The influence of imidazolium counterions on the luminescence properties of Cnmim[Eu(tta)₄] tetrakis complexes in solid-state and ionic liquid solutions

abstract

A series of lanthanide tetrakis complexes C(n)mim[Ln(tta)(4)] where Ln(3+): Eu3+ and Gd3+, C(n)mim: imidazoliumbased counterions (n from 3 to 8) and tta: thenoyltrifluoroacetonate were synthesized by a one-pot method. The Cnmim[Ln(tta)(4)] complexes are thermostable up to 210(degrees)C and present an isomorphic-like character for the complexes with n = 5, 6, and 7. The phosphorescence spectral profile of the C(n)mim[Gd(tta)(4)] complexes showed intense emission broadbands, in which the barycenters are slightly shifted to energies from the 18,950 to 18,450 cm(-1) range. The Cnmim[Eu(tta)(4)] complexes in solutions of the corresponding [C(n)mim]Br ionic liquids show similar emission spectral profiles as their corresponding in the solid state, indicating that the coordination polyhedron does not undergo a significant variation when the chemical environment is changed. Relatively high values of the intensity parameter Omega(2) in both media are presented. The Omega(4) values of the complexes in solutions of ionic liquids are also similar, reinforcing that there are small changes in the polyhedral coordination from the solid state to the ionic liquid solution. The series presents high intrinsic emission quantum efficiencies, 90% >= Q(Eu)(Eu) >= 53%. In addition, theoretical calculations on the intramolecular energy transfer (IET) reveal the participation of the F-7(0)-> D-5(1) and F-7(1)->(5)G(2) transitions for the IET via S1 while the IET via T1 state is dominated by the F-7(0)-> D-5(1) and F-7(1)-> 5D0 transitions. Therefore, due to their high luminescent features, these Eu3+ tetrakis complexes are potential candidates to be applied as optical markers in the solid-state or even in ionic liquid solutions.

keywords

INTRAMOLECULAR ENERGY-TRANSFER; BETA-DIKETONATE COMPLEX; INTENSITY PARAMETERS; LANTHANIDE COMPLEXES; OPTICAL-PROPERTIES; QUANTUM YIELD; EU3+; SALTS; COORDINATION; FLUORESCENCE

subject category

Optics

authors

Paolini, TB; Assunçao, IP; Costa, IF; Blois, L; Felinto, MCFC; Moura, RT, Jr; Teotonio, EES; Malta, OL; Neto, ANC; Brito, HF

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)

The shape of water: Nanothermometry as a tool to unveil the structure of liquid water and water-based nanofluids (PTDC/NAN-PRO/3881/2020)

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

acknowledgements

The authors are grateful to the Brazilian funding agencies CNPq and FAPESP for financial support. H.F. Brito is grateful to FAPESP (21/081110-2 and 21/08111-2) and CNPq for the research grant (306951/2018-5). This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, The Shape of Water (PTDC/NAN-PRO/3881/2020), and LogicALL (PTDC/CTM-CTM/0340/2021) financed by national funds through the FCT/MCTES (PIDDAC). E.E.S. Teotonio thanks the Universidade Federal da Paraiba (PVA13345-2020) for financial support. I.F. Costa thanks FAPESP (2022/12709-3) for his fellowship.