Circularly polarized luminescence of tetrakis complexes of lanthanide ions containing chiral counterions

• Grant number: 24/20278-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2025
• End date: December 31, 2025
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Inorganic Chemistry
• Principal Investigator: Fernando Aparecido Sigoli
• Grantee: Francisco Antonny Gonçalves Militão Santos
• Host Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 21/08111-2 - Development of rare earth based light converters: luminescent markers, optical sensors, and amplifiers, AP.TEM

Abstract

Coordination complexes of trivalent lanthanide ions are studied because they show narrow emission bands attributed to intraconfigurational 4f-4f transitions. The use of chiral complexes of lanthanide ions, especially Eu(III), makes it possible to obtain the so-called circularly polarized luminescence (CPL). CPL is characterized by the spontaneous emission of left- and/or right-handed circularly polarized light with different intensities, and the difference between these intensities gives rise to a CPL spectrum. The Eu(III) ion is an essential spectroscopic probe for the evaluation and application of the CPL phenomenon, since by adjusting the symmetry of the first coordination sphere it is possible to obtain electronic transitions with contributions from the electric and magnetic dipole moments, a characteristic that is fundamental for CPL. In this field of research, there has been a notable increase in studies involving CPL in lanthanide complexes and, as mentioned, especially of Eu(III) ions, using enantiomerically pure chiral polydentate ligands. The applicability of these systems depends on obtaining high CPL emission brightness values, which are directly proportional to the values of the chiral luminescence dissymmetry factor |glum| and the specific emission quantum yield of the chiral emission band. However, difficulties are encountered in obtaining chiral complexes that have high values of the chiral luminescence dissymmetry factor and high emission quantum yields. Therefore, this work aims to study the chiral photoluminescent properties of anionic tetrakis complexes of non-chiral ¿-diketones having high emission quantum yields and to use chiral cationic counterions to promote CPL luminescence. These chiral complexes will be evaluated in order to obtain high values of dissymmetry and emission quantum yields and, therefore, high CPL brightness.