Absorption, Fluorescence, and Magnetic Circular Dichroism Spectra of and Molecular Orbital Calculations on Tetrabenzotriazaporphyrins and Tetranaphthotriazaporphyrins

Abstract

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 K 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.

Spectroscopy, Electrochemistry, and Molecular Orbital Calculations of Metal-Free Tetraazaporphyrin, -chlorin, -bacteriochlorin, and -isobacteriochlorin

“…The intensity of the Faraday B terms of the Q band decreases in the order TAP>TAC>TAB, and this reflects the degree of splitting of the Q band 23–25. The sign pattern of the MCD B term bands of all compounds is −/+ with increasing energy, as is also seen for low‐symmetry Pc derivatives,26–30 although those of hydrogenated porphyrins were often inverted 21, 31…”

Electrochemical and photophysical characterization of non-peripherally-octaalkyl substituted dichlorotin(IV) phthalocyanine and tetrabenzotriazaporphyrin compounds

“…1 and Table 1), as expected for a macrocycle with lower symmetry than that of the Pc ring. Mack et al [30] have calculated the electronic energy levels for TBTAP molecules; a splitting in the lowest unoccupied molecular orbital (LUMO) leads to split Q-and B-bands [30].…”

“…These include two phthalocyanine derivatives, (Cl) 2 SnPc(C 6 H 13 ) 8 (3a) and (Cl) 2 SnPc(C 10 H 21 ) 8 (3c), and the corresponding dichlorotin octaalkyl-tetrabenzotriazaporphyrin, (Cl) 2 Sn(IV)TBTAP (3b), an example of a rarer class of macrocycle but one closely related to the phthalocyanines [30]. …”

Formation and electronic properties of ring-oxidized and ring-reduced radical species of the phthalocyanines and porphyrins

“…The synthetic chemistry of these ring compounds has flourished, with a great many compounds being reported that exhibit properties at the extremes of the 'normal' range. To some extent, synthetic development has been greater recently with the tetraaza-, triaza-and subphthalocyanine cores than with the porphyrin core-see as an example the detailed review of synthetic and spectroscopic characterization of the subphthalocyanines by Kobayashi [20] and the spectroscopic properties and molecular orbital calculations for the triazaporphyrins [21]. Recently, also, there has been an increase in the synthesis and characterization of linked porphyrins and phthalocyanines, e.g.…”