Thermal Dependence of the Luminescent Properties of Mononuclear Tb-III Macrocyclic Complexes

A family of six terbium(III) complexes with hexaaza macrocyclic ligands, together with the isostructural yttrium(III) species, is reported and the thermal dependence of the photophysical properties of the terbium(III) complexes is analysed. The coordination number is defined by the anions, nitrate or isothiocyanate, which act as secondary ligands. While complexes with nitrate anions are decacoordinated species, presenting a N6O4 first coordination sphere, complexes derived from isothiocyanate are nonacoordinated with exclusively nitrogen donor atoms. Regarding the optical properties, only the macrocyclic ligands derived from aliphatic amines act as sensitizers for the terbium(III) cations, and the complexes emit in the green region, according to the obtained CIE coordinates. The isothiocyanato ligand plays a detrimental role on the luminescence of the corresponding complexes, since their emission is weaker as compared to that of the nitrato counterparts. The greater achieved thermal sensitivity for one of the studied terbium(III) complexes was 3.2 %K-1 at 300 K.