COPPER(II) BIPYRIDINE AND CROWN ETHER-BIPYRIDINE COMPLEXES - X-RAY STRUCTURES, CHARACTERIZATION, AND PROPERTIES AS HISTAMINE-RECEPTORS

he synthesis and characterization, including the crystal structure, of the complex (2) of Cu(II) with the crown-ether bipyridine ligand, car bonyl]-1-aza-4,7,10,13-tetraoxacyclopentadecane (1), are described. Co mpound 2, C27H49N3O18Cl2Cu, crystallizes in the triclinic space group P1 with cell constants a = 10.160(1), b = 13.014(1), c = 15.934(2) Ang strom, alpha = 74.18(1)degrees, beta = 84.83(1)degrees, gamma = 71.54( 1)degrees, V = 1923.0(4) Angstrom(3), Z = 2, d(calc) = 1.448 g cm(-3). The crystal structure was solved by vector search methods and refined by full-matrix least-squares on F-2 to R = 0.086 for 3163 observed re flections (I > 2 sigma(I)), 83 restraints and 390 parameters. The crys tals contain two formula units per cell as a dimer, with each carbonyl oxygen of one monomer complex coordinating to the copper ion of the o ther. Each copper has elongated octahedral coordination geometry, with two nitrogens of one bipyridyl unit and four oxygens, viz. two water molecules, one perchlorate, and one carbonyl, as ligand donor atoms. T here are no exchange interactions between the coppers as concluded fro m magnetic susceptibility measurements. Determination of the associati on constants of 2 with histamine.HCl and histamine.HClO4 in ethanol yi elds values of 70 and 1000 M(-1), respectively. It is proposed that th e imidazole and protonated amine group of histamine have binding inter actions with the Cu(II) ion and the crown ether ring, respectively, of 2. From a solution of Cu(II) bipyridine complexes in the presence of both histamine and chloride, crystals of C20H16ClCuN4.ClO4 with space group P2(1)/c and cell constants a = 10.7498(5), b = 12.2394(7), c = 1 6.9776(9) Angstrom, beta = 112.248(4), V = 2067.5(2) Angstrom(3), Z = 4, and d(calc) = 1.641 g cm(-3) were isolated. The structure was solve d by heavy atom Patterson methods and refined to R = 0.05 for 2447 obs erved reflections and 344 parameters, without restraints. The Cu(II) i on in this complex, {Cu(bipyridine)(2)Cl}ClO4, which did not contain h istamine, is five-coordinated, with 4 nitrogen donors of bipyridyl lig ands and one chloride.