Soliman Saied M, Albering Jörg, Abu-Youssef Morsy A M
Department of Chemistry, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, 21321 Alexandria, Egypt.
Institute of Chemical Technology of Materials, Graz University of Technology, A-8010 Graz, Austria.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Feb 5;136 Pt B:1086-98. doi: 10.1016/j.saa.2014.09.133. Epub 2014 Oct 22.
The molecular structure and relative stabilities of the six possible isomers of 6-hydroxy-3(2H)-pyridazinone (DHP) in the gas phase and in solutions of different polarities are predicted using the B3LYP/6-311++G(d,p) method. The oxo-hydroxo isomer is the most stable form in the gas phase and in solution. These results agree with our reported X-ray structure. The effect of solvents on the spectroscopic properties of the most stable isomer has been studied using the polarized continuum method (PCM) at the same level of theory. The vibrational spectra of the compound studied are calculated and compared with the experimentally measured FTIR spectra. The electronic spectra in gas phase and in solution were calculated using the TD-DFT method. The most intense absorption band is predicted at 312.4 nm and belongs mainly to a π→π(*) transition. In polar solvents, this spectral band undergoes a hypsochromic shift. Two stable dimer forms were calculated at same level of theory. Dimer A is more stable than dimer B, by 6.66 kcal mol(-1). The former is stabilized by stronger O-H⋯O H-bonds compared to the weaker N-H⋯O interactions in the latter. The effect of these H-bonding interactions on the molecular structure and vibrational spectra of these compounds are predicted. NBO analyses were carried out to investigate the stabilization energy of various inter- and intramolecular charge transfer interactions within the systems studied.
采用B3LYP/6-311++G(d,p)方法预测了6-羟基-3(2H)-哒嗪酮（DHP）六种可能异构体在气相和不同极性溶液中的分子结构及相对稳定性。氧代-羟基异构体在气相和溶液中是最稳定的形式。这些结果与我们报道的X射线结构一致。使用极化连续介质模型（PCM）在相同理论水平下研究了溶剂对最稳定异构体光谱性质的影响。计算了所研究化合物的振动光谱，并与实验测得的傅里叶变换红外光谱进行了比较。采用含时密度泛函理论（TD-DFT）方法计算了气相和溶液中的电子光谱。预测最强吸收带出现在312.4 nm处，主要属于π→π(*)跃迁。在极性溶剂中，该光谱带发生蓝移。在相同理论水平下计算了两种稳定的二聚体形式。二聚体A比二聚体B更稳定，相差6.66 kcal mol(-1)。与后者较弱的N-H⋯O相互作用相比，前者通过更强的O-H⋯O氢键得以稳定。预测了这些氢键相互作用对这些化合物分子结构和振动光谱的影响。进行了自然键轨道（NBO）分析，以研究所研究体系中各种分子间和分子内电荷转移相互作用的稳定能。
