Self-Assembly of Repeated Rhomboidal Coordination Polymers from

Oct 16, 2004 - Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan ... Thes...
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Self-Assembly of Repeated Rhomboidal Coordination Polymers from 4,4′-Dipyridyl Disulfide and ZnX2 Salts (X ) SCN, NO3, ClO4) Ryo Horikoshi and Masahiro Mikuriya*

CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 1 223-230

Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan Received March 10, 2004

ABSTRACT: 4,4′-Dipyridyl disulfide, 4pds, reacted with ZnX2 to afford M:L 1:2 one-dimensional coordination polymers [Zn(SCN)2(4pds)2‚(DMF)2]n [1‚(DMF)2], [Zn(NO3)2(4pds)2]n (2), [Zn(NO3)2(4pds)2(H2O)2‚(CH3OH)‚(H2O)]n [2(H2O)2‚(CH3OH)‚(H2O)], [Zn(NO3)2(4pds)2(H2O)‚(H2O)4]n [2(H2O)‚(H2O)4], [Zn(ClO4)2(4pds)2(DMSO)2]n [3(DMSO)2], and [Zn(ClO4)2(4pds)2(H2O)2‚(4pds)4]n [3(H2O)2‚(4pds)4]. These compounds have repeated rhomboidal structures and show a variety of guest inclusion properties without modification of the rhomboidal backbone. The clathration properties and the chirality of the products are dependent on recrystallization solvents. Compounds 1‚(DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O) have an achiral chain structure, accommodating guest molecules between the chains. Compounds 2, 2(H2O)‚(H2O)4, and 3(DMSO)2 have a chiral structure, constructed from only one enantiomer of 4pds. In 2(H2O)‚(H2O)4, each chain is linked by counteranions and guest water molecules via hydrogen bonding to construct a three-dimensional architecture. Compound 3(H2O)2‚(4pds)4 also shows a chiral chain structure, carrying free 4pds molecules via hydrogen bonds with coordination water molecules. Compound 3(DMSO)2 crystallizes in a chiral space group, while others are achiral. Introduction Crystal engineering of hybrid organic-inorganic materials such as coordination polymers has received considerable attention in recent years.1-3 Coordination polymers are constructed by combination of the organic bridging ligand “spacer” with the metal ion “node”, which affords a series of interesting networks with various shapes and sizes of cavities.4-14 Such cavities can be utilized for reservoirs and accommodate small molecules, solvent molecules, or counteranions.4-12 The spacer 4,4′-dipyridyl disulfide, 4pds, adopts a twisted structure and C-S-S-C torsion angle of ca. 90° in the solid state, which leads to a topologically interesting supramolecular assembly when combined with metal salts.15-23 In addition, the 4pds ligand shows the axial chirality with the M- and P-forms of enantiomers (Scheme 1). Because of this feature, some metal complexes of 4pds are found to contain chiral structural motifs, but no bulk chiral crystals have been obtained so far. We reported previously the synthesis and structures of 1:1, 1:2, and 4:2 M:L stoichiometry coordination polymers and 2:2 discrete macrocyclic complexes of 4pds ligand with M(hfac)2, silver(I) salts, and copper(II) carboxylates.20-23 In the previous reports, we have demonstrated that the solvent system, geometry of the metal ions, and the shape of counteranions play a crucial role in determining the assembled structures. To realize the possibility of supramolecular engineering with 4pds, we have chosen the zinc(II) salts as the node. The d10 metal ion of zinc(II) is known to produce a variety coordination environment and various types of assembled structures, when combined with appropri* To whom correspondence should be addressed. Fax: +81-79-5659077. E-mail: [email protected].

Scheme 1. Enantiomers of 4pds

ate polydentate ligands.24 Furthermore, to investigate the solvent dependence of the assembled structure of complexes with 4pds, we performed recrystallization of the products from different solvent systems. Here, we describe the synthesis and structural characterization of the M:L 1:2 one-dimensional coordination polymers [Zn(SCN)2(4pds)2‚(DMF)2]n [1‚(DMF)2], [Zn(NO3)2(4pds)2]n (2), [Zn(NO3)2(4pds)2(H2O)2‚(CH3OH)‚(H2O)]n [2(H2O)2‚ (CH3OH)‚(H2O)], [Zn(NO3)2(4pds)2(H2O)‚(H2O)4]n [2(H2O)‚ (H2O)4], [Zn(ClO4)2(4pds)2(DMSO)2]n [3(DMSO)2], and [Zn(ClO4)2(4pds)2(H2O)2‚(4pds)4]n [3(H2O)2‚(4pds)4]. These complexes show a repeated rhomboidal framework and exhibit a variety of guest clathration properties without modification of the backbone. The guest inclusion properties and the chirality of the products were dependent on the recrystallization solvents. Experimental Section General Methods. All reagents and solvents were commercially available. Infrared spectra were recorded on a JASCO MFT-2000 spectrometer as KBr pellets. Elemental analysis was performed on a ThermoFinnigan FLASH EA1112 analyzer. Thermogravimetric analysis was performed under a nitrogen atmosphere at a heating rate of 5 °C/min on a Seiko TG/DTA 220U, in the temperature range of 20-350 °C. [Zn(SCN)2(4pds)2‚H2O]n (1‚H2O). To a solution of 4pds (44 mg, 2 × 10-4 mol) in methanol (0.5 mL) was added zinc(II) thiocyanide (18 mg, 1 × 10-4 mol) in methanol (0.5 mL). A white precipitate formed immediately. The reaction mixture

