Blanco Susana, Pinacho Pablo, López Juan Carlos
Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid , E-47011 Valladolid, Spain.
J Phys Chem Lett. 2017 Dec 21;8(24):6060-6066. doi: 10.1021/acs.jpclett.7b02948. Epub 2017 Dec 5.
Water self-association dominates the formation of microsolvated molecular clusters which may give rise to complex structures resembling those of pure water clusters. We present a rotational study of the complex formamide-(HO) formed in a supersonic jet and several monosubstituted isotopologues. Formamide and water molecules form a four-body sequential cycle through N-H···O, O-H···O, and O-H···O═C hydrogen bonds, resulting in a chiral structure with a nonplanar skeleton that can be overlapped to that of water pentamer. The analysis of the N-nucleus quadrupole coupling effects shows the depletion of the electron density of the N atom lone pair with respect to the bare formamide that affects the amide group C-N and C═O distances. The study of the observed tunneling doublets shows that formamide-(HO) follows a path to invert its structure driven by the flipping of water subunits and passing through successive nonplanar configurations, a motion reminiscent of the pseudorotation of water pentamer.
水的自缔合作用主导了微溶剂化分子簇的形成，这些分子簇可能会产生类似于纯水簇的复杂结构。我们对在超声速射流中形成的甲酰胺-(HO)络合物以及几种单取代同位素变体进行了转动研究。甲酰胺分子和水分子通过N-H···O、O-H···O和O-H···O═C氢键形成一个四体序列循环，从而产生一种具有非平面骨架的手性结构，该结构可与水五聚体的结构重叠。对N核四极耦合效应的分析表明，相对于裸露的甲酰胺，N原子孤对电子的电子密度有所降低，这影响了酰胺基团的C-N和C═O距离。对观测到的隧穿双峰的研究表明，甲酰胺-(HO)通过水分子亚基的翻转，沿着一条路径反转其结构，并经过连续的非平面构型，这种运动让人联想到水五聚体的假旋转。
