Add time:08/29/2019         Source:sciencedirect.com

The room temperature electron paramagnetic resonance (EPR) spectrum of cis-diaquobis(1,1,1,5,5,hexafluoroacetylacetonato)manganese(II), Mn(hfa)2, and trans-diaquobis(1,1,1,5,5,5-hexafluoroacetylacetonato)manganese(II) hydrate, Mn(hfa)2·H2O, doped into a single crystal of the corresponding zinc(II) chelates has been studied. The crystal structures of the two host chelates have been determined by X-ray crystallographic methods. The trans complex crystallizes in the orthorhombic space group Pnma with 4 molecules in a cell of dimensions a = 7.430(5), b = 21.965(8), c = 11.096(4) Å; the structure has been refined to a final R-factor of 0.057 based on 821 independent reflections. The cis complex crystallizes in the monoclinic space group C2/c with 4 molecules in a cell of dimensions a =21.339(3), b = 8.228(3), c = 9.761(4) Å, β = 95.99(2)°; the structure has been refined to a final R-factor of 0.041 based on 1170 independent intensities. The spin-Hamiltonian parameters have been determined by the use of energy expressions, complete to the second order of approximation, and by fitting the 30-line spectrum along each of the principal magnetic-axes by the method of least squares. The following results were obtained for the usual spin-Hamiltonian parameters. Mn(hfa)2: gx = 2.0098 = 0.0003, gy= 1.9999 = 0.0003, gz = 2.0002 = 0.0003, Ax = 86.44 × 10−4 cm−1, Ay = 86.52 × 10−4 cm−1, Az = 86.53 × 10−4 cm−1, D = 158.81 × 10−4 cm−1, E = 8.4 × 10−4 cm−1 . Mn(hfa)2·H2O: gz = 1.9960 = 0.0003, Az = 85.68 × 10−4 cm−1 , D = 374.45 × 10−4 cm−1, E = 66.24 × 10−4 cm−1. The spectrum of Mn(hfa)2·H2O doped into single crystals of the corresponding magnesium chelate has also been observed. The spin-Hamiltonian parameters are the same, within experimental error, as those for the zinc host lattice.

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