Polarization measurement and configuration analysis of the triplet-triplet absorption spectra of substituted naphthalenes

Abstract

The polarization of triplet-triplet absorption spectra for 1- and 2-methoxynaphthalene, 1,5-, 1,8-, 2,7-, and 2,3-naphthalenediols, and 1,4-dimethoxynaphthalene was measured by the photoselection method. Calculations of the triplet states of these molecules were made by the Pariser-Parr-Pople method, and the resulting wavefunctions were subjected to the configuration analysis. The T-T absorption spectra of the β-substituted naphthalenes are relatively simple and closely resemble that of naphthalene. In the α-substituted naphthalenes, the T-T absorption spectra are not only remarkably different from that of naphthalene but also different from one another. Comparison of experimental and theoretical results leads to reasonable assignments of the individual absorption bands involving some modification of previous assignments. The apparent complexity of T-T absorption spectra of the α-substituted naphthalenes can be interpreted in relation to the enhanced 3B 1g + ← 3B 2u + and 3A g − ← 3B 2u + transitions of naphthalene.