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Solid State Sciences 12 (2010) 2163e2169

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Solid State Sciences

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Three new zinc(II) complexes constructed by biphenyl-2,20,6,60-tetracarboxylicacid: Effect of solvents and terminal ligands

Lin Cheng, Shaohua Gou*, Liming ZhangSchool of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, China

a r t i c l e i n f o

Article history:Received 21 June 2010Accepted 19 September 2010Available online 8 October 2010

Keywords:Biphenyl-2,20 ,6,60-tetracarboxylic acidZinc(II) complex(6, 3) topologyTerminal ligand

* Corresponding author.E-mail address: sgou@seu.edu.cn (S. Gou).

1293-2558/$ e see front matter � 2010 Elsevier Masdoi:10.1016/j.solidstatesciences.2010.09.018

a b s t r a c t

Interaction of biphenyl-2,20 ,6,60-tetracarboxylic acid (H4bta) and Zn(II) ions in DMF led to the formationof a one-dimensional coordination polymer, while in the presence of 1,10-phenanthroline and 1H,10H-2,20-biimidazole as terminal ligands in H2O, analogous interactions induced the generation of two-dimensional layers with (6, 3) topology. The bta ligands in these three coordination polymers adopth4,m2-tetradentate, h

5,m4-pentadentate and h4,m4-tetradentate coordination modes, respectively, and thecorresponding angles of two benzene rings of bta ligands are 70.52, 83.81 and 73.35�, in accordance withthe coordination modes and steric hindrance effect of the terminal ligands.

� 2010 Elsevier Masson SAS. All rights reserved.

1. Introduction

The self-assembled construction of coordination polymers is ofcurrent interest in the field of supramolecular chemistry and crystalengineering owing to their potential applications as functionalmaterials, as well as their intriguing variety of architecturesand molecular topologies [1,2]. Polycarboxylate ligands, such as1,2-benzenedicarboxylate [3], 1,3,5-benzenetricarboxylate [4],and 1,2,4,5-benzenetetracarboxylate [5], have been extensivelyemployed in the preparation of such coordination polymers inpossession of multidimensional networks and interesting proper-ties. In contrast, the biphenyl-2,20,6,60-tetracarboxylic acid (H4bta)ligand (Scheme 1), as a member of multidentate O-donor ligands, israrely used [6]. However, its following structure features inspire ourresearch interests: (a) it has four carboxylic groups that may becompletely or partially deprotonated, upon the pH; (b) it is a flex-ible ligand, since two phenyl rings can be rotated around the CeCsingle bond; (c) the ligand can be used to construct chiral coordi-nation polymers due to the non-coplanarity of two phenyl rings.

Furthermore, it is well-known that self-assembly process ishighly affected by several factors such as the ligand’s nature,mediums, templates, metaleligand ratios, pH values, counterions,solvents and additional ligands [7]. Phen (1,10-phenanthroline) andH2biim (1H,10H-2,20-biimidazole) have been always used toconstruct new coordination polymers as the additional ligands that

son SAS. All rights reserved.

are coordinated to metal ions as terminal ligands due to theireffective p/p stacking and/or hydrogen-bonding effect.

To investigate the influence of solvents and terminal ligands[phen and H2biim] in the assembly processes of the H4bta ligandand metal ions as well as the framework structures of theircomplexes, we synthesized three zinc(II) complexes, namely, [Zn(bta)(H2NMe2)2]n (1), [Zn2(bta)(phen)2(H2O)]n (2) and {[Zn2(bta)(H2biim)2(H2O)].H2O}n (3) (H4bta¼ biphenyl-2,20,6,60-tetracarbox-ylic acid, phen¼ 1,10-phenanthroline and H2biim¼ 1H,10H-2,20-biimidazole). X-ray single-crystal diffraction study indicated that 1is a one-dimensional chain, while 2 and 3 are both two-dimen-sional layers with (6, 3) topology.

2. Experimental section

2.1. Materials and measurements

All solvents and reagents were of analytical grade and usedwithout further purification. H4bta was prepared in the samemanner as reported previously [8].

