Magnetic and Electrical Behaviors of the Homo- and Heterometallic 1D and 3D Coordination Polymers Based on the Partial Decomposition of the [Cr(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]<sup>3−</sup> Building Block
oleh: Lidija Kanižaj, Pavla Šenjug, Damir Pajić, Luka Pavić, Krešimir Molčanov, Marijana Jurić
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2020-11-01 |
Deskripsi
One-dimensional (1D) oxalate-bridged homometallic {[Mn(bpy)(C<sub>2</sub>O<sub>4</sub>)]·1.5H<sub>2</sub>O}<i><sub>n</sub></i> (<b>1</b>) (bpy = 2,2’-bipyridine) and heterodimetallic {[CrCu<sub>3</sub>(bpy)<sub>3</sub>(CH<sub>3</sub>OH)(H<sub>2</sub>O)(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>][Cu(bpy)Cr(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]·CH<sub>2</sub>Cl<sub>2</sub>·CH<sub>3</sub>OH·H<sub>2</sub>O}<i><sub>n</sub></i> (<b>2</b>) coordination polymers, as well as the three-dimensional (3D) heterotrimetallic {[CaCr<sub>2</sub>Cu<sub>2</sub>(phen)<sub>4</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>6</sub>]·4CH<sub>3</sub>CN·2H<sub>2</sub>O}<i><sub>n</sub></i> (<b>3</b>) (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 <b>1</b> and <b>2</b> were formed. The antiferromagnetic interactions between the manganese(II) ions were mediated by oxalate ligands in the chain [Mn(bpy)(C<sub>2</sub>O<sub>4</sub>)]<i><sub>n</sub></i> of <b>1</b>, with intra-chain super-exchange interaction ? = (−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 <b>2</b> comprises a 1D coordination anion [Cu(bpy)Cr(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]<i><sub>n</sub><sup>n</sup></i><sup>−</sup> (<b>Cr2–Cu4</b>) with alternating [Cr(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]<sup>3</sup><i><sup>−</sup></i> and [Cu(bpy)]<sup>2+</sup> units mutually bridged through the oxalate group. Another chain (<b>Cr1–Cu3</b>) is similar, but involves a homodinuclear unit [Cu(bpy)(H<sub>2</sub>O)(<i>µ</i>-C<sub>2</sub>O<sub>4</sub>)Cu(bpy)(CH<sub>3</sub>OH)]<sup>2+</sup> (<b>Cu1–Cu2</b>) coordinated as a pendant group to a terminal oxalate oxygen. Magnetic measurements showed that the <b>Cu1</b><b>−</b><b>Cu2</b> cationic unit is a strongly coupled antiferromagnetic dimer, independent from the other magnetic ions within ferromagnetic chains <b>Cr1–Cu3</b> and <b>Cr2–Cu4</b>. A 3D polymer {[CaCr<sub>2</sub>Cu<sub>2</sub>(phen)<sub>4</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>6</sub>]·4CH<sub>3</sub>CN·2H<sub>2</sub>O}<i><sub>n</sub></i> (<b>3</b>) comprising three different metal centers (Ca<sup>2+</sup>, Cr<sup>3+</sup> and Cu<sup>2+</sup>) oxalate-bridged, contains Ca<sup>2+</sup> atoms as nodes connected with four Cr<sup>3+</sup> atoms through oxalate ligands. The network thus formed can be reduced to an underlying graph of diamondoid (<b>dia</b>) or (6<sup>6</sup>) topology. Magnetization of <b>3</b> shows the ferromagnetic oxalate-bridged dimers [Cu<sup>II</sup>Cr<sup>III</sup>], whose mutual interaction could possibly originate through the spin polarization of Ca<sup>2+</sup> orbitals. Compounds <b>1</b> and <b>3</b> exhibit lower electrical conductivity at room temperature (RT) in comparison to compound <b>2</b>.