Cyanonaphthalene and cyanonaphthyl radicals: Vibrational structures via computed negative ion photoelectron spectra and thermochemistry of 1- and 2-cyanonaphthalene

Abstract

A double harmonic oscillator model is applied to compute the negative ion photoelectron spectra (NIPES) of the 1- and 2-cyanonaphthalene (CNN) radical anions. The computed Franck–Condon factors utilize optimized structures and harmonic vibrational frequencies obtained using density functional theory with the B3LYP 6-311++G (2d,2p) basis set while considering the mode-mixing Duschinsky effects. To test the accuracy of our model, the NIPES of α and β naphthyl radical anions were computed, and a strong agreement between the slow electron velocity-map ion imaging spectra and the predicted spectra was found. The adiabatic electron affinities (EAs) of the ground singlet states (S0) in 1-CNN and 2-CNN are 0.856 and 0.798 eV, respectively. The origin of the lowest-lying triplet (T1) states in 1-CNN and 2-CNN is found to be 3.226 and 3.266 eV, resulting in singlet–triplet energy splittings (ΔEST) of 2.370 and 2.468 eV, respectively. Both the NIPES for electron detachment to the S0 and T1 states exhibit well-resolved vibrational features, allowing for the assignment of several vibrational fundamental frequencies. Following deprotonation, several isomers are formed, with the most stable deprotonated radical anions in 1-CNN and 2-CNN, corresponding to the removal of the most acidic proton, with EAs of 2.062 and 2.16 eV. The rich spectroscopic and thermochemical data obtained in the current study make the CNN radical anions and their deprotonated species interesting systems for investigation in gas-phase, negative-ion experiments.