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

Abstract

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 N 6 O 4 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 À 1 at 300 K.

Dual visible and near-infrared luminescence in mononuclear macrocyclic erbium(iii) complexes via ligand and metal centred excitation

“…Reagent grade chemicals and HPLC quality solvents were used as received. The synthesis of erbium(III) complexes 1-3 was performed according to the reported procedures 19,20 (see the ESI †).…”

Luminescence of Macrocyclic Mononuclear DyIII Complexes and Their Immobilization on Functionalized Silicon-Based Surfaces

“…For Dy-EDA , a broad band with a maximum at 425 nm was also observed, which is related to the ligand emission. This was corroborated by comparing with the emission spectrum of the Y III analogue . The intensity of the ligand emission band of Dy-EDA is greater than the characteristic emission bands of the Dy III ion, indicating that the energy transfer mechanism from the ligand to the lanthanide is inefficient.…”

“…This was corroborated by comparing with the emission spectrum of the Y III analogue. 20 The intensity of the ligand emission band of Dy-EDA is greater than the characteristic emission bands of the Dy III ion, indicating that the energy transfer mechanism from the ligand to the lanthanide is inefficient. Conversely, Dy-DAP did not show bands related to ligand emission, evidencing that the ligand acts as an efficient antenna in the sensitization of Dy III luminescence.…”

“…The excited states of the macrocyclic ligands derived from ethylenediamine (L 1 ) and 1,3-diaminepropane (L 2 ) were reported at 21 097 and 23 094 cm −1 , respectively. 20 According to Latva et al 21 one condition for an efficient energy transfer from the ligand to the metal center is related to the energy gap (ΔE) between the excited state of the ligand and the emissive state of the Ln III ion. For the Dy III ion, the emissive state is the 4 F 9/2 level, which is located at 20 833 cm −1 .…”

Influence of symmetry on the magneto-optical properties of a bifunctional macrocyclic DyIII complex

“…21 In this way, these macrocyclic ligands have been used as chromophores in luminescence studies and depending on the lateral spacer on the macrocycle they have been shown to act as efficient "antennas" in the luminescence of Ln III ions. [22][23][24][25] According to these reports, [2 + 2] Schiff-base macrocycles with 3-carbon chain lateral spacers are better antennas that those with 2-carbon ones, while the use of axial nitrate anions showed an increase of the luminescence in these systems. These features are in direct contrast to the design strategies previously discussed for a high performance SMM: the weak crystal field of axial nitrate anions and higher macrocycle distortion due to the length of the lateral spacer.…”