Experimental charge density study and topological properties of Fidarestat

Abstract

Charge density studies on a few octahedrally coordinated Fe(II) complexes will be presented. The spin state of Fe(II) exhibits either high spin (HS) or low spin (LS) depending upon the ligand field strength of the coordinated ligands. Electron density distribution around the metal should be greatly different for the two spin states, namely a quintet 5 T 2 and a singlet 1 A 1 states. In order to eliminate any possible experimental differences, we choose a few systems where a HS and a LS state coexist in the same lattice. The comparison of these two spin states are quite clear, it gives a good example for the illustration of the d-orbital distributions of the 3d-transition metal as well as the metal-ligand bond for HS and LS state respectively in Fe(II) complexes. Complimentary x-ray absorption spectroscopy and the IR stretching frequency are also measured to monitor the spin transition. A DFT calculation is studied on one of the isolated molecules, comparable electron density distribution as well as the topological properties associated with the bond critical point with respect to the experimental observations will be discussed. The analysis of chemical bonding in real space can be performed using different position dependent functionals. Recently proposed Electron Localizability Indicator (ELI) is based on integrals over specially designed micro-cells [1]. Loosely speaking, ELI is proportional to the charge that is needed to form a same-spin electron pair. Thus, ELI is connected with the correlation of electronic motion of same-spin electrons [2]. In regions of space, where the bonding occurs, the same-spin electron try to avoid each other. The examination of metal-ligand bonds is complicated by the participation of the inner shell metal orbitals [3]. Some strategies, how to approach this difficult task will be presented. MS10 O2 Metal-ligand bonds in coordination compounds[1] Kohout M., Int. J. Quantum Chem., 2004, 97, 651. [2] Kohout M., Pernal K., Wagner F.R., Grin, Yu., Theor. Chem. Acc. 2004, 112, 453. [3] Kohout M., Wagner F.R., Grin, Yu., Theor. Chem. Acc. 2002, 108, 150. . Experimental deformation densities allow a first qualitative view of the non-spherical density and reveal fine details, coherent with the chemistry of the molecule, as for instance lack of electron density in the C-F bond [4][5][6], and larger density accumulation on imidazole moiety C-N and C-O bonds. The topological analysis of the total electron density performed using the VMoPro program [7] will be discussed. As the electrostatic properties are of major importance in numerous biological processes, accurate electrostatic potential and interaction energies calculations of the human aldose reductase complex with fidarestat will also be discussed. This will enable to give useful insight on the specific inhibition activity. Phys. Chem. B. 108,[3663][3664][3665][3666][3667][3668][3669][3670][3671][3672] [7] Jelsch, C., Guillot, B., Lagoutte, A. & Lecomte, C. (2005 The nature of the metal-metal bond in polynuclear transition me...