EPR Spectral Data Research Articles

Synthesis and Biological Studies of Schiff Base Metal(II) Complexes Derived from Isatin

Potentially bioactive Schiff base metal complex is a kind of attractive reagents due to specific activities of pharmacology and physiology. Medical inorganic chemistry has exploited metal ions' unique properties to design new drugs. In this study a novel Cu(II), Ni(II), Mn(II) and Co(II) Schiff base complexes have been from p - nitroaniline, isatin and 2, 2′ bipyridyl. The elemental analyses of the complexes are confined to the stoichiometry of the type L1L2M [M = Cu(II), Ni(II), Mn(II) and Co(II)], respectively, where L is Schiff base ligand in the ratio of 1:1:1. Structures have been proposed from elemental analyses, IR, UV, 1H NMR, ESR spectral data and magnetic studies. The measured low molar conductance values in DMF indicate that the complexes are nonelectrolytes. The IR data tells us the association of C=N nitrogen atom in co - ordination to the metal ion. The UV spectral studies and magnetic measurements suggested the octahedral geometry around metal ion under investigation. The EPR spectral data shows additional proof for the octahedral geometry. In addition, the antioxidative activity was also determined. The ligand's antioxidative activity and its complexes demonstrate that, compared to the ligand, the complexes exhibit higher scavenging activity. The antibacterial activity of these compounds was studied in vitro by the disc diffusion assay against two Gram-positive bacteria like Staphylococcus aureus, Bacillus subtilis and two Gram-negative bacteria like Escherichia coli and Klebsilla pneumonia. The complexes show significant growth inhibitory activity than ligands.

Cu(II) and Ni(II) Complexes of Bidentate E-N-(4-Isopropyl benzylidene)isonicotinohydrazide: Synthesis, Characterization, DNA Cleavage and Antioxidant Activity

The reaction of Cu(NO3)2·3H2O and Ni(NO3)2·6H2O with E-N-(4-isopropylbenzylidine)isonicotinohydrazide derived from isonicotinic acid hydrazide with 4-isopropyl benzaldehyde were synthesized and characterized structurally by physico-chemical and spectral techniques. The metal-ligand ratio in metal complexes is in the order of metal:ligand1:ligand2 (1:1:1) indicating the formulae of the complexes as [M(SB)2(NO2)2] (where M = Cu2+ & Ni2+, SB = C16H17N3O). The magnetic moment and electronic spectral data suggest tetragonal geometry for Cu(II) complex and octahedral geometry for Ni(II) complex around the central metal ions. The FT-IR and Far-IR spectroscopic data suggest the bidentate nature of ligand. The geometry of the Cu(II) complex and its covalence is confirmed by EPR spectral data. The Thermal decomposition of metal complexes has been identified using thermogravimetric analysis. The conductometric measurements proved the non-electrolytic behaviour of all the compounds. With the help of the agarose gel electrophoresis method, the DNA cleavage studies of Schiff base metal complexes were predicted. Also, the in-vitro antioxidant activity of Cu(II) complex was determined by a free radical scavenging assay.

Synthesis and Spectral Characterization of Mn(II) and Co(II) Complexes with Tetradentate Macrocyclic Ligand

Manganese(II) and cobalt(II) complexes were synthesized with [N4] tetradentate macrocyclic ligand using different metal salts i.e. MnCl2, Mn(NO3)2, CoCl2 and Co(NCS)2. The ligand was prepared by condensation of glyoxal and carbahydrazide. All these were characterized by elemental analysis, molar conductance measurements, magnetic moment, IR, mass, electronic and EPR spectral studies. Elemental analysis indicates that the complexes have composition MLX2 where (X = Cl–, NO3 –,NCS–). All the complexes were found to be non-electrolytic in nature so can be formulated as [MLX2]. Infrared spectra of metal complexes suggest that the ligand behaves as tetradentate. On the basis of magnetic moment, electronic and EPR spectral data, all the metal complexes were found to be high spin with octahedral geometry.