10.1021/cg049909+ CCC: $30.25 © 2005 American Chemical Society Published on Web 10/16/2004

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Table 1. Crystallographic Data compd

1‚(DMF)2

2

2(H2O)2‚(CH3OH)‚(H2O)

2(H2O)‚(H2O)4

3(DMSO)2

3(H2O)2‚(4pds)4

CCDC no. empirical formula formula weight crystal size (mm) crystal system space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) V (Å3) Z Fcalcd (g cm-3) µ (mm-1) F(000) 2θ scan range R (int) total reflections unique reflections R1, wR2 [I > 2σ (I)]a goodness-of-fit on F2 max/min electron density (e Å-3)

227480 C28H30N8O2S6Zn 768.41 0.1 × 0.1 × 0.1 triclinic P1 h (no. 2) 9.208(4) 10.364(4) 10.612(4) 106.197(6) 96.058(8) 110.384(7) 888.2(6) 1 1.437 1.082 396 4.46-57.30 0.0603 3950 3252 0.0488, 0.1494 1.071 0.957/-0.686

227482 C20H16N6O6S4Zn 630.00 0.2 × 0.1 × 0.1 monoclinic P21/c (no. 14) 10.879(4) 11.961(4) 19.774(7) 90 103.901(8) 90 2497.7(15) 4 1.675 1.368 1280 3.94-57.02 0.0530 5093 2971 0.0500, 0.0799 1.023 0.647/-0.250

227481 C22H32N6O12S4Zn 766.15 0.2 × 0.1 × 0.1 monoclinic P21/n (no. 14) 9.417(2) 19.312(5) 9.750(3) 90 110.785(4) 90 1657.8(7) 2 1.535 1.058 792 4.22-56.66 0.1877 3760 2930 0.0544, 0.1469 0.966 0.831/-0.751

230279 C20H26N6O11S4Zn 720.14 0.3 × 0.3 × 0.1 orthorhombic Pbca (no. 61) 20.581(3) 10.6652(17) 26.410(4) 90 90 90 5795.0(15) 8 1.650 1.202 2959 3.08-56.66 0.0341 6688 4187 0.0323, 0.0739 0.993 0.285/-0.453

230280 C24H28Cl2N4O10S6Zn 861.13 0.7 × 0.6 × 0.3 tetragonal P4 h (no. 81) 12.979(6) 12.979(6) 10.817(7) 90 90 90 1822.2(17) 2 1.569 1.219 880 3.14-56.58 0.1363 4080 3497 0.0773, 0.2066 1.093 0.645/-0.886

230281 C60H52Cl2N12O10S12Zn 1622.23 0.5 × 0.01 × 0.01 monoclinic C2/c (no. 15) 35.962(4) 10.8546(14) 20.449(2) 90 115.208(6) 90 7222.2(14) 4 1.492 0.824 3327 3.96-56.80 0.0579 8148 4048 0.0590, 0.1351 1.010 0.307/-0.169

a

R1 ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]1/2.

