The title compound, C15H11N3O, (I), was obtained by the air oxidation of 3,5-diphenyl-4,5-dihydro-1,2,4-triazin-6(1H)-one. In the crystal structure, (I) forms centrosymmetric hydrogen-bonded dimers through pairs of N—H...N hydrogen bonds. The molecular structure of (I) deviates somewhat from planarity in the crystalline state, whereas a density functional theory (DFT) study predicts a completely planar conformation (Cspoint-group symmetry) for the isolated molecule. The solid-state conformation of (I) is stabilized by intramolecular hydrogen bonds,viz.one C—H...O interaction, which forms a six-membered ring, and three C—H...N interactions that each form five-membered rings. To estimate the influence of the intramolecular hydrogen-bonded rings on the aromaticity of the phenyl rings, the HOMA (harmonic oscillator model of aromaticity) descriptor of π-electron delocalization has been calculated for conformations of (I) with and without intramolecular hydrogen bonds. In the planar conformation of (I), the HOMA values for both benzene rings are lower than in hypothetical conformations without intramolecular hydrogen bonds.
通过空气氧化 3,5-二苯基-4,5-二氢-1,2,4-三嗪-6(1H)-酮,得到了标题化合物 C15H11N3O (I)。在晶体结构中,(I) 通过成对的 N-H...N 氢键形成中心对称的氢键二聚体。(I) 的分子结构在一定程度上偏离了结晶态的平面性,而密度泛函理论(DFT)研究则预测孤立分子具有完全平面的构象(Cspoint-group 对称性)。(I) 的固态构象由分子内氢键稳定,即一个 C-H...O 相互作用形成六元环,三个 C-H...N 相互作用分别形成五元环。为了估计分子内氢键环对苯环芳香性的影响,我们计算了有分子内氢键和无分子内氢键的 (I) 构象的 π 电子外迁描述因子 HOMA(芳香性谐振子模型)。在 (I) 的平面构象中,两个苯环的 HOMA 值均低于无分子内氢键的假设构象。