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Effect of Substitution on the ESR Spectra and Electronic Ground State of ZnTPP Cation Radicals

✍ Scribed by Paresh C. Dave; D. Srinivas

Publisher: John Wiley and Sons
Year: 2000
Tongue: English
Weight: 393 KB
Volume: 2000
Category: Article
ISSN: 1434-1948
DOI: 10.1002/(sici)1099-0682(200003)2000:3<447::aid-ejic447>3.0.co;2-z

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✦ Synopsis

Zinc(II) complexes of substituted tetraphenylporphyrins, Zn[T(X-P)P], where X = H, p-F, p-Cl, m-Cl, p-CH 3 O, and m-CH 3 O, have been synthesized and characterized. Peripheral substitution shows marked changes in the chemical shifts of the phenyl proton resonances and E 1/2 values of the redox couples in the anodic region while the UV/Vis spectra are unaffected. The monocation radicals of these complexes are generated by chemical oxidation with bromine. The ESR spectra reveal the formation of two types of radical species, Zn[T(X-P)P] +⋅ Br -(species I) and Zn[T(X-P)(Br n -P)] +⋅ Br -(species II): Species I at 298 K shows a spectrum, with well-resolved bromine hyperfine features, characteristic of a 2 A 2u electronic ground state while species II, except for the complex with X = m-CH 3 O, shows a featureless, isotropic reson-

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