Rotational spectroscopy of the benzofuran–water complex: Conformations and preferred noncovalent interactions

Abstract

We investigated the non-covalent interactions occurring between benzofuran and water. The weakly-bound complex was produced using a supersonic jet expansion and was subsequently characterized utilizing high-resolution Fourier transform microwave spectroscopy. Through the analysis of the rotational spectrum, we were able to confirm the detection of two distinct conformations within the complex. The most stable conformation demonstrates a structure that is almost coplanar. This structure involves one hydrogen atom from a water molecule interacting with the oxygen atom of benzofuran, thus forming an O_w–H_w···O hydrogen bond. Concurrently, the oxygen atom serves as a proton acceptor, forming an O_w···HC hydrogen bond with one hydrogen atom of the phenyl ring. The secondary conformation positions the two OH bonds such that they are oriented towards the face of benzofuran, resulting in the formation of two O_w–H_w···π hydrogen bonds. The non-covalent bonding topology of the first conformation bears resemblance to the corresponding furan-water complex, while the second conformation aligns with the benzofuran-hydrogen sulfide complex. The strength and the nature of these hydrogen bonding interactions is delineated by the application of natural bond orbital theory, energy decomposition, and electronic density analysis methodologies.