Does borazine–water behave like benzene-water? A matrix isolation infrared and ab initio study

Abstract

Borazine is isoelectronic with benzene and is popularly referred to as inorganic benzene. The study of non-covalent interactions with borazine and comparison with its organic counterpart promises to show interesting similarities and differences. The motivation of the present study of the borazine-water interaction, for the first time, stems from such interesting possibilities. Hydrogen-bonded complexes of borazine and water were studied using matrix isolation infrared spectroscopy and quantum chemical calculations. Computations were performed at M06-2X and MP2 levels of theory using 6-311++G(d,p) and aug-cc-pVDZ basis sets. At both the levels of theory, the complex involving an N-H⋯O interaction, where the N-H of borazine serves as the proton donor to the oxygen of water was found to be the global minimum, in contrast to the benzene-water system, which showed an H-π interaction. The experimentally observed infrared spectra of the complexes corroborated well with our computations for the complex corresponding to the global minimum. In addition to the global minimum, our computations also located two local minima on the borazine-water potential energy surface. Of the two local minima, one corresponded to a structure where the water was the proton donor to the nitrogen of borazine, approaching the borazine ring from above the plane of the ring; a structure that resembled the global minimum in the benzene-water H-π complex. The second local minimum corresponded to an interaction of the oxygen of water with the boron of borazine, which can be termed as the boron bond. Clearly the borazine-water system presents a richer landscape than the benzene-water system.

Combined TDDFT and AIM Insights into Photoinduced Excited State Intramolecular Proton Transfer (ESIPT) Mechanism in Hydroxyl- and Amino-Anthraquinone Solution

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Discerning Near-Isoergic Isomers. A Matrix Isolation Infrared and ab Initio Study of the Propargyl Alcohol Dimers

“…In all the experiments, typical deposition rates of ∼3 mmol/h of the matrix gas were employed. The experimental method has been described in detail elsewhere. − Spectra of the matrix-isolated species were recorded using a Fourier transform infrared spectrometer, operating at a resolution of 0.5 cm –1 .…”

Intermolecular Complexes and Molecular Conformations Directed by Hydrogen Bonds: Matrix Isolation and Ab Initio Studies

“…The first system that we studied was the BNH-H 2 O for a comparison with the C 6 H 6 -H 2 O complex. 41 In contrast to the C 6 H 6 -H 2 O system, which showed only an O-H···π complex, the BNH-H 2 O system showed a richer landscape of structures (Fig. 8).…”

“…9). 41 To continue the comparison with benzene, we also studied the BNH-C 2 H 2 system. 42 Experimentally, we observed two complexes; one where the N-H of BNH interacted with the carbon of C 2 H 2 (Bent NH···C) and another where the ≡C-H of C 2 H 2 formed a hydrogen bond with the N of borazine (Bent CH … N) ( Fig.…”