Spectroscopic and theoretical investigation of solvent effect on N-H•••O, N-H•••N and N-H•••π interactions in complexes of N-monosubstituted benzamides

In this research, experimental and theoretical spectral analysis of N-monosubstituted benzamides was performed by mid-infrared spectroscopy and density functional theory. The MIR spectroscopic characteristics for N-H center dot center dot center dot O, N-H center dot center dot center dot N and N-H center dot center dot center dot pi hydrogen-bonded complexes and also the equilibrium constants for 1:1 complex formation are given. The structures of selected N-substituted benzamides (as proton donors), benzene, acetonitrile, and tetrahydrofuran (as proton acceptors), as well as their complexes, were optimised at the M06-2X/6-311++G (d,p) level of theory. The solvent effect on hydrogen-bonded complexes and the correlations between the equilibrium constants and molecular descriptors of N-monosubstituted benzamides were also investigated using a principal component analysis.