Faculty of Chemistry, Institute of Functional Material Chemistry, Northeast Normal University, 130024 Changchun, Jilin, People's Republic of China.
J Phys Chem B. 2011 Sep 29;115(38):11053-62. doi: 10.1021/jp2061305. Epub 2011 Sep 7.
In the present work, the electronic structures and properties of a series of 2-ureido-4[1H]-pyrimidinone(UPy)-based monomers and dimers in various environments (vacuum, chloroform, and water) are studied by density functional theoretical methods. Most dimers prefer to form a DDAA-AADD (D, H-bond donor; A, H-bond acceptor) array in both vacuum and solvents. Topological analysis proved that intramolecular and intermolecular hydrogen bonds coexist in the dimers. Frequency and NBO calculations show that all the hydrogen bonds exhibit an obvious red shift in their stretching vibrational frequencies. Larger substituents at position 6 of the pyrimidinone ring with stronger electron-donating ability favor the total binding energy and free energy of dimerization. Calculations on the solvent effect show that dimerization is discouraged by the stronger polarity of the solvent. Further computations show that Dimer-1 may be formed in chloroform, but water molecules may interact with the donor or acceptor sites and hence disrupt the hydrogen bonds of Dimer-1.
在本工作中，通过密度泛函理论方法研究了一系列在不同环境（真空、氯仿和水）下的 2-脒基-4[1H]-嘧啶酮（UPy）基单体和二聚体的电子结构和性质。大多数二聚体在真空和溶剂中都优先形成 DDAA-AADD（D，氢键供体；A，氢键受体）排列。拓扑分析证明二聚体中存在分子内和分子间氢键。频率和 NBO 计算表明，所有氢键在伸缩振动频率上都表现出明显的红移。嘧啶酮环 6 位上具有较强供电子能力的较大取代基有利于二聚体的总结合能和自由能。溶剂效应的计算表明，溶剂的更强极性不利于二聚化。进一步的计算表明，Dimer-1 可能在氯仿中形成，但水分子可能与供体或受体位点相互作用，从而破坏 Dimer-1 的氢键。
