Electronic structure of four-coordinate C3v nickel(II) scorpionate complexes: investigation by high-frequency and -field electron paramagnetic resonance and electronic absorption spectroscopies.
نویسندگان
چکیده
A series of complexes of formula TpNiX, where Tp*- = hydrotris(3,5-dimethylpyrazole)borate and X = Cl, Br, I, has been characterized by electronic absorption spectroscopy in the visible and near-infrared (NIR) region and by high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy. The crystal structure of TpNiCl has been previously reported; that for TpNiBr is given here: space group = Pmc2(1), a = 13.209(2) A, b = 8.082(2) A, c = 17.639(4) A, alpha = beta = gamma = 90 degrees , Z = 4. TpNiX contains a four-coordinate nickel(II) ion (3d8) with approximate C3v point group symmetry about the metal and a resulting S = 1 high-spin ground state. As a consequence of sizable zero-field splitting (zfs), TpNiX complexes are "EPR silent" with use of conventional EPR; however, HFEPR allows observation of multiple transitions. Analysis of the resonance field versus the frequency dependence of these transitions allows extraction of the full set of spin Hamiltonian parameters. The axial zfs parameter for TpNiX displays pronounced halogen contributions down the series: D = +3.93(2), -11.43(3), -22.81(1) cm(-1), for X = Cl, Br, I, respectively. The magnitude and change in sign of D observed for TpNiX reflects the increasing bromine and iodine spin-orbit contributions facilitated by strong covalent interactions with nickel(II). These spin Hamiltonian parameters are combined with estimates of 3d energy levels based on the visible-NIR spectra to yield ligand-field parameters for these complexes following the angular overlap model (AOM). This description of electronic structure and bonding in a pseudotetrahedral nickel(II) complex can enhance the understanding of similar sites in metalloproteins, both native nickel enzymes and nickel-substituted zinc enzymes.
منابع مشابه
Geometric and electronic structure of a peroxomanganese(III) complex supported by a scorpionate ligand.
A monomeric Mn(II) complex has been prepared with the facially-coordinating Tp(Ph2) ligand, (Tp(Ph2) = hydrotris(3,5-diphenylpyrazol-1-yl)borate). The X-ray crystal structure shows three coordinating solvent molecules resulting in a six-coordinate complex with Mn-ligand bond lengths that are consistent with a high-spin Mn(II) ion. Treatment of this Mn(II) complex with excess KO2 at room tempera...
متن کاملElectronic Structure Investigation of Octahedral Complex and Nano ring by NBO Analysis: An EPR Study
To calculation non-bonded interaction of the [CoCl6]3- complex embedded in nano ring, we focus on the single wall boron-nitride B18N18 nano ring. Thus, the geometry of B18N18 nano ring has been optimized by B3LYP method with EPR-II (Electron paramagnetic resonance) basis set and geometry of the [CoCl6]3- complex has been optimized at B3LYP method with Aldrich’s VTZ basis set and Stuttgart RSC 1...
متن کاملElectronic Structure Investigation of Octahedral Complex and Nano ring by NBO Analysis: An EPR Study
To calculation non-bonded interaction of the [CoCl6]3- complex embedded in nano ring, we focus on the single wall boron-nitride B18N18 nano ring. Thus, the geometry of B18N18 nano ring has been optimized by B3LYP method with EPR-II (Electron paramagnetic resonance) basis set and geometry of the [CoCl6]3- complex has been optimized at B3LYP method with Aldrich’s VTZ basis set and Stuttgart RSC 1...
متن کاملElectron Paramagnetic Resonance Studies of the Effects of π-donor Ligand and B18N18 Nanoring Field on Energy Gaps
To investigation non-bonded interaction of the [CuF4]2- complex inside nanoring, we focus on the single wall boron-nitride B18N18 nanoring. Thus, the geometry of B18N18 nanoring has been optimized by B3LYP method with EPR-II basis set and geometry of the [CuF4]2- complex has been optimized at B3LYP method with Def2-TZVP basis set and Stuttgart RSC 1997 Effective Core Potential. Also electronic ...
متن کاملElectron Paramagnetic Resonance Studies of the Effects of π-donor Ligand and B18N18 Nanoring Field on Energy Gaps
To investigation non-bonded interaction of the [CuF4]2- complex inside nanoring, we focus on the single wall boron-nitride B18N18 nanoring. Thus, the geometry of B18N18 nanoring has been optimized by B3LYP method with EPR-II basis set and geometry of the [CuF4]2- complex has been optimized at B3LYP method with Def2-TZVP basis set and Stuttgart RSC 1997 Effective Core Potential. Also electronic ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Inorganic chemistry
دوره 45 22 شماره
صفحات -
تاریخ انتشار 2006