Comparison of core-hole excitation spectra of organic donor/acceptor molecules in the vapor and condensed phases: p-nitroaniline, 2-amino-6-nitronaphthalene and 1-amino-4-nitronaphthalene

Abstract

Vapor phase N1s and O1s core-hole spectra of the org. donor/acceptor mols. 2-amino-6-nitronaphthalene (2,6-ANN) and 1-amino-4-nitronaphthalene (1,4-ANN) are presented and compared to condensed phase results. 2,6-ANN and 1,4-ANN exhibit broad single peak N1s(NO2) signals in the gas phase which are split into resolvable components in the solid. The spectral differences noted on going from the vapor phase to the solid parallel previous results on p-nitroaniline (PNA). Unlike the situation encountered in PNA (and 2,6-ANN), however, O1s(NO2) spectrum of 1,4-ANN also indicates a moderately increased splitting as well as an apparent decrease in shake-up intensity on going from the vapor to the condensed phase. Spectral differences between the 2 phases are addressed within the CNDO/S(CI) equiv.-core approxn. including up to doubly excited singlet-coupled configurations as a means of elucidating the apparent core-hole induced intermol. coupling. Comparison computations are presented on PNA, 2,6-ANN, and 1,4-ANN. X-ray crystallog. measurements on 2,6-ANN indicate an intermol. donor/acceptor pairing scheme as in PNA. Dimer models were used to computationally address solid state interactions. The N1s(NO2) spectral differences obsd. in PNA, 2,6-ANN, and 1,4-ANN on going from the vapor to the condensed phase are attributed to strong core-hole induced intermol. orbital mixing.