Synthesis and Characterization of Four Novel Supramolecular Compounds Based on Metal Zinc and Cadmium

Abstract

Four zinc(II) or cadmium(II) supramolecular compounds, namely, [Zn(ox)(Him)] n (1), [Zn(bta) 2 ] n (2), [Zn(H 2 O) 4 (na) 2 ] n (3), and [Cd 2 (ox)(OH) 2 ] n (4) (ox ) oxalate anion, Him ) imidazole, bta ) benzotriazole anion, and na ) nicotinic anion), have been synthesized. Among them, 1 is constructed to be a 3-D supramolecular framework by covalent and noncovalent interactions, 2 containing two bta coordination modes displays a 2-D layer structure linked by covalent bonds, the 3-D network of 3 is mainly constructed by strong hydrogen bonds, while 4 exhibits a 3-D framework with 1-D channels only constructed by covalent interactions. The different metal centers and ligand dimensions result in the different structures although they were obtained from similar reaction systems. All of these compounds display strong fluorescence emissions in the blue region, which may be assigned to charge transfer between metal and ligand (for 1, 3, and 4) and the π f π* transition of bta (for 2).

Syntheses and Characterizations of Two New Cadmium Complexes Based on Oxalate

“…Similar results are also reported in the the literature. 5 These results also suggest that subtle modification of the reactant can influence both the compositions and structures of the complexes and thereby influence the properties of the complexes.…”

“…[1][2][3][4] Oxalic acid (H 2 ox) or oxalate has been focused upon as a ligand for a long time because of its ability to bind metal centers strongly with diverse coordination modes (Scheme 1), e.g., μ 2 -, μ 3 -, μ 4 -, μ 5 -, μ 6 -bridging or bidentate chelation for metal centers. [5][6][7] These bridging coordination modes can provide both rigidity and preferred coordination specificity for metal centers, 8 and thus easily form chains or planes, thereby allowing the formation of higher dimensional structures. 6 In the reported Cd-ox complexes, most display a 3-D structure 5,[9][10][11][12] and the bridging oxalate units can be classified into two types: the in-plane bridges forming the integral layer, and the out-of-plane bridges linking the layers into a 3-D structure.…”

“…[5][6][7] These bridging coordination modes can provide both rigidity and preferred coordination specificity for metal centers, 8 and thus easily form chains or planes, thereby allowing the formation of higher dimensional structures. 6 In the reported Cd-ox complexes, most display a 3-D structure 5,[9][10][11][12] and the bridging oxalate units can be classified into two types: the in-plane bridges forming the integral layer, and the out-of-plane bridges linking the layers into a 3-D structure. 4 Furthermore, oxalate can act not only as hydrogen-bond acceptor but also as hydrogen-bond donor to form or strengthen supramolecular structures or to allow guest structures by hydrogen-bonding interactions since oxalic acid can be partially or fully deprotonated.…”

“…For example, the reaction of CdCl 2 Á2.5H 2 O, oxalic acid, imidazole, and H 2 O can give a 3-D complex [Cd 2 (ox)(OH) 2 ] n , in which imidazole is not found as the ligand or guest. 5 If Cd(Ac) 2 Á2H 2 O, oxalic acid, imidazole, butan-2-ol, and H 2 O were taken as the starting materials, the 3-D complex [Cd(C 2 O 4 ) 2 (C 3 N 2 H 4 ) 3 Single-Crystal Structure Determination. A crystal of each complex was carefully selected and attached to a thin glass fiber.…”

Construction of Three New Coordination Polymers Based on Dicarboxylate and Different Organic N-Donor Ligands

“…Thus, they may be assigned to intraligand (p-p*) fluorescent emission. The enhancement of luminescence is perhaps a result of the coordination of those ligands to a metal center, effectively increasing the rigidity and asymmetry of the ligands, thereby reducing the non-radiative decay of the intraligand (p-p*) excited state [22][23][24].…”