APPLICATIONS OF CHEMOMETRIC METHODS TO SPECTROSCOPIC STUDIES OF AGGREGATE FORMATION AND TWISTED INTRAMOLECULAR CHARGE-TRANSFER IN THE GAS-PHASE AND IN NONPOLAR-SOLVENTS

Principal component analysis-self-modeling and non-linear least-square s spectral resolution methods were applied to quantitative fluorescenc e studies of the aggregate formation and the twisted intramolecular ch arge transfer (TICT) state emission of p-(N,N-diethylamino)ethylbenzoa te (DEAEB) in the gas phase and in low-density supercritical ethane. A broad Gaussian-like fluorescence band at approximately 400 nm was obt ained and assigned to the emission of DEAEB microcrystals or microsoli ds. It is shown that the red-shifted band can essentially be eliminate d by keeping the sample undisturbed for a period of time and by select ing appropriate excitation wavelengths. The results support the conclu sion that even in the gas phase the contribution of DEAEB TICT state e mission is still significant. It is also demonstrated that a quantitat ive characterization of the excited state equilibrium between the loca lly excited and TICT states of DEAEB in non-polar solvents can be acco mplished by application of a spectral resolution method.