Electron Spin Resonance Spectral Studies Research Articles

Copper(II) complexes formed in the extraction of copper from hydrochloric acid solutions by an α-hydroxyoxime

Absorption and electron spin resonance (ESR) spectral studies have been carried out for the copper(II) complexes formed in the extraction of copper from hydrochloric acid solutions of varying acidity by 5,8-diethyl-7-hydroxy-6-dodecanone oxime (H 2Ox; an active component of LIX 63) in kerosene. For the extraction from aqueous solutions of pH > 1 it was deduced that two linkage isomers of Cu(HOx) 2 which possess O,O- and O,N-bonded structures are formed in the organic phase, depending on the pH value. At high pH the O,N-bonded structure is favoured since the donating site on the nitrogen atom of the oxime group is not occupied by a hydrogen ion. For the extraction from aqueous solutions containing more than 1 mol dm −3 of hydrochloric acid, it was confirmed that the copper(II) ion is taken up through the reaction: CuCl 2(aq)+2H 2Ox(org)⇄Cucl 22H 2Ox(org) .

Preparation, characterization and reactions of vanadium(IV) β-diketonate complexes

The β-diketone complexes of vanadium(IV), VO(dik) 2 (where dik ≡; btfac, tfac, ttfac, acac, bzac and bzbz) have been prepared either by the reaction of vanadium pentoxide with the appropriate ligand in toluene under reflux for 24 h or by the reaction of a warm aqueous or ethanolic solution of vanadium sulphate with the ligand. The oxovanadium(IV) complexes react with sulphur oxide dichloride and dibromide and phosphorus pentachloride to form dihalovanadium(IV) diketonate complexes. These compounds have been characterized by elemental analysis, melting point measurements, IR and Raman spectra, magnetic susceptibility measurements, electron spin resonance (ESR) and mass spectral studies and X-ray powder diffraction.

Optical Absorption and Electron Spin Resonance Spectral Studies of Copper(II) Chalcone Complexes in different Solvents

Optical Absorption and Electron Spin Resonance Spectral Studies of Copper(II) Chalcone Complexes in different Solvents

Synthesis and Characterization of Copper (II) Complexes with Some Nitrogen-Oxygen Donor Ligands

Abstract Cu (II) complexes of the general composition Cu (ligand)2X2 (where X = Cl−, Br−, NO3 −, CH3COO−, ClO4 − and 1/2 SO4 2-) have been synthesised and characterised by elemental analysis, magnetic moment, ir, electronic and electron spin resonance spectral studies. All the complexes are paramagnetic showing magnetic moment corresponding to one unpaired spin.

ESR and lyoluminescence measurements on Tris (hydroxymethyl) aminomethane

Electron spin resonance (ESR) and lyoluminescence (LL) measurements on Tris (hydroxymethyl) aminomethane have been carried out at different gamma exposures. The ESR spectral studies indicate the formation of two free radical species. The radical species formed at low dose range is responsible for LL emission and the second radical species formed at high exposure range inhibits the LL process. Studies on the effect of radical scavengers and oxygen on LL output also show that free radicals produced are the principal causative agents for the lyoluminescence and that oxygen is one of the reactants.

Stereochemical versatility of Cu(II): Cu(II) complexes of benzyl methyl ketone semicarbazone

Copper(II) complexes of the general composition Cu(ligand) 2X 2 (where X = Cl, Br, NO 3, ClO 4, and 1 2 SO 4) and Cu(ligand)(CH 3COO) 2 have been synthesised with benzymethylketonesemicarbazone. All the complexes prepared have been characterised by elemental analysis, magnetic moment, conductance, IR, electronic and electron spin resonance spectral studies. The complexes Cu(ligand) 2X 2 (X = Cl, Br, NO 3) and Cu(ligand)(CH 3COO) 2 may have tetragonal symmetry while the Cu(ligand) 2X 2 (ClO 4 and 1 2 SO 4) may be five-coordinate trigonal bipyramidal in structure.

Bis(thiosemicarbazonato) chelates of Co(II), Ni(II), Cu(II), Pd(II) and Pt(II)

Bis chelates of Co(II), Ni(II), Cu(II), Pd(II) and Pt(II) with the enolic form of diethyl ketone and methyl n-propyl thiosemicarbazones were synthesized and characterized by elemental analyses, magnetic moments, i.r. and electronic and electron spin resonance spectral studies. All the complexes were found to have the composition ML 2 [where M = Co(II), Ni(II), Cu(II), Pd(ii) and Pt(II) and L = thiosemicarbazones of diethyl ketone and methyl n-propyl ketone]. Co(II) and Cu(II) complexes are paramagnetic and may have polymeric six-coordinate octahedral and square planar geometries, respectively. The Ni(II), Pd(II) and Pt(II) complexes are diamagnetic and may have square planar geometries. Pyridine adducts (ML 2·2Py) of Ni(II) and Cu(II) complexes were also prepared and characterized.

