Abstract

The [Cu(2,2′-bipy)]²⁺ corner unit (1) (2,2′-bipy = 2,2′-bipyridyl), made available by the metathesis of the chlorides in [Cu(2,2′-bipy)Cl₂] with poorly coordinating anions [triflate (1a), BF₄⁻ (1b) and NO₃⁻ (1c)], has been reacted with a variety of bifunctional ligands, such as 4,4′-bipyridyl (4,4′-bipy), trans-4,4′-azobis(pyridine) (azpy), 1,2-bis(4-pyridyl)ethane (bpetha), trans-1,2-bis(4-pyridyl)ethene (bpethe), 1,3-bis(4-pyridyl)propane (bpp), pyrazine (pyz), i-nicotinate (i-nic) and others. Interesting motifs have been obtained and characterized, including one-dimensional polymeric chains of different kinds, molecular rings and other architectures, depending on the ligand and the counterion. Zig-zag chains exhibiting a variated period have been observed within the species [(1)(4,4′-bipy)(CF₃SO₃)](CF₃SO₃) (2a), [(1)(azpy)(H₂O)(CF₃SO₃)](CF₃SO₃) (3a), [(1)(bpethe)(BF₄)](BF₄) (2b), [(1)(azpy)(H₂O)](NO₃)₂·H₂O (2c) and [(1)(i-nic)(H₂O)](NO₃)·2H₂O (3c). Though the topology of these species is not exceptional, one of them (2c) exhibits a peculiar supramolecular organization of the chains, resulting in warp-and-woof two-dimensional sheets. With the non-rigid ligands bpp and bpetha other motifs can be obtained: the former ligand gives a festoon polymer, [(1)(bpp)(EtOH)](BF₄)₂ (3b), while molecular rings are generated with the latter one in the species [(1)(bpetha)(CF₃SO₃)₂]₂ (4a). Pyrazine with 1a gives dinuclear species that are joined by triflate anions into ladder-like polymers in [{(1)(H₂O)(CF₃SO₃)}₂(pyz)](CF₃SO₃)₂ (5a), exhibiting in the crystal structure channels running parallel to the ladders. With the asymmetric ligand 2,4′-bipyridyl (2,4′-bipy) the monomeric species [(1)(2,4′-bipy)(H₂O)(BF₄)₂] (4b) is obtained, that forms 1D chains via hydrogen bonds. A different starting species, obtained from [Cu(2,2′-bipy)Cl₂] by partial metathesis of the chlorides was also employed: reaction with heptanedinitrile (hdn) gives the derivative [{(1)Cl}₂(hdn)](BF₄)₂ (5b), consisting of chains of dinuclear [(2,2′-bipy)Cu(μ-Cl)₂Cu(2,2′-bipy)] moieties joined by the bidentate flexible ligand.