Structural elucidation and location of Mn(II) ion in Tetraaquabis(hydrogen maleato)cadium(II): Single crystal EPR studies

Electron paramagnetic resonance study of Mn2+ ion-doped Tetraaquabis(hydrogen maleato)cadmium(II) single crystal was carried out at X-band frequency to ascertain its structural properties. EPR spectrum exhibits group of five fine structure transitions each splits into six hyperfine components. The spin Hamiltonian parameters calculated from the crystal rotations are: gxx = 2.109, gyy = 2.029, gzz = 2.008, Axx = −9.51 mT, Ayy = −8.30 mT, Azz = −8.09 mT, Dxx = 20.29 mT, Dyy = 4.11 mT, Dzz = −24.40 mT, E = 8.09 mT and it indicates Mn2+ ion has orthorhombic symmetry. The direction cosines of spin Hamiltonian parameters (g, A and D) are suggesting that Mn2+ ion has entered the lattice interstitially and its exact location has been established with the help of position of atoms in the host lattice. Covalency of Mn-ligand bonds are evaluated using Matumura’s plot is 7.3%. FT-IR and powder XRD data confirm the formation of host lattice. Optical absorption study suggests distortion around incorporated ion. The observed bands are assigned as transitions from the 6A1g(S) ground state to various excited quartet levels of Mn2+ ion in distorted octahedral crystalline field. The theoretical band positions are estimated using energy expressions and good agreement is observed with the experimental values. The best fit values of the crystal field (Dq) and Racah inter electronic repulsion parameters were evaluated from the observed band positions.