Synthesis and Characterization of Mn (II), Fe(II), Co(II), Ni(II) and Cu(II) Complexes of Salicylaldehyde Semicarbazone

Abstract Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) complexes of salicylaldehyde semicarbazone have been prepared and characterized by elemental analysis, magnetic moments, electronic spectra and electron spin resonance spectral studies. All of the complexes are of the general composition, M(SASC−)2.nH2O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and SASC = salicylaldehyde semicarbazone). All of the complexes are high-spin and have six-coordinate octahedral geometry.

Characterisation of the complexes of VIVO, CrIII, FeIII, CoIII, NiII and CuII with phenanthrenequinone monoxime

Coordination complexes of phenanthrenequinone monoxime with VIVO, CrIII, FeIII, NiII or CuII have been synthesised and characterized by magnetic moment, i.r., and thermogravimetric analysis, and electronic and electron spin resonance spectral studies.

Electron spin resonance and optical resonance studies on copper(II) complexes with vanadate, molybdate and tungstate anions

A series of complexes of the form Cu(An) n L x · yH 2O, where An = vanadate, molybdate or tungstate anion, L = pyridine, α-, β- or γ-picoline, n = 1 or 2; x = 1−4 and y = 0−3, have been synthesized and characterized by electron spin resonance, photoacoustic and electronic spectral studies as well as infrared spectroscopy in the solid and solution state. The different coordination sites of the ligands and anions have been interpreted from infrared and electronic spectral data. Electron spin resonance spectral data show the square planar or distorted octahedral (in a few cases five-coordinate geometry) stereochemistry around copper(II) in these complexes. Parameters such as g ∥, g ⊥, A ∥, A ⊥, 〈 g〉, 〈 A〉, α 2 and β 2 1 calculated from electron spin resonance data indicate the presence of unpaired electrons in d x 2− y 2 or d z 2 orbitals. The results of electronic and photoacoustic spectral studies are in good accord with ESR data.

Synthesis and characterization of copper(II) complexes of a macrocyclic ligand

Copper(II) complexes of the general composition Cu(L)X2 (X=Cl−, Br−, NO 3 − , ClO 4 − , MeCOO− or 0.5 SO 4 2− , L=tetradentate twelve-membered macrocyclic ligand) have been synthesised and characterised. The complexes have been characterised by elemental analysis, conductance measurements, magnetic susceptibility, i.r., electronic and electron spin resonance spectral studies. The complexes are found to have octahedral geometry except Cu(ligand)SO4 which has been assigned a five-coordinated square pyramidal geometry.

Electron spin resonance and photoacoustic spectral studies on manganese(II) and copper(II) sulphate and thiocyanate complexes with hexamethylenetetramine

Electron spin resonance and photoacoustic spectral studies on manganese(II) and copper(II) sulphate and thiocyanate complexes with hexamethylenetetramine

Electron spin resonance and optical absorption spectral studies on some manganese(II) complexes with 2,2′-bipyridyl, 4,4′-bipyridyl and their dioxides

Coordination compounds formed by the interaction of manganese(II) chloride, thiocyanate, acetate and sulphate with 2,2′-bipyridyl (2,2′-Bipy), 4,4′-bipyridyl (4,4′-Bipy) and their dioxides have been characterized by electron spin resonance and optical absorption spectral studies in solid and solution states to determine the spin-Hamiltonian constant for manganese(II), metal-ligand bond parameters and the tentative environments around manganese(II). The metal-ligand σ,-bond in the compounds studied herein in formamide solution is found to be moderately covalent. The compounds seem to have an essentially axial symmetry with g-value close to 2.0. The magnetic moments, electronic and photoacoustic spectra of these complexes are also recorded and interpreted in the solid state.

Synthesis and Characterisation of Chromium(III) Complexes of Some Semicarbazones and Thiosemicarbazones

Abstract Chromium (III) complexes of the types [CrL2 Cl2] Cl, [CrL2NO3](NO3)2, where L is the semicarbazones or thiosemicarbazones of acetone, ethyl methyl ketone and 2-methyl cyclohexanone have been synthesised. The complexes formed have been characterised by physico-chemical techniques, viz., magnetic moments, electronic and electron spin resonance spectral studies. All the complexes formed have been found to be octahedral.

Synthesis and Characterisation of Manganese(II) Complexes of Some Semicarbazones and Thiosemicarbazones

Abstract Manganese(II) complexes of the general composition Mn(ligand)2X2, where X = cl, Br, I and the ligands are R1R2C = NNHCOHH and R1R2C = NNHCSNH2 (R1 =R2 = cycloheptane and cyclopantane) have been prepared and characterised by elemental analysis, magnetic moments, infrared, electronic spectra and electron spin resonance spectral studies. All these complexes are of octahedral geometry.

