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 ΔSrot, whereas the largest contributions to the ΔSvib have vibrations associated with the τS1C20 coordinate.
Figure
Optimized B3LYP/6-311++G(d,p) geometry of 1-(2-mercaptoethyl)amino]-9,10-anthraquinone (MEAA) and vibrational contributions to entropy (ΔSvib, in J mol?1?K?1) relative to the most stable conformer