Superbasicity of imines with bicyclo[5.1.0]octa-1,3,5,7-tetraene scaffold due to electron delocalization in the conjugated acids

Abstract

Gas phase basicity of organic superbases with bicyclo[5.1.0]octa-1,3,5,7-tetraene (fused cyclopropene and cycloheptatriene) scaffold and an imine group as proton acceptor site was computationally assessed using B3LYP/6-311++G(d,p) method. The basicity of these imines originates from the electron delocalization and consequently delocalization of the positive charge upon protonation leading to stability of the conjugated acid. Also, the effects of different electron donating groups (EDGs) and hydrogen bond formation on the basicity enhancement were studied. The calculated PAs were 1000–1307 kJ mol−1 indicating superbasicity and hyperbasicity of the studied organic bases. These organic bases can deprotonate H2SO4 and FHSO4 in the gas phase and produce stable ion pair clusters.