Can an OH radical form a strong hydrogen bond? A theoretical comparison with H₂O

Abstract

In this study, we apply UCCSD/6-31++G** to investigate the ability of an OH radical acting as a hydrogen bond acceptor with HF, HCl, and H(2)O (HO...HX; X=F, Cl, OH) or as a hydrogen bond donor with H(2)O and H(2)S (OH...XH(2); X=O and S). We also replace OH with H(2)O and make a fair comparison between them. Additionally, the counterpoise method (CP) has been used to examine the effect of basis set superposition error (BSSE). Our results reveal that OH is a stronger hydrogen bond donor but a weaker hydrogen bond acceptor than H(2)O. This conclusion is independent of the correction for BSSE and can be rationalized by the NBO analysis, the results of which indicate that OH radical has a lower n(O) and sigma*(O-H) in energy than that of H(2)O.

A theoretical analysis of the weakly bound complexes HM ··· HXY (M=O and S; XY=CN and NC): comparison with H2M ··· HXY complexes

“…However, the interaction energy is more negative for the OH complex than for the H 2 O complex when HCN and HNC act as the proton acceptor. This supports the conclusion that OH is a weaker proton acceptor, but a stronger proton donor, than H 2 O [25]. A similar conclusion is obtained when SH is compared with H 2 S.…”

“…As an oxidant, it can damage all types of macromolecules, including carbohydrates, nucleic acids, lipids and amino acids [23]. Quantum chemical calculations have been performed to study hydrogen-bonded complexes involving the hydroxyl radical, such as HCOOH-OH [24], H 2 O-OH [25], and H 2 S-OH [26] complexes. Like the hydroxyl radical, the sulfydryl radical (SH) also plays an important role in astrophysics and atmospheric chemistry and acts as the intermediate in the transformation between organic and inorganic sulfurs.…”

Effects of O18 isotopic substitution on the rotational spectra and potential splitting in the OH–OH2 complex: Improved measurements for O16H–O16H2 and O18H–O18H2, new measurements for the mixed isotopic forms, and ab initio calculations of the A2′-A2″ energy separation

“…10,11 Theoretically, it has been studied by a variety of computational methods, which have focused on energetics, structure, and reactivity. 1-3, 5,6,8,[12][13][14][15][16][17]20,21,[23][24][25] Theory and experiment concur that the system is a hydrogen bonded complex with OH acting as the proton donor, and calculations suggest a small potential barrier at the planar configuration. This latter feature is similar to that in the closed-shell complex FH-OH 2 , for which large-amplitude vibrational motion of the water subunit renders the complex effectively planar.…”

Microwave spectrum of the OD–OH2 complex: A strong deuterium isotope effect on angular momentum quenching in the hydroxyl moiety

“…The OH-OH 2 complex, in particular, has attracted considerable attention, and indeed a variety of experimental [5][6][7][8][9][10] and computational [6,[10][11][12][13][14][15][16][17][18][19][20][21][22][23] studies have explored the structure, energetics, and reactivity of the adduct. OH-OH 2 has a C s equilibrium geometry, with the OH bond directed in the vicinity of a lone electron pair on the water, but large amplitude motion of the water through a very small barrier in the C 2v configuration renders the complex effectively planar.…”