Polarized Specular Reflectance Spectra of Fe(β-dtpy)2·4THF: AD2hModel of Porphyrins

Abstract

Transition metal complexes of β-dtpy (1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinide) are spectrally similar to metallophthalocyanines (derivatives of porphyrin) but with the advantage of being D2h instead of D4h so that many degenerate electronic transitions are identifiable separately. We have prepared and characterized Fe(β-dtpy)2·4THF, whose crystal structure allows three spectral polarizations to be measured. We have assigned the visible and ultraviolet transitions that correspond to the Q and Soret regions of porphyrinic complexes; these assignments differ markedly from the traditional “four-orbital” model. The secondary Q peak (R) is a separate electronic transition rather than a vibronic component, and the Soret transition has been reassigned.