Mononuclear and polynuclear halide and nitrate Cu(II) compounds with 1,4,5-triazanaphthalene as a ligand: Characterization, magnetism and X-ray structures

Using the ligand 1,4,5-triazanaphthalene (abbreviated as tan) in combination with Cu(II) salts, three mononuclear compounds, Cu(tan)2Cl2 (1), Cu(tan)2Br2 (3), Cu(tan)2(NO3)2 (5) and three polynuclear compounds, [Cu(tan)Cl2]n (2), [Cu(tan)Br2]n (4), [Cu(tan)(NO3)2]n (6) have been synthesized and characterized by UV–Vis, EPR, FTIR and Far-FTIR spectroscopies. The crystal structures of compounds 1, 3, 5 and 6 are reported, as well as that of the dioxane adduct of compound 4, [Cu(tan)Br2(C4H8O2)](C4H8O2) (4A). The structure of (2) was solved by X-ray powder diffraction. The coordination geometry around the Cu(II) atoms is tetrahedral for (1) and (3), square–pyramidal for (4A) and distorted octahedral for (5) and (6). Magnetic susceptibility measurements on the polynuclear compounds revealed weak antiferromagnetic interactions between the Cu(II) atoms with interaction constants (J) of J = −9.1 and −10.5 cm−1, for 4 and 6, respectively. For compound 2 two options for possible interactions were considered, with interaction constants which vary for Jrung −22.0 to −13.5 cm−1 and Jrail −19.6 to −17.0 cm−1. These figures are discussed in the light of relevant structural parameters and literature.