Computationally design aspects of superbasic amidine-arsinine 1-oxide binary frameworks

Abstract

Novel Brønsted superbases (1–10) were designed on the basis of arsinine 1-oxide core by changing the species of proton absorption site, type and situation of electron-donating substituents in the gas phase and CH3CN medium. The conjugate acids of the designed structures are stabilized through positive charge distribution and/or formation of an intramolecular hydrogen bond. To explore the various structural aspects of the designed molecules for reaching the higher basicity values in gas phase and solution phase in CH3CN solvent, proton affinity (PA), gas phase basicity (GB), pKa, and Nucleus-IndependentChemicalShifts 1 Å above the arsinine 1-oxide ring center along with zz axis (NICS(1)zz) parameters as well as natural bond orbital (NBO) charges calculated and obtained for each structure. The basicity strength of proposed structures was evaluated using B3LYP/6–311 + G(d,p) level of theory. The protonation of all designed structures was studied from both possible sites in gas and CH3CN phase and PA, GB, pKa, and NICS(1)zz values were calculated for each case. It was found that most designed compounds demonstrate superbasicity characteristics and especially amidine-arsinine 1-oxide core structure including two phosphazene electron donating groups (10) shows highest superbasicity properties. The most important finding of the study was the considerable synergistic effect between amidine and arsinine 1-oxide moieties for creating remarkable basicity strength. Aromaticity alterations of the arsinine 1-oxide ring also was monitored during protonation process.