A new unsymmetrical polyamine macrocycle incorporating two phenolic functions: synthesis, basicity and coordination behavior toward copper(II)

A new 26-membered macrocyclic ligand: 3,6,10,18,22,25-hexaaza-31,32-dihydroxy-14,29-dimethyl-tricyclo[25,3,1,111,17]dotriaconta-1(30),12,14,16(32),27,28-hexaene (L or BTBP) and a homodinuclear copper complex have been synthesized and characterized with elemental analysis, NMR, FAB MS and X-ray. The ligand maintains dinuclear integrity for copper(II) complexes, while facilitating the formation of non-bridged dicopper centers. Potentiometric equilibrium studies indicate that a variety of protonated, mononuclear and dinuclear complexes are formed with Cu(II) from pH 2 to 12 in aqueous solution. The stability constants and species distribution, as a function of the pH of the 1:1 and 1:2 [ligand/Cu(II)] complexes, were determined in KCl supporting electrolyte (μ=0.100 M) at 25 °C. The neutral homodinuclear complex [Cu2C28H44N6O2Br2)]·2(CHCl3)·2(CH3OH) forms monoclinic crystals, of space group P21/c, with a=14.319(3), b=21.801(4), c=7.0417(14) Å, β=100.893(4)°, and Z=2. Each copper is complexed by half of the coordination sites of the dinucleating macrocycle, and the anionic bromide enters into the coordination sphere and occupies an axial position to complete a square-pyramidal polyhedron.