Structural Diversity of Six Coordination Polymers Based on the Designed X-Shaped Ligand 1,1,1,1-Tetrakis[(3-pyridiniourea)methyl]methane

Abstract

In this study, six coordination polymers (CPs), {[Ag₂(L)(CF₃SO₃)]·CF₃SO₃·2H₂O·DMF}_n (1), {[Ag(L)]·SbF₆·4DMF·H₂O}_n (2), {[Zn(L)_0.5(I)₂]·3.75H₂O}_n (3), {[Cd₂(L)(I)₄(H₂O)(DMF)]·4H₂O·3DMF}_n (4), {[Hg₂(L)(I)₄]·H₂O·4DMF}_n (5) and {[Hg₂(L)(Cl)₄]·2H₂O·3DMF}_n (6), were obtained based on the designed X-shaped urea-based ligand. X-ray single crystal diffraction analysis revealed that complex 1 displayed a 3D (3,4)-connected {6·8²}{6⁴·8²}-tcj net. Complex 2 featured a 2D 4-connected {4³·6³} sheet. Complexes 3 and 5 exhibited a 1D polymeric loop chain. Complex 4 displayed a 1D polymeric fishbone chain. Complex 6 showed a 2D 4-connected {4⁴·6²}-sql sheet. Structural comparison revealed that not only the metal ions, but also the anions played crucial roles in the control of final structures.

1. Introduction

Coordination polymers (CPs), which act as fluorescence probes, photoelectric sensors, zeolites, drug delivery systems, catalysts, molecular switches, and devices used in the chemical, industrial and medical fields, have attracted considerable attention due to their fascinating structures and potential applications [1,2,3]. Although research on their coordination chemistry is focused on building functional CPs, the design and assembly of CPs are of interest as their applications are determined by their properties, which are essentially determined by their structures [4,5].

Usually, CPs are constructed from organic ligands and inorganic metal building species under suitable conditions [6,7]. For example, 1D CPs are considered to have the least structural framework, in particular, metal coordination-based noncovalent interactions between 1D infinite chains can lead to interesting higher-dimensional architectures [8,9]. These include linear, helical, rotaxane, ladder and ribbon/tape structures, which have been successfully demonstrated in recently years [10,11]. Of these structures, tape-like or ribbon polymers are of special interest, not only due to their beautiful architecture, but also their pores or cavities which facilitate the encapsulation of guest molecules, such as in gas adsorption [12]. However, difficulties have arisen due to the need for a complementary ligand/cation pair, which is capable of offering reversible and mutually favorable interconnections. In practice, many factors such as the coordination modes of the metal ions, counter-anions, as well as steric bulk, solvent, metal−ligand ratio, and the pH of the system need to be considered [13]. Therefore, the development of new ligands with highly pre-organized and flexible coordination properties remain a challenge [14].

Recently, bis- and tris(pyridylurea)-based ligands have been proved to be both excellent anion receptors and building blocks for novel supramolecular CPs architectures [15,16]. For example, a number of metal–ligand supramolecular networks of oligo(pyridylurea)-based ligands have been investigated. In contrast, the networks based on tetrakis(pyridylurea)-based ligands which possess more coordination points and flexible chains, may lead to more fascinating and diverse ones, are still rare. It is believed that different coordination environments can be achieved by adjusting their conformation, length or inherent angle of the terminal coordinative groups [17,18].

Inspired by the abovementioned points and following our recent studies [19], we designed a novel X-shaped urea-based ligand L (Figure 1), reacted it with transition metal ions, and finally obtained the following six CPs with distinct structures: {[Ag₂(L)(CF₃SO₃)]·CF₃SO₃·2H₂O·DMF}_n (1), {[Ag(L)]·SbF₆·4DMF·H₂O}_n (2), {[Zn(L)_0.5(I)₂]·3.75H₂O}_n (3), {[Cd₂(L)(I)₄(H₂O)(DMF)]·4H₂O· 3DMF}_n (4), {[Hg₂(L)(I)₄]·H₂O·4DMF}_n (5), and {[Hg₂(L)(Cl)₄]·2H₂O·3DMF}_n (6). Most interestingly, a 1D loop chain was successfully formed by the X-shaped urea-based ligand.

