Effect of paramagnetic doping on an inorganic polymer triaquadipotassiumbis(malonato)zincate: spectroscopic investigation

Abstract

Spectroscopic investigations on Mn(II)-doped triaquadipotassiumbis(malonato)zincate [K 2 (H 2 O) 3 ][Zn(mal) 2 ], an inorganic polymer, have been carried out at room temperature using single crystal electron paramagnetic resonance (EPR), ultraviolet-visible, FT-IR and powder XRD techniques. Single crystal rotations along the three orthogonal axes show more than 30 lines of patterns in EPR spectra, indicating the presence of two sites, one with a large D value and the other with a smaller D value. The calculated spin-Hamiltonian parameters are as follows. Site 1: g xx = 2.099, g yy = 2.092, g zz = 1.988, A xx = 9.77, A yy = 9.71, A zz = 8.96 mT, D xx = −29.09, D yy = −11.90, D zz = 40.99 mT; Site 2: g xx = 2.040, g yy = 1.995, g zz = 1.924, A xx = 9.51, A yy = 9.09, A zz = 8.80 mT, D xx = −11.94, D yy = −7.51 and D zz = 19.45 mT. The direction cosines of g/A/D do not match with the direction cosines of Zn-O bonds in the host lattice for either site, suggesting that both the Mn(II) sites entered the lattice interstitially. Optical results indicate a strong covalent bonding between the metal ion and ligands, with site symmetry being primarily octahedral. The FT-IR and powder XRD data confirm the retention of the crystal structure, even after incorporating a paramagnetic probe. Various admixture coefficients, bonding and optical parameters have also been calculated.