Hydrothermal Syntheses, Characterization And Computation For Structure Of Niobium-Transition Metal Mixed Complexes With Organic Amines

Early d⁰ transition metal oxide fluoride anions such as [NbOF₅]²- and [TaOF₅]²- interest researchers because their inherent distortions mimic those in the [NbO_6/2] octahedral in LiNbO₃, an excellent solid state nonlinear optical material. In the [NbOFs]²- anion, the Nb atom is displaced from the center of the octahedron towards the O atom to form a short Nb=O bond and long trans Nb —F bond. The distortion can be exploited when designing new materials that exhibit important structure-dependent properties such as piezoelectricity, second-order nonlinear optical activity and ferroelectricity. So the goal of this work is to synthesis and preparation of niobium—transition metal mixed complexes with organic amines by hydrothermal routes on the basis of going over a great deal of references of inorganic-organic hybrid crystals and in order to enrich the coordination chemistry of niobium oxide fluoride complexes with organism. The main work is as follows:1. Twelve new niobium—transition metal mixed complexes (1¹2) including [NbOFs]²-have been synthesized with 1,10-phenanthroline, α,α'-bipyridine, pyridine, imidazole and benzimidazole acting as ligands and characterized by IR spectra, UV-Vis spectra, TG and X-ray single analysis. [Mn(phen)₂(H₂O)₂][NbOF₅] (1), [Zn(phen)₂(H₂O)₂][Nb0F₅] (2) and [Cd(phen)₂(H₂O)₂] [NbOF₅] (3) have also been studied by bond valence sum and computation for structure. The structural analyses of 1³ show that they have similar structures and they are all ionic complexes. There are electrostatic force, hydrogen bond and %—% stacking interaction between molecules which result in three-dimensional stereo structures.2. A novel niobium—transition metal mixed complexes (Him)₂[Cd(im)₂Nb₂O₃F₈]-2H₂O (13) with imidazole including [Nb₂O₃F₈]⁴- has been synthesized and characterized by IR spectra, TG and X-ray single analysis. Bond valence sum and computation for structure of it have also been studied. As indicated by structural analysis, the backbone of 13 is a one-dimensional linear chain which is comprised of alternating [Nb₂O₃F₈]⁴- anions and Cd(C₃H₄N₂)₂²+ Bond valence sum displays that 01, 03 and F3 have much more negative charge, so they act as bridge ligands. [Nb₂O₃F₈]⁴- anions have much tension in 13, which is revealed by computation for structure.