2. Results and Discussion

2.1. Structural Description of {[Ag₂(L)(CF₃SO₃)₂]·2H₂O·DMF}_n (1)

Structural analysis revealed that complex 1 crystallized in the monoclinic system, space group P2₁/c. As shown in Figure 2a, the asymmetric unit consists of two crystallographically independent Ag^I ions, one L ligand, one coordinated CF₃SO₃^– anion, one free CF₃SO₃^– anion, two lattice water molecules and one free DMF solvent molecule. Ag(1) ion is tricoordinated with two N atoms (N9 and N10E) from two different L ligands, and one O atom (O9) from the coordinated CF₃SO₃^– anion, while Ag(2) ion is dicoordinated with two N atoms (N11 and N12A) from two different L ligands. In addition, the Ag-N bond lengths span the range of 2.110 Å–2.132 Å, and the Ag-O distance is 2.541 Å. In complex 1, the L ligand acts as the X-shaped bridge to connect four Ag^I ions using the pyridine N atoms, with the τ₄ parameter of the central C atom in the {CAg₄} tetrahedron = 0.44(7) with α = 152.22° and β = 144.69° (τ₄ = [360° − (α + β)]/141°; α and β are the two largest bond angles), a 2D wave [Ag2(L)]n sheet is successfully constructed with the nearest Ag···Ag distances being 9.290 Å (Ag1···Ag2) and 9.846 Å (Ag1···Ag2C, Symmetry code: C: −1 + x, y, −1 + z) (Figure 2b). It is worth noting that the neighboring [Ag₂(L)]_n sheets interacted with each other through the Ag···Ag bonds with a bond length of 3.198 Å (Ag2···Ag2B). A 3D framework (Figure 2c) was finally constructed, in which the [Ag₂(L)]_n sheets were arranged alternately. After omitting the lattice solvent molecules as well as the CF₃SO₃^– anions, the framework showed interesting porous nets with porosity of approximately 27.3%, calculated by PLATON [20].

From the viewpoint of topology, the final 3D structure can be simplified into an interesting (3,4)-connected tcj net with the Point symbol of {6·8²}{6⁴·8²} by denoting the L ligands, and the Ag^I ions as 4-connected and 3-connected nodes, respectively (Figure 2d).

2.2. Structural Description of {[Ag(L)]·SbF₆·4DMF·H₂O}_n (2)

Structural analysis revealed that complex 2 crystallized in the triclinic space group P-1. The asymmetric unit consists of one Ag^I ion, one L ligand, one free SbF₆^– anion, four free DMF molecules and one lattice water molecule (Figure 3a).

The central Ag^I ion is tetracoordinated with four N atoms from four different L ligands, leaving a distorted {AgN₄} tetrahedral geometry with a τ₄ parameter of 0.82(0). In addition, the Ag-N bond lengths span the range of 2.239 Å–2.415 Å. Different to that in complex 1, the L ligands also act as the X-shaped linkers connecting the Ag^I ions using the pyridine N atoms to form a 2D [Ag(L)]_n bilayer with the nearest Ag···Ag distances being 10.980 Å and 14.652 Å (Figure 3b). The τ₄ parameter of the central C atom in the {CAg₄} tetrahedron is 0.49(7) with α = 150.38° and β = 139.48°. Interestingly, the bilayer holds a 1D channel, with an opening area of approximately 8.914 × 12.346 Ų along the a direction, in which the free solvents fulfilled. The adjacent [Ag(L)]_n bilayer interacted with each other through hydrogen bonds, further expanding into a 3D supramolecular structure (Figure 3c). From the viewpoint of topology, the bilayer structure of complex 2 can be defined as a 4-connected sheet with the Point symbol of {4³·6³} by denoting the L ligands as well as the Ag^I ions both as 4-connected nodes (Figure 3d).

2.3. Structural Description of {[Zn(L)_0.5(I)₂]·3.75H₂O}_n (3)

Structural analysis revealed that complex 3 crystallized in the tetragonal space group I4/m. The asymmetric unit consists of one Zn^II ion, a half of L ligand, two coordinated I^– anions, and three and three-quarter lattice water molecules. As shown in Figure 4a, the central Zn^II ion is tetracoordinated with two N atoms from two different L ligands [Zn1-N1 = 2.019(7) Å, and Zn1-N1D = 2.013(4) Å] and two I^– anions [Zn1-I1 = 2.636(9) Å, and Zn1-I2 = 2.576(5) Å], leaving a distorted {ZnN₂I₂} tetrahedral geometry with a τ₄ parameter of 0.88(5).

