The luminescent metal-organic complexes of rare earth metals are advanced materials
with wide application potential in chemistry, biology, and medicine. The luminescence of these
materials is due to a rare photophysical phenomenon called antenna effect, in which the excited
ligand transmits its energy to the emitting levels of the metal. However, despite the attractive
photophysical properties and the intriguing from a fundamental point of view antenna effect, the
theoretical molecular design of new luminescent metal-organic complexes of rare earth metals is
relatively limited. Our computational study aims to contribute in this direction, and we model
the excited state properties of four new phenanthroline-based complexes of Eu(III) using the TDDFT/TDA approach. The general formula of the complexes is EuL2A3
, where L is a phenanthroline
with –2–CH3O–C6H4
, –2–HO–C6H4
, –C6H5 or –O–C6H5 substituent at position 2 and A is Cl− or
NO3
−. The antenna effect in all newly proposed complexes is estimated as viable and is expected to
possess luminescent properties. The relationship between the electronic properties of the isolated
ligands and the luminescent properties of the complexes is explored in detail. Qualitative and
quantitative models are derived to interpret the ligand-to-complex relation, and the results are
benchmarked with respect to available experimental data. Based on the derived model and common
molecular design criteria for efficient antenna ligands, we choose phenanthroline with –O–C6H5
substituent to perform complexation with Eu(III) in the presence of NO3¯. Experimental results
for the newly synthesized Eu(III) complex are reported with a luminescent quantum yield of about
24% in acetonitrile. The study demonstrates the potential of low-cost computational models for
discovering metal-organic luminescent materials