Influence of Hydroxycoumarin Substituents on the Photophysical Properties of Chiroptical Tb(III) and Eu(III) Complexes

abstract

In this article, the synthesis, density functional theory (DFT) structural characterization, and spectroscopic investigation of chiral and heteroleptic Tb(III) and Eu(III) complexes are presented. These molecules are characterized by two different ligands: the enantiopure N,N '-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N '-diacetic acid (H2bpcd) and a hydroxycoumarin-based ligand bearing different substituents in C(3) position (i.e., acetyl group in Coum, ethyl ester in CoumA, secondary and tertiary amides in CoumB and CoumC, respectively). The coumarin ligands exhibited different luminescence sensitization efficiency toward Tb(III) and Eu(III) ions in the related complexes of chemical formula [Ln(bpcd)(Coum)], [Ln(bpcd)(CoumA)], [Ln(bpcd)(CoumB)], [Ln(bpcd)(CoumC)]. Through theoretical calculations of intramolecular energy transfer (IET) processes (ligand-to-metal) in Eu(III) and Tb(III) complexes, along with quantum yield calculations, we provide a reasonable explanation for the observed differences in their luminescence properties. The nature of the coumarin ligand also affects the chiroptical properties of the Tb(III) complexes [i.e., circularly polarized luminescence (CPL) and electronic circular dichroism (ECD)].

keywords

CIRCULARLY-POLARIZED LUMINESCENCE; ASSISTED ENERGY-TRANSFER; RARE-EARTH IONS; EUROPIUM(III) COMPLEXES; MULTIPHONON RELAXATION; EXCITED-STATES; EMISSION; EU3+; TB3+; SENSITIZATION

subject category

Chemistry

authors

Ruggieri, S; Mizzoni, S; Cavalli, E; Sissa, C; Anselmi, M; Gualandi, A; Cozzi, PG; Neto, ANC; Melchior, A; Zinna, F; Willis, OG; Di Bari, L; Piccinelli, F

Groups

G2 - Photonic, Electronic and Magnetic Materials

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

Molecular logic devices and computing based on luminescent materials actuated by physical inputs (LogicALL)

acknowledgements

The authors thank the Italian Ministry of Education, University and Research for the funds (PRIN: Progetti di Ricerca di Rilevante Interesse Nazionale-Bando 2017 Prot. 20172M3K5N). O.G.W. is grateful for the financial support received from the European Commission Research Executive Agency, Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement no. 859752-HEL4CHIROLED-H2020-MSCA-ITN-2019. Authors from the University of Parma benefited from the equipment and support of the COMP-HUB Initiative, funded by the "Departments of Excellence" program of the Italian Ministry for Education, University and Research (MIUR, 2018-2022). Authors from the University of Verona gratefully thank the Facility "Centro Piattaforme Tecnologiche" (CPT) to access the Fluorolog 3 (Horiba-Jobin Yvon) spectrofluorometer and Luca Zuppiroli, from the University of Bologna, department of Industrial Chemistry, for performing the mass spectrometry measurements. Moreover, they thank Capucine Nonis and Thomas Erbland, students from SIGMA Clermont-Universite Clermont Auvergne, for participating at the development of the project during their internship in Verona. A.M. acknowledges the University of Udine for the grant "Ricerca Collaborativa" DM737/2001. A.M. and F.P. acknowledge the Italian Ministry of University and Research for the received funds [PRIN (Progetti di Ricerca di Rilevante Interesse Nazionale, Bando 2022 PNRR) project "TheCURA", Grant No. P20222TPZS]. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020, & LA/P/0006/2020 and LogicALL (PTDC/CTMCTM/0340/2021) financed by Portuguese funds through the FCT/MEC (PIDDAC).