Syntheses, structure, and properties of the metal complexes with 3-(2-pyridyl)pyrazole-based ligands: Tuning the complex structures by ligand modifications

In our efforts to design metal complexes with tailored structures, four 3-(2-pyridyl)pyrazole-basecl ligands, 8-[3-(2-pyridyl)pyrazolmethyl]quinoline (L-1), 1,4-bis[3-(2-pyridyl)pyrazolyl]-trans-2-butene (L-2), 2,3-bis[3-(2-pyridyl)pyrazolmethyl]quinoxaline (L-3), and 1,3,5-tri[3-(2-pyridyl)pyrazolmethyl]-2,4,6-trimethylbenzene (L-4), have been synthesized and characterized, and their metal complexes with Cu-II, Ni-II, Co-II, and Cd-II ions have been prepared and structurally characterized by single-crystal X-ray diffraction. Using V to react with CuX2 (X = Ac, NO3-, or ClO4-) or Cd(ClO4)(2)center dot 6H(2)O, yielded four mononuclear complexes, [Cu(L-1)(2)(OAc)](OAc)(H2O)(6) (1) [triclinic, space group P(1) over bar, a = 10.513(11) angstrom, b = 13.875(14) angstrom, c = 15.776(16) angstrom, alpha = 70.98(2)degrees, beta = 83.57(2)degrees, gamma = 69.665(18)degrees, Z = 2], [Cu(L-1)(2)(NO3)](NO3)(H2O)(5.5) (2) [monoclinic, space group C2/c, a = 12.395(3) angstrom, b = 26.267(6) angstrom, c = 26.362(7) angstrom, beta = 92.635(5)degrees, Z = 8], [Cu(L-1)(2)(H2O)](ClO4)(2) (3) [orthorhombic, space group Pbca, a = 13.326(4) angstrom, b = 21.715(6) angstrom, c = 26.318(8) angstrom, Z = 8], and [Cd(L-1)(3)](ClO4)(2)(H2O)(5/2) (4) [triclinic, space group P(1) over bar, a = 12.485(5) angstrom, b = 15.142(6) angstrom, c = 15.190(6) angstrom, alpha = 83.104(7)degrees, beta = 75.796(7)degrees, gamma = 79.584(7)degrees, Z = 2]. The reaction of L-2 with Cu(ClO4)(2)center dot 6H(2)O or Co(NO3)(2)center dot 6H(2)O yielded two double helical dinuclear complexes: [Cu-2(L-2)(2)(H2O)(2)](ClO4)(4)(H2O) (5) [triclinic, space group P(1) over bar, a = 10.791(4) angstrom, b = 13.923(7) angstrom, c = 19.756(9) angstrom, alpha = 72.297(12)degrees, beta = 78.201(14)degrees, gamma = 68.683(13)degrees, Z = 2] and [Co(L-2)(NO3)(H2O)](2)(NO3)(2) (6) [orthorhombic, space group Pbcn, a = 18.170(7) angstrom, b = 13.240(5) angstrom, c := 19.064(7) angstrom, Z = 4]. When L-2 was replaced by L-3 to react with Cu(ClO4)(2)center dot 6H(2)O or Ni(BF4)(2)center dot 6H(2)O, another mononuclear complex, [Cu(L-3)-(ClO4)](ClO4) (7) [triclinic, space group P(1) over bar, a = 10.1298(6) angstrom, b = 12.3163(6) angstrom, c = 12.9485(7) angstrom, alpha = 111.533(2)degrees, beta = 106.068(2)degrees, gamma = 99.921(2)degrees, Z = 2], and a novel tetranuclear complex, [Ni-2(L-3)(2)(H2O)(4)](2)(SO4)(2)(BF4)(4)(H2O)(8)(CH3OH)(8) (8) [triclinic, space group P(1) over bar, a = 13.818(8) angstrom, b = 16.645(8) angstrom, c = 20.937(11) angstrom, alpha = 109.508(10)degrees, beta = 107.144(9)degrees, gamma = 90.923(9)degrees, Z = 2], were obtained. L-4 reacts with Cu(ClO4)(2)center dot 6H(2)O, to yield a novel trinuclear complex, [Cu-3(L-4)(H2O)(9)](ClO4)(5)OH)(CH3CN)-(H2O)(4.5) (9) [monocliriic,. space group C2/c, a = 32.067(12) angstrom, b = 25.610(9) angstrom, c = 17.498(7) angstrom, = 115.187(6)degrees, Z = 4]. These results show that the nuclearity of metal complexes may be tuned by ligand modifications, and the nature of ligands, metal ions, counteranions, and solvent molecules play important roles in the formation of such coordination architectures. The emission properties of complexes 7 and 8 have been further studied.