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The spontaneous self-assembly reactions of 2,3,5,6-tetrafluorobenzenedicarboxylic acid (H2BDC-F4) with Ca(NO3)2·4H2O in different solvents resulted in the generation of hydrophilic 3D chiral and achiral Ca(II)–organic frameworks {[Ca4(BDC-F4)4(H2O)4]·4H2O}n (1) and [Ca(BDC-F4)(MeOH)2]n (2), respectively. Complex 1 exhibits higher water solubility compared to 2, and further dissolution of 1 in water results in a new achiral crystal, [Ca(BDC-F4)(H2O)4]n (3). All complexes have been characterized by elemental analysis, IR spectroscopy, and single-crystal and powder X-ray diffraction techniques. Complex 1 crystallizes in the tetragonal P41212 chiral space group and features a rare binodal 5-connected network, directed by a unique 3D chiral (10,3)-a water aggregation consisting of two distinct helical arrays. Complex 2 crystallizes in the space group C2/c and has a binodal 4-connected pts net. Complex 3 crystallizes in the space group P21/m and presents a 2D layer framework containing the unprecedented polymeric [CaII–H2O]n chain based on triple μ2-O aqua bridges. The structural discrepancies illustrate the solvent-induced effect on the construction and structural transformation of chiral and achiral coordination frameworks. Moreover, gas (N2 and CO2) adsorption studies show that the dehydrated framework 1a exhibits excellent selective CO2 gas uptake at 195 K.

A series of CdII coordination polymers have been designed and hydrothermally synthesized by using a bent dipyridyl tecton 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and R-isophthalic acids (H2ip-R; R = –H, –CH3, –OCH3, –tBu, –OH, and –NO2), which exhibit diverse 1D and 2D polymeric coordination networks. The results demonstrate that the substituent effect of R-isophthalates does play a decisive role in directing the structural assemblies of this system, in which secondary interactions such as H-bonding and π⋯π stacking are generally observed to extend the coordination motifs. Notably, the 3-bpo building block shows adaptable conformations (cisoid-I, cisoid-II, and transoid) to facilitate the structural diversity of these complexes. Solid state properties such as thermal stability and fluorescence for these crystalline materials will also be presented.

A new family of ZnII and CdII coordination complexes 1–8 with a multifunctional building block trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene (bpe) have been prepared at ambient conditions in water–methanol solution, by varying the auxiliary benzenedicarboxyl co-ligands from the familiar isophthalic acid (H2ip) and terephthalic acid (H2tp) to their derivatives 5-hydroxylisophthalic acid (H2hip) and tetrabromo-terephthalic acid (H2tbta). Single-crystal X-ray diffraction indicates that these complexes display a variety of coordination motifs, from the discrete mononuclear species (8) to infinite 1-D (1 and 7), 2-D (3, 5, and 6), and 3-D (2 and 4) metal–organic networks. Furthermore, extended supramolecular architectures are constructed for these complexes via predictable secondary interactions such as hydrogen bonding and aromatic stacking. A comprehensive structural analysis and comparison of 1–8 reveals that their crystalline lattices can be properly regulated by a selection of different metal ions (ZnII or CdII) and benzenedicarboxyl co-ligands, as well as the versatile building functionality of the bpe tecton , which can be readily involved in both coordination and secondary interactions. Notably, this work first demonstrates that bpe can also be applied as an angular bridging spacer by using both the 4- and 2-pyridyl groups to construct novel CdII coordination frameworks.

Nine 5-methylnicotinate (L–CH3−) coordination complexes, namely, {[Ni(L–CH3)2(H2O)2](H2O)}n (1), [Ni2(L–CH3)4(H2O)]n (2), Ni(HL–CH3)2Cl2 (3), [Cd2(L–CH3)2(SO4)(H2O)6]n (4), [Cd(L–CH3)2(H2O)]n (5), {[Cu(L–CH3)2(H2O)2](H2O)}n (6), {[Co(L–CH3)2(H2O)2](H2O)}n (7), [Mn(L–CH3)2(H2O)2]n (8), and [Pb(L–CH3)2]n (9), were synthesized with different metal salts. For complexes 1–3, the use of different NiII salts (SO42−, OAc−, or Cl−) leads to three distinct coordination motifs, including a 3D lvt framework, a 3D self-interpenetrating (3·4·5)(32·43·53·6·74·82) network, and a mononuclear species, respectively. For CdII, two different 1D chain complexes can be assembled from HL–CH3 with CdSO4 (4) and Cd(OAc)2 or CdCl2 (5). However, such an anion effect has not been observed for the CuII (6), CoII (7), MnII (8), and PbII (9) complexes, which show a 3D lvt network for 6 and 7, a 2D (4,4) layer for 8, and a 3D (3,5)-connected (4·62)(4·67·82) network for 9. These results demonstrate that the diverse coordination motifs for 1–9 (from 0D, 1D, 2D, to 3D) can be effectively adjusted by the metal-ligating tendency and metal-dependent counter-anion effect. Thermal stability and solid-state fluorescence have also been investigated.

