Structural, Potential Surface and Vibrational Spectroscopy Studies of Hypophosphorous Acid in the Gas Phase and Chain Conformation. A Theoretical Study
Structural, Potential Surface and Vibrational Spectroscopy Studies of Hypophosphorous Acid in the Gas Phase and Chain Conformation. A Theoretical Study
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气相和链构象中次磷酸的结构、电位表面和振动光谱研究。
DOI：
10.5012/jkcs.2005.49.2.129
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
S. Tayyari
中科院分区：
文献类型：
--
作者：
I. Ahmadi;H. Rahemi;S. Tayyari
在HF、MP2和DFT-B3LYP理论水平上，采用6-31G**基组，对次磷酸(HPA)的势能面、分子结构和振动结构进行了理论研究。为了逼近固态光谱，我们优化了单、二、三、四和五聚体结构，计算了VCD和IR的振动模式的频率和强度。结果发现，随着链中HPA分子数目的增加，某些振动频率接近于实验的固态值。在垂直于P-O键的平面上，计算了HPA的势能面，在这个平面上，氢可以通过O=P-O-H二面角旋转360度。在平面上发现了一个向上和向下的圆形谷，该谷以P-O键的延续为中心。在与O=P-O平面的夹角为±42.5时有两个极小值，给出了两个镜面构象和一个鞍点，在与O=P-O平面的夹角处的高度为284.87 cm，在与同一平面的夹角处有一个高度为2089.40 cm的复合势垒。在复杂的屏障顶部，有一口深度为15.65厘米的小井。为了研究两种构象之间的隧道效应和路径，认为分子具有C-S对称性和对称的双最小势垒，中间有284.87 cm高的势垒。利用所构造的势，用变分法和谐振子波函数研究了单体P-O-H(受阻旋转)的扭转运动，并计算了红外频率和振动模的相对强度。由于井的宽度和势垒的三角形状，隧道作用可能发生在基态
The potential energy surfaces (PES), molecular and vibrational structure of hypophosphours acid (HPA) were investigated by HF, MP2 and DFT-B3LYP level of theory using 6-31G** basis set. In order to approach solid state spectra we optimized mono-, di-, tri-, tetraand penta-mer structures and computed frequencies and intensities of the vibrational modes of VCD and IR. It is found that by increasing the number of HPA molecules in the chain, some of calculated vibrational frequencies approach to the experimental solid state values. The potential energy surfaces of HPA are calculated in a wide range on the plane perpendicular to the P-O bond where the hydrogen can rotate 360 degree through O=P-O-H dihedral angle. A circular valley is found going up and down on the plane, the valley is centered to the continuation of P-O bond. There are two minima at angles ±42.5 to the O=P-O plane giving two mirror conformers and one saddle point in between with a height of 284.87 cm at the angles 0 and a complex barrier with a height of 2089.40 cm at the angle 180 to the same plane. On top of the complex barrier, there is a small well with depth of 15.65 cm. To study the tunneling effect and pathway between the two conformers, the molecule is considered to have C S symmetry and a symmetric double minimum potential energy well with a barrier of 284.87 cm height in the middle. With the constructed potential, the torsional motion of P-O-H (Hindered Rotation) of the monomer, using variation method and harmonic oscillator wave functions is studied and IR frequencies and relative intensities of vibrational modes are calculated. Due to the width of the well and the trigonometric shape of the barrier, tunneling can occur at the ground state