Polynuclear copper(II) carboxylates with 2,2′-bipyridine or 1,10-phenanthroline: Synthesis, characterization, X-ray structures and magnetism

[Cu2(phen)2(μ-O2CH)2(O2CH)2]n (1) and [Cu6(bpy)6(μ-O2CC2H5)7(H2O)2)](PF6)5 · 2H2O (2) were synthesized and characterized by elemental analyses, electronic and EPR spectra and X-ray structure analyses. Compound 1 consists of four independent polymeric chains of dinuclear [Cu2(phen)2(μ-O2CH)2(O2CH)2] subunits with the asymmetric bidentate bridging formato groups linking Cu atoms in an anti–anti configuration. All Cu(II) ions are in a distorted square-pyramidal geometry. The hexanuclear copper(II) molecule of compound 2 is constructed from three different dinuclear units connected to each other via two syn–anti-μ3-η1;η2 carboxylato bridges. All copper(II) ions are in the distorted square-pyramidal geometry. Two terminal dinuclear units are similar in structure in which both Cu(II) ions are doubly bridged by the syn–syn carboxylato anions, while those of the central dinuclear entity are triply bridged by two μ3-η1;η2 carboxylato anions via monoatomic bridging fashion and one syn–syn carboxylato anion. The magnetic susceptibility (5–350 K) of compound 2 was measured and agree with a weak antiferromagnetic interaction between the Cu(II) centers.

Graphical abstractThe novel polynuclear [Cu2(phen)2(μ-O2CH)2(O2CH)2]n (1) and [Cu6(bpy)6(μ-O2CC2H5)7(H2O)2)](PF6)5 · 2H2O (2) were synthesized and characterized by elemental analyses, electronic and EPR spectra and X-ray structure analyses. Compound 1 consists of four independent zigzag polymeric chains of dinuclear [Cu2(phen)2(μ-O2CH)2(O2CH)2] subunits with the asymmetric bidentate bridging formato groups linking Cu atoms in an anti–anti configuration. The hexanuclear copper(II) molecule of compound 2 contains three different dinuclear units with the syn–syn-μ-η1;η1 and syn–anti-μ3-η1;η2 propionate bridges. Either intra- or intermolecular π–π stacking interactions among aromatic moieties of alpha-diimine chelating didentates remarkably play a key role to stabilize the polynuclear structure of 1 and 2. The magnetic susceptibility measurement (5–350 K) of compound 2 reveals a weak antiferromagnetic interaction between the Cu(II) centers.Figure optionsDownload full-size imageDownload as PowerPoint slide