Structures and fluorescent properties of picolinato zinc(II) and cadmium(II) complexes based on tridentate and tetradentate benzimidazole ligands

• Published in: Journal of coordination chemistry Vol. 69; no. 24; pp. 3776 - 3791
• Main Authors: Feng, Rui, Huang, Fang-Fang, Yuan, Jia-Li, Lu, Zheng, Fang, Tao, Nie, Feng-Mei
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 16.12.2016; Taylor & Francis Ltd
• Subjects: Benzimidazole; Cadmium; cadmium(II) complex; Chains; Emission; Fluorescence; Infrared spectroscopy; Ligands; picolinic acid; Stacking; Topology; Zinc; zinc(II) complex
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2016.1238464

Five picolinato zinc(II) and cadmium(II) complexes, [Zn(ntb)(pic)]ClO 4 ·CH 3 OH·2H 2 O (1), [Zn(bbma)(pic)]NO 3 ·2CH 3 OH (2), [Cd(ntb)(pic)]ClO 4 ·0.75CH 3 OH·H 2 O (3), [Cd 2 (bbma) 2 (pic) 2 ](ClO 4 ) 2 (4), and [Cd 2 (bbp)(bbp -H )(pic) 2 (C 2 H 5 OH)]ClO 4 (5), have been synthesized, where pic is the anion of picolinic acid, ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine, and bbp is 2,6-bis(benzimidazol-2-yl)pyridine. All the complexes were characterized by X-ray single-crystal diffraction, elemental analysis, IR, fluorescence spectroscopy, and thermal gravimetric analysis. 1-3 are mononuclear complexes in which picolinate adopts a N,O-chelating mode. 4 is a symmetrical dinuclear complex bridged by two anti-parallel picolinates in a N,O,O-coordination mode. 5 is also a dinuclear complex in which only one picolinate is a bridge. A 1-D double chain is formed by extensive H-bonds and π-π stacking in 1, while single zigzag chains are formed in 5. Complexes 2-4 all exhibit 6 3 -hcb 2-D frameworks. They extend to form four-connected 6 6 -dia 3-D topological nets for 2 and 4 and five-connected 4 6 ·6 4 -bnn 3-D topological nets for 3. The five complexes show emission maxima in the blue region in the solid state.