was stirred for 30 min, and then, the precipitate was filtered off and washed with methanol (3 × 0.5 mL). Extraction of the precipitate with methanol followed by addition of diethyl ether afforded a white solid of 1‚H2O (33 mg, yield 52%). Anal. calcd % (found %) for 1‚H2O ) C22H18N6OS6Zn: C, 41.27 (41.20); H, 2.83 (2.83); N, 13.13 (13.57). [Zn(SCN)2(4pds)2‚(DMF)2]n [1‚(DMF)2]. Compound 1‚H2O was recrystallized from DMF to give compound 1‚(DMF)2 as colorless crystals, which were suitable for X-ray analysis. IR νKBr(cm-1): 2070 (SCN), 1674 (DMF, CdO). [Zn(NO3)2(4pds)2‚(H2O)1.5]n [2‚(H2O)1.5]. This material was prepared as described for 1‚H2O using 4pds (44 mg, 2 × 10-4 mol) and zinc(II) nitrate (30 mg, 1 × 10-4 mol), giving a white solid of 2‚(H2O)1.5; 57% yield (42 mg). Anal. calcd % (found %) for 2‚(H2O)1.5 ) C20H19N6O7.5S4Zn: C, 36.53 (36.56); H, 2.71 (2.91); N, 12.83 (12.79). IR νKBr(cm-1): 1420-1360 (NO3). X-ray quality crystals of 2 were grown by slow evaporation of a DMF solution. [Zn(NO3)2(4pds)2(H2O)2‚(CH3OH)‚(H2O)]n [2(H2O)2‚(CH3OH)‚(H2O)]. Compound 2‚(H2O)1.5 was recrystallized from methanol to give compound 2(H2O)2‚(CH3OH)‚(H2O) as colorless crystals, which were suitable for X-ray analysis. IR νKBr(cm-1): 3600-3100 (OH), 1420-1360 (NO3). [Zn(NO3)2(4pds)2(H2O)‚(H2O)4]n [2(H2O)‚(H2O)4]. Compound 2‚(H2O)1.5 was recrystallized from distilled water to give compound 2(H2O)‚(H2O)4 as transparent crystals, which were suitable for X-ray analysis. IR νKBr(cm-1): 3600-3100 (OH), 1420-1360 (NO3). [Zn(ClO4)2(4pds)2‚(CH3OH)2]n [3‚(CH3OH)2]. This material was prepared as described for 1‚H2O using 4pds (44 mg, 2 × 10-4) and zinc(II) perchlorate (37 mg, 1 × 10-4), yielding a white solid of 3‚(CH3OH)2; 72% yield (58 mg). Anal. calcd % (found %) for 3‚(CH3OH)2 ) C22H24Cl2N4O10S4Zn: C, 34.36 (34.85); H, 3.15 (3.30); N, 7.29 (7.59). IR νKBr(cm-1): 1104, 1060 (ClO4). Safety Note. Perchlorates of metal complexes with organic ligands are potentially explosive. Only small amounts of materials should be prepared, and these should be handled with great caution. [Zn(ClO4)2(4pds)2(DMSO)2]n [3(DMSO)2]. Compound 3‚ (CH3OH)2 was recrystallized from DMSO to give compound 3(DMSO)2 as transparent crystals, which were suitable for X-ray analysis. IR νKBr(cm-1): 1102, 1061, (ClO4), 1024 (DMSO, SdO). [Zn(ClO4)2(4pds)2(H2O)2‚(4pds)4]n [3(H2O)2‚(4pds)4]. Compound 3‚(CH3OH)2 was recrystallized from distilled water to give compound 3(H2O)2‚(4pds)4 as transparent crystals, which

were suitable for X-ray analysis. Anal. calcd % (found %) for 3(H2O)2‚(4pds)4 ) C60H52Cl2N12O10S12Zn: C, 44.42 (43.63); H, 3.23 (2.98); N, 10.36 (10.09). IR νKBr(cm-1): 3600-2800 (OH), 1104, 1060 (ClO4). X-ray Diffraction Studies. X-ray diffraction data for single crystals were collected on a Bruker SMART APEX CCD diffractometer equipped with a graphite crystal and incident beam monochromator using Mo KR radiation (λ ) 0.71073 Å) at 293 K. Crystal data, data collection parameters, and analysis statistics for all of the present compounds are listed in Table 1. Selected bond angles and bond lengths are given in Table 2. The frames were integrated in the Siemens SAINT+ software package,25 and the data were corrected for absorption using the SADABS program.26 The structures were solved by the direct method (SHELXL 9727) and expanded using Fourier techniques. The nonhydrogen atoms were refined anisotropically. The hydrogen atoms attached to carbon atoms were inserted at the calculated positions and allowed to ride on their respective parent atoms. The hydrogen atoms attached to oxygen atoms of 2(H2O)2‚(CH3OH)‚(H2O) could not be located, while those of 3(H2O)2‚(4pds)4 were located in the electron density maps and refined at fixed distances from the respective parent atoms. The absolute structure of 3(DMSO)2 was determined based on the Flack parameter. Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Center as supplementary publication nos. CCDC 227480 [1‚(DMF)2], CCDC 227482 (2), CCDC 227481 [2(H2O)2‚(CH3OH)‚(H2O)], CCDC 230279 [2(H2O)‚ (H2O)4], CCDC 230280 [3(DMSO)2], and CCDC 230281 [3(H2O)2‚ (4pds)4]. Copies of the data can be obtained free of charge on application to the CCDC.

Results and Discussion Synthesis and Structural Features of M:L 1:2 One-Dimensional Coordination Polymers. The general reaction scheme is listed in Scheme 2. The combinations of zinc(II) salts with 4pds produced onedimensional coordination polymers with 1:2 M:L stoichiometry, in which the zinc(II) center adopts an octahedral geometry and the 4pds ligands occupy the equatorial positions of zinc(II) ion. The products, except for 2, include solvent molecules between the chains or the apical positions of zinc(II) ion.