Ru(III)-pseudohalide complexes with alkynyl functionalized salicylaldimine ligand and heterocyclic coligand: Synthesis, characterization, electrochemical and luminescence properties

A new series of hexa-coordinated Ru(III) complexes of the type [Ru(L)(phen)X2] (1a-3a) and [Ru(L)(bipy)X2](1b-3b) [where, X = NCS, N3, CN] have been prepared by the reaction of RuCl3·H2O with 2-((E)-(4-(2-(4-methoxyphenyl)ethynyl)phenylimino)methyl)-4-(2-(4-methoxy phenyl)ethynyl)phenol (L) in presence of 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) as a ligand. The molecular structure of ligand L was confirmed by single crystal X-ray diffraction. All complexes were characterized on the basis of elemental analysis, magnetic moment, TGA, IR, UV–Vis, EPR and mass spectral studies. The EPR spectral data and magnetic susceptibility measurement showed octahedral geometry around Ru(III). The electrochemical properties of all complexes indicate quasireversible redox behaviour corresponding to Ru(III)/Ru(IV) and Ru(III)/Ru(II) couple and are variable to π-acidic character of phen and bipy. All complexes exhibit strong emissions from lowest energy ILCT state with some LMCT character in DMF (10-4 M) at room temperature indicating that alkynyl functionality on salicylaldimine ligand enhances the emission property of the complexes and varies considerably with quenching ability of pseudohalides.

Mixed alkali effect on borosilicate glass structure with vanadyl ion as spin probe

Mixed alkali borosilicate glasses doped with 2% vanadium oxide were synthesized by conventional melt-quench method. The Micro structure of the materials was analysed using XRD, SEM and EDX spectrum. Optical nature of glasses was studied by computing optical bandgaps with absorption spectral data. Covalent nature of glasses was estimated correlating optical bandgap energy with EPR spectral data. The metallization criterion of glasses was evaluated from the physical parameters. FTIR and Raman spectral techniques were used to identify the structural groups of the borates and silicates that are formed with addition of modifiers. Emission spectra were recorded at excitation wavelength of 350 nm and their thermal nature was also studied using TGA/DTA techniques.

United calculation of the optical and EPR spectral data for Co2+-doped CdS crystal

This article reports a united calculation of the optical band positions and EPR parameters (g factors g//, g⊥ and zero-field splitting D) for Co2+ ion at the trigonal tetrahedral Cd2+ site of CdS crystal by using the complete diagonalization (of energy matrix) method built on the cluster approach. In the approach, the one-electron basis functions are the molecular orbitals composed of the d orbitals of central dn ion and p orbitals of ligands (rather than only the pure d orbitals in the conventional crystal-field theory), and so the contributions from not only the spin-orbit parameter of dn ion, but also that of ligand ion are contained. The calculated results are in rational agreement with the twenty-two (nineteen optical band positions and three EPR parameters) observed spectral values found in the literature. The defect structure (particularly, the angular distortion) of the trigonal Co2+ center in CdS: Co2+ is also acquired by the calculation. The outcomes are discussed.

Investigations of the optical and EPR spectral data for the trigonal Cr3+ center in ZnGa2O4: Cr3+ crystal with a unified method-complete diagonalization of energy matrix

The optical and EPR spectral data of the trigonal Cr3+ centers in ZnGa2O4: Cr3+ crystal are unifiedly calculated by applying the complete diagonalization of energy matrix method resting on the two-spin-orbit-parameter model, where the one-electron basis functions are the molecular orbitals and the contributions from both the spin-orbit parameters of dn ion and ligand ion are included. Thus, the Racah parameters B, C, two spin-orbit parameters and two orbit reduction factors can be evaluated from a adjustable parameter, the covalence factor, and so only three adjustable parameters are used in the calculation. The ten calculated spectral data (seven optical band positions and three EPR parameters, g factors g//, g⊥ and zero-field splitting D) are rationally consistent with the experimental values. The defect structure of the trigonal Cr3+ center is also given. These outcomes are discussed.