In building complex 3, the L ligand also acts as the X-shaped linker to connect four Zn^II ions through pyridine N atoms, successfully forming a 1D [Zn(L)]_n loop chain structure with the nearest Zn···Zn distances being 14.506 Å for Zn1···Zn1C and 14.480 Å for Zn1···Zn1A (Figure 4b and Figure 4c). The τ₄ parameter of the central C atom in the {CZn₄} tetrahedron is 0.67(0) with α = β = 132.78°. In addition, the ellipsoidal loop structure contains two Zn^II ions and two half L ligands, with an opening area of 6.819 × 17.517 Ų. The neighboring loop chain structure further interacted with each other through hydrogen bonding, finally resulting in a 3D supramolecular structure (Figure 4d).

2.4. Structural Description of {[Cd₂(L)(I)₄(H₂O)(DMF)]·4H₂O·3DMF}_n (4)

When CdI₂ was used to replace ZnI₂, the obtained polymic chains changed from 1D loop chains to fishbone chains. Complex 4 crystallized in the triclinic system P-1. There are two Cd^II ions, one L ligand, four coordinated I^– anions, one coordinated DMF molecule, one coordinated water molecule, three free DMF molecules, and four lattice water molecules in the asymmetric unit. As shown in Figure 5a, the coordination environments of Cd^II ions are different to the Zn^II ion in complex 3.

Cd(1) is octacoordinated by three N atoms from three L ligands, two O atoms from coordinated DMF and water molecules, and one I^– anion, resulting in distorted {CdN₃O₂I} octahedral coordination geometry. The Cd(2) located in the distorted {CdNI₃} tetrahedral geometry, was completed by one N atom from one L ligand and three I^– anions, with a τ₄ parameter of 0.88(1). In addition, the Cd-O/N bond lengths are in the range of 2.325(5)–2.406(7) Å, and the Cd–I distances span the range of 2.727(6)–2.854(9) Å, respectively. During the formation of complex 4, each L ligand linked with three Cd1 and one Cd2 ions, resulting in a 1D [Cd₂L]_n chain, in which the two nearest Cd···Cd distances were 9.279 Å for Cd2···Cd1B and 12.092 Å for Cd1···Cd1A (Figure 5b). The other coordination sites of the Cd^II ions are occupied by the solvent molecules and I^– anions, finally resulting in a 1D fishbone polymeric chain structure (Figure 5c). The τ₄ parameter of the central C atom in the {CCd₄} tetrahedron is 0.36(0) with α = 158.18° and β = 151.07°. The adjacent fishbone chains are further expanded into the 3D supramolecular structure through hydrogen bonding (Figure 5d).

2.5. Structural Description of {[Hg₂(L)(I)₄]·H₂O·4DMF}_n (5)

Complex 5 crystallized in the monoclinic system C2/m. There are two crystallographically independent Hg^II ions, one L ligand, four I^– anions, one lattice water molecule, and four free DMF molecules in the asymmetric unit. The coordination environments of the two Hg^II ions are similar, both located in the distorted tetrahedral {HgN₂I₂} geometry, surrounded by two N atoms from two different L ligands and two I^– anions (Figure 6a). The τ₄ parameters for Hg(1) and Hg(2) are 0.76(5) and 0.81(3), respectively. Moreover, the Hg-N bond lengths are 2.402(6) Å and 2.452(6) Å, and the Hg-I distances span the range of 2.641(9)–2.650(5) Å, respectively.

In complex 5, each L ligand is linked with two Hg1 and two Hg2 ions, resulting in a 1D [Hg₂L]_n loop chain, in which the two nearest Hg···Hg distances are 14.315 Å for Hg1···Hg2 and 15.665 Å for Hg1···Hg2A (Figure 6b). In addition, the I^– anions further occupied the other coordination sites of the Hg^II ions, finally resulting in a 1D loop chain structure. The τ₄ parameter of the central C atom in the {CHg₄} tetrahedron is 0.65(5) with α = 137.49° and β = 130.21°. When the L ligand was defined as X-shaped 4-connected nodes, the loop chain structure can be simplified into a 1D chain (Figure 6c). Through hydrogen bonding, these chains can be further expanded into a 3D porous supramolecular structure, in which the solvents occupied the channels (Figure 6d).

