Cation-induced crown porphyrin dimers of oxovanadium(IV)

Thanabal, V and Krishan, V (1982) Cation-induced crown porphyrin dimers of oxovanadium(IV). In: Inorganic Chemistry, 21 (10). pp. 3606-3613.

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Abstract

Oxovanadium(1V) porphyrins appended with crown ether (benzo-15-crown-5) at the 5 (mono), the 5 and 10115 (cis/trans bis), the 5, 10, and 15 (tris), and the 5, 10, 15, and 20 (tetrakis) positions have been synthesized. The cation complexation behavior of these cavity-bearing porphyrins has been studied by using optical aborption and ESR spectral methods. The cations K+, Cs+, NH4+, and Ba2+, which require two crown ether cavities for complexation, induce dimerization of the porphyrins. The cation-induced dimerization constants for a representative tetrasubstituted porphyrin vary as K+ > Ba2+ > Cs+ - NH4+, and the relative stabilities of the dimers are dependent on the type of the substitution, tetrakis > tris > cis bis. ESR spectra recorded at a sample temperature of 77 K have low-field components attributed to Ah& = f 2 transitions, providing further evidence for the existence of dimers in solutions. The eclipsed sandwich dimers have V-V distances in the range 4.70 A. The relative distributions of oxovanadium crown porphyrins in terms of monomeric and dimeric forms rest on the geometric dispositions of the crown ether appendages.

Item Type:	Journal Article
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	01 Jul 2009 11:40
Last Modified:	19 Sep 2010 05:35
URI:	http://eprints.iisc.ernet.in/id/eprint/20892

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