Unified research of the EPR and optical spectral data for Cr3+-doped Lu3Al5O12 crystal

In this article, we apply a complete diagonalization (of energy matrix) method to simultaneously calculate the spin-Hamiltonian (or EPR) parameters (g factors g//, g⊥ and zero-field splitting D) and optical band positions (or crystal field energy levels) of Cr3+-doped Lu3Al5O12 (LuAG) crystal. The method is based on the two-spin-orbit-parameter model where besides the effects of spin-orbit parameter of central dn ion in the common crystal-field theory, those of ligand ions are contained. The calculated results indicate that by using only three adjustable parameters, the eight observed spectroscopic data (three EPR data and five optical bands) are reasonably explained. This suggests that this diagonalization method is effective and applicable in the unified calculation of EPR and optical spectral data for d3 ions in crystals. The local lattice distortion caused by the Cr3+ impurity in LuAG crystal is also estimated. The outcomes are discussed.

Research on the optical and EPR spectral data and the local structure for the trigonal Mn4+ centers in MgTiO3 crystal

The optical bands and EPR (or spin-Hamiltonian) parameters (g factors g//, g⊥ and zero-field splitting D) for Mn4+ ions at the trigonal octahedral Ti4+ site of MgTiO3 crystal are uniformly computed by virtue of the complete diagonalization (of energy matrix) method based on the two-spin-orbit-parameter model, where besides the effects of spin-orbit parameter of central dn ion on the spectral data (in the classical crystal field theory), those of ligands are also contained. The computed eight optical and EPR spectral data with four suitable adjustable parameters (note: differing from those in the previous work within cubic symmetry approximation where the used Racah parameters violate the nephelauxetic effect, the present Racah parameters obey the effect and hence are suitable) are rationally coincident with the experimental values. In particular, the calculated ground state splitting 2D, the first excited splitting ΔE(2E) and g-anisotropy Δg (=g//−g⊥) (they depend strongly on the angular distortion of d3 centers) are in excellent agreement with the observed values, suggesting that the angular distortions caused by the impurity-induced local lattice relaxation obtained from the above calculation for the trigonal Mn4+ impurity center in MgTiO3: Mn4+ crystal seem to be acceptable.

Studies of the optical and EPR spectral data for the trigonal strong field Cr3+ centers in Cr3+-doped Ca3Ga2Ge4O14 and Sr3Ga2Ge4O14 crystals

This paper represents the unified theoretical computations for the trigonal strong field Cr3+ centers (assigned to Cr3+ at octahedral Ga3+ sites) in Cr3+-doped Ca3Ga2Ge4O14 and Sr3Ga2Ge4O14 crystals. The computations adopt the complete diagonalization (of energy matrix) method based on the two-spin-orbit-parameter model where the contributions from both the spin-orbit parameter of central dn ion (in the classical crystal field theory) and that of ligand ion are contained. The calculated six optical bands and three spin-Hamiltonian parameters (g factors g//, g⊥ and zero-field splitting D) with only three adjustable parameters are reasonably coincident with the observed values. The very small local lattice relaxation in the Cr3+ centers in both crystals indicates the similarities of valence and ionic radius between Cr3+ ion and the replaced host ion. This supports the assignment that the trigonal strong field Cr3+ centers in both crystals are due to Cr3+ at octahedral Ga3+ site rather than octahedral Ge4+ site (the latter may be the weak field Cr3+ center).

