Spectra of zinc tetrabenzporphyrin in n-octane

Abstract

A detailed spectroscopic study of zinc tetrabenzporphyrin in n-octane reveals the following: (i) the relative magnitude of solute-solvent interaction in the ground and excited states increases in the order T₁ < S₀ < S₁ < S₂. (ii) The potential energy surface minima of the ground and excited states are very similar within the framework of the Franck-Condon principle. (iii) The absence of any hot-band emission from the Q band (S₁) and any emission from the Soret band (S₂) indicates that significant amounts of energy degrade to the lowest vibrational level of S₁. (iv) An earlier report on monomer phosphorescence is mainly due to aggregation. Selective narrow-band excitation is shown to be a useful technique to unravel complex spectra of porphyrins in Shpolskii-type matrices. Accurate measurements can be made of the energies for electronic transitions between the ground and excited states of molecules isolated in the various sites of the host matrix. The intensity ratios for electronic and vibronic bands can also be determined.