A new dimeric perchlorate‐bridged copper(II) complex with the Schiff's base ligand 2‐[(4‐methyl‐pyridin‐2‐ylimino)‐methyl]‐phenol has been synthesized. The complex has been characterized using elemental analysis, ultraviolet–visible and infrared spectroscopy, conductivity, magnetic studies and EPR techniques. Single‐crystal EPR studies indicate that zero‐field splitting (D) is relatively small, and that the half‐field transition is not observed due to its low intensity. An interesting observation in the frozen solution is that the low‐field side of the zero‐field splitting line splits into seven lines, due to interaction between the two copper ions. The magnetic susceptibility data indicate a weak ferromagnetic property and that the complex is a 1:2 electrolyte. Another set of EPR resonances corresponding to higher D and g values, compared to the system reported, are noticed, whose origin is not yet known. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Single crystal EPR study of VO(II)-doped magnesium potassium phosphate hexahydrate has been carried out at room temperature. Single crystal rotations in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice in place of magnesium ions by replacing the equatorial and axial coordinated water molecules. The spin Hamiltonian parameters obtained for the two substitutional sites are: site 1: g1 = 1.9800, g2 = 1.9774, g3 = 1.9296, A1 = 7.25 mT, A2 = 8.09 mT, A3 = 18.69 mT and site 2: g1 = 1.9802, g2 = 1.9765, g3 = 1.9296, A1 = 6.82 mT, A2 = 8.48 mT, A3 = 18.75 mT, respectively. Superhyperfine, from protons of ligand water molecules, has been observed at certain orientations. It has been concluded that VO bond directions of the two substitutional ions are orthogonal to each other.

Electron paramagnetic resonance studies on single crystals of hexaimidazole cobalt(II) sulphate doped with VO(II) are carried in the temperature range 77–300 K at X‐band frequencies. Single crystal EPR spectra indicate the presence of vanadyl impurity positioned in four sites with intensity ratios of 45:36:6:1. Angular variation studies in all the three orthogonal planes confirm that both the intense vanadyl sites have occupied interstitial positions in the lattice. The spin Hamiltonian parameters, calculated for the two sites, indicate orthorhombic nature for the impurity. However, the analysis of powder spectrum reveals the presence of only one site. The spin‐lattice relaxation parameters have been calculated at various temperatures from line width measurements. The admixture coefficients have also been calculated. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Single crystal electron paramagnetic resonance (EPR) studies of Cu(II) doped cobalt ammonium phosphate hexahydrate have been carried out from 300 to 77 K, with single crystal rotation in all the three planes at 153 K, since the spectra are well resolved at this temperature. The angular variation studies indicate only one site in substitutional position with spin-Hamiltonian parameters as g: 2.404, 2.155, 2.063 and A: 11.58, 3.49, 2.07 mT. The reduction in one of the principal A value has been explained by considering considerable admixture of d(x(2)-y(2)) ground state with d(zeta(2)) excited state. The admixture coefficients of ground state wave function are: a = 0.2500; b = 0.9663; c = 0.0520; d = 0.0210; e = -0.0210, where a and b correspond to admixture coefficients for d(zeta(2)) and d(x(2)-y(2)) , respectively. Parameters kappa = 0.5140; P = 113 X 10(-4) cm(-1); alpha(2) = 0.7897; alpha = 0.8887; and alpha' = 0.5262 have also been calculated, indicating considerable covalency. The powder spectrum at room temperature is unresolved, whereas it is better resolved at 77 K, with spin-Hamiltonian parameters matching well with the single crystal values of 153 K. Powder spectrum at 77 K has been simulated, which agrees with the experimental one. The spin-lattice relation times are measured from the line width of the resonance lines recorded at different temperature.

Single crystal electron paramagnetic resonance (EPR) studies of Mn(II) doped zinc potassium phosphate hexahydrate have been carried out at room temperature. Single crystal rotations along the three orthogonal axes indicate orthorhombic symmetry with spin-Hamiltonian parameters as: g(xx) = 1.9997; g(yy) = 1.9538; g(zz) = 1.9524, D(xx) = 15.49 mT; D(yy) = 0.22 mT; D(zz) = -15.71 mT, A(xx) = 11.70 mT; A(yy) = 10.53 mT; A(zz) = 10.42 mT and a = 0.8 x 10(-4) cm(-1). A large E term indicates considerable distortion from axial symmetry. The impurity is found to enter the lattice substitutionally. The distortion axis for the impurity has been identified along one of the Zn-O bond directions in the crystal.

Single crystal EPR study has been carried at room temperature for VO(II) doped zinc sodium phosphate hexahydrate. Single crystal rotations in each of the three mutually orthogonal crystallographic planes namely bc, ac, and ab indicate three chemically inequivalent sites, with intensity ratios of 25:13:1. The spin Hamiltonian parameters obtained for the two intense sites are: Site I: gxx=1.983, gyy=1.985, gzz=1.933; Axx=7.39mT, Ayy=7.15mT, Azz=19.03mT; Site. II: gxx=1.985, gyy=1.985, gzz=1.937; Axx=7.36mT, Ayy=7.25mT, Azz=18.67mT. The two VO bond directions in the two sites are approximately at right angles to each other. The powder spectrum clearly indicates two chemically inequivalent sites, confirming the single crystal analysis. Admixture coefficients, Fermi contact, and dipolar interaction terms have also been evaluated.