Uniform calculation of the optical and EPR spectral data for the trigonal (CrO6)9− octahedral clusters in Y3Al5O12 crystal

The complete diagonalization (of the energy matrix) method is applied in this paper for the unified calculation of optical and EPR spectral data of the trigonal (CrO6)9− octahedral clusters in Y3Al5O12 (YAG) crystal. The method is based on the two-spin–orbit-parameter model where, besides the contributions from the spin–orbit parameter of central dn ion in the traditional crystal-field theory, those from the spin–orbit parameter of ligand ions via the covalence effect are considered. The computed 32 spectroscopic data values (29 crystal field energy levels and three spin-Hamiltonian parameters, namely the g factors g// and g⊥, and the zero-field splitting D) are in reasonable agreement with the experimental values, despite using only four adjustable parameters. This suggests that the method is valid in the uniform calculation of optical and EPR spectral data for d3 ions in crystals. The impurity-induced angular distortion of the (CrO6)9− clusters in YAG crystal was also evaluated.

SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY OF MANGANESE(II) AND NICKEL(II) COMPLEXES OF 7-DIETHYLAMINOBENZYL-8-HYDROXYQUINOLINE

8-Hydroxyquninoline Mannich base namely 7-diethylaminobenzyl-8-hydroxyqunioline(DEBQ) was synthesized and characterized by elemental analysis and spectral studies. Chelates of DEBQ with manganese(II) and nickel(II) were isolated and structurally characterized by elemental analysis, electrical conductance, magnetic susceptibility measurement, thermal analysis, IR,UV-Vis, EPR and Mass spectral data. The Mannich base ligand is bidentate and chelates through the phenolic oxygen and the aliphatic tertiary amino nitrogen atoms. Based on the magnetic and electronic spectral data all the MnII complexes are assigned an octahedral geometry and NiII complexes are assigned a tetrahedral geometry. Antimicrobial susceptibility screening of the Mannich base shows that it possesses excellent activity when compared to the standard drugs and the metal complexes studied. Among the chelates, MnII chelate is more potent than NiII chelate. Thermal analysis of a few compounds shows two stage decomposition patterns.

Unitized research of the optical and EPR spectral data for Cr3+ ions in La3Ga5Ge O14 crystal

The complete diagonalization (of energy matrix) method founded on the two-spin-orbit-parameter model is employed to calculate uniformly the optical and EPR spectral data for Cr3+ ions at the trigonal octahedral Ga3+ site of La3Ga5GeO14 (LGGO) crystal. Differing from the one-spin-orbit-parameter model in the conventional crystal field theory where the contribution only from spin-orbit parameter of central dn ions is considered, the present model takes account of the contributions from both the spin-orbit parameters of dn ion and ligand ion via covalence effect. The calculated results show that the observed eight optical and EPR spectral data (five optical bands and three EPR parameters g//, g⊥ and D) can be rationally explained with only three adjustable parameters. The small impurity-caused local lattice relaxation is due to the similarity of valence state and size between the substitutional ion Cr3+ and the host ion Ga3+.

A treatise on benzimidazole based Schiff base metal(II) complexes accentuating their biological efficacy: Spectroscopic evaluation of DNA interactions, DNA cleavage and antimicrobial screening

Two novel imidazole derived Schiff bases, (Z)-1-(1H-benzo[d]imidazol-2-yl)-N-benzylidenemethanamine (L1) and 1-(1H-benzo[d]imidazol-2-yl)-N-(4-nitrobenzylidene) methanamine, and a series of their transition metal complexes of the types [M(L1)2]Cl2 and [M(L2)2]Cl2 where, M=Cu(II), Ni(II), Co(II) and Zn(II) have been designed and synthesized. These compounds were characterized by various spectral and physicochemical data. UV–Vis, magnetic susceptibility and molar conductivity data indicate that all the complexes adopt square planar geometry. The EPR spectral data of the Cu(II) complexes have provided supportive evidence to the conclusion derived on the basis of electronic absorption and magnetic moment values. Moreover, the interaction of complexes with DNA via intercalation has been explored by absorption, fluorescence spectroscopy, cyclic voltammetry, viscosity and circular dichroism. Agarose gel electrophoresis technique reveals that the complexes are good metallonucleases. All the compounds have relatively high antibacterial and antifungal potencies. Among the metal complexes, Cu(II) complexes exhibit higher efficacy against all the pathogens.

