Coordination chemistry of thioether–pyridazine macrocycles. I. Synthetic, structural, and spectroscopic studies of Cu(II) and Cu(I) complexes of novel thioether–pyridazine macrocycles that contain two or three pyridazine subunits

Abstract

The preparations of thioether–pyridazine macrocycles containing three (L1) and two (L2) pyridazine subunits and their copper complexes are described. The ligands are characterized by 1H nuclear magnetic resonance and mass spectrometry and in one case by X-ray crystallography, and the complexes by infrared, electronic, and electron spin resonance (esr) spectra and in some cases by X-ray crystallography. The complex [Cu3(L1)2Cl6]•2CHCl3 (1) crystallized in the triclinic system, space group [Formula: see text] with a = 13.661(2) Å, b = 14.174(3) Å, c = 9.412(2) Å, α = 101.08(2)°, β = 96.94(2)°, γ = 75.76(2)°, V = 1728.2(6) Å3, and Z = 2 (R = 0.056, Rw = 0.048 for 2080 reflections). Two monodentate pyridazine rings in each ligand bind to one square-planar copper centre with the third monodentate pyridazine in each ligand linking the two to the central square-planar copper. The complex [Cu(L2)Cl2] (2) crystallized in the orthorhombic system, space group Pnma, with a = 8.571(1) Å, b = 16.104(3) Å, c = 13.961(2) Å, V = 1927(1) Å3, and Z = 4 (R = 0.037, Rw = 0.033 for 1070 reflections). A cis square-planar structure exists for 2 with monodentate pyridazines. [Cu(L2)2]•(ClO4)2•CH3CN•CHCl3 (5) crystallized in the triclinic system, space group [Formula: see text] with a = 12.888(4) Å, b = 17.462(6) Å, c = 10.906(1) Å, α = 96.07(2)°, β = 104.18(2)°, γ = 94.51(2)°, V = 2352(1) Å3, and Z = 2 (R = 0.053, Rw = 0.044 for 2941 reflections). Two ligands involving monodentate pyridazine rings bind to a square-planar copper(II) centre. The protonated ligand salt [L2H](ClO4)•H2O (6) crystallized in the monoclinic system, space group P21/n, with a = 14.762(4) Å, b = 8.637(5) Å, c = 16.267(4) Å, β = 92.78(2)°, V = 2072(1) Å3, and Z = 4 (R = 0.064, Rw = 0.053 for 1456 reflections). No sulfur coordination is observed in these complexes and there is no apparent spin exchange in the trinuclear derivative.