Synthesis,characterization And Photoluminescence Properties Of Copper(?) Complexes Based On Bipyridine Ligands

Copper(?)complexes,as a cheap and abundant material,have attracted wide attention due to their rich structure and photophysical properties as well as their potential applications in optoelectronic,catalytic and biological systems.Due to their strong coordination ability and structural diversity,bridged pyridinyl ligands and chelated pyridinyl ligands have been studied in depth.In particular,the complexes based on Cu I-pyridine(py)ligands showed superior structural diversity.So far,the coordination patterns of bridged pyridinyl ligands and chelated pyridinyl ligands as well as the structure of copper clusters constructed with Cu(?)are relatively single,and the functional applications of copper clusters are relatively limited.In previous studies on bipyridine-Cu I clusters,there are also many problems such as insufficient data and imperfect experimental methods.In order to systematically study the copper clusters constructed by bipyridine ligands and Cu(?)with different excellent functional applications,by adding flexible coordination atoms and using reduction conversion method,dibromodipyridine ligands were modified to have a variety of coordination patterns,and Cu(?)was used to construct complex and diverse copper clusters.In this paper,four thioether bipyridine ligands were prepared successfully:organic ligand 5,5'-bis(2-thiol pyridine)-2,2'-bipyridine(L1),5,5'-bis((benzyl sulfide)methyl))-2,2'-bipyridine(L2),organic ligand 6,6'-bis(2-thiol pyridine)-2,2'-bipyridine(L3),6,6'-bis((benzyl sulfide)methyl)-2,2'-bipyridine(L4).Eight complexes were synthesized by using these four ligands:Cu₆(C₅H₄NS)₆(1),Cu₄(L1)₄(NO₃)₄(2),Cu₄I₄(L4)₂(3),Cu₂I₂L4(4),Cu₁₂I₁₂(L2)₄(H₂O)₄(5),Cu₂I₂(L2)₂(?-C₂O₄)(6),Cu₄I₄(L3)₂(7),Cu C₁₇H₁₆N₄O₇S(8).Complex 1 has a deformed Cu₆ octahedron configuration,and obvious S-Cu interaction has been found in the complex.Complex 2 is a binuclear copper ion coordination polymer,whose asymmetric unit consists of four divalent copper ions in a twisted triangular bicone configuration.Complex 3 is a tetranuclear complex with a typical stepped-cubane Cu₄I₄ unit.The Cu₄I₄ unit is composed of two rhombodimer Cu₂I₂ units connected by sharing two?₃-I^-.Complex 4 is a tetraconuclear complex with two long rhomboid Cu₂I₂ units,in which two Cu(?)ions still exhibit a twisted tetrahedral geometry,but show different binding patterns.Complex 5 is a coordination polymer with Cu₄(H₂O)₄ structural unit with water molecular coordination.There are two kinds of copper ions and three types of copper clusters in complex 5.Two of the four L2 ligands connect four copper ions to the coordination environment of Cu₂O₃ in a face to face way to construct Cu₄ cubes,which is surrounded by two types of Cu I clusters(Cu₂I₃S₂ and Cu₄I₆S₄).Complex 6 is a binuclear Cu(II)complex bridged by oxalate.Complex 7 is a stepped Cu₄I₄ tetraconuclear copper cluster.Its structure is the same as the Cu₄I₄ tetra-core copper cluster obtained by direct reaction of ligand L3and Cu I.Complex 8 is a mononuclear divalent copper complex with intramolecular hydrogen bond formation.Complex 1 and 7 were synthesized by reduction conversion.The ultraviolet spectrum shows that complex 1 and 7 have the strongest absorption at 450 nm,and has a large range of absorption in the visible region.Complex 3 can be thermally converted to complex 4,that is,the copper cluster core of the complex is thermally transformed from the stepped four-core copper cluster 3 to the butterfly-shaped binuclear copper cluster 4.The ultraviolet spectrum shows that complex 4 has a wider range of visible light absorption than complex3.L2-Cu I solution is very reductive and can reduce carbon dioxide to oxalic acid.XPS energy spectrum showed that there were two valence states of copper ions in complex 5,and the ultraviolet spectrum showed that complex 5 had a larger absorption range than complex 6 in the visible region.The photoluminescence spectra of complexes 3,4 and 7showed that they had classical LE and HE emission bands in the center of copper clusters.Complex 5 has photoluminescence quenching due to the coordination of water molecules.Complex 1 has emission peaks of LE(Low Energy)emission band and HE(High Energy)emission band at 552 nm,which are different from those in the center of classical copper cluster.In this paper,by regulating different ligand structures,a number of complex with rich coordination structures were synthesized,thus regulating the different functional applications of the complex and the differences in the photoluminescence properties of the complex.