Luminescence in Ln3+dipivaloylmethanate complexes: Spectroscopic and theoretical investigation on the energy transfer and LMCT state

abstract

Three novel lanthanide dipivaloylmethanate (dpm) complexes of general formula [Ln(dpm)(NO3)2(tchpo)2], where Ln: Eu3+, Gd3+ and Tb3+, and tchpo: tricyclohexylphosphine oxide neutral ligand have been prepared and characterized by elemental analyses, absorption infrared spectroscopy, thermalgravimetric analyses, diffuse reflectance, and luminescence spectroscopies. Furthermore, the [Tb(dpm)(NO3)2(tchpo)2] complex was structurally characterized by the single crystal X-ray diffraction analysis. This complex exhibited high luminescence intensity in the green region. On the other hand, the analogous Eu3+-complex exhibited very low luminescence intensity due to an efficient luminescent quenching process via ligand-to-metal charge transfer (LMCT) state. Theoretical studies employing Time-Dependent Density Functional Theory (TD-DFT) calculations along with results obtained from the JOYSpectra platform, support this experimental result. Remarkably, despite the high values of non-radiative intramolecular energy transfer from excited ligand states (S1 and T1) to the excited levels of the Ln3+ ions, in the [Eu(dpm)(NO3)2(tchpo)2], the highest S1-LMCT rate (W = 1.2 x 1010 s-1) emphasizes that the primary luminescence quenching pathway is via depopulation of excited ligand states. Interestingly, the nitrogen atoms from nitrate ions play an essential role in the lanthanide chemical environment, which has been suggested by the analyses of the ligand field parameters charge factors (g) and effective polarizabilities (alpha ') values.

keywords

LANTHANIDE NITRATE COMPLEXES; NUCLEAR-MAGNETIC-RESONANCE; CHARGE-TRANSFER STATE; METAL-COMPLEXES; BASIS-SETS; CRYSTAL; PARAMETERS; MODEL; EU

subject category

Chemistry; Crystallography

authors

Arruda, JG; Silva, IF; Faustino, WM; Costa, IF; Brito, HF; Neto, ANC; Näther, C; Terraschke, H; Felinto, MCFC; Deflon, VM; Teotonio, EES

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)

acknowledgements

This work was funded by the Universidade Federal da Paraiba (PRODUTIVIDADE UFPB 03/2020, PVA13345-2020) . The authors also thank Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ: 317047/2021-3) and Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) and Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP: 2021/08111-2 and 2022/12709-3) . 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 financed by Portuguese funds through the FCT/MEC (PIDDAC) .r (PRODUTIVIDADE UFPB 03/2020, PVA13345-2020) . The authors also thank Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ: 317047/2021-3) and Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) and Fundacao de Amparo a` Pesquisa do Estado de Sao Paulo (FAPESP: 2021/08111-2 and 2022/12709-3) . 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 financed by Portuguese funds through the FCT/MEC (PIDDAC) .