Structural studies and redox reactivity of platinum complexes of 14-membered tetraaza macrocyclic ligands

Pt(II) monomeric complexes of N-containing macrocycles have been synthesized and characterized in solution by H-1 NMR, C-13 NMR, and electrospray mass spectroscopy (ESMS) and in the solid state by X-ray crystallography. Crystals of [Pt(cyclam)](ClO4)(2) (cyclam = 1,4,8,11 -tetraazacyclotetradecane) are orthorhombic, space group P2(1)cn, a = 9.596 (3), b = 14.595 (21), c = 24.8782 (20) Angstrom, Z = 8. The structure was solved by direct methods and was refined by the full-matrix least-squares method to R = 0.073 and R-w = 0.093 for 2976 reflections with I greater than or equal to 2.5 sigma(I). Crystals of [Pt(N-methylcyclam)]-(ClO4)(2) . CH3CN (N-methylcyclam = 1,4,8,11 tetramethyl-1,4,8,11-tetraazacyclotetradecane = NMe(4)cyclam = tmc) are orthorhombic, space group Pmcn, a = 9.574 (8), b = 14.116 (5), c = 17.5456 (15) Angstrom, Z = 4. The structure was solved by direct methods and was refined by the full-matrix least-squares method to R = 0.067 and R-w = 0.091 for 2216 reflections with I greater than or equal to 2.5 sigma(I). Cyclic voltammetry and EPR spectroscopy have been used to study the redox reactivity of the Pt(II) and Pt(IV) complex ions. The solution chemistry of Pt(IV) complexes based on cyclam and N-methylcyclam was investigated by electrospray mass spectrometry. Electrospray mass spectral evidence has been obtained for the formation of [Pt(III)(cyclam)Cl-2](+) and [Pt(III)(N-methylcyclam)Cl-2](+) ions.