Single crystal EPR studies of Mn(II)-doped zinc ammonium phosphate hexahydrate (ZnNH4PC4·6H2O) have been reinvestigated at room temperature. Single crystal rotations along the three orthogonal axes indicate that the spin Hamiltonian parameters for the interstitial site are:g xx = 1.966,g yy = 1.972,g zz = 1.976;D xx = -12.28 mT,D yy = -2.09 mT andD zz = 14.37 mT;A xx = 9.06 mT,A yy = 9.06 mT andA zz = 11.09 mT;a = -0.11 mT. These parameters differ considerably from the previous report of Chand and Agarwal and indicate the orthorhombic nature of the paramagnetic impurity. The impurity is found to enter the lattice interstitially, in contrast to earlier prediction of substitutional position. The percentage covalency of the Mn-0 bond has been estimated.

A dicopper complex of a Schiff's base, 2-[(4-methyl-pyridin-2-ylimino)-methyl]-phenol, with a bridging acetato ligand has been synthesized and characterized by single crystal XRD, EPR, magnetic susceptibility, IR, UV–Vis, CV and elemental analysis. One of the copper atoms in the binuclear complex adopts a square-pyramidal geometry, while the other copper assumes a square-planar geometry. A seven line pattern observed at half-field in the frozen solution EPR spectrum confirms the interaction between the two copper ions.

A bimetallic nickel(II) complex with the ligand Hsalamp (2-[(4-methylpyridin-2-ylimino)-methyl]-phenol), having the molecular formula, Ni2C26H22 N4O10Cl2, is synthesized and characterized by elemental, UV-Vis, IR and EPR studies. The IR spectrum confirms the presence of coordinated perchlorate ion and the UV-Vis. spectrum substantiates that the geometry around the metal ion is distorted square pyramidal. In the solvent methanol, the complex undergoes dissociation indicating the nature of the complex to be 1:2 electrolyte. The single crystal EPR studies indicate that the zero-field splitting is not large and the spectra can be observed even at room temperature, not so common for a nickel(II) ion. The spin Hamiltonian parameters calculated from single crystal rotations are: g - 2.377, 2(.)219, 2(.)071 -and D - 9(.)7, 4(.)2 and - 13(.)9 mT. Optical and electron paramagnetic spectral data have been used to obtain the parameters Dq, B and C.

Electron paramagnetic resonance (EPR) studies of vanadyl ions, VO(II), as paramagnetic impurity in cadmium sodium phosphate hexahydrate (CdNaPO4·6H2O, CSPH) is studied at room temperature. The EPR analysis shows the presence of two magnetically different sites. The intense vanadyl ion has entered the lattice substitutionally and the other ion with weak intensity cannot be followed during the crystal rotations, but is clearly seen in the powder spectra indicating that they are chemically inequivalent in nature. The spin-Hamiltonian parameters obtained from the single crystal analysis have matched with the values of site-I of powder spectra, the values being: g∥=1.922 g⊥=1.980, A∥=19.72mT; A⊥=8.63mT. The spin-Hamiltonian parameters evaluated from powder EPR data are: Site I: g∥=1.922; g⊥=1.995, A∥=19.86mT; A⊥=8.24mT; Site II: g∥=1.933; g⊥=1.996, A∥=20.72mT; A⊥=7.77mT. The admixture coefficients have matched fairly well with reported values.

Single crystal EPR studies of VO(II) doped magnesium ammonium phosphate hexahydrate have been carried out at room temperature. The results indicate that the paramagnetic impurity has entered substitutional and interstitial sites in the lattice. The maximum hyperfine coupling value for one site and the minimum hyperfine constant for the other site have occurred at the same angle and vice versa. The spin Hamiltonian parameters obtained from single crystal data for these two sites are: Site 1: g|| = 1.941; g⊥ = 1.994, A|| = 19.23 mT; A⊥ = 7.14 mT; Site 2: g|| = 1.946; g⊥ = 1.997, A|| = 19.07 mT; A⊥ = 7.29 mT. From these observations, it has been concluded that the two-vanadyl impurities are located approximately at right angles to each other. Superhyperfine interaction with the protons of ligand water molecules have been noticed at a few orientations. EPR powder spectrum of the sample showed a set of eight parallel and perpendicular features indicating the presence of only one magnetically distinct site and the spin Hamiltonian parameters calculated from this spectrum matched with single crystal data. The admixture coefficients have also been calculated, and agree well with the reported values.

Single crystal EPR studies of VO(II)-doped cadmium potassium phosphate hexahydrate (CPPH) have been carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice only substitutionally in place of Cd(II). Spin Hamiltonian parameters have been obtained from single crystal data. Powder spectra show a set of eight parallel and perpendicular features indicating the presence of only one site. The admixture coefficients have been calculated from the data, which agree well with the literature values.