Theoretical study of 8‐hydroxyquinoline derivatives as potential antennas in lanthanide complexes: Photophysical properties and elucidation of energy transfer pathways

Abstract

A series of 8‐hydroxyquinoline derivatives were theoretically characterized and tested as potential antennas in a set of designed lanthanide complexes. The molecular structure and ligand localized nature of the excited states were studied in the framework of the multiconfigurational methods CASSCF/NEVPT2 combined with TD‐DFT‐based approaches, which allow applying a fragmentation scheme in the analysis of the most probable sensitization pathway via antenna effect. The photophysical properties of all the complexes and antennas were carefully analyzed, predicting the most probable energy transfer pathways. Rate constants for photophysical processes involved in the mechanism showed a significant contribution of the vibronic coupling in all cases, and the predominant intersystem‐crossing between S1 and T1 states was demonstrated from the analysis of the nature of the wave function of those states. The energy transfer process described herein demonstrates the possibility of Eu(III) and Nd(III) sensitization by the studied ligands. The proposed methodology gives a complete picture of the antenna excited state dynamics.

Expanding the Knowledge of the Selective-Sensing Mechanism of Nitro Compounds by Luminescent Terbium Metal–Organic Frameworks through Multiconfigurational ab Initio Calculations

“… , In terms of the population of the T 1 electronic state, the radiative deactivation channel of the S 1 electronic state via the fluorescence mechanism is an unfavorable process . In this way, in comparison to a radiative deactivation processes such as fluorescence, an efficient antenna requires a quick ISC channel S 1 → T 1 . , Thus, the calculated rate constants for the fluorescence and ISC process are crucial to support the hypothesis of the efficient T 1 state population via the ISC channel. , In this sense, the analysis of the BTTA antenna excited state dynamic parameters indicates that the rate of nonradiative ISC channels S 1 → T 1 is 3.22 × 10 8 s –1 . This result shows that the k ISC (S 1 → T 1 ) value is 1 order of magnitude bigger than the k F rate, k F (S 1 → S 0 ) = 7.72 × 10 7 s –1 ; see Figure .…”

“…76 In this way, in comparison to a radiative deactivation processes such as fluorescence, an efficient antenna requires a quick ISC channel S 1 → T 1 . 76,80 Thus, the calculated rate constants for the fluorescence and ISC process are crucial to support the hypothesis of the efficient T 1 state population via the ISC channel. 84,85 In this sense, the analysis of the BTTA antenna excited state dynamic parameters indicates that the rate of nonradiative ISC channels S 1 → T 1 is 3.22 × 10 8 s −1 .…”

“…This procedure involved the geometry optimizations and frequency calculations of the ground state and the first excited states (singlet and triplet) of the Tb-1 , Tb-2, Tb-1/ NB, and Tb-2/ NM systems. Using the ORCA ESD module of the ORCA 5.0 software package, we calculated the intersystem crossing (ISC), phosphorescence, and fluorescence rates, which we will refer to as k ISC , k P , and k F , respectively. , …”

“…Using the ORCA ESD module of the ORCA 5.0 software package, we calculated the intersystem crossing (ISC), phosphorescence, and fluorescence rates, which we will refer to as k ISC , k P , and k F , respectively. 76,80…”