A Unified Calculation of the Optical and EPR Spectral Data for the Trigonal Cr3+Center in Cr3+-Doped α-RbAl(SO4)2·12H2O Alum Crystal

A Unified Calculation of the Optical and EPR Spectral Data for the Trigonal Cr3+Center in Cr3+-Doped α-RbAl(SO4)2·12H2O Alum Crystal

Unified research of the optical and EPR spectral data for the trigonal Cr3+ centers in emerald crystals

The complete diagonalization (of energy matrix) method founded on the two-spin–orbit-parameter model (where the contributions from both the spin–orbit parameter of central dn ion and that of ligand ions are contained) is adopted to calculate together the optical and EPR spectral data for the trigonal Cr3+ centers in emerald crystal. The computed 18 optical and EPR spectral data (15 optical band positions and three spin-Hamiltonian parameters) with only five adjustable parameters are in rational accordance with the experimental values. The calculations indicate that the above diagonalization method is able to explain unifiedly the optical and EPR spectral data for d3 ions in crystals.

Unified research on the optical and EPR spectral data for the Cr3+ion in the low-temperature trigonal phase of a LaAlO3crystal

The crystal field energy levels (or optical band positions) and EPR parameters ( g factor g// , g ⊥ and zero-field splitting D ) for the Cr 3+ ion in the trigonal phase of a LaAlO 3 crystal are calculated together through the complete diagonalization (of energy matrix) method. The method is founded on the two-spin-orbit-parameter model in which the contributions from both the spin-orbit parameter of the central d n ion and that of the ligand ion (the latter is ignored in the conventional crystal field theory) are considered. From the calculations, the observed seven optical band positions and three EPR parameters ( g// , g ⊥, D ) for LaAlO 3 :Cr 3+ at T ≈ 4.2 K are reasonably and unifiedly explained with only four adjustable parameters, and the impurity-induced local angular distortion of the Cr 3+ center in LaAlO 3 is estimated.

Research on the Optical and EPR Spectral Data and the Local Structure for the Tetragonal Nb4+Center in Glasses

Research on the Optical and EPR Spectral Data and the Local Structure for the Tetragonal Nb4+Center in Glasses

Unified calculation of optical and EPR spectral data for Cr3+-doped KAl(MoO4)2 crystal

This paper reports an unified calculation of optical and EPR spectral data for Cr3+ ion at the trigonal Al3+ site of KAl(MoO4)2 crystal from the complete diagonalization (of energy matrix) method based on the two-spin–orbit-parameter model. In this model, differing from that in the conventional crystal-field theory, not only the contributions from the spin–orbit parameter of central dn ion, but also those from the spin–orbit parameter of ligand ion via covalence effect are taken into account. The calculation shows that by using only three adjustable parameters, the observed twelve optical and EPR spectral data (nine optical band positions and three EPR parameters g||, g⊥ and D) are reasonably explained in a unified way with this method. The results are discussed.

Unified calculations of optical and EPR data for Cu3+ ion in Al2O3 crystal

The optical band positions and EPR parameters ( g factors g ∥ , g ⊥ and zero-field splitting D ) for Cu 3+ ion in Al 2 O 3 crystal are calculated by using the complete diagonalization (of energy matrix) method based on the two-spin–orbit-parameter model. In the model, both the contribution to the spectral data from the spin-orbit parameter of central 3d n ion and that of ligand ion are contained. The calculated results show reasonable agreement with the experimental values. The defect structure of Cu 3+ impurity center is estimated from the calculations. • Unified calculation for the optical and EPR spectral data of Cu 3+ in Al 2 O 3 is made. • The complete diagonalization (of energy matrix) method is used in the calculation. • The diagonalization method is based on the two-spin–orbit-parameter model. • The defect structural data is obtained from the calculation.