Influence of metal ions, coligands and reaction conditions on the structuralversatility and properties of 5-pyrimidyl-tetrazolate containing complexes

摘要

Eight new complexes containing the versatile multidentate ligand 5-pyrimidyl-tetrazolate (pmtz),namely [Cu(μ_3-pmtz)]_n (1), [Pd_2(μ-pmtz)_2Cl_2] (2), [Ni(pmtz)(en)_2]Cl.2H_2O(3), [Cu(tren)(pmtz)(C1O_4)](4), [Co_2(tren)_2(μ-pmtz)(μ-O_2)](ClO_4)_3.3H_2O(5),[Fe_2(pmtz)_4(H_2O)_2(μ-O)].5H_2O (6),[(UO_2)_4(μ-pmtz)_2(OH)_μ_3-O)_H_2O)_4]?6H_2O(7)and [Dy_pmtz)_4(pmtz)(6](pmtz)?6H_8),have been prepared by either conventional solution or hydrothermal techniques and characterised bysingle-crystal X-ray diffraction. Those compounds prepared under hydrothermal conditions ((1), (2),(7) and (8)) exhibit chelating/bridging coordination modes that connect two or three metal ions generating polynuclear species. Thus, compound 1 is a 2D polymer where the ligand exhibits a newchelating/bridging κ~2N_1,N_7:κN_2:κN_3coordination mode, whereas complexes (2) and(7)are dinuclearand tetranuclear species, respectively, in which the ligand displays a κ~2N_1,N_7:κN_2coordination mode.The increase of the metal size favours the adoption of the κ~2N_1,N_7:κ~2N_4,N_(11) bis(chelating)bridgingmode. This is the case of compound (8) that contains bulky Dy~(III) metal ions. Despite the large size ofthe UO~(2+)metal ion, the pmtz ligand in(7)does not adopt the expected bis(chelating)bridging modebecause the uranyl cation hydrolyzes to the highly stable bis(μ_3-oxo) tetranuclear unit. Conventionalmild solution conditions lead to complexes containing monodentate or chelating coordination modes.Thus, compounds (3) and (6) are mononuclear and μ-oxo dinuclear species, respectively, which contain chelating pmtz ligands. Compound (4) is mononuclear with the ligand acting in a newmonodentate form through the N_1 atom of the tetrazolato ring, whereas(5)is a dinuclear complexwhere pmtz adopts a new exo-bidentate N_2,N_3bridging coordination mode. Variable-temperaturemagnetic measurements of (6) indicate that the oxo-bridge mediates a very strong antiferromagneticinteraction between the iron(III) ions with a J = —222.7 cm~(-1). Luminescence measurements show thatthe pmtz ligands act as "antenna" for energy absorption and transfer to the uranyl emissive state.