EPR Spectra Of Cu2 Research Articles

Synthesis, spectroscopic and biological studies of metal complexes of an ONO donor pyrazolylhydrazone – Crystal structure of ligand and Co(II) complex

A new pyrazolylhydrazone, 2-(2-(1,5-dimethy-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazolyl-4-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (HL) and its Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were synthesized and structurally characterized by elemental analysis, molar conductance, magnetic measurements and spectral (IR, 1H NMR, UV–vis, HRMS) measurements. All complexes possess ML2 stoichiometry with L behaving as monoanionic tridentate ONO donor. Single crystal X-ray diffraction reveals that HL and CoL2 crystallize in orthorhombic system with Pbcn space group. Hydrogen bonding interactions between molecules of CoL2 results in the formation of an infinite zig-zag chain extending along the ‘b’ axis. EPR spectrum of Cu(II) complex at 77 K suggests mononuclear and distorted octahedral geometry for [CuL2]. Antimicrobial activity of HL and its complexes were investigated and minimum inhibitory concentrations identified. Bacterial and fungal organisms used were gram-positive Staphylococcus aureus, gram-negative Escherichia coli, Aspergillus niger and Candida albicans.

Design, Spectroscopic Characterization, Thermal, 3D Molecular Modeling, XRD and in Vitro Antioxidant and Antimicrobial Screening of Novel N2O2 Tetradentate Schiff’s Base Metal Complexes

In the present study, new Co(II), Ni(II) and Cu(II) complexes were synthesized from the reaction of tetradentate Schiff’s base ligand (H2L)= (N, N'-(pyridine- 2,6- diyl) bis (2- (((Z)- (2- hydroxynaphthalen-1-yl) methylene) amino) benzamide that was synthesized via condensation of 2-amino-N-{2-[(2-amino-benzoylamino) pyridine]-benzamide} with 2-hydroxy-1-naphthaldehyde. The ligand and its metal (II) complexes were characterized by microanalyses, magnetic, spectral, powder X-ray diffraction (XRD) and thermal studies. An octahedral geometry has been proposed for [Co(L)(H2O)2].3H2O (1), [Ni(L)(H2O)2].1½H2O (2) and square planar for [Cu(L)](3) and [Cu(H2L)(OH)Br](4). EPR spectra of Cu(II) complexes are consistent with d x²-y² ground state. 3D molecular modeling studies have been carried out for ligand and complex (1). Average crystallite size (D) and dislocation density (δ) were calculated from XRD. All compounds were screened for their in vitro antioxidant activity. The results showed that the ligand possesses excellent activity compared to the reference (Ascorbic acid drug) and complex (4) was the most potent one. Moreover, the current compounds were tested for their antimicrobial activity.

Cobalt(III) complex of substituted nalidixic acid: Synthesis, characterization (IR, UV, EPR), single crystal X-ray, antimicrobial activity, Hirshfeld surface analysis and molecular docking

The mixed–ligand title complex, [Co(nal)2(py)2].4H2O (Hnal=nalidixic acid, py=pyridine), was synthesized. Its structural properties were characterized by X–ray diffraction technique (XRD) and elemental analysis. The spectroscopic properties are investigated by Fourier transform infrared spectroscopy (FT–IR), UV–Vis spectroscopy and EPR spectroscopy. The Co(II) ion has slightly distorted octahedral geometry surrounded by two oxygen atoms of keto and carboxyl groups bonded as chelate from nalidixate, two nitrogen atoms from two pyridine ligands. The monomer are connected by C–H···O and C–H···C interactions to form sheet structures. The FT-IR studies of the complex were commented, focusing on the shifts in the vibrational peaks between the complex form and free nalidixic acid. The powder EPR spectra of Cu(II)-doped complex were investigated at room and at liquid nitrogen temperature. The EPR and UV–Vis spectroscopy studies showed that the unpaired electrons were found in the dx2−y2 orbitals by calculating the spin-Hamiltonian and bond parameters. 2D and 3D Hirshfeld analyses were performed in order to quantify the order and nature of intermolecular interactions in crystal network. Antibacterial activity of complex was studied against S. aureus, B. subtilis, P. aeruginosa, E. coli, C. albicans and A. flavus by using the micro dilution. The optimized complex is docked to 5J9B (S. aerous), 5BMM (E. Coli), 5HTG (C. Albicans), 1ZUV (B. Subtilis), 4F0V (P. aeruginosa) and 4YNU (A. flavus).

