Elius Hossain Md, Mahmudul Hasan Md, Halim M E, Ehsan M Q, Halim Mohammad A
Department of Chemistry, University of Dhaka, Dhaka 1000, Bangladesh.
Department of Chemistry, University of Dhaka, Dhaka 1000, Bangladesh.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Mar 5;138:499-508. doi: 10.1016/j.saa.2014.11.084. Epub 2014 Nov 29.
Some transition metal complexes of phenylalanine of general formula [M(C9H10NO2)2]; where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) are prepared in aqueous medium and characterized by spectroscopic, thermo-gravimetric (TG) and magnetic susceptibility analysis. Density functional theory (DFT) has been employed calculating the equilibrium geometries and vibrational frequencies of those complexes at B3LYP level of theory using 6-31G(d) and SDD basis sets. In addition, frontier molecular orbital and time-dependent density functional theory (TD-DFT) calculations are performed with CAM-B3LYP/6-31+G(d,p) and B3LYP/SDD level of theories. Thermo-gravimetric analysis confirms the composition of the complexes by comparing the experimental and calculated data for C, H, N and metals. Experimental and computed IR results predict a significant change in vibrational frequencies of metal-phenylalanine complexes compared to free ligand. DFT calculation confirms that Mn, Co, Ni and Cu complexes form square planar structure whereas Zn adopts distorted tetrahedral geometry. The metal-oxygen bonds in the optimized geometry of all complexes are shorter compared to the metal-nitrogen bonds which is consistent with a previous study. Cation-binding energy, enthalpy and Gibbs free energy indicates that these complexes are thermodynamically stable. UV-vis and TD-DFT studies reveal that these complexes demonstrate representative metal-to-ligand charge transfer (MLCT) and d-d transitions bands. TG analysis and IR spectra of the metal complexes strongly support the absence of water in crystallization. Magnetic susceptibility data of the complexes exhibits that all except Zn(II) complex are high spin paramagnetic.
一些通式为[M(C9H10NO2)2]的苯丙氨酸过渡金属配合物（其中M = Mn(II)、Co(II)、Ni(II)、Cu(II)和Zn(II)）在水介质中制备，并通过光谱、热重（TG）和磁化率分析进行表征。采用密度泛函理论（DFT）在理论水平B3LYP下使用6 - 31G(d)和SDD基组计算这些配合物的平衡几何结构和振动频率。此外，使用CAM - B3LYP/6 - 31 + G(d,p)和B3LYP/SDD理论水平进行前沿分子轨道和含时密度泛函理论（TD - DFT）计算。热重分析通过比较C、H、N和金属的实验数据与计算数据来确定配合物的组成。实验和计算得到的红外结果表明，与游离配体相比，金属 - 苯丙氨酸配合物的振动频率有显著变化。DFT计算证实Mn、Co、Ni和Cu配合物形成平面正方形结构，而Zn采用扭曲的四面体几何结构。与金属 - 氮键相比，所有配合物优化几何结构中的金属 - 氧键更短，这与先前的研究一致。阳离子结合能、焓和吉布斯自由能表明这些配合物在热力学上是稳定的。紫外 - 可见光谱和TD - DFT研究表明，这些配合物表现出典型的金属到配体的电荷转移（MLCT）和d - d跃迁带。金属配合物的TG分析和红外光谱有力地支持了结晶中不存在水。配合物的磁化率数据表明，除Zn(II)配合物外，所有配合物都是高自旋顺磁性的。
