A new diaza-18-crown-6 ligand containing two quinolin-8-ylmethyl side arms: Crystal structures and characterization of the ligand, the protonated ligand and its mononuclear barium(II) and dinuclear copper(II) complexes

A new 7,16-bis(quinolin-8-ylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctad ecane ligand, L, has been prepared and its crystal structure reported. In a ddition, the structure of the protonated ligand H2L has been determined. H2 L is of interest because of interatomic interactions between the ligand and perchlorate ions. The mononuclear Ba(II) (BaL), and dinuclear Cu(II) (Cu2L ) complexes of L have been prepared and their crystal structures determined . Stability constants and other thermodynamic data valid in methanol at 23 or 25 degrees for these and several other complexes of L have been obtained . Among the metal ions studied, L forms the most stable complex with Ba2+. In addition, L selectively binds Cu2+ over Ni2+ by about 3 orders of magnit ude. Some of the complexes have been studied using nmr and uv-vis spectrosc opic techniques. Crystal data are given for L, space group, P2(1)/c, a = 8. 8325(14) Angstrom, b = 13.808(3) Angstrom, c = 13.310(3) Angstrom; beta = 9 4.72(2)degrees Z = 2, R = 0.0727; for H2L, space group, P2(1)/c, a = 14.685 (3) Angstrom, b = 15.035(6) Angstrom, c = 17.369(4) Angstrom, beta = 90.366 (12)degrees Z = 4, R = 0.0781; for BaL, space group, Pbcn, a = 17.314(3) An gstrom, b = 9.539(2) Angstrom, c = 22.081(3) Angstrom, Z = 4, R = 0.0354; a nd for Cu2L, space group, Cc, a = 19.762(2) Angstrom, b = 14.413(2) Angstro m, c = 14.935(2) Angstrom, beta = 98.753(12)degrees, Z = 4, R = 0.0564. Cu2 + forms a hydroxo-bridged dinuclear complex with L while Ba2+ forms a monon uclear complex with L in which its two side arms are not involved in comple xation.