2.6. Structural Description of {[Hg₂(L)(Cl)₄]·2H₂O·3DMF}_n (6)

X-ray single-crystal analysis revealed that complex 6 crystallized in monoclinic system, P2₁ space group and the asymmetric unit consists of two Hg^II ions, one L ligand, four Cl^– anions, two lattice water molecules, and three free DMF molecules. One half of a bimb ligand lies in the independent inversion center, and a half of lattice water molecules. As shown in Figure 7a, two Hg^II ions display similar coordination environments, completed by two N atoms from two different L ligands and two Cl^– anions, both located in the distorted tetrahedral {HgN₂Cl₂} geometry, with the τ₄ parameter for Hg(1) and Hg(2) at 0.73(6) and 0.75(8), respectively. In addition, the Hg-N bond lengths are in the range of 2.397(8)–2.449(3) Å, and the Hg-Cl distances span the range of 2.314(6)–2.330(6) Å, respectively.

In the assembly of complex 6, each L ligand is linked with two Hg1 and two Hg2 ions, resulting in a 2D [Hg₂L]_n bilayer, in which the two nearest Hg···Hg distances are 13.019 Å for Hg1···Hg2 and 14.856 Å for Hg1···Hg2B (Symmetry code: B: 1 + x, y, z) (Figure 7b). The Cl^– anions further occupied the other coordination sites of the Hg^II ions, finally resulting in a 2D sheet. The τ₄ parameter of the central C atom in the {CHg₄} tetrahedron is 0.78(1) with α = 130.11° and β = 119.71°. When the L ligand was defined as X-shaped 4-connected nodes, the bilayer can be simplified into a 2D 4-connected {4⁴·6²}-sql sheet (Figure 7c). In addition, these bilayers interacted with the adjacent bilayers through hydrogen bonding, and finally expanded into a 3D supramolecular structure (Figure 7d).

2.7. Structural Comparison

As shown in

Table 1. Detailed comparisons of complexes 1–6.

	Metal Salts	τ4 Parameter a	Average M-Ccentral (Å)	M-L Motifs	Final Structure
1	AgCF3SO3	0.44 (7)	9.310	2D [Ag2L]n sheet	3D (3,4)-connected {6·82}{64·82}-tcj net
2	AgSbF6	0.49 (7)	9.568	2D [AgL]n sheet	2D 4-connected {43·63} sheet
3	ZnI2	0.67 (0)	9.559	1D [Zn2L]n loop chain	1D polymeric loop chain
4	CdI2	0.36 (0)	8.825	1D [Cd2L]n fishbone chain	1D polymeric fishbone chain
5	HgI2	0.65 (5)	9.883	1D [Hg2L]n loop chain	1D polymeric loop chain
6	HgCl2	0.78 (1)	9.587	2D [Hg2L]n bilayer	2D 4-connected{44·62}-sql sheet

^a τ₄ parameter of the central C atom in the {CM₄} tetrahedron.

and Figure 8, although the L ligand acts as X-shaped 4-connected linkers in all six complexes, the obtained [ML_x]_n motifs are distinct from the 2D [Ag₂L]_n sheet, 2D [AgL]_n sheet, 1D [M₂L]_n loop chain, 1D [Cd₂L]_n fishbone chain, and the 2D [Hg₂L]_n bilayer, which can be mainly attributed to the flexibility of the L ligand (τ₄ parameter of the central C atom in the {CM₄} tetrahedron was introduced to indicate the degree of flexibility), the anions, and the coordination preferences of metal ions: (i) the τ₄ parameter of the central C atom of the {CM₄} tetrahedron transformed from 0.36(0) for 4 to 0.78(1) for 6, indicating that the flexible backbone of the ligand expanded directions, which are distinct when connecting the metal ions by rotating, twisting, folding, or bending; (ii) the coordination sites of the Ag^I ions can be 2 and 3 in complex 1, and 4 in complex 2, the Zn^II ions in complex 3 and Hg^II ions in complex 5/6 tend to adopt tetrahedral geometry, while the Cd^II ion was located in distorted octahedral coordination geometry in complex 4; (iii) the different anions also play important roles in determining the structural diversity, and the reaction conditions are the same except the metal salts. The anions can coordinate with the metal ions or just act as the charge balance. By comparing complexes 1/2 and 5/6, we noted that different anions also have preferences in controlling the structures. It is noteworthy that the Ag···Ag connections in complex 1 further expanded the final structure into a 3D framework. In addition, other motifs were further expanded into the 3D supramolecular structures through hydrogen bond. Overall, by adjusting the starting reaction salts, six CPs were obtained with structures ranging from a 1D polymeric fishbone chain (4), 1D polymeric loop chain (3 and 5), 2D 4-connected {4⁴·6²}-sql sheet (6), 2D 4-connected {4³·6³}sheet (2), to a 3D (3,4)-connected {6·8²}{6⁴·8²}-tcj net (1).