C, H and N microanalyses were performed on a PerkineElmer1400C analyzer. Infrared spectra (4000e400 cm�1) were measuredwith a Bruker Vector 22 FT-IR spectrophotometer on KBr disks.

2.2. Preparation of complexes

2.2.1. [Zn(bta)(H2NMe2)2]n (1)Amixture of H4bta (0.066 g, 0.2 mmol), Zn(NO3)2$6H2O (0.118 g,

0.4 mmol), NEt3 (0.4 mL), and DMF (10 mL) was heated in a 25-mL

Scheme 1. Structure of H4bta.

Table 2Selected bond lengths (�A) and angles (�) for complexes 1e3.

1

Zn1eO4 1.945(3) Zn1eO8 1.953(3)Zn1eO1a 1.951(3) Zn1eO5a 1.958(3)O4eZn1eO8 121.56(11) O4eZn1eO5a 111.48(11)O1aeZn1eO4 95.45(11) O1aeZn1eO8 111.79(11)

2Zn1eO1w 2.207(2) Zn1eO4 1.954(2)Zn1eN2 2.114(2) Zn1eN1 2.148(2)Zn1eO7a 2.025(2) Zn1eO8a 2.729(2)Zn2eO1 2.142(2) Zn2eN4 2.080(2)Zn2eO2 2.146(2) Zn2eO6b 1.959(2)Zn2eN3 2.113(2)O1weZn1eO4 93.24(8) O4eZn1eN1 121.55(9)

L. Cheng et al. / Solid State Sciences 12 (2010) 2163e21692164

Teflon-lined vessel at 180 �C for 3 days, followed by slow cooling(5 �C h�1) to room temperature. After filtration and washing withH2O, colorless block crystals were collected and dried in air(0.058 g, yield ca. 12% based on H4bta). Anal. Calcd (%) forC20H22N2O8Zn: C, 49.65; H, 4.58; N, 5.79. Found: C, 50.12; H, 4.25;N, 4.79. Main IR (KBr, cm�1): 3435(w), 3047(b), 2794(w), 2741(w),1657(vs), 1603(s), 1569(vs), 1470(w), 1389(m), 1353(m), 1315(m),1215(w), 1153(w), 1105(w), 1018(w), 888(w), 834(w), 787(m), 772(w), 712(m).

2.2.2. [Zn2(bta)(phen)2(H2O)]n (2)Amixture of H4bta (0.066 g, 0.2 mmol), Zn(NO3)2$6H2O (0.118 g,

0.4 mmol), NaOH (0.032 g, 0.8 mmol), phen (0.144 g, 0.8 mmol) and

Table 1Crystal and structure refinemental data for complexes 1e3.

Complex 1 2 3

Empirical formula C20H22N2O8Zn C40H24N4O9Zn2 C28H22N8O10Zn2

Formula weight 483.79 835.41 761.32Crystal system Orthorhombic Monoclinic MonoclinicSpace group Pna21 P21/c P21/ca (�A) 13.203(2) 16.0518(19) 18.622(9)b (�A) 8.9082(14) 13.2540(16) 10.582(5)c (�A) 17.077(3) 17.011(2) 15.479(7)a [�] 90 90 90b [�] 90 113.194(2) 108.839(9)g [�] 90 90 90V [�A3] 2008.5(6) 3326.6(7) 2887(2)Z 4 4 4Dcalcd, (Mg/m3) 1.600 1.668 1.752m [mm�1] 1.275 1.511 1.737F(000) 1000 1696 1544Ref. collected/unique 7536/3205

(Rint¼ 0.032)6518/496(Rint¼ 0.032)

25,723/5637(Rint¼ 0.050)

parameters 296 496 449R1a 0.0344 0.0389 0.0362wR2b 0.0891 0.1036 0.0962GOF 1.067 1.052 1.095

a R1¼PkFoj � jFck/

PjFoj.b wR2¼ [

Pw(Fo2� Fc

2)2/P

w(Fo2)2]1/2.

