Relationship between structure and entropy contributions in an anthraquinone mercapto derivative.

The structural and thermodynamic properties of an anthraquinone derivative were studied by means of quantum-chemical calculations. Conformational analysis using ab initio and density functional theory methods revealed 14 low-energy conformers. In order to discuss similarities and differences in entropy of the conformers, the rotational and vibrational contributions to entropy were correlated with changes in conformer structure. The component of the moment of inertia perpendicular to the molecular plane gives significant input to DeltaSrot, whereas the largest contributions to the DeltaSvib have vibrations associated with the tau (S1C20) coordinate.