Strategic Design and Utilization of Molecular Flexibility for Straddling the Application of Organic Superbases: A DFT Study

Abstract

The density functional theory (DFT) calculations were performed for a series of new molecular frameworks that have potential to work as organic superbases. In the present report, we have exploited and strategically substituted 2 and 6 positions of the pyridine by a potential anchoring group, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). The value of proton affinities (PAs) of the molecular frameworks was calculated in the gas phase as well as in acetonitrile solution. The designed non-ionic and neutral organic superbases were found to have higher basicity than that of the benchmarked molecule, 1,8-bis(dimethylamino)-naphthalene (DMAN). The zero-point vibrational energy (ZPVE) and PAs values were calculated for the designed molecular frameworks at B3LYP/6-311+G**//B3LYP/6-31+G* level of theory. For compression, we have also performed the optimization of all the structures at M06-2X/6-311 +G**//M06-2X/6-31+G* level of theory. The molecular framework 9 has highest PAs values 1151.2 and 1246.3kJ mol(-1) in the gas phase and in acetonitrile solution, respectively at B3LYP/6-311+G**//B3LYP/6-31+G* level of theory. The designed molecular frameworks have better flexibility, which enables it for selective extraction of the smaller to larger size molecules by varying the size of the cavity, as required for the various applications. In this context, we have explored the application of designed molecular frameworks for the selective extraction of UO22+ over VO2+.