2.8. Powder X-ray Diffraction Analyses (PXRD)

In order to check the phase purity of these complexes, the PXRD patterns of the title series of complexes were confirmed at room temperature. As shown in Supplementary Materials Figure S1, the peak positions of the simulated and experimental PXRD patterns are in agreement with each other, demonstrating the good phase purity of the complexes. The dissimilarities in intensity may be due to the preferred orientation of the crystalline powder samples.

3. Experimental Section

3.1.Materials and Methods

All chemical reagents were obtained from commercial sources and used without further purification. IR spectra were measured on a NEXUS 670 FTIR spectrometer in the range of 400–4000 cm^–1. Elemental analyses were carried out on a CE instruments EA 1110 elemental analyzer. X–ray powder diffractions of the title series of complexes were measured on a Panalytical X–Pert pro diffractometer with Cu–Kα radiation.

3.2. Synthesis of the Ligand and Complexes

3.2.1. Design of 1,1,1,1-tetrakis[(3-pyridiniourea)methyl]methane (L)

Pentaerythrityltetramine (1 mmol, 0.132 g) was dissolved in ethanol (10 mL) and then added dropwise into a toluene solution (50 mL) of 3-isocyanatopyridine (4 mmol, 0.592 g). The mixture was refluxed for 2 h, then the resulting clear colorless mixture was slowly cooled to room temperature, the white precipitate was filtered off, washed with toluene and diethyl ether twice, and recrystallized from ethanol. The yield was 68%. Anal. (%) calcd. for C₂₉N₁₂O₄H₃₂: C, 56.85; H, 5.26; N, 27.44. Found: C, 56.63; H, 5.32; N, 27.71. IR (KBr pellet, cm⁻¹): 3337 (s), 3058 (w), 2938 (w), 1677 (s), 1546 (vs), 1519 (vs), 1481 (s), 1420 (s), 1306 (s), 1235 (s), 1142 (w), 1104 (w), 1033 (w), 869 (w), 798 (m), 705 (m), 629 (w). The¹H-NMR spectrum (Figure S1) also proved the structure. The asymmetric unit as well as the 3D packing diagram of the L·2H₂O species is given in Figure 9.

3.2.2. Preparation of {[Ag₂(L)(CF₃SO₃)]·CF₃SO₃·2H₂O·DMF}_n (1)

AgCF₃SO₃ (0.454 g, 0.4 mmol) in ethanol (20 mL) was added dropwise with stirring into a solution of L (0.226 g, 0.1 mmol) in a mixed solution of ethanol/DMF (20 mL) and stiiring was continued at room temperature for several days. Colourless block crystals suitable for X-ray diffraction studies were obtained by slow diffusion of the filtrate after 5 days. The crystals were filtered off, washed with the mother solution and diethyl ether, and dried in air to give 1 in 55% yield based on L. Anal. (%) calc. for C₃₄H₄₃Ag₂F₆N₁₃O₁₃S₂: C, 33.05; H, 3.51; N, 17.74. Found: C, 33.01; H, 3.56; N, 17.82. IR (KBr pellet, cm⁻¹): 3370 (s), 2934 (w), 1665 (s), 1603 (m), 1548 (vs), 1420(m), 1262 (vs), 1167 (m), 1104 (w), 1037 (m), 880 (w), 805 (m), 702 (m), 641(m), 573 (w), 519 (w).

