Magnetic and Electrical Behaviors of the Homo- and Heterometallic 1D and 3D Coordination Polymers Based on the Partial Decomposition of the [Cr(C(2)O(4))(3)](3−) Building Block

One-dimensional (1D) oxalate-bridged homometallic {[Mn(bpy)(C(2)O(4))]·1.5H(2)O}(n) (1) (bpy = 2,2’-bipyridine) and heterodimetallic {[CrCu(3)(bpy)(3)(CH(3)OH)(H(2)O)(C(2)O(4))(4)][Cu(bpy)Cr(C(2)O(4))(3)]·CH(2)Cl(2)·CH(3)OH·H(2)O}(n) (2) coordination polymers, as well as the three-dimensional (3D) heterotrimetallic {[CaCr(2)Cu(2)(phen)(4)(C(2)O(4))(6)]·4CH(3)CN·2H(2)O}(n) (3) (1,10-phenanthroline) network, have been synthesized by a building block approach using a layering technique, and characterized by single-crystal X-ray diffraction, infrared (IR) and impedance spectroscopies and magnetization measurements. During the crystallization process partial decomposition of the tris(oxalato)chromate(III) happened and 1D polymers 1 and 2 were formed. The antiferromagnetic interactions between the manganese(II) ions were mediated by oxalate ligands in the chain [Mn(bpy)(C(2)O(4))](n) of 1, with intra-chain super-exchange interaction 𝐽 = (−3.134 ± 0.004) K; magnetic interaction between neighbouring chains is negligible making this system closer than other known Mn-chains to the ideal 1D Heisenberg antiferromagnet. Compound 2 comprises a 1D coordination anion [Cu(bpy)Cr(C(2)O(4))(3)](n)(n)(−) (Cr2–Cu4) with alternating [Cr(C(2)O(4))(3)](3)(−) and [Cu(bpy)](2+) units mutually bridged through the oxalate group. Another chain (Cr1–Cu3) is similar, but involves a homodinuclear unit [Cu(bpy)(H(2)O)(µ-C(2)O(4))Cu(bpy)(CH(3)OH)](2+) (Cu1–Cu2) coordinated as a pendant group to a terminal oxalate oxygen. Magnetic measurements showed that the Cu1−Cu2 cationic unit is a strongly coupled antiferromagnetic dimer, independent from the other magnetic ions within ferromagnetic chains Cr1–Cu3 and Cr2–Cu4. A 3D polymer {[CaCr(2)Cu(2)(phen)(4)(C(2)O(4))(6)]·4CH(3)CN·2H(2)O}(n) (3) comprising three different metal centers (Ca(2+), Cr(3+) and Cu(2+)) oxalate-bridged, contains Ca(2+) atoms as nodes connected with four Cr(3+) atoms through oxalate ligands. The network thus formed can be reduced to an underlying graph of diamondoid (dia) or (6(6)) topology. Magnetization of 3 shows the ferromagnetic oxalate-bridged dimers [Cu(II)Cr(III)], whose mutual interaction could possibly originate through the spin polarization of Ca(2+) orbitals. Compounds 1 and 3 exhibit lower electrical conductivity at room temperature (RT) in comparison to compound 2.