Theoretical calculations of methylquinolinium tricyanoquinodimethanide (CH3Q–3CNQ) using a solvation model

To better understand the unimolecular electrical rectification in γ-(hexadecyl)quinolinium tricyanoquinodimethanide (C16H33Q–3CNQ), γ-(methyl)quinolinium tricyanoquino-dimethanide (CH3Q–3CNQ) was studied by semi-empirical SM5.4/AM1 and ab initio (SCRF/SCIPCM/B3LYP/6-31G*) solvation models. DFT single-point calculations agree well with the semi-empirical calculations. CH3Q–3CNQ in acetonitrile may exist in both trans and cis zwitterionic forms; the trans form is 3.1 kcal mol−1 more stable than the cis form, and separated from it by a 11.3 kcal mol−1 barrier. The conformational minima in solution do not correspond to minima in the gaseous state. The calculated solvated-phase dipole moment of CH3Q–3CNQ is in good agreement with the measured moment of C16H33Q–3CNQ.