Composition control is a powerful
tool for obtaining
high-performance
lanthanide (Ln) luminescent materials with adjustable optical outputs.
This strategy is well-established for hierarchically structured nanoparticles,
but it is rarely applied to molecular compounds due to the limited
number of metal centers within a single unit. In this work, we present
a series of molecular cluster-aggregates (MCAs) with an icosanuclear
core {Ln2Eu2Tb16} (Ln = Ce, Pr, Nd,
Sm, Gd, Dy, Ho, Er, Tm, and Yb) in which we explore composition control,
akin to nanoparticles, to modulate the optical output. More specifically,
we target to understand how the presence of a third LnIII doping ion would impact the well-known TbIII →
EuIII energy transfer and the ratiometric optical thermometry
performance based on the TbIII/EuIII pair. Photophysical
properties at room and at varying temperatures were investigated.
Based on experimental data and well-established intrinsic features,
such as spin–orbit coupling strength and LnIII 4f energy levels’ structure, we discuss the possible
luminescent processes present in each MCA and provide insight into
qualitative trends that can be rationally correlated throughout the
series.