Synthesis, crystal structure, spectroscopic (FT-IR, UV–Vis, EPR) and Hirshfeld surface analysis studies of Zn(II)-benzoate coordination dimer

Mixed ligand coordination dimer [Zn2(BA)4(NA)2].(BAH), (BAH=Benzoic acid, NA=nicotinamide), synthesized and its supramolecular architecture was investigated. The structural properties of the coordination dimer were characterized by X-ray diffraction (XRD), elemental analysis, spectroscopic methods (EPR, UV–Vis and FT-IR), thermogravimetric analysis and Hirshfeld surface analysis. The complex crystallized in the monoclinic crystal system and the P21/c space group. Two benzoate anions bind to zinc metals as chelates, while the other two-benzoate anions bridge between two metals. The coordinate environment of the Zn1 atom has a nearly ideal square pyramidal geometry and the τ factor defined by Addison is 0.09. The coordination environment of the Zn2 atom has an extremely distorted (4 + 1) pseudo-square pyramidal geometry and the τ factor was found to be 0.35. Hydrogen bonds and π⋯π weak interactions form a three-dimensional supramolecular structure. IR spectroscopic studies of the complex were performed in the middle IR region, focusing mainly on the characteristic vibrations of benzoic acid and nicotinamide, taking into account ligand functional groups within the complex. The EPR spectra of Cu(II)-doped complex were investigated at room and at liquid nitrogen temperature. As a result of EPR analysis, spin hamiltonian parameters were obtained. In addition, zero field splitting parameters of the dimer-complex was obtained as Dobs = 0.60 cm−1 and E ≈ 0. Thermogravimetric Analysis (TGA) was carried out thermal properties. 2D and 3D Hirshfeld analyses were performed in order to quantify the order and nature of intermolecular interactions in crystal network.

The Estimation of Blood Paramagnetic Center Changes during Burns Management with Biodegradable Propolis-Nanofiber Dressing.

The evolution of the paramagnetic center system in blood during the healing of skin burn wounds dressed with a biodegradable apitherapeutic nanofiber dressing was examined. The aim of this study was to determine the changes in paramagnetic centers in blood during the influence of apitherapeutic nanofiber dressings on the healing process. The blood samples were tested before burn infliction (day 0) and, respectively, on the 10th and 21st days of the experiment. Paramagnetic centers in the blood of the pig used as the model animal were examined with an X-band (9.3 GHz) electron paramagnetic resonance spectroscopy. The EPR spectra were measured with Bruker spectrometer at 230 K with a modulation frequency of 100 kHz. The EPR lines of the high spin Fe3+ in methemoglobin, high spin Fe3+ in transferrin, Cu2+ in ceruloplasmin, and free radicals were observed in the multicomponent spectra of blood. For the application of the apitherapeutic nanofiber dressing, the amplitudes of the EPR signals of Fe3+ in methemoglobin were similar up to 10 days. For the experiment with the apitherapeutic formulation, the heights of EPR signals of Fe3+ in transferrin were lower after 10 days and 21 days of therapy, compared to day 0. For the application of the apitherapeutic formulation the signals of Cu2+ in ceruloplasmin and free radicals, strongly decreased after 10 days of therapy, and after 21 days it increased to the initial values characteristic for day 0. The apitherapeutic formulation caused that after 21 days the EPR spectrum of Cu2+ in ceruloplasmin and free radicals was considerably high. The apitherapeutic formulation interaction after 10 days and after 21 days of therapy resulted in the low EPR lines of Fe3+ in methemoglobin. EPR spectra of blood may be useful for presentation of the changes in its paramagnetic centers during the healing process of the burn wounds.

Spectroscopic, structural characterization and magnetic studies of Cu(II)-sulfathiazole complex with 1,10-Phenanthroline and N-(2-hydroxyethyl)-Ethylenediamine ligands

Abstract Cu(II)-sulfathiazole (Hstz:4-amino-N-(1,3-thiazol-2-yl) benzene sulfonamide) complex with phen (1,10-Phenanthroline) and Hydeten (N-(2-hydroxyethyl)-Ethylenediamine) has been synthesized and characterized by single crystal X-ray diffraction, IR, EPR and UV–Vis spectroscopy, thermal analysis. The [Cu(stz)(Hydeten)(Phen)].(stz)(Phen) complex crystallizes in the orthorhombic space group Pca21, Z = 4. The sulfathiazole anion acts as a monodentate ligand through the thiadiazole N atom contiguous to the deprotonated sulfonamide group. The trigonality factor (τ = (β-α)/60) value of the copper complex is 0.14 and this value expresses having slightly distorted square pyramidal environment of the Cu(II) ions coordination. The powder EPR spectra of Cu(II) complex were recorded at room temperature and liquid nitrogen temperature. The EPR spectral analysis has led to that the ground state of the unpaired electron of copper ion is d x 2 − y 2 . As results of the minimum inhibitory concentration (MIC) values obtained as results of the antimicrobial study for stz and complex, it was seen that the metal-stz complex was more effective than free stz.

