Copper(II) complexes with the quinquedentate ligands H2Ln (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(H2Ln)]X2 and are abbreviated as 1X2, and 2X2 (n = 1, 2 for 2-substituent = H, Me; X = ClO4, NO3, Cl). X-ray crystal structures of 1(NO3)2, and 2(Cl)2 were determined: 1(NO3)2, monoclinic, space group P21/c (No. 14), a = 9.610(4) Å, b = 13.463(5) Å, c = 15.568(5) Å, β= 98.12(3)°, and Z = 4; 2(Cl)2, monoclinic, space group P21/n (No. 14), a = 9.884(2) Å, b = 15.073(3) Å, c = 15.295(2) Å, β= 98.57(2)°, and Z = 4. The complex assumes Δ or Δ enantiomorphs due to the spiral arrangement of the quinquedentate ligand around the copper(II) ion, and these Δ and Δ enantiomorphs of the cation for 1(NO3)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 [CuHLn]ClO4, 1′ClO4 (n = 1) and 2′ClO4 (n - 2), were obtained. Crystal data for 1′ClO4: Pbca (No. 61) with a = 13.211(3) Å, b = 25.387(3) Å, c = 10.939(3) Å, and Z = 8.; 2′-ClO4, 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 ClO4-, 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′ClO4 and 2.815(4) A ̊for 2′ClO4 to give a one-dimensional helical structure running along the a-axis. Through the hydrogen bonds, the Δ isomer only aggregates with the Δ isomer and the Δ isomer only aggregates with the Δ isomer to give an extended helical chain structure described as ΔΔΔΔΔ... or ΔΔΔΔΔ..., respectively.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry