Absorption, fluorescence, and magnetic circular dichroism spectra of and molecular orbital calculations on tetrabenzotriazaporphyrins and tetranaphthotriazaporphyrins

Extensive analyses of the electronic absorption, magnetic circular dichroism (MCD), and fluorescence emission and excitation spectra of peripherally-substituted tetrabenzotriazaporphyrin (TBTrAP) and tetranaphthotriazaporphyrin (TNTrAP) complexes are reported. ZINDO calculations of the UV-visible absorption spectra of free base and dianionic (deprotonated) TBTrAP and TNTrAP complexes are described. The optical spectra of TBTrAP and TNTrAP are assigned on the basis of molecular orbital (MO) calculations using the ZINDO program and the theory that has been developed previously to account for the spectral properties of porphyrin and phthalocyanine complexes. Analysis of the absorption and MCD spectra of the ring-reduced anion radical species of Pc and TBTrAP complexes shows that the optical spectra of [TBTrAP(-3)](-) are markedly different from those of analogous Pc species. EPR signals observed at 77 It for Pc(-3) radical species provide evidence for a doublet ground state, while the absence of an EPR signal for [TBTrAP(-3)](-) indicates that the species dimerizes upon reduction. The absorption and MCD spectra of the dimeric [TBTrAP(-3)](-) species are found to be consistent with the band assignment developed previously to account for the spectral properties of main group Pc anion radicals.