Characterization by Potentiometric Procedures of the Stability Constants of the Binary and Ternary Complexes of Cu(II) and Duloxetine Drug with Amino Acids

Potentiometric titration method has been used to define stoichiometries and stability constants of ternary complexes of Cu(II) with duloxetine (D) and some selected amino acids (L). The protonation constants of the ligands and the stability constants of the binary and ternary complexes of Cu(II) with the ligands were calculated from the potentiometric data using the HYPERQUAD program. The formation constants of the complexes formed in aqueous solutions and their concentration distributions as a function of pH were evaluated at 25°C and ionic strength 0.10 mol·L−1NaNO3. Respective stabilities of ternary complexes have been determined compared with the corresponding binary complexes in terms ofΔlog Kand %R.S. values. A novel binary and ternary duloxetine (D) drug with glycine and its Cu(II) complexes has been synthesized and characterized by several spectroscopic methods. Electronic spectra and magnetic susceptibility measurements reveal square planar geometry for both complexes. The elemental analyses and mass spectral data have justified the [Cu(D)(Gly)] and [Cu(D)Cl(H2O)] composition of complexes, where D = duloxetine and Gly = glycine. The EPR spectra of Cu(II) complexes support the mononuclear structures. Thermal properties and decomposition kinetics of Cu(II) complexes are investigated.

Cobalt(II), nickel(II) and copper(II) complexes of N-{(2-pyridyl)methyliden}-6-coumarin: Characterization, DNA interaction, catecholase activity and theoretical interpretation

[M(X)2(N,N/)2] (M = Co(II), Ni(II), Cu(II); X = N3−, SCN−; N,N/ = N-{(2-pyridyl) methyliden}-6-coumarin, a bidentate diimine pyridyl-N (N), imine-N (N/) chelator) have been characterized by different physicochemical data. The structural confirmation has been done for [Ni(N3)2(N,N/)2] by single crystal X-ray diffraction data. On considering the sequence of coordination of azide-N (N3−), pyridyl-N (N) and imine-N (N/) the structure of [Ni(N3)2(N,N/)2] follows cis-cis-cis-(ccc)-Ni(N3)2(N,N/)2] configuration. The complexes are paramagnetic and the EPR spectra of Cu(II) complexes provide information about hyperfine and super-hyperfine structures. The cyclic voltammogram shows M(II)/M(III), Cu(I)/Cu(II) and reductions of chelated diimine ligand. Only [Cu(N3)2(N,N/)2] (3) shows efficient catecholase activity (rate, 4.93 × 10−4 min−1) while [Cu(SCN)2(N,N/)2] (6) is very slow and other complexes are silent. The complexes show significant interaction with DNA and [Cu(N3)2(N,N/)2] (3) shows highest binding constant 5.58 × 105 (ΔG, −7.43 kcal mol−1) amongst these complexes.

Molecular docking and DFT studies on some nano-meter binuclear complexes derived from hydrazine-carbothioamide ligand, synthesis, thermal, kinetic and spectral characterization

New metal ion complexes were prepared using Cr(III), Co(II), Pd(II) and Cu(II) ions. The Schiff base ligand used is a multi-dentate chelating compound. The IR, 1HNMR and mass spectra are used to verify the structural and molecular formula of the organic ligand. The ligand coordinates as a neutral tetra-dentate towards Cr(III) and Pd(II) ions, whereas a bi-negative tetra-dentate towards Co(II) and Cu(II) ions in bi-nuclear complexes. The electronic spectral data were investigated to propose the geometry of four coordination numbers surrounding all metal ions except Cr(III) ion (six coordination). The covalency parameters were calculated for Cr(III) and Co(II) complexes using their electronic spectra. The EPR spectrum of Cu(II) complex introduces parameters supporting the electronic data. X-ray diffraction patterns are displaying the nano-crystalline character for the ligand, Co(II) and Cu(II) complexes. Their particle sizes calculated applying referenced equations propose the nano-sized feature isolated for them. TEM images also proposed the nano-meter appearance of the synthesized compounds. The DFT studies on the organic compound and its isolated complexes were carried out implementing Materials Studio package to calculate the characteristic parameters after geometry optimization. Molecular docking and theoretical statistics were done to expect the biological behavior of the organic compound and its complexes. The biological activity was studied against different organisms and the negative result is the main feature.

