Synthesis,Structure And Properties Of Polypyridine Complexes

The objective of this study is to construct a pyridine substituted tripyridine complex with stimulus response.Functional tripyridine:4’-（n-pyridine）-tripyridine（n=1,2,3）was used as the ligand to synthesize 9 metal complexes successfully by combining rare earth metal ions(Pr（Ⅲ）,Sm（Ⅲ）,Eu（Ⅲ）,Dy（Ⅲ）and Er（Ⅲ）with transition metal ions(Co（Ⅱ）and Cu（Ⅱ）by various synthesis methods.Their single crystal structure was analyzed and characterized by PXRD powder diffraction,infrared spectrum,ultraviolet-visible spectrum.1.Using 4’-（2-pyridine）-tripyridine（2-pyterpy）as ligand,5 complexes were synthesized with rare earth ions（Pr,Sm,Eu,Dy,Er）by thermal solvent method:[Pr（2-pyterpy）（NO₃）₂（μ-OCH₃）]₂（1Pr）and[Sm（2-pyterpy）（NO₃）₂（μ-OCH₃）]₂（2Sm）,[Eu（2-pyterpy）（NO₃）₂（μ-OCH₃）]₂（3Eu）,[Dy（2-pyterpy）（NO₃）₂（μ-OCH₃）]₂（4Dy）and[Er（2-pyterpy）（NO₃）₂（μ-OCH₃）]（5Er）.X-ray diffraction analysis of single crystal shows that the complexes 1Pr and 2Sm belong to the monoclinic system and the P2（1）space group,which are asymmetric dimers.Complex 5Er belongs to C2/c space group,monoclinic system,and is a symmetrical dimer structure.It was found that under the ligand of 2-pyterpy,the lanthanide contraction effect caused the crystal structures of the 5 complexes 1Pr and 2Sm,3Eu and 4Dy and 5Er to be divided into three groups.The uv-visible absorption and fluorescence spectra of the 3Eu complex are sensitive to the acid-base balance in solution and are expected to be designed as p H sensors or molecular switches.Magnetic studies have shown that the complexes 1Pr,2Sm,3Eu and 4Dy have antiferromagnetic interactions with each other.2.Using 4’-（2-pyridine）-tripyridine（2-pyterpy）and 4’-（3-pyridine）-tripyridine（3-pyterpy）as ligands,4 complexes were synthesized with transition metal ions(Co（Ⅱ）and Cu（Ⅱ）by solution method:[Co^Ⅱ（2-pyterpy）₂]（PF₆）₂·0.75Me OH（6）and[Cu ₂^Ⅱ（2-pyterpy）₄]（PF₆）₄·1.5Me OH（7）,[Cu ^Ⅱ（2-pyterpy）₂]（BF₄）₂（8）and[Cu ^Ⅱ（3-pyterpy）Cl]（BF₄）（9）.X-ray diffraction analysis of single crystal shows that complexes 6 and 7 are asymmetric binuclear structures,and the central ions Co（Ⅱ）and Cu（Ⅱ）are in the six-coordination state.Each asymmetric structural unit is passed betweenπ-πStacking and intermolecular forces to form a network structure.The complex 9 center ion Cu（Ⅱ）is in a five-coordination state,and its structure is one-dimensional chain.It can be explained that ligand 3-pyterpy has a smaller steric hindrance than ligand 2-pyterpy,and it is easy to coordinate with mono-tridentate bridging under the same synthetic conditions.