Remarkable effects of substitution on stability of complexes and origin of the C–H⋯O(N) hydrogen bonds formed between acetone's derivative and CO2, XCN (X = F, Cl, Br)

Abstract

The interactions of the host molecules CH₃COCHR₂ (R = CH₃, H, F, Cl, Br) with the guest molecules CO₂ and FCN (X = F, Cl, Br) induce significantly stable complexes with stabilization energies, obtained at the CCSD(T)/6-311++G(3df,2pd)//MP2/6-311++G(2d,2p) level, in the range of 9.2–14.5 kJ mol⁻¹ by considering both ZPE and BSSE corrections. The CH₃COCHR₂⋯XCN complexes are found to be more stable than the corresponding CH₃COCHR₂⋯CO₂ ones. The overall stabilization energy has contributions from both the >CO⋯C Lewis acid–base and C–H⋯O(N) hydrogen bonded interactions, in which the crucial role of the former is suggested. Remarkably, we propose a general rule to understand the origin of the C–H⋯O(N) hydrogen bonds on the basis of the polarization of a C–H bond of a proton donor and the gas phase basicity of a proton acceptor. In addition, the present work suggests that the >CO group can be a valuable candidate in the design of CO₂-philic and adsorbent materials, and in the extraction of cyanide derivatives from the environment.