New Polynuclear Manganese(II) Complexes with Orotic Acid and some of its Derivatives: Crystal Structures, Spectroscopic and Magnetic Studies

Article abstract of DOI:10.1039/DT9950004005

Three polynuclear manganese(II) complexes containing orotic acid (2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid, H₃L¹) or one of its substituted derivatives <3-methyl- (H₂L²) or 5-nitro-2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid (H₃L¹)> have been synthesized and characterized by X-ray crystallography.UV/VIS and magnetic susceptibility measurements.Complex 1 consists of neutral 1)2(H2O)6> units, which form polymer chains along the z axis with a Mn(1)...Mn(2) distance in the unit cell of 5.628(1) Angstroem while the Mn(2)...Mn(2) distance in the chain is 4.715(1) Angstroem.Each unit cell of complex 2 contains one neutral centrosymmetric dimer 2)2(H2O)6> containing a short Mn...Mn distance <3.472(2) Angstroem> and an antiferromagnetic exchange interaction is present.The experimental data were fitted to the susceptibility equations resulting from the Hamiltonian H = -2JS₁S₂ to give exchange parameter J = -1.3 cm^-1 and g = 1.95.From EPR spectra of 2, the hyperfine interaction parameter A = -0.27 GHz and the zero-field splitting parameter D = +/-2.93 GHz have been calculated.Each unit cell of complex 3 consists of one dinuclear anion 3)2(H2O)4Cl2>^2- and of one cation ²⁺.The Mn(1) and Mn(2) atoms and the water molecule of the cation ²⁺ are situated at inversion sites.The dinuclear anions are associated to form chains but the shortest Mn...Mn distance of 5.642(3) Angstroem is observed within the 3)2(H2O)4Cl2>^2- unit between Mn(1) and Mn(2).

Full text of DOI:10.1039/DT9950004005

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