 410 nm for 1, 3, 5, and 6, λex ) 403 nm for 2, λex ) 402 nm for 4, see Figure S1, Supporting Information), respectively. Compared with those of the free L1, L2, L3, and L4 ligands (see Figure S2, Supporting Information), the photoluminescence of all these complexes is ligand-based emission, and the emission bands of 1, 2, and 4 are bathochromic, while those of 3, 5, and 6 are hypsochromic in some sort. In conclusion, six new AgI coordination compounds, possessing tetranuclear molecular cages or 1-D polymer structures, based on four structure related dithioether ligands, have been prepared and structurally characterized. The structural comparison of 1-6 indicates that the terminal groups of the ligands and counteranions affect the coordination modes of AgI and structures of such complexes. In addition, these complexes also exhibit strong blue emission in the solid state at room temperature. Acknowledgment. This work was financially supported by the National Science Funds for Distinguished Young Scholars of China (No. 20225101) and the National Natural Science Foundation of China (No. 20373028). Supporting Information Available: Crystallographic information files (cif). This material is available free of charge via the Internet at http://pubs.acs.org.

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