H2O (10 mL) was heated in a 25-mL Teflon-lined vessel at 180 �C for3 days, followed by slow cooling (5 �C h�1) to room temperature.After filtration and washing with H2O, colorless block crystals werecollected and dried in air (0.459 g, yield ca. 55% based on H4bta).Anal. Calcd. for C40H24N4O9Zn2: C, 57.50; H, 2.90; N, 6.71. Found: C,57.35; H, 3.24; N, 6.29%. Main IR (KBr, cm�1): 3419(b), 3058(w),1699(w), 1574(s), 1516(m), 1458 (w), 1424(vs), 1376(m), 1222(w),1143(w), 1101(w), 864(w), 848(m), 774(w), 728(w), 707(w).

2.2.3. {[Zn2(bta)(H2biim)2(H2O)].H2O}n (3)An analogous way to 2 was used by replacing phen with

H2biim (0.107 g, 0.8 mmol). Yield: 46% (0.319 g). Anal. Calcd. forC28H22N8O10Zn2: C, 44.17; H, 2.91; N, 14.72. Found: C, 44.59; H,3.36; N, 14.38%. Main IR (KBr, cm�1): 3399(b), 3054(w), 1569(s),1516(m), 1458(w), 1425(m), 1372(b), 1143(w), 1101(w), 848(m), 774(w), 725(m), 706(w), 639(w).

2.3. X-ray crystallography

Diffraction intensities for all the compounds were collected ona Bruker SMART CCD diffractometer (MoKa, l 0.71073�A). Absorp-tion corrections were applied by using multiscan program SADABS[9]. The structures were solved by direct methods and refined withfull-matrix least-squares technique with the SHELXTL programpackage [10]. Anisotropic thermal parameterswereapplied to all thenon-hydrogen atoms. The organic hydrogen atoms were generated

O1weZn1eN1 143.48(9) O4eZn1eN2 102.82(9)O1weZn1eN2 84.36(8) O4eZn1eO7a 99.92(9)O1weZn1eO7a 91.47(8) O4eZn1eO8a 143.80(7)O1weZn1eO8a 67.23(7) N1eZn1eN2 77.76(9)O7aeZn1eN1 92.88(8) O8aeZn1eN2 105.03(9)O8aeZn1eN1 86.93(8) O7aeZn1eO8a 53.07(8)O7aeZn1eN2 157.07(10) O1eZn2eO2 61.73(8)O1eZn2eN3 106.66(9) O6beZn2eN4 108.93(10)O1eZn2eN4 103.15(9) O2eZn2eN4 92.34(9)O1eZn2eC13 31.00(9) O2eZn2eO6b 94.75(9)O1eZn2eO6b 140.91(8) N3eZn2eN4 79.86(9)O2eZn2eN3 164.41(10) O6beZn2eN3 100.54(9)

3Zn1eO1 1.971(2) Zn1eO1w 2.204(2)Zn1eN2 2.109(3) Zn1eN1 2.134(2)Zn1eO6a 2.048(2) Zn2eO7 1.953(2)Zn2eN5 2.040(2) Zn2eO3b 1.936(2)Zn2eN6 2.048(2) O1weZn1eN1 135.20(8)O1eZn1eO1w 98.28(8) O1weZn1eN2 85.77(9)O1eZn1eN1 126.28(9) O1weZn1eO6a 87.68(8)O1eZn1eN2 104.85(9) N1eZn1eN2 79.11(9)O1eZn1eO6a 90.70(8) O6aceZn1eN1 95.37(8)O6aeZn1eN2 163.84(9) N5eZn2eN6 83.86(9)O7eZn2eN5 120.97(9) O3beZn2eN5 118.53(9)O7eZn2eN6 116.09(9) O3beZn2eN6 116.97(9)O3beZn2eO7 101.19(8)

Symmetry code for 1: a, 1/2þ x, 1/2� y, z; for 2: a, x,�1þ y, z; b,�1/2þ x, 1/2� y, z;for 3: a, 1� x, �y, �z; b, 2� x, �1/2þ y, 1/2� z.

