FLUORESCENCE, FLUORESCENCE-EXCITATION AND ABSORPTION-SPECTRA OF TRANS-1-(2-ANTHRYL)-2-PHENYLETHENE CONFORMERS

Fluorescence spectra of trans-1-(2-anthryl)-2-phenylethene (APE) obtai ned under varying conditions of excitation wavelength and oxygen conce ntration in toluene are resolved into two distinct components by appli cation of principal component analysis with self-modeling (PCA-SM). Se lf-modeling is guided by the constraint that Stern-Volmer quenching pl ots for the individual conformers be independent of excitation wavelen gth. The same process applied on a matrix of fluorescence-excitation s pectra leads to resolved conformer-specific fluorescence-excitation sp ectra. Consistency between the fluorescence and the fluorescence-excit ation spectrum of each conformer is established. The fluorescence-exci tation spectra and literature fluorescence quantum yields are used to resolve the UV absorption spectrum of APE. The pure conformer spectra obtained in this work are compared with those from earlier PCA-SM trea tments in which self-modeling procedures were based on the Lawton and Sylvestre nonnegativity constraint and on a maximal spectral dissimila rity constraint.