The DFT Study On Second-order NLO Property Of The Pyridyl Metal-carbonyl Complexes

In recent years, as the birth of laser and the rapid development of laser technology, nonlinear optics becomes an important embranchment of the field of modern optics, in which the interaction of intense laser with matter is studied. At the same time, it has become an important project to find new nonlinear optical materials, due to their wide use and attractive application foreground, for example, in laser frequency doubling, laser frequency mixing, parametric amplification and oscillation, integrated optics, optical communication, and other fields. Much emphasis has been put on organic nonlinear optical materials because they have many advantages,such as large nonlinear optical coefficient,wide response wave band,good flexibility,high optical damage threshold,low cost,and easy combination and modification.Molecule-based materials with chemical modified properties are the studied field of modern high technology and novel material. The metal complexes with organic and inorganic merit have been attracted a lot of attention because of the potential NLO properties. Comparing to the pure the organic molecules, complexes molecules can offer a very large variety of NLO structures in relation to the metal d configuration, oxidation state and spin state, etc. All of these structures not only can increase the NLO properties, but can also enhance the environmental stability.Pyridyl carbonyl complexes are an important type of NLO materials; there are many conclusions of those pyridyl carbonyl complexes of NLO properties have been obtained by the experimental and theoretical studies. The studies of the relation between the electronic structure and NLO properties of those complexes would promote the exploitations and applications of its NLO properties.Hence, we calculate and analyze the second-order NLO properties of the pyridyl carbonyl complexes with octahedral structures in this thesis. The aims of my thesis work are:(1) To calculate the electronic structures and second-order NLO properties of pyridyl metal-pentacarbonyl (M=Cr(0), Mn(I), Fe(II), Co(III)) complexes with octahedral structures in theoretical level;(2) To calculate the second-order NLO properties of pyridyl metal-tetracarbonyl (M= Fe(II), Ru(II)) complexes.My thesis mainly consists of the following aspects: the first section is the review of the theoretical foundation of the study on the NLO property of organic and metal complex, the research approach and research development. The second section discussed the electronic structure and second-order NLO property of the octahedral structural pyridyl metal-pentacarbonyl (M=Cr(0), Mn(I), Fe(II), Co(III)) complexes. The third section calculated the geometrical structure and second-order NLO properties of the center metal (M= Fe(II), Ru(II)) and R ligand group. Based on the geometrical structures and molecular orbitals and second-order NLO properties, the role of the (M= Fe(II), Ru(II)) and R ligand in those metal complexes has been discussed.The DFT method has been employed, in order to analyze the second-order NLO properties of pyridyl metal-carbonyl complexes. The results of our studies in this thesis are: 1. The DFT B3LYP method has been employed, in order to calculate the second-order NLO properties of the center metal (M= Fe(II), Ru(II)) and R ligand group. Bond length between center metal and nitrogen (N) become short when the charge of the center metal increase. The polarizability and second-order NLO properties increase while conjugate bridge extended.2. For the calculation of R and pyridine ligand with metal tetracarbonyl (M = Fe (II), Ru (II)) complex effects of second-order NLO. The results showed that: the allocation of the large volume of complex, second-order NLO factor increasing and as the allocation for the carbonyl of the complex, energy gap of the front molecular orbital is small, the second-order NLO coefficient increased significantly. Ru(II) ion enhances the second-order NLO responses of the complexes because of the decreasing the occupied orbtials→unoccupied orbitals gaps, and increasing the electronic density distribution of coordinated atoms and adjacent carbon atoms in the conjugate chain.