Copper(II) bipyridine and crown ether-bipyridine complexes: X-ray structures, characterization, and properties as histamine receptors
Martens CF, Schenning APHJ, Feiters MC, Beurskens G, Smits JMM, Beurskens PT, Smeets WJJ, Spek AL, Nolte RJM
SUPRAMOLECULAR CHEMISTRY 8 (1): 31-44 1996

Abstract:
he synthesis and characterization, including the crystal structure, of the complex (2) of Cu(II) with the crown-ether bipyridine ligand, 1[5-2,2'-bipyridyl)carbonyl]-1-aza-4,7,10,13-tetraoxacyclopentadecane (1), are described. Compound 2, C27H49N3O18Cl2Cu, crystallizes in the triclinic space group P1 with cell constants a = 10.160(1), b = 13.014(1), c = 15.934(2) Angstrom, 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 reflections (I > 2 sigma(I)), 83 restraints and 390 parameters. The crystals contain two formula units per cell as a dimer, with each carbonyl oxygen of one monomer complex coordinating to the copper ion of the other. 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. There are no exchange interactions between the coppers as concluded from magnetic susceptibility measurements. Determination of the association constants of 2 with histamine.HCl and histamine.HClO4 in ethanol yields values of 70 and 1000 M(-1), respectively. It is proposed that the imidazole and protonated amine group of histamine have binding interactions 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 = 16.9776(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 solved by heavy atom Patterson methods and refined to R = 0.05 for 2447 observed reflections and 344 parameters, without restraints. The Cu(II) ion in this complex, {Cu(bipyridine)(2)Cl}ClO4, which did not contain histamine, is five-coordinated, with 4 nitrogen donors of bipyridyl ligands and one chloride.