The synthesis, crystal structure and metal complexes of a new macrocyclic dinucleating ligand, 3,6,9,17,20, 23-hexaaza-29,30-dihydroxy-13,27-dimethyl-tricyclo[23,3,1,111,15]triaconta-1(28),11,13,15(30),25,26-hexaene

A new dinucleating 24-membered hexaazadiphenol macrocyclic ligand, 3,6,9,17,20,23-hexaaza-29,30-dihydroxy-13,27-dimethyl-tricyclo[23,3,1,111,15] triaconta-1(28),11,13,15(30),25,26-hexaene, BDBPH, was synthesized by the NaBH4 reduction of the Schiff base obtained from the [2+2] condensation between diethylenetriamine and diformyl-p-cresol. The hexahydro-bromide salt of BDBPH, BDBPH·6HBr·4H2O, crystallizes in the monoclinic system, space group P21/c, with a=14.441(5), b=11.482(4), c=12.090(6) Å, α=90, β=96.92, γ=90°, V=1990.0(14) Å3, and Z=2. The protonation constants of BDBPH and the stability constants of BDBPH complexes with Cu(II), Zn(II), Mn(II), Cd(II), and Fe(III) in 1:1 and 2:1 systems (metal:BDBPH) were determined by potentiometric measurement at 25.0°C and μ=0.100 M KCl. Potentiometric equilibrium studies indicate that a variety of deprotonated, protonated mononuclear and dinuclear, as well as hydroxo-bridged complexes, form in the p[H] range 2–12 in aqueous solution. The species distributions and the characteristics of these complexes are also described.