Table 3Selected hydrogen-bond lengths (�A) and bond angles (�) of 1e3 (D, donor atom; A,acceptor atom).

DeH/A DeH [�A] H/A [�A] D/A [�A] DeH/A [�]

1N1eH1A/O4 0.80(5) 2.11(5) 2.850(4) 154(4)N1eH1B/O2j 1.10(6) 1.76(6) 2.854(5) 172(5)N2eH2B/O7c 1.04(4) 1.82(4) 2.826(5) 161(4)N2eH2C/O5o 0.90(7) 2.53(6) 3.268(4) 141(4)N2eH2C/O6o 0.90(7) 1.94(7) 2.767(4) 153(5)

2O1weH1WA/O7 0.8500 1.8800 2.723(3) 171.00.N1eH1A/O4 0.80(5) 2.11(5) 2.850(4) 154(4)N1eH1B/O2j 1.10(6) 1.76(6) 2.854(5) 172(5)N2eH2B/O7b 1.04(4) 1.82(4) 2.826(5) 161(4)N2eH2C/O5o 0.90(7) 2.53(6) 3.268(4) 141(4)N2eH2C/O6o 0.90(7) 1.94(7) 2.767(4) 153(5)

3O1weH1WA/O6 0.85 1.93 2.784(3) 180N3eH3B/O5j 0.81(4) 2.21(4) 2.909(3) 144(4)O2WeH2Wb/O2 0.8500 2.03 2.803(7) 150N4eH4B/O5j 0.83(3) 2.06(3) 2.779(3) 144(3)N7eH7A/O8f 0.86(3) 1.94(3) 2.742(4) 156(4)N8eH8A/O3f 0.80(4) 2.35(4) 2.936(4) 131(3)N8eH8A/O8f 0.80(4) 2.40(4) 3.052(3) 140(3)

Symmetry code for 1: c,�1/2þ x, 1/2� y, z; j, x, 1þ y, z; o, 1� x, 1� y, 1/2þ z; for 2:b, 1/2þ x, 1/2� y, z; j, x, 1þ y, z; o, 1� x, 1� y, 1/2þ z; for 3: f, 2� x, �y, �z; j, x,�1þ y, z.

L. Cheng et al. / Solid State Sciences 12 (2010) 2163e2169 2165

geometrically (CeH 0.96�A); the hydrogen atoms of aqua andsecondary amines were located from difference maps and refinedwith isotropic temperature factors. The crystallographic data andselectedbonds lengthandangles are listed inTables1and2. Selectedhydrogen-bond distances and bond angles are listed in Table 3.

3. Results and discussion

3.1. Synthesis and spectral characterization

1 was synthesized in DMF, while 2 and 3 were obtained withH2O via a similar way. Interestingly,1 is a one-dimensional chain, in

Fig. 1. Local coordination environments of Zn(II) ions in 1 (a), 2 (b) and 3 (c). All the hydrog�1þ y, z; b, �1/2þ x, 1/2� y, z; for 3: a, 1� x, �y, �z; b, 2� x, �1/2þ y, 1/2� z.

which H2NMe2 maybe come from the decomposition of DMF ascounterions at the high temperature under solvothermal condi-tions [11]. However, both 2 and 3 are two-dimensional layers with(6, 3) topology in the presence of additional ligands.

Infrared spectra of 1e3 displaymiddle peaks characteristic of theC]O stretching vibration of carboxylate in the 1603e1569 cm�1

region [12]. In the 1315e1516 cm�1 region, the absorption bands arein accordance with the skeletal vibrations of aromatic and hetero-cyclic rings for these complexes [12].

3.2. X-ray crystallographic studies of complexes

3.2.1. [Zn(bta)(H2NMe2)2]n (1)Single-crystal XRD study has revealed that [Zn(bta)(H2NMe2)2]

(1) crystallizes in an orthorhombic system with acentric spacegroup Pna21. The asymmetric unit of 1 contains one bta ligand, oneZn(II) ion and two in situ generated H2NMe2 cations.

Each Zn(II) ion is surrounded by four carboxylate oxygen atomsfrom two bta ligands, forming a slightly distorted tetrahedron(Fig. 1a). The average ZneO bond distance of ZnO4 tetrahedron is1.952�A, comparable with those in the Zn(II) compounds coordi-nated by four carboxylate oxygen atoms (1.949e1.962�A) [13], andthe angles of OeZneO are between 95.45(11) and 121.56(11)�. Thebta ligand acts in the h4,m2-tetradentate fashion in 1 (Fig. 2a),bridging the tetrahedral Zn(II) ions in the bischelating fashion intoa one-dimensional chain running along the crystallographic a axiswith the shortest Zn/Zn distance of 6.639�A, as shown in Fig. 3a. Itis noted that the angle of two benzene rings in a ligand is 70.52�.

Additionally, as shown in Fig. 3b, complex 1 is joined into a 3Dsupramolecular network together via NeH/O hydrogen-bonds(N1/O4 2.850(4), N1/O1j 2.854(5), N2/O7c 2.826(5) andN2/O6o2.767(4)�A, symmetrycode: j, x,1þ y, z; c,1/2þ x,1/2� y, z;o, 1� x, 1� y, 1/2þ z) between the bta anions and the free H2NMe2cations, in which each bta anion acts as four hydrogen-bondacceptorswith two coordinated and twouncoordinated carboxylateoxygen atoms, while each H2NMe2 cation serves as doublehydrogen-bond donors. Meanwhile, each bta anion is hydrogenbonded to four H2NMe2 cations, and each H2NMe2 cation links twobta anions, coming from two adjacent one-dimensional chains.

en atoms are omitted for clarity. Symmetry codes for 1: a, 1/2þ x, 1/2� y, z; for 2: a, x,

Fig. 2. Coordination modes of bta ligands observed in 1 (a), 2 (b) and 3 (c).

L. Cheng et al. / Solid State Sciences 12 (2010) 2163e21692166

3.2.2. [Zn2(bta)(phen)2(H2O)]n (2)Compound2 crystallizes in a triclinic systemof spacegroupP21/c.

The asymmetric unit of 2 contains two crystallographically inde-pendent Zn(II), one bta ligand, two phen ligands and one coordi-nated water molecule. As shown in Fig. 1b, Zn1 displays a slightlydistorted tetragonal pyramidal geometry, being surrounded by twocarboxylate oxygen atoms [Zn1eO4 1.954(2) and Zn1eO7a 2.025

Fig. 3. Structures of one-dimensional chain constructed by Zn(II) ions and h4,m2-tetrad

(2)�A, symmetry code: a, x,�1þ y, z] from two bta ligands, as well asby one chelating phen [Zn1eN1 2.148(2) and Zn1eN2 2.114(2)�A]and one water molecule [Zn1eO1w 2.207(2)�A]. Zn2 also adoptsa N2O3 geometry, being coordinated by one chelating and onemonodentate carboxylates [Zn2eO1 2.142(2), Zn2eO2 2.146(2) andZn2eO6b 1.959(2)�A, symmetry code: b, �1/2þ x, 1/2� y, z] fromtwo bta ligands, as well as one chelating phen ligand [Zn2eN3 2.113

entate bta ligands (a) and the two-dimensional supramolecular structure (b) in 1.

L. Cheng et al. / Solid State Sciences 12 (2010) 2163e2169 2167

(2) and Zn2eN4 2.080(2)�A]. On the other hand, each bta ligand iscoordinated to two Zn1 and two Zn2 atoms in a h5,m4-pentadentate(three-monodentate and one-chelating) mode (Fig. 2b). In a btaanion, the angle of two benzene rings is 83.81�.

