Investigation of the conformation and hydrogen bonds in adamantylthiacalix[4]arene by IR spectroscopy and DFT

Thiacalix [4]arene (TC4A), p-tert-butylthiacalix [4]arene (t-BuTC4A) and p-(1-adamantyl)thiacalix [4] arene (1-AdTC4A) IR spectra were studied. Calculated energies and IR spectra of the various conformers (cone, partial cone, 1,2-alternate, and 1,3-alternate) were compared. The cone is the most stable conformation for all studied thiacalix [4]arenes. Theoretical IR spectrum of adamantylthiacalix [4]arene molecule in the form of a cone is consistent with experiment. Classification of bands in the IR spectrum of adamantylthiacalix [4]arene has been implemented. The strength of H-bonding in the thiacalix [4] arenes depends on the type of the substituent. In the conformation of the cone cyclic system of H-bonds are implemented for all the studied thiacalix [4]arenes. Introduction of adamantyl substituents leads to convergence of oxygen atoms in molecules of thiacalix [4]arene and H-bonds are strengthened. Conformation cone of molecules of thiacalix [4]arenes does not change when heated to a temperature of 180 degrees C and dissolving in a neutral solvent. (C) 2018 Elsevier B.V. All rights reserved.