Copper(II) Complexes of N,N'-Bis((2-substituted-imidazol-4-yl)methylene)-3,3'-diaminodi- propylamine (2-Substituent = H, Me): Delta and Lambda Enantiomorphs of the Protonated Complex and Helical Structure of the Deprotonated Complex Formed by Hydrogen Bonds.
Copper(II) complexes with the quinquedentate ligands H(2)L(n)() (n = 1, 2) of the 1:2 condensation products of 3,3'-diaminodipropylamine and each of 4-formylimidazole and 4-formyl-2-methylimidazole have been synthesized and characterized, where the complexes have the general formula of [Cu(H(2)L(n)())]X(2) and are abbreviated as 1X(2), and 2X(2) (n = 1, 2 for 2-substituent = H, Me; X = ClO(4), NO(3), Cl). X-ray crystal structures of 1(NO(3))(2), and 2(Cl)(2) were determined: 1(NO(3))(2), monoclinic, space group P2(1)/c (No. 14), a = 9.610(4) Å, b = 13.463(5) Å, c = 15.568(5) Å, beta = 98.12(3) degrees, and Z = 4; 2(Cl)(2), monoclinic, space group P2(1)/n (No. 14), a = 9.884(2) Å, b = 15.073(3) Å, c = 15.295(2) Å, beta = 98.57(2) degrees, and Z = 4. The complex assumes Delta or Lambda enantiomorphs due to the spiral arrangement of the quinquedentate ligand around the copper(II) ion, and these Delta and Lambda enantiomorphs of the cation for 1(NO(3))(2) and 2(Cl)(2) coexist as the racemic form in the crystals. When the protonated complexes were treated with NaOH, the mono-deprotonated complexes with the formula [CuHL(n)()]ClO(4), 1'ClO(4) (n = 1) and 2'ClO(4) (n = 2), were obtained. Crystal data for 1'ClO(4): Pbca (No. 61) with a = 13.211(3) Å, b = 25.387(3) Å, c = 10.939(3) Å, and Z = 8.; 2'.ClO(4), Pbca (No. 61) with a = 16.554(4) Å, b = 20.609(4) Å, c = 12.423(3) Å, and Z = 8. The structures consist of an electronically monopositive copper(II) complex involving a deprotonated imidazole moiety and a protonated imidazole moiety per molecular unit and a mononegative anion ClO(4)(-), where an imidazolate nitrogen atom N(2) of the copper(II) complex is hydrogen bonded to the imidazole nitrogen atom N(6) ( denotes the symmetry operation of (1)/(2) + x, (1)/(2) - y, -z) of the adjacent unit with the hydrogen bond distance of N(2).N(6) of 2.842(6) for 1'ClO(4) and 2.815(4) Å for 2'ClO(4) to give a one-dimensional helical structure running along the a-axis. Through the hydrogen bonds, the Delta isomer only aggregates with the Delta isomer and the Lambda isomer only aggregates with the Lambda isomer to give an extended helical chain structure described as DeltaDeltaDeltaDeltaDelta. or LambdaLambdaLambdaLambdaLambda., respectively.