As shown in Figs. 1b and 4a, Zn1 and Zn2 are coordinated byphen/H2O and phen, respectively, resulting in two kinds of nodes:[Zn(phen)(H2O)] and [Zn(phen)]. Two bta ligands link two [Zn(phen)(H2O)] nodes to build a binuclear [Zn2(bta)(phen)2(H2O)2]unit with the Zn1/Zn1 distance of 4.921�A, which is connected tofour adjacent units by four [Zn(phen)] nodes with four nakedcarboxylate oxygen atoms of [Zn2(bta)(phen)2(H2O)2] unit. Four Zn2atoms in the four [Zn(phen)] nodes linked by a binuclear unit arecoplanar and form a Zn4 parallelogramwith the Zn2/Zn2 distance

Fig. 4. Structures of two-dimensional laye

of 15.751 and 6.931�A, and the ZneZneZn angle of 87.04 and 92.96�,respectively. Meanwhile, two binuclear [Zn2(bta)(phen)2(H2O)2]units are joined into a [Zn8(bta)6(phen)8(H2O)4] (Zn8) metallocycleby four [Zn(phen)] nodes and twobta ligands. Each Zn8metallocycleis connected to two adjacent metallocycles by sharing their binu-clear [Zn2(bta)(phen)2(H2O)2] units and four adjacentmetallocyclesby sharing their edges, being built by one [Zn(phen)] node and twobta ligands, resulting in a two-dimensional (2D) layer along the abplane (Fig. 4a). From the topological point of view, each binuclear[Zn2(bta)(phen)2(H2O)2] unit canbe considered as a two-connectingnode,which is connectedby four bridging [Zn(phen)(H2O)] nodes astwo-connecting linkers. Consequently, the 2D network can beregarded as a (6, 3) structure, as shown in Fig. 4b.

r (a) and the (6, 3) topology (b) of 2.

Fig. 5. Two-dimensional structure of 3.

L. Cheng et al. / Solid State Sciences 12 (2010) 2163e21692168

The 2D layers are further constructed into a 3D supramolecularstructure by effective p/p stacking between the interlayer adja-cent phen rings with the centroidecentriod separation of 4.498�A.

3.2.3. {[Zn2(bta)(H2biim)2(H2O)].H2O}n (3)By replacing phen with H2biim, {[Zn2(bta)(H2biim)2(H2O)].H2O}n

(3)wasobtained.3alsocrystallizes ina triclinic systemof spacegroupP21/c consisting of two crystallographically independent Zn(II), onebta ligand, two H2biim ligands and one coordinated water molecule,aswell asone freewatermolecule in anasymmetricunit. Just like thatin 2 (Fig. 1c), Zn1 in 3 also displays a slightly distorted tetragonalpyramidal geometry, being surrounded by two carboxylate oxygenatoms [Zn1eO11.971(2) and Zn1eO6a 2.048(2)�A, symmetry code: a,1� x,�y,�z] fromtwobta ligandsandonechelatingH2biim[Zn1eN12.134(2) and Zn1eN2 2.109(3)�A], as well as one water molecule[Zn1eO1w 2.204(2)]. The bond angles are in the range of 79.11(9)e163.84(9)�. However, the coordination environment of Zn2 in 3,different from that in 2, is a slightly distorted tetrahedron, beingcoordinatedby twomonodentate carboxylates [Zn2eO71.953(2) andZn2eO3b 1.936(2)�A, symmetry code: b, 2� x,�1/2þ y,1/2� z] fromtwo bta ligands and one chelating H2biim ligand [Zn2eN5 2.040(2)and Zn2eN6 2.048(2)�A]. Meanwhile, each bta ligand in 3 is coordi-nated to two Zn1 and two Zn2 ions, the same as that in 2, but ina h4,m4-tetradentate (four-monodentate) mode, which is differentfrom that in 2, as shown in Fig. 2c. In a bta anion, the angle of twobenzene rings is 73.35�.