Elaborated spectral analysis and modeling calculations on Co(II), Ni(II), Cu(II), Pd(II), Pt(II), and Pt(IV) nanoparticles complexes with simple thiourea derivative

A series of metal complexes was synthesized using a simple thiourea derivative. The prepared complexes were characterized using different techniques (FTIR, ESR, X-ray diffraction [XRD], TG/DTA, and TEM). The FTIR spectrum of the ligand shows the presence of its tautomer forms (keto–enol). The ligand coordinates as a neutral bidentate in the Pt(IV), Pd(II), and Pt(II) complexes. In the case of Co(II) and Ni(II) complexes, the ligand is mono-negative bidentate. The proposed complexes are four to six coordinate. The geometries are proposed based on electronic spectral data and magnetic measurements and were verified using other tools. The XRD patterns reflect the nanocrystalline structures except for the Cu(II) complex, which is amorphous. The TEM images for platinum complexes show nanosize particles and homogeneous metal ion distribution on the complex surface. The EPR spectrum of Cu(II) complex verified the octahedral geometry of the complex. Molecular modeling was performed to assign the structural formula proposed for the ligand based on the characterization results.

Synthesis, molecular structure, and spectral analysis of copper(II) complexes derived from pyridinediols

A series of mononuclear copper(II) complexes was synthesized by reaction of different 2,6-disubstituted pyridines with elemental Cu in a CCl4/DMSO solvent system. Physical properties were analyzed using IR, optical spectroscopy, mass spectrometry, and EPR. Single-crystal X-ray diffraction for complexes 2a and 4a revealed that the molecular structure of 2a is composed of a six-coordinate unit in which two ligands are linked to Cu(II) by oxygen and nitrogen donors. Conversely, in the molecular structure of 4a, the Cu(II) has a slightly distorted trigonal bipyramidal arrangement, where the coordination environment around the copper ion is five-coordinate. EPR spectra of Cu(II) complexes were illustrated elaborately and some theoretical data were abstracted from EPR curves to support the proposed structures.

Synthesis, spectroscopic characterization, analgesic, and antimicrobial activities of Co(II), Ni(II), and Cu(II) complexes of 2-[N,N-bis-(3,5-dimethyl-pyrazolyl-1- methyl)]aminothiazole

Synthesis of new series of Cu(II), Co(II), and Ni(II) from the ligand 2-[N,N-bis-(3,5-dimethyl-pyrazolyl-1-methyl)]aminothiazole is described. The ligand and its complexes were characterized by various techniques such as elemental analysis, FT-IR, UV–Visible, 1H and 13C NMR spectra, mass spectrum, and conductometry. The electronic absorption spectra and magnetic susceptibility measurements suggest a square planar geometry for Cu(II) complex and distorted tetrahedral geometry for the other metal(II) complexes. The EPR spectrum of Cu(II) complex recorded at 77°K confirms the distorted square planar geometry. The antimicrobial activities of the ligand and metal complexes against the bacterial species such as Xanthomonas maltophilia, Chromobacterium violaceum, Acinetobacter,Staphylococci, Streptococci, and the fungus Candida albicans are carried out and the results indicated that all compounds exhibit more antibacterial activity than the standard drug. The synthesized compounds were investigated for analgesic activity and they act as potent analgesic drugs.

Synthesis, characterization, molecular modeling and antioxidant activity of Girard′s T thiosemicarbazide and its complexes with some transition metal ions

The chelation behavior of N-{[(allylamino) thiomethyl] hydrazinocarbonylmethyl} trimethylammonium chloride (H3ATHC) towards VO2+, Co2+, Ni2+, Cu2+, Zn2+ and UO22+ ions have been studied. The structures of the complexes were elucidated using elemental analyses, spectral (IR, UV–visible, 1H NMR and ESR and mass) as well as magnetic and thermal measurements. The ligand acted as ON bidentate, ONS tridentate donor forming mononuclear complexes. A tetrahedral geometry for Co2+, square-planar for Ni2+ and Cu2+, an octahedral for Zn2+ and a square-pyramidal arrangement for VO2+ complexes were proposed, respectively. The EPR spectra of Cu2+ and VO2+ complexes confirmed the suggested geometries with values of α2 and β2 indicating that the in-plane σ-bonding and in-plane π-bonding are appreciably covalent, and were consistent with very strong in-plane σ bonding in the complexes. Also, the bond length, bond angle, HOMO, LUMO, dipole moment and charges on the atoms have been calculated. Also, the thermal behavior and kinetic parameters were determined using Coats–Redfern and Horowitz–Metzger methods. Furthermore, the synthesized compounds were screened for their superoxide-scavenging activity in the PMS/NADH-NBT system as well as their scavenging effect on ABTS (2,2′-azino-bis(3-ethyl benzthiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl(DPPH) radicals. Among these compounds, the ligand and Zn2+ complex, exhibited the potent ABTS (2,2′-azino-bis(3-ethyl benzthiazoline-6-sulfonic acid) radical scavenging activity, comparable to that of vitamin C.

Synthesis, characterization, biological activity of binuclear Co(II), Cu(II) and mononuclear Ni(II) complexes of bulky multi-dentate thiosemicarbazide

The chelation behavior of 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbonyl) bis (N-ethylhydrazine-1-carbothioamide) (H6ETS)(1) towards Co2+, Ni2+and Cu2+ have been studied. The spectral data revealed that the ligand acts as a bi- and/or mono-negative multi-dentate. The isolated Ni(II) and Cu(II) complexes are square-planar while the Co(II) is tetrahedral. EPR spectrum of Cu(II) complex confirmed simulated an axial spin-Hamiltonian exhibiting a four-line pattern with nitrogen super-hyperfine couplings originating from imine hydrazinic nitrogen atoms and possess a significant amount of tetrahedral distortion leading to a pseudo-square-planar geometry with unpaired electron has dx2-y2 ground state. Also, the thermal behavior and kinetic parameters were determined. Furthermore, the title compounds were investigated for their antibacterial activity using inhibition zone diameter and for DNA degradation, superoxide-scavenging activity as well as hydroxyl radicals that generated by the oxidation of cytochrome c in L-ascorbic acid/CuSO4–cytochrome c system.

EPR and optical absorption studies of Cu2+ doped L-histidinium dihydrogen phosphate–phosphoric acid single crystal

The EPR spectra of Cu2+ in l-histidinium dihydrogen phosphate phosphoric acid at room temperature reveal the presence of two magnetically inequivalent Cu2+ sites in the lattice. The principal values of the g- and A-tensors indicate existence of rhombic symmetry around the Cu2+ ion. From the direction cosines of the principal values of the g- and A-tensors, the locations of Cu2+ in the lattice have been identified as substitutional sites. Optical absorption study shows four bands confirm the rhombic symmetry. Photoluminescence study also confirms the rhombic symmetry around the ions.

Molecular structure, vibrational and EPR spectra of Cu(II) chloride complex of 4-amino-1-methylbenzene combined with quantum chemical calculations

Transition metal complex of CuCl2 with L=4-amino-1-methylbenzene, i.e., [CuCl2L2], has been synthesized and characterized by elemental analyses, FT-IR, dispersive Raman and EPR methods. The geometrical structure and vibrational spectra of L and [CuCl2L2] have been investigated in terms of density functional calculations employing the 6-311G+(d,p) basis set. The normal modes have been assigned on the basis of the percent potential energy distribution (PED) of the internal motions in each vibrational modes. The effects of the coordination on vibrational modes have been investigated. The experimental vibrational and EPR spectral studies and theoretical calculations find the title complex as a doublet with one unpaired electron.

Spectroscopic evaluation for VO(II), Ni(II), Pd(II) and Cu(II) complexes derived from thiosemicarbazide: A special emphasis on EPR study and DNA cleavage

Some thiosemicarbazide complexes were prepared and deliberately investigated by all allowed tools. The ligand coordinates as a mono negative bidentate towards VO(II) and Ni(II) as well as a neutral bidentate towards Pd(II) and Cu(II) ions. Electronic spectral data beside the magnetic measurements facilitate the structural geometry proposal. EPR spectra of Cu(II) and VO(II) complexes were recorded in their solid state. Spin Hamiltonian parameters and molecular orbital coefficient for Cu(II) and VO(II) complexes were calculated and supporting the octahedral geometry of Cu(II) complex and a square pyramidal for VO(II) one. The biological activity investigation was studied by the use of all prepared compounds. The VO(II) and Cu(II) complexes display the susceptible biotoxicity against a gram-positive bacterium. Also, Cu(II) complex displays the same toxicity against gram-negative bacteria used. The effect of all compounds on DNA were photographed. A successive degradation for the DNA target was observed with Pd(II) and Ni(II) complexes beside their original ligand.

Reasons for the line broadening in the epr spectra of copper ions in Li2-2x Zn2+x (MoO4)3 lithium-zinc molybdate crystals

An EPR study of Li2−2xZn2+x(MoO4)3 crystals activated by copper ions shows that they occupy the M2 site, one of the three possible sites of both lithium and zinc. In the EPR spectra of Cu2+ copper a broadening of HFS lines and a nonequidistant splitting between them, which are unusual for the orientation H‖gzz, Azz, are observed. In this work possible reasons for such a broadening of HFS lines from copper ions are analyzed: a distortion of the oxygen octahedron due to the introduction of copper ions, second order perturbation theory corrections, superposition of HFS from 63Cu and 65Cu isotopes, and the effect of the charge redistribution in the oxygen octahedron because the cation vacancy providing charge compensation can be located at different distances from the copper ion. It is shown that the first three reasons do not explain the features observed in the EPR spectra. In the case of cation vacancies located in the M3 site and remote at different distances from the copper ion, the charge redistribution in the oxygen octahedron of copper should occur along with the dispersion of HFS parameters and the g-factor. The studies performed in X and Q bands confirm this assumption. The width of HFS lines from copper ions in the EPR spectra measured in the Q band is three times more compared to that measured in the X band.

Three novel dipicolinate complexes with the pyridine-2,6-dimethanol – A combined structural, spectroscopic, antimicrobial and computational study

Three new dipicolinate complexes, [M(dmp)(dpc)]·H2O [M = Co(II) (1); Zn(II) (2); Ni(II) (3); dmp: pyridine-2,6-dimethanol; dpc: dipicolinate or pyridine-2,6-dicarboxylate], were synthesized and combined with experimental and theoretical study on molecular, vibrational and electronical properties. The central M(II) ion in all complexes is bonded to dpc and dmp ligands through pyridine nitrogen atom together with two oxygen atom, forming the distorted octahedral geometry. The complex molecules, connected via O–H⋯O hydrogen bonds, form a supramolecular structure. The complexes were also screened for antimicrobial activity against human pathogenic Gram-positive, Gram-negative bacteria and fungi. Among the tested microorganisms, Streptococcus pneumoniae was the most sensitive strain, especially to H2dpc and its complexes. The EPR spectra of Cu2+ doped polycrystalline complexes indicate that the paramagnetic center has a rhombic symmetry. Although the supramolecular interactions have some influences on the molecular geometry in solid state phase, calculated data show that the predicted geometries can reproduce the structural parameters. The electronic station in the frontier orbitals of the dipicolinate complexes calculated from the experimental data is compared to the results of time-depended DFT calculations with the polarizable continuum model and UV–Vis spectrum of the complexes has been discussed on this basis. Calculated vibrational frequencies using the DFT and HF method are consistent with the experimental IR data.

EPR and Optical Absorption Spectral Investigations of Cu2+ in Bi2O3-ZnO-B2O3-Li2O Glasses

Electron paramagnetic resonance and optical absorption studies of Bi2O3-ZnO-B2O3-Li2O glasses were made by introducing Cu2+ as spin probe. The EPR spectra of Cu2+ in all the glass samples recorded in the X-band frequency have similar spectral features. The variation in glass composition influences the spin Hamiltonian parameters calculated from the spectra. The spin Hamiltonian parameters indicate that the Cu2+ ions are coordinated with six ligand atoms in a distorted octahedron elongated along one of the axes and the ground state of the Cu2+ is dx2−y2 orbital. The optical absorption spectra exhibited a broad band corresponding to d-d transition bands of Cu2+ ion. The values of bonding parameters indicate a covalent nature for the in-plane σ bonding and pure ionic nature for the in-plane and out-of-plane π bonding. The theoretical optical basicity parameter values were evaluated, and it was observed that the value of Γσ increases whereas Γπ decreases with the increase in optical basicity.