Hydrogen-bonded complexes between dimethyl sulfoxide and monoprotic acids: molecular properties and IR spectroscopy

Abstract

MP2/6-31++G(d,p) and DFT B3LYP/6-31++G(d,p) calculations were performed of the structure, binding energies, and vibrational modes of complexes between dimethyl sulfoxide (DMSO) as a proton acceptor and monoprotic linear acids HX (X = F, Cl, CN) as well as monoprotic carboxylic acids HOOCR (R = -H, -CH3, -C6H5) in 1:1 and 1:2 stoichiometric ratios. The results show that two different structures are possible in the 1:2 ratio: in the first, the DMSO molecule interacts with both acid molecules (leading to a "Y" structure); in the second, the DMSO interacts with only one monoprotic acid. The second structure shows a lower stability per hydrogen bond. The spontaneities of the reactions to form the 1:1 and 1:2 complexes are greatly influenced by the X group of the linear acid. With the exception of HCN, all the reactions are spontaneous. In the 1:2 complexes with Y structure, we observed that the hydrogen atoms of the linear acid are coupled in symmetric and asymmetric modes, while this type of coupling is absent from the other 1:2 complexes.

Effect of a Competitive Solvent on Binding Enthalpy and Chain Intermixing in Hydrogen-Bonded Layer-by-Layer Films

“…40 Likewise, DMSO can also bind with carboxylic acids, with in excess of one hydrogen bond formed per DMSO molecule. 41 Because of its capacity for hydrogen bonding, its polar nature, and its high boiling point (189 °C), DMSO may be retained within the films and contribute to an increase in film thickness. To differentiate between possible contributions of DMSO and polymers to film thickness, films deposited from buffer−DMSO mixed solvents were first dried in dry nitrogen gas for 2 min, then thoroughly rinsed and exposed to DMSOfree buffer (0.025 M phosphate, adjusted to pH 2.5) for 30 min, and finally dried.…”

“…This bonding results in nonideal behavior of DMSO/water mixtures, which exhibit eutectic points at 0.25 and 0.33 molar fraction of DMSO, corresponding to 57 and 66 vol % of DMSO, respectively . Likewise, DMSO can also bind with carboxylic acids, with in excess of one hydrogen bond formed per DMSO molecule …”

“…39,55 DMSO−water clusters, such as DMSO• 2H 2 O or DMSO•3H 2 O, 40 persist over a wide range of mixed solvent compositions, including those with low DMSO content. 38,56 On the other hand, DMSO can form complexes of varying stoichiometry with carboxylic acids, 41 and its hydrogen bonding with PMAA is likely to cause dissolution of PVP−PMAA complexes in pure DMSO. 37 In DMSO−water solutions of PMAA, competition of water−PMAA, water− DMSO, and DMSO−PMAA interactions occurs, resulting in a change in balance between enthalpic and entropic contributions to the free energy of polymer−polymer complex association.…”

Structural and spectroscopic characterization and DFT studies of 2-amino-1,10-phenanthrolin-1-ium chloride

“…Among the molecular building blocks, charged species play an important role in molecular association processes in chemistry and biology [1,2]. Nevertheless, hydrogen bonding represents a very special class of chemical interactions that may bring about significant changes in the molecular and spectroscopic properties [3][4][5]. In particular, in order to observe or verify the changes in spectroscopic properties, the substituents or groups should directly involve in hydrogen bonding [6,7].…”

“…In particular, in order to observe or verify the changes in spectroscopic properties, the substituents or groups should directly involve in hydrogen bonding [6,7]. Hydrogen bonding interaction can be readily confirmed by FT-IR as observing the displacement of the frequency signals associated with stretches of the groups take part in hydrogen bonding [3]. NMR spectroscopy is another very useful technique that unambiguously shows the changes in chemical shift of the hydrogen nuclei forming the hydrogen bond [8].…”