Conformational analysis of octa- and tetrabromo tetraphenylporphyrins and their Ni(II) and Tb(III) complexes
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Molecular mechanics (MM) calculations were used to analyze the puckering of metalloporphyrins as a function of metal ion size and the position of substituents on the porphyrin periphery, on a three series of octa- and tetrabromo tetraphenylporphyrins: without metal, and with Ni(II), and Tb(III) as representative small and large metal ions, respectively. Molecular energy optimization calculations were carried out using the Consistent Force Field (CFF) program, with the parameters developed previously and new parameters for bromine atom. Normal-coordinate structural decomposition (NSD) analysis was performed on the equilibrium structures obtained by MM calculations. The conformers are also stereochemically characterized, compared with available X-ray structures and with the conformers obtained in our previous MM study using chloro instead of bromo P-pyrrole substituents. (C) 2004 Elsevier Inc. All rights reserved.
Keywords:porphyrins / non-planar conformations / molecular mechanics / Ni(II) porphyrins / Tb(III) porphyrins / normal-coordinate structural decomposition
Source:Journal of Inorganic Biochemistry, 2004, 98, 8, 1293-1302
- Elsevier Science Inc, New York