SOLVATION AND AXIAL LIGATION PROPERTIES OF ABROMO-5,10,15,20-TETRAPHENYLPORPHYRINATO)ZINC(II)

Citation
P. Bhyrappa et al., SOLVATION AND AXIAL LIGATION PROPERTIES OF ABROMO-5,10,15,20-TETRAPHENYLPORPHYRINATO)ZINC(II), Journal of the Chemical Society. Dalton transactions, (12), 1993, pp. 1901-1906
Citations number
27
Categorie Soggetti
Chemistry Inorganic & Nuclear
ISSN journal
03009246
Issue
12
Year of publication
1993
Pages
1901 - 1906
Database
ISI
SICI code
0300-9246(1993):12<1901:SAALPO>2.0.ZU;2-9
Abstract
The solvation of (2,3,7,8,1 2,13,17,18-octabromo-5,10,1 5,20-tetraphen ylporphyrinato)zinc(II) [Zn(obtpp)], in twelve different solvents resu lts in large red shifts of the B and Q bands of the porphyrin accompan ied by enhanced absorbance ratios of the Q bands. These observations a re ascribed to the destabilisation of the highest occupied molecular o rbital a2u of the porphyrin arising from a flow of charge from the axi al ligand to the porphyrin ring through the zinc(II) ion. The binding constants of adducts of [Zn(obtpp)] with neutral bases have been found to be an order of magnitude greater than those observed for the corre sponding adducts of (5,10,15,20-tetraphenylporphyrinato)zinc and vary in the order piperidine > imidazole > pyridine > 3-methylpyridine > py ridine-3-carbaldehyde. The enhanced binding constants and large spectr al shifts are interpreted in terms of the electrophilicity of [Zn(obtp p)] induced by the electron-withdrawing bromine substituents in the po rphyrin core. The structure of [Zn(obtpp)(PrCN)2] has been determined; it reveals six-co-ordinated zinc(II) with two long Zn-N distances [2. 51(4), 2.59(3) angstrom]. The porphyrin is non-planar and displays a s addle-shaped conformation.