Extinction Coefficients of Triplet–Triplet Absorption Spectra of Organic Molecules in Condensed Phases: A Least-Squares Analysis

A global least-squares technique is developed to assist in the critical evaluation of data consisting of large sets of measurements. The technique is particularly designed to handle sets of data where many of the measurements are relative measurements. A linearization procedure is used to reduce the inherently nonlinear problem to a traditional multivariate linear regression. The technique developed here is used to evaluate extinction coefficients, ε’s, of triplet–triplet absorption (TTA) spectra of organic molecules in condensed phases. A previous assumption, that there are no solvent effects on the TTA spectra, is investigated and modified so that a group of compounds measured in benzene is treated separately. The set of 445 ε’s obtained from the global least-squares fit, including these solvent effects, is presented in the accompanying tables. How these least-squares results can be used in a hierarchy of TTA ε standards is discussed. Further solvent effects such as the separation of polar and nonpolar media and the influence of temperature are probed.