Belarmino Márcia K D L, Cruz Vanessa F, Lima Nathália B D
Departamento de Química Fundamental, Universidade Federal de Pernambuco (UFPE), 50740-540, Recife, PE, Brazil.
J Mol Model. 2014 Nov;20(11):2477. doi: 10.1007/s00894-014-2477-0. Epub 2014 Oct 25.
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.
采用MP2/6 - 31++G(d,p)和DFT B3LYP/6 - 31++G(d,p)方法，对作为质子受体的二甲亚砜（DMSO）与单质子线性酸HX（X = F、Cl、CN）以及单质子羧酸HOOCR（R = -H、-CH₃、-C₆H₅）以1:1和1:2化学计量比形成的配合物的结构、结合能和振动模式进行了计算。结果表明，在1:2的比例下可能存在两种不同的结构：第一种是DMSO分子与两个酸分子相互作用（形成“Y”结构）；第二种是DMSO仅与一个单质子酸相互作用。第二种结构中每个氢键的稳定性较低。形成1:1和1:2配合物反应的自发性受线性酸的X基团影响很大。除HCN外，所有反应都是自发的。在具有Y结构的1:2配合物中，我们观察到线性酸的氢原子以对称和不对称模式耦合，而其他1:2配合物中不存在这种耦合类型。