Repeated Rhomboidal Coordination Polymers

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Table 2. Selected Bond Lengths (Å) and Angles (deg)a

Scheme 2. General Reaction Scheme

1‚(DMF)2 Zn-N(1) 2.220(2) N(2)#2-Zn-N(3) 90.94(9) Zn-N(3) 2.084(2) N(1)-Zn-N(2)#1 93.53(8) Zn-N(2) 2.227(2) N(1)-Zn-N(3) 89.66(9) N(1)-Zn-N(1)#1 180 N(1)#1-Zn-N(2)#1 86.47(8) N(1)-Zn-N(2)#2 86.47(8) N(1)#1-Zn-N(3) 90.34(9) N(1)-Zn-N(3)#1 90.34(9) N(2)#1-Zn-N(2)#2 180 N(1)#1-Zn-N(2)#2 93.53(8) N(2)#1-Zn-N(3)#1 90.94(9) N(1)#1-Zn-N(3)#1 89.66(9) N(2)#2-Zn-N(3)#1 89.06(9) N(2)#1-Zn-N(3) 89.06(9) 2 Zn-N(1) Zn-N(3) Zn-O(1) Zn-N(2) Zn-N(4) Zn-O(4) N(1)-Zn-N(2) N(1)-Zn-N(4) N(1)-Zn-O(4) N(2)-Zn-O(1)

2.159(3) 2.146(3) 2.214(3) 2.171(3) 2.153(3) 2.191(3) 90.58(11) 89.33(12) 88.23(11) 88.08(11)

N(3)-Zn-N(4) N(3)-Zn-O(4) N(4)-Zn-O(4) N(1)-Zn-N(3) N(1)-Zn-O(1) N(2)-Zn-N(3) N(2)-Zn-O(4) N(3)-Zn-O(1) N(4)-Zn-O(1) O(1)-Zn-O(4)

91.23(12) 88.09(12) 98.25(11) 176.33(13) 98.40(11) 89.11(12) 85.74(11) 85.25(11) 87.98(11) 170.98(10)

2(H2O)2‚(CH3OH)‚(H2O) Zn-N(1) 2.257(2) N(2)#1-Zn-O(1) 91.55(10) Zn-O(1) 2.147(2) O(1)-Zn-O(1)#1 180 Zn-N(2) 2.153(2) N(1)-Zn-N(2) 90.48(9) N(1)-Zn-N(1)#1 180 N(1)-Zn-O(1) 91.01(9) N(1)-Zn-N(2)#1 89.52(9) N(1)#1-Zn-N(2) 98.52(9) N(1)-Zn-O(1)#1 88.99(9) N(1)#1-Zn-O(1) 88.99(9) N(1)#1-Zn-N(2)#1 90.48(9) N(2)-Zn-N(2)#1 180 N(1)#1-Zn-O(1)#1 91.01(9) N(2)-Zn-O(1)#1 91.55(10) N(2)-Zn-O(1) 88.45(10) N(2)#1-Zn-O(1)#1 88.45(10) Zn-N(1) Zn-N(3) Zn-O(1) Zn-N(2)#2 Zn-N(4) Zn-N(4) N(1)-Zn-N(2)#2 N(1)-Zn-N(4) N(1)-Zn-O(4) N(2)#2-Zn-N(4) N(2)#2-Zn-O(4)

2(H2O)‚(H2O)4 2.1578(15) N(3)-Zn-O(1) 2.1936(16) N(4)-Zn-O(1) 2.247(2) O(1)-Zn-O(4) 2.1899(16) N(1)-Zn-N(3) 2.1466(15) N(1)-Zn-O(1) 2.111(17) N(2)#2-Zn-N(3) 88.03(6) N(2)#2-Zn-O(1) 173.99(6) N(3)-Zn-N(4) 87.25(6) N(3)-Zn-O(4) 92.54(6) N(4)-Zn-O(4) 95.75(6)

81.80(7) 104.72(7) 168.20(8) 92.21(6) 81.28(7) 168.26(6) 86.64(7) 88.44(6) 95.99(6) 86.74(6)

