Mononuclear and Polynuclear Copper(II) Complexes Derived from Pyridylalkylaminomethylphenol Polypodal Ligands

Four mononuclear complexes [Cu(HL1)CI]PF6 center dot CH3OH (1), [Cu(HSL1)CI]PF6 center dot 0.75H(2)O (2), [Cu(HL2)CI]PF6 center dot CH3OH (3), [Cu(HSL2)CI]PF6 center dot 1.5CH(3)OH (4), and two polynuclear complexes [Cu-2(SL2)(2)](PF6)(2)center dot 2CH(3)OH (5) and {Cu[Cu(SL2)(CI)](2)}(PF6)(2) (6) (HL1: 2-[(bis(2-pyridylmethyl)-amino)methyl]-4-methylphenol; HSL1: 2-[(bis(2-pyridylmethyl)amino) methyl]-4-methyl-6-(methyl-thio)phenol; HL2: 2-[(2-pyridylmethyl)(2'-pyridylethyl)-aminomethyl)]-4-methylphenol; HSL2: 2-[(2-pyridylmethyl)(2'-pyridylethyl)amino-methyl]-4-methyl-6-(methythio)phenol were obtained and characterized. The crystal structures of the mononuclear complexes 1-4 show the copper centers in a square-base pyramidal environment with the phenolic oxygen coordinated at the axial position. Dinuclear complex 5 has two copper centers with different geometry and bridged by phenoxo oxygens; one of the copper atoms is square pyrmidal while the other can be described with a highly distorted octahedral geometry with a long Cu-S distance (2.867 angstrom). Density functional theory calculations were used to obtain the reported structure of 6, since single crystals suitable for X-ray diffraction were not isolated. Magnetic studies done for 5 and 6 show an antiferromagnetic behavior for 5 (J = -134 cm(-1)) and a ferromagnetic behavior for 6 (J = +11.9 cm(-1)). Redox potentials for the mononuclear complexes were measured by cyclic voltammetry; the values show the effect of the chelating ring size (-213 mV and - 142 mV for Cu-HL1 and Cu-HL2, respectively) and the presence of the thiomethyl substituent (-213 mV and -184 mV for Cu-HL1 and Cu-HSL1, respectively).