Structural Evolution and Tuneable Photoluminescence of f-Element Bearing Coordination Polymers of the 2,4,6-tri-α-pyridyl-1,3,5-triazine Ligand
Exploring the family of f-element bearing single-molecule coordination polymers via solvothermal reactions has yielded fourteen new rare-earth single-molecule complexes with three distinct phases, Ln(TPTZ)(NO3)3CH3CN (LnTPTZ-1, Ln = Pr and Nd), [Ln(TPTZ)(NO3)3(H2O)]·CH3CN (LnTPTZ-2, Ln = Pr – Er), and [Ln(TPTZ)(NO3)3(H2O)]·2CH3CN (LnTPTZ-3, Ln = Tm – Lu), as well as the a uranyl coordination polymer UO2(TPTZ)(NO3)2 (UTPTZ). All of the structures exhibit zero-dimensional topologies via the self-assemblies of f-element cations with 2,4,6-tri-α-pyridyl-1,3,5-triazine (TPTZ), a tridentate semiaperture ligand featuring three ortho-N atoms on its pyridine and triazine rings. Due to the effect of the lanthanide contraction, structural evolutions of the lanthanide complexes including decrease in unit cell dimensions and Ln–O/N bond lengths across the isomorphous structures, and more dramatically the transitions of the overall topologies were observed. In addition, a rather unusually bent Oyl=U=Oyl unit with a highly distorted hexagonal bipyramid coordination environment was identified in UTPTZ. The homoleptic structure of EuTPTZ-2 and TbTPTZ-2 allows for fine-tune the molar ratio Eu/Tb in a single EuxTb1−xTPTZ-2 complex and concomitantly giving rise to versatile photoluminescent colour of such material. Explicitly, it exhibits multicolour photoluminescence ranging from green to red under the excitation of UV light and an excellent linear relationship in colour tunability could be obtained.