3(DMSO)2 Zn-N(1) 2.172(4) N(2)-Zn-O(1)#3 89.1(2) Zn-O(1) 2.143(5) N(2)#3-Zn-O(1)#3 92.4(2) Zn-N(2) 2.185(4) N(1)-Zn-N(1)#3 92.7(2) N(1)-Zn-N(2) 88.45(16) N(1)-Zn-O(1)#3 92.1(2) N(1)-Zn-N(2)#3 175.5(2) N(1)#3-Zn-N(2) 175.5(2) N(1)-Zn-O(1) 86.5(2) N(1)#3-Zn-O(1)#3 86.5(2) N(1)#3-Zn-O(1) 92.1(2) N(2)-Zn-O(1) 92.4(2) N(1)#3-Zn-N(2)#3 88.45(16) N(2)#3-Zn-O(1) 89.1(2) N(2)-Zn-N(2)#3 90.7(2) O(1)-Zn-O(1)#3 178.0(3) 3(H2O)2‚(4pds)4 Zn-N(1) 2.171(3) N(2)#4-Zn-O(1) 91.61(11) Zn-O(1) 2.145(3) O(1)-Zn-O(1)#4 173.91(17) Zn-N(2)#4 2.180(3) N(1)-Zn-N(2)#2 88.74(10) N(1)-Zn-N(1)#4 93.59(15) N(1)-Zn-O(1) 87.99(11) N(1)-Zn-N(2)#4 177.62(11) N(1)#4-Zn-N(2)#4 88.74(10) N(1)-Zn-O(1)#4 87.84(12) N(1)#4-Zn-O(1) 87.84(12) N(1)#4-Zn-N(2)#2 177.62(11) N(2)#2-Zn-N(2)#4 88.94(15) N(1)#4-Zn-O(1)#4 87.88(11) N(2)#2-Zn-O(1)#4 91.61(11) N(2)#2-Zn-O(1) 92.74(12) N(2)#4-Zn-O(1)#4 92.74(12) a Symmetry code: #1, -x, -y, -z; #2, x, y, z; #3, -x, -y, z; #4, -x, y, -z + 1/2.

The complexation of ZnX2 (X ) SCN, NO3) with 4pds ligand produced white solids [Zn(SCN)2(4pds)2‚H2O]n (1‚H2O) and [Zn(NO3)2(4pds)2‚(H2O)1.5]n [2‚(H2O)1.5]. The white solid 1‚H2O was slightly soluble in common organic solvent, while 2‚(H2O)1.5 showed a high solubility in methanol, DMF, DMSO, and distilled water.

Recrystallizations of 1‚H2O from DMF and 2‚(H2O)1.5 from methanol produced achiral coordination polymers [Zn(SCN)2(4pds)2‚(DMF)2]n [1‚(DMF)2] and [Zn(NO3)2(4pds)2(H2O)2‚(CH3OH)‚(H2O)]n [2(H2O)2‚(CH3OH)‚(H2O)], respectively. Recrystallizations of 2‚(H2O)1.5 from DMF and distilled water gave chiral chain complexes [Zn(NO3)2(4pds)2]n (2) and [Zn(NO3)2(4pds)2(H2O)‚(H2O)4]n [2(H2O)‚ (H2O)4], respectively. The reaction of Zn(ClO4)2 and 4pds also produced [Zn(ClO4)2(4pds)2]n (3), which was isolated as a white solid 3‚(CH3OH)2. Recrystallizations of 3 from DMSO and distilled water gave a chiral chain complex [Zn(ClO4)2(4pds)2(DMSO)2]n [3(DMSO)2] and an armed chain complex [Zn(ClO4)2(4pds)2(H2O)2‚(4pds)4]n [3(H2O)2‚ (4pds)4], respectively. Although the frameworks of the products are similar to each other, three types of chain structures are observed as shown in Scheme 3. Scheme 3a,b shows achiral and chiral chain structures in this system, respectively. The achiral chain consists of both the Mand the P-forms of enantiomers of 4pds, which corresponds to 1‚(DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O). The chiral chain contains either the M- or the P-forms of enantiomers, corresponding to 2, 2(H2O)‚(H2O)4, and 3(DMSO)2. Scheme 3c shows the armed chain structure, corresponding to 3(H2O)2‚(4pds)4. Among these complexes, 3(DMSO)2 crystallizes in a chiral space group, while the others are achiral as bulk crystals. Achiral Chain Structures: [Zn(SCN)2(4pds)2‚ (DMF)2]n [1‚(DMF)2] and [Zn(NO3)2(4pds)2(H2O)2‚ (CH3OH)‚(H2O)]n [2(H2O)2‚(CH3OH)‚(H2O)]. The coordination geometries at the metal centers of 1‚(DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O) are illustrated in Figure 1a,b, respectively, and selected bond distances and angles are collected in Table 2. The zinc ions of 1‚(DMF)2 are bonded to two nitrogen atoms of thiocyanato ligands and four pyridyl nitrogen atoms of 4pds ligands, while those of 2(H2O)2‚(CH3OH)‚(H2O) are coordinated by two water molecules and four pyridyl nitrogen atoms of the 4pds ligands. The Zn-N and Zn-O distances of 1‚ (DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O) are typical values, and there are no significant departures from octahedral coordination geometry. Figure 2a,b shows the repeated rhomboidal chains of 1‚(DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O), respectively,