3.2.3. Preparation of {[Ag(L)]·SbF₆·4DMF·H₂O}_n (2)

The same synthetic procedure as for 1 was used, except that AgCF₃SO₃ was replaced by AgSbF₆, giving colorless block crystals. The precipitate that formed was collected by filtration, and dried at room temperature to give 2 in 43% yield based on L. Anal. (%) calc. for C₇₉H₁₁₇Ag₂F₁₂N₃₁O₁₇Sb₂: C, 38.57; H, 4.79; N, 17.65. Found: C, 38.52, H, 4.83; N, 17.70. IR (KBr pellet, cm⁻¹): 3352 (s), 3085 (w), 2933 (w), 1682 (s), 1600 (m), 1546 (vs), 1420 (m), 1300 (s), 1235 (s), 1109 (w), 1037 (m), 874 (w), 805 (m), 705 (m), 629 (m).

3.2.4. Preparation of {[Zn(L)_0.5(I)₂]·3.75H₂O}_n (3)

The same synthetic procedure as for 1 was used, except that AgCF₃SO₃ was replaced by ZnI₂, giving colorless block crystals. The precipitate that formed was collected by filtration, and dried at room temperature to give 3 in 36% yield based on L. Anal. (%) calc. for C₅₈H₉₄N₂₄O₂₃Zn₄I₈: C, 25.13; H, 3.42; N, 12.13. Found: C, 24.97; H, 3.46; N, 12.17. IR (KBr pellet, cm⁻¹): 3374 (s), 3074 (w), 2938 (w), 2861 (w), 1682 (s), 1606 (s), 1557 (vs), 1503 (vs), 1486 (s), 1420 (m), 1306 (s), 1241 (s), 1104 (w), 1060 (m), 880 (w), 805 (m), 749 (m), 694 (m), 651 (m), 564 (w), 421 (w).

3.2.5. Preparation of {[Cd₂(L)(I)₄(H₂O)(DMF)]·4H₂O·3DMF}_n (4)

The same synthetic procedure as for 1 was used, except that AgCF₃SO₃ was replaced by CdI₂, giving colorless block crystals. The precipitate that formed was collected by filtration, and dried at room temperature to give 4 in 39% yield based on L. Anal. (%) calc. for C₄₁H₇₀Cd₂I₄N₁₆O₁₃: C, 28.51; H, 4.08; N, 12.97. Found: C, 28.45; H, 4.12; N, 13.02. IR (KBr pellet, cm⁻¹): 3358 (s), 3189 (m), 3129 (m), 2933 (w), 1655 (vs), 1595 (m), 1546 (vs), 1481 (s), 1420 (s), 1300 (s), 1235 (s), 1109 (m), 1055 (w), 874 (w), 809 (w), 700 (m), 667 (m), 416 (w).

3.2.6. Preparation of {[Hg₂(L)(I)₄]·H₂O·4DMF}_n (5)

The same synthetic procedure as for 1 was used, except that AgCF₃SO₃ was replaced by HgI₂, giving colorless block crystals. The precipitate that formed was collected by filtration, and dried at room temperature to give 5 in 28% yield based on L. Anal. (%) calc. for C₄₁H₆₂Hg₂I₄N₁₆O₉: C, 26.88; H, 3.41; N, 12.23. Found: C, 26.82; H, 3.45; N, 12.28. IR (KBr pellet, cm⁻¹): 3374 (s), 2933 (w), 1677 (s), 1612 (m), 1546 (vs), 1486 (m), 1420 (m), 1306 (s), 1235 (m), 1109 (w), 1050 (w), 874 (w), 804 (m), 749 (m), 694 (w), 646 (w).

3.2.7. Preparation of {[Hg₂(L)(Cl)₄]·2H₂O·3DMF}_n (6)

The same synthetic procedure as for 1 was used, except that AgCF₃SO₃ was replaced by HgCl₂, giving colorless block crystals. The precipitate that formed was collected by filtration, and dried at room temperature to give 6 in 25% yield based on L. Anal. (%) calc. For C₃₈H₅₈Cl₄Hg₂N₁₅O₉: C, 32.32; H, 4.14; N, 14.88. Found: C, 32.28; H, 4.18; N, 14.92. IR (KBr pellet, cm⁻¹): 3364 (s), 3091 (w), 2927 (w), 1666 (s), 1612 (m), 1546 (vs), 1481 (m), 1420(m), 1300 (m), 1235 (m), 1109 (w), 1050 (w), 880 (w), 804 (m), 743 (w), 700 (w), 629 (w), 416 (w).

