Half a grid is better than no grid: competition between 2,2':6',2''-terpyridine and 3,6-di(pyrid-2-yl)pyridazine for copper(II).

The reaction between Cu(NO(3))(2).3H(2)O, 2,2':6',2''-terpyridine (tpy) and 3,6-di(pyrid-2-yl)pyridazine (1) in a 2 : 2 : 1 molar equivalent ratio in aqueous MeCN in the presence of excess NH(4)PF(6) leads to competition between the assembly of the dinuclear half-grid [Cu(2)(1)(tpy)(2)]PF(6).2H(2)O and the mononuclear complex [Cu(1)(2)(OH(2))]PF(6). The yield of [Cu(2)(1)(tpy)(2)]PF(6).2H(2)O has been optimized using microwave conditions. [Cu(1)(2)(OH(2))]PF(6) can be selectively produced by treating Cu(NO(3))(2).3H(2)O with 1 (1 : 2 molar equivalents) in aqueous MeCN in the presence of NH(4)PF(6). The single crystal structures of [Cu(2)(1)(tpy)(2)]PF(6).4MeNO(2) and [Cu(1)(2)(OH(2))]PF(6) are presented. In the Cu(2)(1)(tpy)(2) cation, ligand 1 bridges the two copper(II) centres, each of which is further coordinated by a tpy ligand. The copper(II) coordination geometry is closely associated with the arrangement of the two tpy ligands which engage in efficient face-to-face pi-stacking. Magnetic data for crystalline [Cu(2)(1)(tpy)(2)]PF(6).4MeNO(2) are consistent with a weak antiferromagnetic interaction between the two copper(II) centres. EPR spectroscopic data for a powder sample of [Cu(2)(1)(tpy)(2)]PF(6).2H(2)O are consistent with the dinuclear structure, but in frozen DMF and DMSO solutions, the data indicate that the dinuclear structure of Cu(2)(1)(tpy)(2) is not preserved.