Theoretical design of molecular superbases has been attracting researchers for more than twenty years. General approaches were developed to make the bases potentially stronger, but less attention was paid to the stability of the predicted structures. Hence, only a small fraction of the theoretical research has led to positive experimental results. Possible stability issues of extremely strong bases are extensively studied in this work using quantum chemical calculations on a high level of theory. Several step-by-step design examples are discussed in detail, and general recommendations are given to avoid the most common stability problems. New potentially stable structures are theoretically studied to demonstrate the future prospects of molecular superbases design.

The possibility of theoretical calculation of the ionization constants of strong organic bases in dimethyl sulfoxide and hexametapole was studied by the DLPNO-CCSD (T) and DFT methods. By comparison with the experimental data available in the literature, it has been established that the error of such calculations lies within 1–2 pKa units. The stability of some ionizing solvents against strong organic bases is investigated, the mechanisms of decomposition of solvent molecules in strongly basic media are predicted, and the corresponding energy barriers are estimated. According to the calculations, among ionizing solvents, hexamethylphosphoramide has the highest resistance to superbases, being able to maintain pH > 50 at room temperature. At the same time, 1,3-dimethyl-2-imidazolidinone gradually decomposes under these conditions, while tetrahydrofuran and pivalonitrile are even less stable.