Seven CdII coordination polymers have been prepared from CdCl2 and 5-halonicotinic acids (HL–X, X = F or Cl) in different solvent media using a similar layered diffusion method. A pair of polymorphic isomers [Cd(L–F)2]n (1 and 2) can be assembled from CH3CN–H2O and CH3OH–H2O systems, respectively, featuring the 3-D (3,5)-connected (4·62)(4·67·82) network (5-connected node for each CdII ion and 2- or 3-connected linker for the two different types of L–F− ligand) and the 3-D (3,6)-connected ant framework with the point symbol of (4·62)2(44·62·88·10). While in DMF–H2O solvent, a 2-D layered complex [Cd(L–F)Cl(DMF)]n (3) is obtained with the (3,5)-connected net of (3·4·5)(32·4·5·62·74) topology, where the chloride anion is involved in coordination. When the HL–Cl ligand is utilized instead of HL–F, the assembling reactions in CH3CN–H2O and DMF–H2O media lead to the 3-D (3,5)-connected network of [Cd(L–Cl)2]n (4) and the 2-D (3,5)-connected net of [Cd(L–Cl)Cl(DMF)]n (6), which are isostructural to complexes 1 and 3, respectively. [Cd(L–Cl)2(H2O)2]n (5) can be generated from the CH3OH–H2O medium, showing a 2-D (4,4) layered structure, and the similar reaction in the C2H5OH–H2O solvent will produce a 3-D coordination framework {[Cd(L–Cl)2(H2O)0.5](C2H5OH)0.75(H2O)0.25}n (7) with the (3,6)-connected (3·4·5)(32·44·55·62·72) net. These structural divergences can be ascribed to the significant solvent modulation and halogen-substituting effect of 5-halonicotinates. Furthermore, their solid-state properties such as thermal stability and fluorescence have also been investigated.

A series of mixed-ligand coordination complexes have been prepared using diffusion method, by reacting the CoII, NiII, ZnII, AgI, CdII, CuII, or PbII nitrate with tetrabromoterephthalic acid (H2tbta) and 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo). These complexes show various 0D, 1D, 2D, and 3D coordination motifs with different geometries of the metal centers, indicating a metal-directed assembly. The synthetic condition will also affect the resulting crystalline products for ZnII species. Crystal structure analysis reveals that secondary interactions such as hydrogen bonding and aromatic stacking will further extend the coordination arrays to diverse supramolecular architectures. All complexes have been characterized by IR, elemental analysis, and powder X-ray diffraction techniques. In addition, the polymeric coordination systems with d10 metal centers show solid-state fluorescent emissions at room temperature, which thus may be applied as potential hybrid luminescent materials.

This work presents a systematic investigation on coordination chemistry of a pharmaceutical agent pamoic acid (H2PA), and also reveals the significant function of supramolecular interactions in managing the resultant crystalline networks with the incorporation of secondary co-ligands. Assemblies of pamoic acid with transition metal ions under similar conditions yield a series of eleven MnII, CuII, ZnII, and CdII complexes, in the absence/presence of the organonitrogen ligands such as 2,2′-bipyridyl (2,2′-bipy), 1,10-phenanthroline (phen), and 4,4′-bipyridyl (4,4′-bipy). These compounds, together with the DMF solvate of pamoic acid, have been characterized by IR, elemental analysis, and single-crystal X-ray diffraction techniques. Generally, these complexes display similar 1-D pamoate-bridged coordination arrays (or 2-D coordination layers by introducing bridging 4,4′-bipy). Remarkably, distinct extended network architectures are further constructed with the aid of weak secondary interactions especially aromatic stacking. Amongst them, complexes 6, 8, 9, and 12, which exhibit unusual interpenetrating networks of (6,3) layers or 3-D 5-connected frameworks regulated by stacking forces, are representative paradigms of this research. Structural evolution under the co-ligand intervention in this series of complexes, as well as the general coordination rule of pamoate, has been further discussed. Thermal stability of these crystalline materials and fluorescent properties of the polymeric ZnII and CdII complexes have also been explored.

A series of new polymeric network complexes [M(bpe)2(SCN)2(CH3OH)(H2O)] (M = CoII for 1 and NiII for 2), [Cu(bpe)2(SCN)2(CH3OH)]2[Cu(bpe)2(SCN)2] (3), [Cu(bpe)2(SCN)2(H2O)]2− [Cu(bpe)2(SCN)2] (4), [Fe(bpe)2(SCN)2(H2O)2] (5) and [Pb(bpe)(SCN)2]n (6) have been designed and prepared from solution assembly of trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene (bpe) and metal thiocyanate at room temperature. X-Ray single-crystal structural determination reveals that the 3-D crystal packing of these complexes is mastered by the interplay of coordinative and secondary non-covalent interactions. The hierarchical regulated strategy in metal–organic supramolecular chemistry is successfully utilized in the rational construction of these architectures, which are, interestingly, influenced by the variation of the concerned assembled elements such as metal ion and solvent medium. The coordination chemistry of thiocyanate ion, especially with PbII, is also summarized.