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Scheme 3. Schematic Illustrations of a Repeated Rhomboid (a) Achiral Chain, (b) Chiral Chain, and (c) Armed Chiral Chain

which are composed by alternated linking of one zinc(II) ion and two enantiomers of 4pds ligands. Thus, both chains are achiral, as shown in Scheme 3a. The intramolecular Zn‚‚‚Zn separation of 1‚(DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O) is similar at ca. 10.61 and 10.89 Å, respectively. The intramolecular metal‚‚‚metal separations of those are comparable to those of macrocyclic complexes [M(hfac)24pds]2‚(solvent).23 The one-dimensional chain structure of 2(H2O)2‚(CH3OH)‚(H2O) is very similar to that of [Cd(4pds)2(H2O)2]‚2NO3‚2EtOH‚ 2H2O.15 The C-S-S-C torsion angles of 86.0 and 90.6° in 1‚(DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O), respectively, are typical values.20 In 1‚(DMF)2, there are no interchain interactions, the parallel chains being interleaved by included DMF molecules, and the interchain distance of Zn‚‚‚Zn is 9.21 Å. The nearest interchain Zn‚‚‚Zn distance (9.42 Å) of 2(H2O)2‚(CH3OH)‚(H2O) is slightly longer than that of 1‚(DMF)2. The compound 2(H2O)2‚(CH3OH)‚(H2O) accommodates counteranions and guest methanol and water molecules between the rhomboidal chains. As shown in Figure 3, the guest molecules form the hydrogen bonds with the coordination water molecules and the counteranions. The hydrogen bond distances in 2(H2O)2‚(CH3OH)‚(H2O) are typical values. The infrared spectra of 1‚(DMF)2 and 2(H2O)2‚(CH3OH)‚(H2O) exhibit characteristic 4pds ligand bands at ca. 1590, 1485, 1220, 815, and 710 cm-1. Compound 1‚(DMF)2 also possesses a strong intensity band at 1672 cm-1 attributed to ν(CdO) vibrations of a guest DMF molecule. Chiral Chain Structures: [Zn(NO3)2(4pds)2]n (2), [Zn(NO3)2(4pds)2(H2O)‚(H2O)4]n [2(H2O)‚(H2O)4],

Figure 1. ORTEP representations (50% thermal provability ellipsoids) of the rhomboidal frameworks of 1‚(DMF)2 (top, a) and 2(H2O)2‚(CH3OH)‚(H2O) (bottom, b) with the numbering schemes. Hydrogen atoms are omitted for clarity.

Figure 2. Repeated rhomboidal structures of 1‚(DMF)2 (top, a) and 2(H2O)2‚(CH3OH)‚(H2O) (bottom, b). Hydrogen atoms are omitted for clarity.

[Zn(ClO4)2(4pds)2(DMSO)2]n [3(DMSO)2], and [Zn(ClO4)2(4pds)2(H2O)2‚(4pds)4]n [3(H2O)2‚(4pds)4]. An ORTEP drawing of the coordination environment around the zinc(II) ions of 2 with atomic numbering schemes is shown in Figure 4a. Selected bond distances and angles are listed in Table 2. The zinc(II) center in 2 adopts an octahedral geometry in which oxygen atoms of nitrato ligands are located on the axial positions, and

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Figure 3. O-H‚‚‚O hydrogen bonding in 2(H2O)2‚(CH3OH)‚ (H2O). Dotted lines indicate hydrogen bonds. O1(H2O)‚‚‚O6(CH3OH) ) 2.635(8) Å, O1(H2O)‚‚‚O5(H2O) ) 2.680(5) Å, and O2(NO3)‚‚‚O5(H2O) ) 2.830(5) Å.

Figure 5. Repeated rhomboidal structures of 2 (top, a), 2(H2O)‚(H2O)4 (middle, b), and 3(DMSO)2 (bottom, c). Hydrogen atoms are omitted for clarity.

Figure 4. ORTEP representations (50% thermal provability ellipsoids) of the rhomboidal frameworks of 2 (top, a), 2(H2O)‚ (H2O)4 (middle, b), and 3(DMSO)2 (bottom, c) with the numbering schemes. Hydrogen atoms are omitted for clarity.

four pyridyl nitrogen atoms of 4pds ligands are bound to the equatorial positions of the metal center. The Zn-N distances in 2 are typical at 2.159(3), 2.171(3), and 2.146(3) Å, while the Zn-O distances are 2.214(3) and 2.191(3) Å. The extended structure of 2 reveals the formation of a polar repeated rhomboid (Figure 5a), which runs along the a-axis. Each chiral chain comprises alternate linking of zinc(II) ion and two of either the M- or the P-form of

