Inorganic Chemistry, Vol.51, No.12, 6517-6528, 2012
Neutral Mononuclear, Dinuclear, Tetranuclear d(7)/d(10) Metal Complexes Containing bis-Pyrazole/Pyridine Ligands Supported by 2,6-bis(3-Pyrazolyl)Pyridine: Synthesis, Structure, Spectra, and Catalytic Activity
A series of novel bis-pyrazole/pyridine comp plexes, [Zn-2(HL1)(2)(mu(2)-SO4)](2)center dot EtOH center dot H2O (1), [Co-2(HL1)(2)(mu(2)-SO4)](2)center dot 2DMF center dot 6H(2)O (2), [Zn-4(HL1)(4)(mu(4)-SO4)][OH](2) (3), [Zn-2(HL2)(2)(mu(2)-SO4)]center dot 2H(2)O (4), [Zn- (H2L2) (H2O)(2)] (SO4)center dot 0.87H(2)O (5) (H2L1 = 2,6-di-(5-phenyl-1H-pyrazol-3-yl)pyridine, H2L2 = 2,6-di-(5-methyl-1Hpyrazol-3-yl)pyridine), were synthesized hydrothermally from the self-assembly of Zn(II) or Co(II) with different types of bipyrazolyl/pyridine derivative ligands. All the complexes were characterized by elemental analysis, IR and UV-vis spectroscopy, powder X-ray diffraction (PXRD), and single-crystal Xray diffraction. Structural analyses revealed that metal atoms (Zn and Co) in complexes 1-5 are five-coordination modes, forming slightly distorted trigonal bipyramidal geometries. In complexes 1-3, H2L1 ligand connected the two metal centers via the tetradentate fashion, and the same form of connection was found in complex 4 with H2L1 ligand. While in complex 5, H2L2 only connected with one metal center via the tridentate fashion, which was different from those in complexes 1-4. Additionally, there are abundant hydrogen bonding interactions in complexes 1-4. Interestingly, for hydrogen bonding connecting fashions being different, the molecules for the complexes 1 and 4 are held together by the hydrogen bond to form a 1D supramolecular structure, whereas complexes 2 and 3 are a hydrogen bonded dimer. In addition, quantum chemical calculations for 1, 3, and 4, thermal behaviors and photoluminescent properties for 1 and 3-5 were performed and discussed in detail. In the mean time, we found that these complexes had potential catalytic activity for the oxidation reaction of cyclohexane.