A density functional theory (DFT) approach was used to investigate the interaction of cystine with Cu9 cluster at B3LYP/LANL2DZ/6-311++G(d,p) level of theory. It was observed that cystine interacts with copper cluster majorly through its disulfide and –COOH groups. The simulated Raman spectrum confirmed the cleavage of disulfide linkage by the disappearance of the –S-S- stretching mode, in good agreement with the earlier reported experimental study. As noted by the peaks observed due to Cu-S and Cu-O stretching mode in the simulated Raman spectrum, cystine is inferred to have chemisorbed on Cu9. Using NBO analysis, it was revealed that oxygen and sulfur donate electron pairs to copper in the Cu9-cystine system. Additionally, the MK[ESP] charge and FMO analysis supported the above mentioned results significantly.

Conformational analysis of psilocin, a psychedelic molecule revealed two stable conformers designated as conformer-A and B which were 4.97 kcal/mol apart in energy among many other high energy conformers. AIM analysis revealed that the conformer-A (global minimum) is stable due to intramolecular H-bond formation between ethyl amine nitrogen and indolic hydroxyl group. This is in contradiction to earlier X-ray crystal studies of this molecule reported in literature. Dimers of both conformer-A and B were studied utilizing DFT method and it was observed that even in the dimer of conformer-A the intramolecular H-bond energy dominates over the intermolecular H-bond. Other calculations namely NBO, FMO, charge analysis, ESP mapping corroborated the AIM results in a significant manner. The spectroscopic study including UV, 1H-NMR and vibrational modes calculation were found to be in good agreement with the data reported in literature.