1. pH-Dependent Assembly and Conversions of Six Cadmium(II)-Based Coordination Complexes.
- Author
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Hua-Cai Fang, Ji-Qin Zhu, Li-Jiang Zhou, Hong-Yang Jia, Shan-Shan Li, Xue Gong, Shu-Bin Li, Yue-Peng Cai, Praveen K. Thallapally, Jun Liu, and Gregory J. Exarhos
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METAL complexes , *ORGANOCADMIUM compounds , *HYDROGEN-ion concentration , *SCHIFF bases , *LIGANDS (Chemistry) , *GUAIACOL , *COMPLEX compounds synthesis , *MOLECULAR structure - Abstract
Six cadmium(II) complexes containing the N2O2donor tetradentate asymmetrical Schiff base ligand 2-{[2-(dimethylamino)ethylimino]methyl}-6-methoxyphenol (HL5), namely, [(Cd3L52Cl4)2]·CH3OH·H2O (1), [Cd(L5)Cl]2·CH3OH (2), [Cd2(HL5)Cl4]n(3), {[Cd3(H2L5)2Cl8]·2H2O}n(4), [(H2L5)2]2·[CdCl4]2â·H2O (5), and [(H2L5)2]2·[CdCl4]2â(6), have been synthesized using cadmium(II) chloride and the asymmetrical Schiff base ligand HL5under different pH conditions at room temperature. The diverse structures show the marked sensitivity of the structural chemistry of the tetradentate asymmetrical Schiff base ligand HL5. Complex 1formed at pH = 10 exhibits a rare zero-dimensional structure of trinuclear cadmium(II). At pH = 8â9, a dinuclear cadmium(II) complex 2is formed. The reaction at pH = 5â7 leads to two one-dimensional structures of 3and 4. A further decrease of the pH to 3â5 results in a zero-dimensional structure 5. Owing to the departure of lattice water molecules in the crystal, complex 5at room temperature can gradually undergo single-crystal-to-single-crystal transformation to result in complex 6.The results further show that conversions of complex 1â5can also be achieved by adjusting the pH value of the reaction solution, 1â 2pH=8â 5pH=3and 3â 4pH=5. Comparing these experimental results, it is clear that the pH plays a crucial role in the formation of the resulting structures, which simultaneously provides very effective strategies for constructing the CdIIcompounds with N2O2donor tetradentate asymmetrical Schiff base ligand. The strong fluorescent emissions of the six compounds (1â6) make them potentially useful photoactive materials. Furthermore, six Schiff base cadmium complexes (1â6), with 2,2-dipheny1-1-picrylhydrazy1 (DPPH) as a co-oxidant exhibited the stronger scavenging activity. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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