3.3. X–ray Crystallography

Intensity data collection was carried out on a Siemens SMART diffractometer equipped with a CCD detector using Mo-Kα monochromatized radiation (λ = 0.71073 Å) at 296 (2) K. The absorption correction was based on multiple and symmetry–equivalent reflections in the data set using the SADABS program. The structures were solved by direct methods and refined by full–matrix least–squares using the SHELXTL package [20,21].

All non–hydrogen atoms were refined anisotropically. Hydrogen atoms except those on water molecules were generated geometrically with fixed isotropic thermal parameters, and included in the structure factor calculations. The hydrogen atoms attached to oxygen were refined with O-H=0.85Å and U_iso(H) = 1.2U_eq(O). Crystallographic data for complexes 1–6 are given in

Table 2. Crystal data for 1–6.

Complex	Ligand	1	2	3	4	5	6
Empirical formula	C29H36N12O6	C34H43Ag2F6N13O13S2	C79H117Ag2Sb2F12N31O17	C58H94I8N24O23Zn4	C41H70Cd2I4N16O13	C41H60Hg2I4N16O8	C38H58Cl4Hg2N15O9
Formula weight	648.70	1235.67	2460.28	2772.25	1727.53	1813.82	1411.97
Crystal system	Triclinic	Monoclinic	Triclinic	Tetragonal	Triclinic	Monoclinic	Monoclinic
Space group	P-1	P21/c	P-1	I4/m	P-1	C2/m	P21
a (Å)	8.7220(10)	18.667(3)	10.9801(8)	17.902(9)	11.842(16)	26.3943(10)	17.782(8)
b (Å)	14.1492(14)	29.678(5)	16.3332(12)	17.902(9)	16.48(2)	15.4834(6)	8.948(4)
c (Å)	14.7268(17)	8.6711(15)	17.1655(12)	15.312(16)	17.71(2)	16.8250(8)	19.152(9)
α (°)	64.258(3)	90	66.498(2)	90	101.147(17)	90	90
β (°)	77.246(3)	102.504(4)	81.929(2)	90.00	108.606(16)	123.338(2)	110.646(7)
γ (°)	72.356(6)	90	87.312(2)	90	92.633(18)	90	90
V (Å3)	1551.6(3)	4689.8(14)	2795.0(3)	4907(6)	3191(7)	5744.4(4)	2852(2)
Z	2	4	1	2	2	2	2
Dcalcd (Mg/m3)	1.388	1.750	1.462	1.876	1.798	1.759	1.644
μ (mmÿ1)	0.101	1.022	0.913	3.555	2.665	7.523	5.623
F (000)	684	2488	1248	2676	1680	2776	1382
Rint	0.0570	0.1292	0.0799	0.0479	0.0486	0.0508	0.0831
Final R indices a	0.0479 (0.1111)	0.0971 (0.1915)	0.0803 (0.2284)	0.1259 (0.2454)	0.0587 (0.1492)	0.0382 (0.1026)	0.0695 (0.1486)
R indices (all data) a	0.0802 (0.1366)	0.1999 (0.2349)	0.1363 (0.2734)	0.1427 (0.2540)	0.1172 (0.1492)	0.0453 (0.1065)	0.1624 (0.1729)
Gof	1.025	1.072	1.048	1.007	1.069	1.042	1.036

^aR₁ = Σ||F_o| − |F_c||/Σ|F_o|, wR₂ = [Σw(F_o²ÿF_c²)²]/Σw(F_o²)²]^1/2.

. Selected bond lengths and angles for 1–6 are listed in Table S1. CCDC reference numbers: 1858388 for L, 1858385 for 1, 1858386 for 2, 1858389 for 3, 1858390 for 4, 1858391 for 5, and 1858387 for 6. Topological analysis was performed by using TOPOS program [22,23,24].

4. Conclusions

In summary, based on the designed X-shaped ligand L, six CPs were obtained with the structures ranging from a 1D polymeric fishbone chain (compound 4), 1D polymeric loop chain (compounds 3 and 5), 2D 4-connected {4⁴·6²}-sql sheet (compound 6), 2D 4-connected {4³·6³}sheet (compound 2), to a 3D (3,4)-connected {6·8²}{6⁴·8²}-tcj net (compound 1). Most importantly, it should be noted that the geometric topologies of these CPs are not only controlled by the metal ions, but also by the related counter anions. Therefore, this work provides more detailed information on the development of unique CP structures in the solid state.