Though Zn2 and bta ligands in 3 have different coordinationmodes from those in 2, 3 has a similar two-dimensional structure to2, being constructed by each [Zn8(bta)6(H2biim)8(H2O)4] (Zn8)metallocycle linking six adjacent Zn8 metallocycles by sharing itstwo acmes and four edges (Fig. 5). The acme is built of binuclear[Zn2(bta)(H2biim)2(H2O)2] unit, in which the Zn1/Zn1 distance is4.720�A, a little shorter than that in 2 (4.921�A); while the edge isconstituted by one [Zn(H2biim)] node and two bta ligands. Mean-while, four Zn2 atoms in the four [Zn(H2biim)] nodes linked bya binuclear [Zn2(bta)(H2biim)2(H2O)2] unit are coplanar and forma Zn4 parallelogram with the Zn2/Zn2 distances of 18.003 and5.499�A, as well as the ZneZneZn angles of 88.27 and 91.76�. The2D network can be regarded as a (6, 3) structure, by consideringeach binuclear [Zn2(bta)(H2biim)2(H2O)2] unit and [Zn(H2biim)(H2O)] node as a two-connecting node and linker, respectively. It isnoted that there are “empty” spaces in the 2D network, which are

filled with free water molecules. These crystal water molecules arestabilized in the apertures of this 2D construction by the hydrogen-bonds, which involves the water molecules and the carboxylateoxygen atoms [O2w/O2 2.803(7)�A] from bta anions.

Additionally, complex 3 is joined into a 3D supramolecularnetwork together via N-H/O hydrogen-bonds (N3/O5j 2.909(3),N4/O5j 2.779(3), N7/O8f 2.742(4), N8/O3f 2.936(4) andN8/O8f 3.052(3)�A, symmetry code: j, x, �1þ y, z; f, 2�x, �y, �z)between bta anions and H2biim ligands. The 3D supramolecularstructure is further stabled by effective p/p stacking between theheterocycles with the centroidecentriod separation of 3.662�A.

3.3. Influences of solvents and terminal ligands on the crystalstructures

All compoundswere obtained by the interaction of H4bta and Zn(NO3)2 at 180 �C under solvothermal conditions, in which 1 wasprepared in DMF, while 2 and 3 were synthesized with phen andH2biim, respectively, in H2O.1 is a one-dimensional chain, in whichH2NMe2 maybe come from the decomposition of DMF under sol-vothermal conditions, while 2 and 3 are both two-dimensionallayers with (6, 3) topology. Meanwhile, in 2 and 3, the coordinationmodes of Zn(II) and bta ligands are different, as well as the inter-layer weak interactions are also different, in which there are H-bonding andp/p stacking interactions in 3 and onlyp/p stackinginteractions in 2, due to the effect of different terminal ligands.

Moreover, the angle between two benzene rings of bta ligandsin 1 is 70.52�, being shorter than those in 2 and 3, which may beattributed that the bischelating coordination mode of bta in 1makes the two benzene ringsmore coplanar. On the other hand, thecorresponding angle (83.81�) in 2 is larger than that (73.35�) in 3,due to the larger steric hindrance of phen than H2biim.

4. Conclusions

In this study, three new complexes with different architectures,[Zn(bta)(H2NMe2)2]n (1), [Zn2(bta)(phen)2(H2O)]n (2) and {[Zn2(bta)(H2biim)2(H2O)].H2O}n (3) were constructed from H4bta and Zn(II)ions, in which 1 is a one-dimensional chain, while 2 and 3 are bothtwo-dimensional layers with (6, 3) topology. The present studydemonstrates that solvents and the nature of terminal ligands aresuggested to be crucial factors for the formation of the structures.

L. Cheng et al. / Solid State Sciences 12 (2010) 2163e2169 2169

Acknowledgements

The authors are grateful to the financial support from NationalNatural Science of Foundation of China (project No. 20801011) andthe Foundation of Southeast University (No. 9207040016).

Appendix A. Supplementary material

CCDC reference numbers 779825e779827 contain the supple-mentary crystallographic data for this paper. These data can beobtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre, 12,Union Road, Cambridge CB2 1EZ, UK; Fax: (internat.) þ44 1223/336033; E-mail: deposit@ccdc.cam.ac.uk].

Supplementary data associated with this article can be found, inthe online version, at doi:10.1016/j.solidstatesciences.2010.09.018.

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