the 4pds ligands, as shown in Scheme 3b. The complex consists of a 1:1 ratio of M- or P-chains and has a centrosymmetric space group (P1 h ). The intrachain Zn‚‚‚Zn separation of 10.88 Å is longer than the interchain Zn‚‚‚Zn separation of 9.82 Å in 2. The C-S-S-C torsion angles of 2 are 87.3 and 87.1°. There are no significant interchain interactions of any note. An ORTEP drawing of 2(H2O)‚(H2O)4 showing the atom-labeling scheme is depicted in Figure 4b. The Zn ion center in 2(H2O)‚(H2O)4 adopts an octahedral geometry with coordination of four nitrogen atoms of the 4pds ligand, water molecule, and counteranion. The Zn-N distances in 2(H2O)‚(H2O)4 are also typical at 2.146(2)-2.194(2) Å, while the Zn-O(w) and ZnO(NO3) distances are 2.111(2) and 2.247(2) Å, respectively. As shown in Figure 5b, the overall chain structure of 2(H2O)‚(H2O)4 is formed by Zn(NO3)(H2O) nodes and two only of either the M- or the P-form of the 4pds ligands, which are extended along the b-axis. In addition, the chains are further bridged by counteranions and water molecules via hydrogen bonding to construct a three-dimensional network. Figure 6 shows the structure of the hydrogen-bonded sheet and Zn(NO3)(H2O) skeletons. This compound has a layered structure, composed of two-dimensional hydrogen-bonded sheets with NO3 anions and water molecules (Figure 6c), which interleaves and bridges the Zn(NO3)(H2O)(4pds)2 chains. The hydrogen bond distances in 2(H2O)‚(H2O)4 are typical values. The intrachain Zn‚‚‚Zn distance in this complex is 10.67 Å. Both C-S-S-C torsion angles of 2(H2O)‚(H2O)4 are 88.9°. The zinc(II) ions in 3(DMSO)2 are octahedral and are bonded to four pyridyl nitrogen atoms and two oxygen atoms of DMSO molecules (Figure 4c). The Zn-N distances in 3(DMSO)2 are typical at 2.172(4), and 2.185(4) Å, while the Zn-O distances are 2.143(5) Å.

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Figure 7. (a) ORTEP representations (50% thermal provability ellipsoids) of the rhomboidal frameworks of 3(H2O)2‚ (4pds)4. (b) Repeated rhomboidal structures of 3(H2O)2‚(4pds)4. Dotted lines indicate hydrogen bonds.

Figure 6. (NO3)(H2O)4 hydrogen-bonded sheet and Zn(NO3)(H2O) skeletons in 2(H2O)‚(H2O)4. 4Pds ligands are omitted for clarity. (a) Schematic illustration of the sheets and skeletons viewed along the b-axis. Gray layers indicate the (NO3)(H2O)4 hydrogen-bonded sheets. (b) Projection along the b-axis, corresponding to panel a. (c) Projection along the c-axis, showing the structure of the (NO3)(H2O)4 hydrogen-bonded sheet. Dotted lines indicate hydrogen bonds. O4(NO3)‚‚‚O10(H2O) ) 2.777(3) Å, O4(NO3)‚‚‚O9(H2O) ) 2.750(3) Å, O5(NO3)‚ ‚‚O8(H2O) ) 2.915(3) Å, O5(NO3)‚‚‚O10(H2O) ) 2.831(3) Å, O8(H2O)‚‚‚O9(H2O) ) 2.730(4) Å, O9(H2O)‚‚‚O10(H2O) ) 2.804(3) Å, O9(H2O)‚‚‚O11(H2O) ) 2.729(3) Å, and O10(H2O)‚‚‚O11 (H2O) ) 2.829(3) Å.

The crystal structure of 3(DMSO)2 involves one-dimensional repeated rhomboids, as shown in Figure 5c, and each chain is chiral. Interestingly, this complex has a chiral space group of P4 h , although the crystal consists of a 1:1 ratio of chains with opposite chirality. This space group is a noncentrosymmetric, and the chirality originates from chiral molecular arrangements in the crystal. The absolute structure was confirmed by referring to the Flack parameter [-0.01(2)]. The intrachain Zn‚‚‚Zn separation of 10.82 Å in 3(DMSO)2 is typical. The C-S-S-C torsion angle of this compound is 88.8°. The chain structures of 2, 2(H2O)‚(H2O)4, and 3(DMSO)2

