title: Charge and Spin States in Schiff Base Metal Complexes with a Disiloxane Unit Exhibiting a Strong Noninnocent Ligand Character: Synthesis, Structure, Spectroelectrochemistry, and Theoretical Calculations.
abstract: Mononuclear nickel(II), copper(II), and manganese(III) complexes with a noninnocent tetradentate Schiff base ligand containing a disiloxane unit were prepared in situ by reaction of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane followed by addition of the appropriate metal(II) salt. The ligand H2L resulting from these reactions is a 2:1 condensation product of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane. The resulting metal complexes, NiL·0.5CH2Cl2, CuL·1.5H2O, and MnL(OAc)·0.15H2O, were characterized by elemental analysis, spectroscopic methods (IR, UV-vis, X-band EPR, HFEPR, (1)H NMR), ESI mass spectrometry, and single crystal X-ray diffraction. Taking into account the well-known strong stabilizing effects of tert-butyl groups in positions 3 and 5 of the aromatic ring on phenoxyl radicals, we studied the one-electron and two-electron oxidation of the compounds using both experimental (chiefly spectroelectrochemistry) and computational (DFT) techniques. The calculated spin-density distribution and localized orbitals analysis revealed the oxidation locus and the effect of the electrochemical electron transfer on the molecular structure of the complexes, while time-dependent DFT calculations helped to explain the absorption spectra of the electrochemically generated species. Hyperfine coupling constants, g-tensors, and zero-field splitting parameters have been calculated at the DFT level of theory. Finally, the CASSCF approach has been employed to theoretically explore the zero-field splitting of the S = 2 MnL(OAc) complex for comparison purposes with the DFT and experimental HFEPR results. It is found that the D parameter sign strongly depends on the metal coordination geometry.
authors.affiliation: †"Petru Poni" Institute of Macromolecular Chemistry, Alea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
authors.forename: Maria
authors.initials: M
authors.lastname: Cazacu
authors.affiliation: †"Petru Poni" Institute of Macromolecular Chemistry, Alea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
authors.forename: Sergiu
authors.initials: S
authors.lastname: Shova
authors.affiliation: †"Petru Poni" Institute of Macromolecular Chemistry, Alea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
authors.forename: Alina
authors.initials: A
authors.lastname: Soroceanu
authors.affiliation: ‡Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK-81237 Bratislava, Slovak Republic.
authors.forename: Peter
authors.initials: P
authors.lastname: Machata
authors.affiliation: ‡Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK-81237 Bratislava, Slovak Republic.
authors.forename: Lukas
authors.initials: L
authors.lastname: Bucinsky
authors.affiliation: ‡Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK-81237 Bratislava, Slovak Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Breza
authors.affiliation: ‡Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK-81237 Bratislava, Slovak Republic.
authors.forename: Peter
authors.initials: P
authors.lastname: Rapta
authors.affiliation: §Department of Biological, Chemical and Physical Sciences, Roosevelt University, 430 South Michigan Avenue, Chicago, Illinois 60605 United States.
authors.forename: Joshua
authors.initials: J
authors.lastname: Telser
authors.affiliation: ∥National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 United States.
authors.forename: J
authors.initials: J
authors.lastname: Krzystek
authors.affiliation: ⊥Faculty of Chemistry, Institute of Inorganic Chemistry, University of Vienna, Währinger Strasse 42, A-1090 Vienna, Austria.
authors.forename: Vladimir B
authors.initials: VB
authors.lastname: Arion
mesh_terms: D060326:Chemistry Techniques, Synthetic; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D004578:Electron Spin Resonance Spectroscopy; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry; D010084:Oxidation-Reduction; D010636:Phenols; D012545:Schiff Bases / Q000737:chemistry; D012821:Silanes / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D010636:Phenols; D012545:Schiff Bases; D012821:Silanes; C059468:disiloxane; C042329:phenoxy radical; D008345:Manganese; D003300:Copper; D009532:Nickel