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

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.


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  (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].

Structural Description of {[Ag2(L)(CF3SO3)2]·2H2O·DMF}n
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 {6·8 2 }{6 4 ·8 2 } by denoting the L ligands, and the Ag1 ions as 4-connected and 3-connected nodes, respectively (Figure 2d). Structural analysis revealed that complex 1 crystallized in the monoclinic system, space group P2 1 /c. As shown in Figure 2a, the asymmetric unit consists of two crystallographically independent Ag I ions, one L ligand, one coordinated CF 3 SO 3 anion, one free CF 3 SO 3 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 CF 3 SO 3 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 τ 4 parameter of the central C atom in the {CAg 4 } tetrahedron = 0.44 (7) with α = 152.22 • and β = 144.69 • (τ 4 = [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 [Ag 2 (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 [Ag 2 (L)] n sheets were arranged alternately. After omitting the lattice solvent molecules as well as the CF 3 SO 3 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 {6·8 2 }{6 4 ·8 2 } by denoting the L ligands, and the Ag I ions as 4-connected and 3-connected nodes, respectively (Figure 2d).

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).
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 SbF 6 anion, four free DMF molecules and one lattice water molecule (Figure 3a).

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 {AgN 4 } tetrahedral geometry with a τ 4 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 τ 4 parameter of the central C atom in the {CAg 4 } 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 Å 2 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 {4 3 ·6 3 } by denoting the L ligands as well as the Ag I ions both as 4-connected nodes ( Figure 3d). 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 Ianions, 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 Ianions [Zn1-I1 = 2.636(9) Å, and Zn1-I2 = 2.576(5) Å], leaving a distorted {ZnN 2 I 2 } tetrahedral geometry with a τ 4 parameter of 0.88 (5). 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 Å 2 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 {4 3 ·6 3 } by denoting the L ligands as well as the Ag I ions both as 4-connected nodes ( Figure 3d).

Structural Description of {[Cd
When CdI 2 was used to replace ZnI 2 , 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 Ianions, 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. 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 Å 2 . The neighboring loop chain structure further interacted with each other through hydrogen bonding, finally resulting in a 3D supramolecular structure (Figure 4d). (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 Ianions, 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 Ianion, resulting in distorted {CdN3O2I} octahedral Complex 5 crystallized in the monoclinic system C2/m. There are two crystallographically independent Hg II ions, one L ligand, four Ianions, 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 {HgN 2 I 2 } geometry, surrounded by two N atoms from two different L ligands and two Ianions ( Figure 6a). The τ 4 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.

Structural Description of {[Cd2(L)(I)4(H2O)(DMF)]·4H2O·3DMF}n
In complex 5, each L ligand is linked with two Hg1 and two Hg2 ions, resulting in a 1D [Hg 2 L] 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 Ianions further occupied the other coordination sites of the Hg II ions, finally resulting in a 1D loop chain structure. The τ 4 parameter of the central C atom in the {CHg 4 } 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).  (5) Complex 5 crystallized in the monoclinic system C2/m. There are two crystallographically independent Hg II ions, one L ligand, four Ianions, 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 Ianions (Figure 6a). The τ4 parameters for Hg(1) and Hg (2) (Figure 6b). In addition, the Ianions 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).

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 Clanions, 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 Clanions, 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  X-ray single-crystal analysis revealed that complex 6 crystallized in monoclinic system, P2 1 space group and the asymmetric unit consists of two Hg II ions, one L ligand, four Clanions, 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 Clanions, both located in the distorted tetrahedral {HgN 2 Cl 2 } geometry, with the τ 4 parameter for Hg(1) and Hg (2)  In the assembly of complex 6, each L ligand is linked with two Hg1 and two Hg2 ions, resulting in a 2D [Hg 2 L] 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 Clanions further occupied the other coordination sites of the Hg II ions, finally resulting in a 2D sheet. The τ 4 parameter of the central C atom in the {CHg 4 } 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 {4 4 ·6 2 }-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). 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 Clanions 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 {4 4 ·6 2 }-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).

Structural Comparison
As shown in Table 1  (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 {4 4 ·6 2 }-sql sheet (6), 2D 4-connected {4 3 ·6 3 }sheet (2), to a 3D (3,4)-connected {6·8 2 }{6 4 ·8 2 }-tcj net (1).

Structural Comparison
As shown in Table 1  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 {4 4 ·6 2 }-sql sheet (6), 2D 4-connected {4 3 ·6 3 }sheet (2), to a 3D (3,4)-connected {6·8 2 }{6 4 ·8 2 }-tcj net (1).

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.

3.1.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.

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.

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.

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.  Figure S1) also proved the structure. The asymmetric unit as well as the 3D packing diagram of the L·2H 2 O species is given in Figure 9.

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.  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.

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. 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. The same synthetic procedure as for 1 was used, except that AgCF 3 SO 3 was replaced by AgSbF 6 , 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. The same synthetic procedure as for 1 was used, except that AgCF 3 SO 3 was replaced by ZnI 2 , 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.

Preparation of {[Cd 2 (L)(I) 4 (H 2 O)(DMF)]·4H 2 O·3DMF} n (4)
The same synthetic procedure as for 1 was used, except that AgCF 3 SO 3 was replaced by CdI 2 , 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. The same synthetic procedure as for 1 was used, except that AgCF 3 SO 3 was replaced by HgI 2 , 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.  (6) The same synthetic procedure as for 1 was used, except that AgCF 3 SO 3 was replaced by HgCl 2 , 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.

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. 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].

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 {4 4 ·6 2 }-sql sheet (compound 6), 2D 4-connected {4 3 ·6 3 }sheet (compound 2), to a 3D (3,4)-connected {6·8 2 }{6 4 ·8 2 }-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.