Unsymmetrical Quadridentate Research Articles

ChemInform Abstract: SYNTHESIS AND CHARACTERIZATION OF COPPER(II) COMPLEXES WITH UNSYMMETRICAL QUADRIDENTATE SCHIFF BASES DERIVED FROM β‐DIKETONE, DIAMINE, AND O‐HYDROXYBENZALDEHYDE LIGANDS

AbstractDie nach bekannten Methoden synthetisierten Cu(II)‐Komplexe (I) unsymm. vierzähniger Schiffscher Basen werden charakterisiert.

Synthesis and characterization of a new family of binuclear copper(II) complexes with a flexible bridge and the π–π type charge-transfer interaction with 1,3,5-trinitrobenzene

copper(II) complexes with unsymmetrical quadridentate Schiff bases, composed of the 1 : 1 : 1 condensation products of salicyladehyde derivatives (salicylaldehyde, 2-hydroxy-1-1-naphthalenecarbaldehyde, o-hydroxyacetophenone), diamine (ethylenediamine, trimethylenediamine), and acetylacetone, react electrophilically with hexamethylene di-isocyanate or m-xylene di-isocyanate in 2 : 1 mol ratio to produce the binuclear copper(II) complexes with a hexamethylene dicarbamoyl or m-xylene dicarbamoyl bridging group. The binuclear copper(II) complexes were characterized by elemental analyses, melting points, molecular weights, and i.r., e.s.r., and electronic spectra. The binuclear copper(II) complex containing a naphthalene moiety as π-electron donor interacts with 1,3,5-trinitrobenzene (tnb) to form a 1 : 1 molecular complex exhibiting a new absorption band attributable to the charge transfer between the naphthalene moiety and tnb, both in the solid and in solution. The 1 : 1 molecular complex between the mononuclear parent complex and tnb showed the charge-transfer band in the solid but not in solution.

Synthesis and characterization of copper(II) complexes with unsymmetrical quadridentate Schiff bases derived from β-diketone, diamine, and o-hydroxybenzaldehyde ligands

Several copper(II) complexes with unsymmetrical quadridentate Schiff bases derived from β-diketone (acetylacetone, benzoylacetone), diamine (ethylenediamine, trimethylenediamine), and o-hydroxybenzaldehyde (salicylaldehyde, o-hydroxyacetophenone, 2-hydroxy-1-naphthalenecarbaldehyde) have been prepared and characterized. The physical properties (melting points, absorption maxima, absorption coefficients) of the unsymmetrical copper(II) complexes are intermediate between the corresponding symmetrical copper(II) complexes. One of the unsymmetrical complexes, trimethylene-N-(acetylacetoneiminato)-N′-salicylideneiminatocopper(II), has been subjected to a single-crystal X-ray analysis; the result verified the detailed structure in which the copper(II) atom assumes a distorted-tetrahedral co-ordination geometry, with a dihedral angle of 19.1 ° between two OCuN planes. The unsymmetrical copper(II) complexes react with ethyl isocyanate and with phenyl isocyanate to produce compounds substituted at the methine position of the β-diketonate moiety. The ligands were prepared by the reaction of the copper(II) complexes with gaseous hydrogen sulphide. The copper(II) complexes and the ligands have been characterized by elemental analyses, i.r., 1H n.m.r., e.s.r., and electronic spectra.

Synthesis and Characterization of Iron(III) Complexes with Unsymmetrical Quadridentate Schiff Bases, and Spin Equilibrium Behavior in Solution

Abstract Several iron(III) complexes with planar unsymmetrical quadridentate Schiff bases composed of 1:1:1 condensation products of acetylacetone, ethylenediamine, and each of salicylaldehyde and o-hydroxyacetophenone have been prepared and characterized, where the Schiff bases are abbreviated as [H2salacen] and [H2hapacen], respectively. The effective magnetic moment of [FeCl(hapacen)] increases gradually from 3.46 BM at 80 K to 5.31 BM at 301 K, and was interpreted by a spin-spin interaction model based on a binuclear structure with an antiferromagnetic interaction parameter of J=−10 cm−1 (S1=S2=5⁄2), while the magnetic moment for [FeCl(salacen)] is 5.86 BM at 80 K and 5.96 BM at 302 K, indicating that the complex is a monomeric species of high-spin type. The bis(imidazole)iron(III) complexes [Fe(im)2(salacen)]BPh4·CH3OH and [Fe(im)2(hapacen)]BPh4·2CH3OH showed a striking thermochromic behavior in various organic solvents, changing from dark red to green with decrease of the temperature. The complexes are essentially of low-spin type in solids, where im and BPh4 denote imidazole and tetraphenylborate, respectively. Electronic, 1H NMR (Evans method), and ESR spectra confirmed that the thermochromism is caused by spin-equilibrium between high-spin(S=5⁄2) and low-spin(S=1⁄2) states of iron(III).

SPIN STATE EQUILIBRIUM OF IRON(III) COMPLEX WITH PLANAR UNSYMMETRICAL QUADRIDENTATE SCHIFF BASE IN SOLUTION

Abstract New iron(III) complex containing planar unsymmetrical quadridentate Schiff base, [FeIm2L]Bφ4, showed a striking thermochromism in solution, changing from dark red to green with decrease of the temperature, where Im, L, and Bφ4 denote imidazole, N-hydroxyacetophenone-N′-acetylacetone-ethylenediimine, tetraphenylborate, respectively. The electronic and ESR spectra established that the thermochromism is caused by the spin equilibrium between high spin(S=5/2) and low spin(S=1/2) of iron(III).

Synthesis and complexes of Unsymmetrical multidentate ligands. Part IV. Quadridentate ligands and the multidentate chemistry of manganese II. Part VII.

The synthesis and characterization is reported of a number of new unsymmetrical quadridentate ligands based on the interaction of o-aminophenol with mono-2-pyridyllhydrazones of various α-diketones. The stability of the ligands has been cofirmed by a study of their Mn((II) and Ni(II) compounds. The ligand derived from benzil was found to be particularly stable, and a further group of unsymmetrical quadridentates has been prepared, this set being based on the interaction of suitable primary amines with benzilmono-2-pyridylhydrazone. The ability of the ligands to act as stable planar ligands has been shown by preparation of various Mn(II) and Ni(II) complexes.