Discrete Complexes and One-Dimensional Coordination Polymers with [Cu(II)(2,2′-bpy)]2+ and [Cu(II)(phen)]2+ Corner Fragments: Insight into Supramolecular Structure and Optical Properties

The combination of [Cu(II)(2,2′-bpy)]2+ and [Cu(II)(phen)]2+ (2,2′-bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline) corner fragments predisposed to π–π stacking interactions with bridging ligands 4,4′-bipyridine (4,4′-bpy), 4,4′-bipyridinethane (bpe), and 4,4′-bipyridinepropane (bpp) in the presence of linear SCN–, or tetrahedral ClO4– or BF4– inorganic anions and/or organic acetate anion provides access to a series of new metal–organic materials including non-centrosymmetric polymeric chains, whose architectures were confirmed through single crystal X-ray crystallographic analysis. The nine reported compounds comprise one mononuclear complex, [Cu(2,2′-bpy)2(CH3COO)](SCN)(H2O) (1), three binuclear complexes, [Cu2(2,2′-bpy)2(CH3COO)2(SCN)2(4,4′-bpy)]0.5dmf (2), [Cu2(phen)2(CH3COO)2(SCN)2(bpe)] (3), [Cu2(phen)2(SCN)4(bpe)] (4), and five one-dimensional coordination polymers, {[Cu(2,2′-bpy)(4,4′-bpy)(ClO4)2](H2O)}n (5), {[Cu(phen)(4,4′-bpy)(BF4)2](H2O)}n (6), {[Cu(2,2′-bpy)(ClO4)(H2O)(bpp)](ClO4)}n (7), {[Cu(phen)(ClO4)(dmf)(bpp)](ClO4)}n (8), and {[Cu(phen)(bpp)(BF4)2][Cu(phen)(bpp)2(BF4)](BF4)}n (9). Coordination polymers represent the neutral (5, 6), cationic (7, 8), or a blend of neutral and cationic chains (9), and differ by the Cu(II) coordination cores, conformations of the bridging ligands, and functions of the anions. All compounds except 7 reveal cooperative π–π stacking interactions of corner fragments. As expected for the paramagnetic d9 Cu(II) complexes, the polymeric solids show the luminescence quenching. The second order nonlinear optical properties of powders of the non-centrosymmetric compounds 8 and 9 were also tested.