The sulfur lone-pair⋯π interaction: The subtle dispersion features of the sulfur interactions in model complexes of disulfides with the heteroaromatic benzofuran

Abstract

A direct observation of the non-covalent interactions between sulfur lone pairs and electron-rich aromatic rings (SLP⋯π) has not been achieved in the gas phase, even though these interactions are crucial for the stability and function of biomacromolecules. Herein, we characterized the SLP⋯π interactions in the dimers of benzofuran with diethyl disulfide and dimethyl disulfide using high-resolution rotational spectroscopy and quantum chemical calculations. The observation of two isomers for each dimer confirmed the leading role of the SLP⋯π interactions, along with cooperative effects from C–H⋯π and C–H⋯O weak hydrogen bonds. The molecular structures, electronic properties, and non-covalent interactions were accurately determined using density functional theory [B3LYP-D3(BJ)] and domain-based local pair natural orbital coupled-cluster theory [DLPNO-CCSD(T)]. The determined atomic distances between sulfur and the benzofuran ring are within the range of 3.465(4)–3.621(5) Å, resembling bonding patterns commonly observed in proteins. Dispersion energy is found to play a significant role in these sulfur interactions, accounting for 67%–71% of the total attractive interactions in the dimers. This study thus offers insights into the structural and energetic properties of SLP⋯π interactions that can serve as a benchmark for future theoretical explorations and molecular design based on disulfide patterns.