Proton transfer and hydrogen bonds in supramolecular, self-assembled structures of imidazolium silanethiolates. X-ray, spectroscopic and theoretical studies

The reaction of 1-methylimidazole, 2-ethyl-4-methylimidazole and 2-ethylimidazole with tris(2,6-diisopropylphenoxy)silanethiol (TDST) leads to the formation of three new salts, which have been characterized by elemental analyses, thermogravimetric analyses, FTIR spectroscopy, and their structures were determined by single-crystal X-ray diffraction. Structural analyses indicate that in all three compounds a proton transfer has occurred from the SH group of TDST onto the imidazole nitrogen atom, giving charge-assisted (+)N–H⋯S(−) hydrogen bonds. The crystallographic characterization of the compounds reveals structural diversity. Compound 1 exhibit zero-dimensional (0-D) hydrogen bonded entities, while compounds 2 and 3 form one-dimensional (1-D) supramolecular networks. The transfer of the proton was confirmed by FTIR spectroscopy in the solid state. Computational studies on the compounds were carried out with the use of the density functional theory (DFT) method with the B3LYP functional at the TZV level.

An anionic sulfur atom from the silanethiolate anion was utilized as an acceptor in charge-assisted hydrogen bonding of the (+)N–H⋯S(−) type. The structures of the synthesised compounds are all different and each is based on non-covalent bonding of H-bonds, which play crucial roles in the formation of supramolecular networks.Figure optionsDownload as PowerPoint slide