Synthesis and Characterisation of Oxovanadium(IV) Complexes of Acetone Semicarbazone and Acetone Thiosemicarbazone

Abstract Oxovanadium(IV) complexes, VOL2X2 (L = acetone semicarbazone and acetone thiosemicarbazone, X = Cl, Br, NO3, ClO4 and 1/24) have been synthesised and characterised by elemental analysis, room temperature magnetic moments, electronic, i.r. and electron spin resonance spectral studies. The complexes have been foundto possess six-coordinate octahedral geometry.

Synthesis, electronic, photoacoustic and electron spin resonance investigations on some tetrathiocyanate binuclear mixed-metal complexes

Complexes of the type M 1M 2(SCN) 4 xL[M 1 = Ni(II); M 2 = Cd(II) and Hg(II) and L = pyridine, morpholine, dioxan, benzo(f)quinoline, 2,2′-bipyridine, 2,2′-bipyridine N, N′-dioxide, isonicotinic acid hydrazide and 1,10-phenanthroline: x = 2 or 4] have been synthesized and characterized by chemical analysis, magnetic susceptibility, infrared, electronic and photoacoustic (PAS) spectra as well as electron spin resonance (ESR) spectral studies in the solid and solution state. The different coordination sites have been investigated in these ligands towards metal coordination and the behaviour of thiocyanate anions studied. Electron spin resonance spectral data for copper complexes show the distorted octahedral stereochemistry around copper(II) in these complexes. The parameters such as g ∥, g ⊥, A ∥, A ⊥, < g>, < A> and α 2 calculated for the copper complexes from their ESR spectra indicate the presence of unpaired electron in d x 2- y 2 or d z 2 orbitals. The photoacoustic and electronic spectra of these complexes were studied in the solid state to see the nature of thiocyanate and overall symmetry of the complexes. The results on electronic and photoacoustic spectral studies are in good agreement with ESR data.

Identification of neutral and anionic 8α-substituted flavin semiquinones in flavoproteins by electron spin resonance spectroscopy

Electron paramagnetic resonance spectral studies of protein-bound 8α-substituted FMN neutral semiquinones (in a complex with Azotobacter apoflavodoxin) show peak-to-peak linewidths (~ 20–23 G) similar to those of normal flavoenzymes which form neutral semiquinones. The anionic form of the 8α-substituted flavin semiquinone of thiamine dehydrogenase shows a narrower peak-to-peak linewidth (12 G) than normal anionic flavin semiquinones (14–15 G). The electron paramagnetic resonance spectral properties of the 8α- N(3)-histidyl FAD semiquinone of succinate dehydrogenase showed a peak-to-peak linewidth of 12 G through the pH range of 6.1 to 9.1 and remained unchanged whether the buffer medium was H 2O or D 2O. From these observations, it is concluded that the covalent flavin semiquinone in succinate dehydrogenase exists in the anionic (red) form.

Electron spin resonance and electronic spectral studies on ligation of dimeric copper(II) complex by solvent molecules

The problem of ligation by various organic solvents was investigated for Cu 2(AoAPh) 2, where AoAPh represents tridentate Schiff base derived from acetylacetone and o-aminophenol. ESR and electronic spectra indicated the dissociation of Cu 2(AoAPh) 2 into two adduct complexes Cu(AoAPh)L under the influence of the polar solvent (L = pyridine, piperidine, DMF, DMSO etc.). The Schiff base 14N superhyperfine splitting was analysed in the ESR spectra. The adducts were isolated in crystalline form. Thermal analysis of these adducts showed the loss of the L ligand and formation of the dimeric complex in temperature range 330–390 K.

Optical absorption and electron spin resonance spectral studies of vanadyl chloro complexes formed in the solvent extraction systems with Aliquat-336, TOA, TOPO and TBP

Optical absorption and electron spin resonance (ESR) spectral studies have been carried out for the complexes formed in the extractions of vanadium(IV) by tricaprylmethylammonium chloride (R 3R′NCl; Aliquat-336), tri- n-octylamine (R 3N; TOA), tri- n-octylphosphine oxide (R 3PO; TOPO) and tri- n-butylphosphate ((RO) 3PO: TBP) in benzene from hydrochloric acid solutions or mixed solutions of hydrochloric acid and lithium chloride. As a result, it is found that the species VOCl 2· nL, VO(OH)Cl· nL and VO 2Cl· nL (L = R 3R′NCl, R 3NHCl, R 3PO, (RO) 3PO; n = 1 for R 3R′NCl and R 3NHCl, n = 2 for R 3PO and (RO) 3PO) are formed in the organic phase.