Synthesis, Structures And Properties Of Complexes With Thiocyanate And Pyridine-tetracarboxylate

The thiocyanate ion is versatile ligand that can bind metal ions in a variety of ways. When magnetic polynuclear complexes are synthesized,the paramagnetic metal ions can be bridged to one-dimensional, two-dimensional and three-dimensional polymeric complexes. The magnetic properties of polynuclear complexes have been studied by many researchers.Pyridine-2,3,5,6-tetracarborxylate is a new bridging ligand which was synthesized in 2006. Carboxylic acid ligands are classical both in inorganic chemistry and biochemistry. They have the characteristics of symmetry and variety. Their complexes are broadly researched and applied in the following fields, including solid chemistry, structure, magnetism, spectrum kinetics, reaction mechanism, the reaction of ligands and analytical chemistry. There are many reports about complexes with pyridine dicarboxylic acid, and the research on pyridine tricarboxylic acid is just spring up in the recent years.In this article, five complexes have been synthesized, (CuL)₃[Mn(NCS)₅]₂ (1) (NiL)₃ [Mn(NCS)₅]₂ (2) (L= 5,7,7,12,14,14-Me- [14] -4,11-dieneN 4, [Me₆[14]dieneN₄]),[K₂Mn₃(PTA)₂(H₂O)₁₂]_n (3), [Mn₂(PTA)(bpy)₂(H₂O)]_n (4),[Cu(H₂PTA)(bpy)]_n (5)。Two factors related to the result that thiocyanate is bridging ligand in complex (1) and is terminal ligand in complex (2), are the difference of solvent,and the coordinate capacity between metal ions and sulfur atoms of thiocyanate.In cimplex(1) and (2) ,every Mn(II) ion is coordinated by five N atoms from thiocyanates ions which has not been mentioned in other articles.In comlex(3), the potassium ion played an inducement role in the molecular self-assembly. The manganese complex (4) has a di-chain polymrric structure. The copper complex(5) has a catenarian polymeric tructure. The different coordination modes of the carboxylate groups were displayed in coordinating with metal ions under different methods of synthesis. The different coordination modes of the carboxylate groups were displayed in coordinating with metal ions under different pH value. It resulted in diverse three dimensional structures of coordination complexes.