Synthesis and Structural and Spectroscopic Characterization of a Complex between Co(II) and Imino-bis(methylphosphonic acid): Gaining Insight into Biologically Relevant Metal-Ion Phosphonate Interacti
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- 作者：H. Jankovics ; M. Daskalakis ; C. P. Raptopoulou ; A. Terzis ; V. Tangoulis ; J. Giapintzakis ; T. Kiss ; and A. Salifoglou
- 刊名：Inorganic Chemistry
- 出版年：2002
- 出版时间：July 1, 2002
- 年：2002
- 卷：41
- 期：13
- 页码：3366 - 3374
- 全文大小：126K
- 年卷期：v.41,no.13(July 1, 2002)
- ISSN：1520-510X
文摘
Cobalt is an essential metal ion involved in key biomolecules, regulating processes in human physiology. As ametal ion, Co(II) assumes forms, which are dictated by the nature of organic binders in biological fluids, and theconditions under which metal ion ligand interactions arise. Among the various low molecular mass metal ion bindersin biological fluids are amino acids, organic acids, as well as their variably phosphorylated forms. As a representativemetal ion binder, the organophosphonate ligand H2O3P-CH2-NH2+-CH2-PO3H- was employed in aqueous reactionswith Co(II), ultimately leading to the isolation of complex [Co(C2H8O6NP2)2(H2O)2] (1) at pH 2. The complex wascharacterized analytically, spectroscopically (FTIR, UV-vis, EPR), and magnetically. Compound 1 crystallizes inthe monoclinic space group P21/n, with a = 7.361(3) Å, b = 8.133(3) Å, c = 14.078(5) Å, 
ges/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 104.40(1)ges/entities/deg.gif">, V =816.3(5) Å3, and Z = 2. X-ray crystallography reveals that 1 is a compound with a molecular type of lattice. In it,there exist mononuclear octahedral sites of Co(II) surrounded by oxygens, belonging to terminal phosphonates andbound water molecules. Both ends of the ligand zwitterionic form are involved in binding to adjacent Co(II) ions,thus creating tetranuclear 32-membered rings, with cavities extending in two dimensions and holes in the thirddimension throughout the lattice of 1. Similar structural features were observed in other metal organophosphonatelattices of potential catalytic and chemical reactivity. The magnetic and EPR data on 1 support the presence of ahigh-spin octahedral Co(II) in an oxygen environment, having a ground state with an effective spin S = 1/2. Thesolution UV-vis and EPR data suggest retention of the high-spin octahedral Co(II) ion, consistent with themagnetization measurements on 1. Collectively, the data reflect the existence of a soluble Co(II)-iminodiphosphonatespecies not unlike those expected in biological fluids containing the specific ligand or ligands similar to that. Bothbiologically relevant perspectives and a synthetic outlook into Co(II)-organophosphonate materials are discussed.