are similar to those of copper derivatives [{Cu(4pds)2(H2O)}‚2NO3‚3H2O]n and [{Cu(4pds)2(SO4)}‚1.5H2O‚CH3OH]n.15 An ORTEP representation of the armed repeated rhomboid 3(H2O)2‚(4pds)4 is shown in Figure 7a. Each chain of 3(H2O)2‚(4pds)4 is chiral, but the complex has a centrosymmetric space group (C2/c) and shows no chirality. The coordination geometry around the metal center in 3(H2O)2‚(4pds)4 is almost identical to that in 2(H2O)2‚(CH3OH)‚(H2O), although the conformations of 4pds ligands are slightly different. The Zn-N distances in 3(H2O)2‚(4pds)4 are typical at 2.171(3) and 2.180(3) Å, while the Zn-O distance is 2.145(3) Å. The coordination water molecules in 3(H2O)2‚(4pds)4 form hydrogen bonds with free 4pds molecules to afford the armed repeated rhomboid, as shown in Figure 7b and Scheme 3c. The 4pds arm moieties do not bridge the chains. The arms may originate from partial dissociation of 3 in the reaction solvent. The O(1)‚‚‚N(3) and O(1)‚‚‚N(5) separations are 2.808(5) and 2.723(5) Å, which are typical values for O-H‚‚‚N hydrogen bonds. The hydrogen bonds between the metal-coordinated solvent and the pyridine derivative are demonstrated in two-dimensional coordination polymers [Mn(bpe)(NCS)2(CH3OH)2]‚ bpe [bpe ) trans-1,2-bis(4pyridyl)ethene]28 and [Fe(azpy)(NCS)2(MeOH)2]‚azpy (azpy ) 4,4′-azopyridine).29 The intrachain Zn‚‚‚Zn separation in 3(H2O)2‚(4pds)4 is 10.86 Å. The C-S-S-C torsion angle of the metallinking 4pds ligand in this compound is 90.2°, while those of free 4pds are 85.9 and 90.3°. The infrared

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Conclusion

Figure 8. TG traces of (a) 1‚(DMF)2, (b) 2(H2O)2‚(CH3OH)‚ (H2O), (c) 2, and (d) 2(H2O)‚(H2O)4.

spectra of 2, 2(H2O)‚(H2O)4, 3(DMSO)2, and 3(H2O)2‚ (4pds)4 show bands arising from the 4pds ligand and the counteranions. Thermal Properties. Figure 8a shows thermogravimetric (TG) analysis of 1‚(DMF)2, which reveals a loss of DMF molecules between 66-111 °C (18.4% weight loss observed; 19.0% calculated). This is followed by a gradual weight loss between 126 and 207 °C, corresponding to the loss of the 4pds ligand (28.4% weight loss observed; 28.6% calculated). Because there is no significant interaction between the rhomboidal chain and the DMF molecule, 1‚(DMF)2 releases the guest molecules rather easily. As shown in Figure 8b, TG analysis of 2(H2O)2‚(CH3OH)‚(H2O) shows the loss of one water molecule and one methanol molecule of crystallization in one step between 42-75 °C (6.9% weight loss observed; 7.0% calculated). This is followed by an abrupt weight loss between 149 and 221 °C corresponding to the loss of the 4pds ligand (31.3% weight loss observed; 30.7% calculated). As shown in Figure 8c, TG analysis of 2 shows a weight loss between 141 and 191 °C, which corresponds to the loss of one of the two 4pds ligands (35.8% weight loss observed; 34.9% calculated). The TG trace of 2(H2O)‚(H2O)4 is shown in Figure 8d, which displays the loss of five water molecules in one step between 30 and 92 °C (12.1% weight loss observed; 12.8% calculated), and this agrees well with the number of solvent water molecules determined by X-ray analysis. This is followed by a weight loss between 143 and 255 °C, corresponding to the loss of the ligand. These thermoanalysis results are consistent with the X-ray crystallographic data. It is interesting to note that the solvent molecules and half of the ligands in the present compounds tend to escape easily, and [ZnX2(4pds)] remains stable at higher temperatures.

The structural analysis of a series of zinc(II) complexes derived from 4pds demonstrates the ability of those compounds to accommodate solvent molecules in a variety fashions. The consequent structures are dependent on recrystallization solvents. Many of the zinc(II) complexes with pyridine derivative show a variety of coordination geometries, while the present complexes show only an octahedral geometry and exhibited the common repeated rhomboidal framework. Interestingly, the local structure of the repeated rhomboids corresponds to the macrocyclic structure found in [M(hfac)24pds]2‚(solvent), formed by two metal ions and two 4pds ligands.23 The macrocyclic moiety affords the space for guests; in [M(hfac)24pds]2‚(solvent), above and below the moiety are fitted by the solvent molecules or the trifluoromethyl group of adjacent molecules. Similarly, the guest molecules and the counteranions in the present complexes are located above and below the rhomboidal framework. The smallest guest is the water molecule in 2(H2O)‚(H2O)4, but the water molecules form a network of hydrogen bonds and can be regarded as large as a whole. These zinc(II) compounds show both achiral and chiral structures, while[M(hfac)24pds]2‚(solvent) contains only chiral macrocyclic motifs. In particular, it is noteworthy that chiral crystals were obtained for 3(DMSO)2 without any introduction of chiral guests. This complex is a rare example of chiral crystals with 4pds ligand, but it contains racemic components of 4pds. The chiral resolution of 4pds in its metal complex yet remains to be achieved. Acknowledgment. We thank Prof. T. Mochida (Toho University) for his helpful discussions. Supporting Information Available: X-ray crystallographic information files (CIF) and tables with X-ray structural information for the present compounds. This material is available free of charge via the Internet at http:// pubs.acs.org.

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