Structural, spectroscopic, FMOs, and non-linear optical properties exploration of three thiacaix(4)arenes derivatives

Computational exploration has been carried out on three p-tertbutylthiacalix[4]arene derivatives, namely cone (a), partial-cone (b), and 1,3-alternate (c). These three compounds are recently synthesized in high yields (80, 95, and 85%, respectively) and characterized by our group, which showed high uptake efficacy of alkali, heavy, and transition metal ions via liquid–liquid extraction. Significantly, these compounds exhibited high uptake capacity for Cu(II) (74.9 %) and Pb(II) (80.0%) upon using cone (a), and partial-cone (b), respectively.In this study, in order to optimize how the thiacalix[4]arene (as a nucleophilic) interacts with the metal ion (as an electrophile), DFT calculations were undertaken. Theoretical IR and UV–Vis spectral features of the titled compounds were computed and compared with their experimental values. Chemical reactivity was ranked based on selected electronic chemical descriptors. Moreover, the active sites of the three compounds were determined by molecular electrostatic potential (MEP) maps. Furthermore, non-linear optical (NLO) properties were investigated and compared with urea as reference material. The results of NLO characteristics showed that the subject compounds are excellent candidates as NLO materials. The enhancement of NLO properties can be qualitatively explained by means of high charge transfer pattern.