| To synthesize the polyoxometalate-based metal-organic complexes with novel structure and excellent properties,the benzonitrile compounds containing different nitrogen N-heterocyclic groups were chosen as initial ligands under hydrothermal or solvent thermal conditions.Seven complexes based different polymetalates and metal ions had been assembled relying on the in situ transformation of cyano to carboxyl ligands,and characterized by X-ray single crystal diffraction,IR,powder X-ray diffraction(PXRD),et al.The structures of all complexes were described in detail.In addition,the electrochemical properties and photocatalytic abilities of these complexes for the degradation of organic dyes were also discussed.1.Considering in situ transformation of 3,5-bis(1H-imidazolyl-1-yl)benzonitrile(DICN)and 3,5-bis(1H-1,2,4-triazolyl-1-yl)benzonitrile(DTCN)to3,5-bis(1H-imidazolyl-1-yl)benzoic acid(DIBA)and 3,5-bis(1H-1,2,4-triazolyl-1-yl)benzoic acid(DTBA)carboxyl ligands under hydrothermal condition,five polyoxometalate-based complexes 1-5 have been prepared by using the DICN and DTCN as organic ligands,and tuning the types of metal ions(Co2+?Ni2+?Zn2+)and polyoxoanions.[Co(HDIBA)(H2O)2(?-Mo8O26)0.5]·H2O(1)[Ni(HDIBA)(H2O)2(?-Mo8O26)0.5]·H2O(2)[Zn(HDIBA)(H2O)2(?-Mo8O26)0.5]·H2O(3)[Ni3(H2O)2(DTBA)2(DTBAH)2(?-Mo8O26)]·6H2O(4)[Co2(H2O)2(H2DIBA)2(HDIBA)2(Co W12O40)]·H2O(5)In the structures of complexes 1-5,the DIBA ligand was generated in situ from DICN ligand.Complex 1-3 were isostructural.The main structural feature was that the[?-Mo8O26]4-ion was modified covalently by two DIBA ligands and by sharing terminal oxygen atom with the DIBA ligand.These structural units were then connected into a 1D chain by Co2+ions.A 2D layered structure which obtained by the connection of the imidazole group of the DIBA ligand,was extended into a 3D supramolecular structure via hydrogen bonding interaction.The[?-Mo8O26]4-polyoxoanion was involved in complex 4 when the DTBA containing triazolyl as the heterocyclic group was selected as the ligand,with the addition of the covalent modification fragment similar to that of complexes 1-3.These fragments were connected by Ni2+ions to form a 1D chain A.Meanwhile,there was another 1D chain B formed by[?-Mo8O26]4-polyoxoanion and Ni2+ions.Chain A and B were arranged alternately to form a 2D layer,which was finally linked by DTBA ligands to form a 3D structure of compound 4.The 1D chain of compound 5 was composed of a kind of binuclear ring units{Co2(DIBA)4}and[Co W12O40]polyoxoanion.The investigation on the properties indicated that compounds 1-5showed a certain electric catalytic activities for the reduction of hydrogen peroxide,bromate,nitrite,Fe(III),and Cr(VI),and the oxidation of ascorbic acid,which better current responses.In addition,compounds 1 and 5 showed better photocatalytic abilities for the degradation of organic dyes CV,CR and MB.2.Using 4-(1H-1,3,7,8-cyclopentadiene[l]phenanthrene-2-yl)benzonitrile(L)as the initial ligand,two polyoxometalate-based on complexes 6 and 7 were synthesized by changing the solvent of reaction system.[Cu2(?2-H2O)(H2O)3(L')2]2(Si W12O40)·2H2O(6)[Cu2(H2O)4(L)2(Si W12O40)]·6H2O(7)In the structure of 6,the L ligand was transformed in situ to the4-(1H-1,3,7,8-cyclopentadiene[l]phenanthrene-2-yl)benzoic acid(L').A 1D structure based double chain was constructed from L'ligands,Cu(II)ions and bridged water molecules.When a small amount of ethanol was added to the reaction system,it was found that the L ligand was not transformed in situ to the L'ligand in compound 7.In other words,the solvent of the reaction system had an important effect on the in situ transformation of ligand L.Each L ligand chelated with one Cu(II)ion,which was connected on the both sides of one[Si W12O40]4-polyoxoanion by Cu-O bonds,giving a Z-type building unit[Cu2(L)2(Si W12O40)].The investigation on the properties indicated that compounds 6 and 7 showed a certain electric catalytic activities for the reduction of hydrogen peroxide,et al,the oxidation of ascorbic acid,with also better current responses.Compound 7dispalyed better photocatalytic ability for the degradation of organic dye CV. |
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