Dynamics of the Energy Transfer Process in Eu(III) Complexes Containing Polydentate Ligands Based on Pyridine, Quinoline, and Isoquinoline as Chromophoric Antennae

Abstract

In this work, we investigated from a theoretical point of view the dynamics of the energy transfer process from the ligand to Eu­(III) ion for 12 isomeric species originating from six different complexes differing by nature of the ligand and the total charge. The cationic complexes present the general formula [Eu­(L)­(H2O)2]+ (where L = bpcd2– = N,N′-bis­(2-pyridylmethyl)-trans-1,2-diaminocyclohexane N,N′-diacetate; bQcd2– = N,N′-bis­(2-quinolinmethyl)-trans-1,2-diaminocyclohexane N,N′-diacetate; and bisoQcd2– = N,N′-bis­(2-isoquinolinmethyl)-trans-1,2-diaminocyclohexane N,N′-diacetate), while the neutral complexes present the Eu­(L)­(H2O)2 formula (where L = PyC3A3– = N-picolyl-N,N′,N′-trans-1,2-cyclohexylenediaminetriacetate; QC3A3– = N-quinolyl-N,N′,N′-trans-1,2-cyclohexylenediaminetriacetate; and isoQC3A3– = N-isoquinolyl-N,N′,N′-trans-1,2-cyclohexylenediaminetriacetate). Time-dependent density functional theory (TD-DFT) calculations provided the energy of the ligand excited donor states, distances between donor and acceptor orbitals involved in the energy transfer mechanism (R L), spin-orbit coupling matrix elements, and excited-state reorganization energies. The intramolecular energy transfer (IET) rates for both singlet-triplet intersystem crossing and ligand-to-metal (and vice versa) involving a multitude of ligand and Eu­(III) levels and the theoretical overall quantum yields (ϕovl) were calculated (the latter for the first time without the introduction of experimental parameters). This was achieved using a blend of DFT, Judd–Ofelt theory, IET theory, and rate equation modeling. Thanks to this study, for each isomeric species, the most efficient IET process feeding the Eu­(III) excited state, its related physical mechanism (exchange interaction), and the reasons for a better or worse overall energy transfer efficiency (ηsens) in the different complexes were determined. The spectroscopically measured ϕovl values are in good agreement with the ones obtained theoretically in this work.

Circularly polarized activity from two photon excitable europium and samarium chiral bioprobes

“…Therefore, the metal here is 9-coordinated differently from what was found for similar complexes previously studied which resulted in being 8-coordinated. 12,46,68 The energy of the isomers trans –OO, trans -NN did not differ significantly (< 0.1 kcal mol −1 ) while cis -OO,NN is 4.6 kcal mol −1 more stable than the others. This finding suggests that in aqueous solutions the latter should be the prevalent one.…”

Near-Unity Energy Transfer from Uranyl to Europium in a Heterobimetallic Organic Framework with Record-Breaking Quantum Yield

“…To quantify the energy transfer efficiency of UO 2 2+ and ligand, intramolecular energy transfer (IET) rates were calculated for SCU-UEu-2 and EuBTEC based on the Judd-Ofelt Spectroscopy (JOYSpectra) program developed by Malta and co-workers (see details in the SI). − Table S6 shows the total forward ( W S and W T ) and backward ( W B S and W B T ) IET rates for both compounds. It is notable that the SCU-UEu-2 exhibits forward rates much larger than backward ones, being 10 8 s –1 for both singlet and triplet state.…”

Quantum Mechanical Assessment of Protein–Ligand Hydrogen Bond Strength Patterns: Insights from Semiempirical Tight-Binding and Local Vibrational Mode Theory

“…[ 133 ], and hydrogen bonds [ 30 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 ]. Recently, the quantitative assessment of bond strength in biological systems applying a QM/MM methodology [ 143 , 144 , 145 ] and the analysis of bonding in actinide and lanthanide compounds have been added to the LMA repertoire [ 146 , 147 , 148 ]. LMA also successfully revised a number of concepts, such as the characterization of metal-ligand interactions, replacing the Tolman electronic parameter (TEP) with the more accurate metal-ligand electronic parameter (MELP), based on local mode force constants [ 149 , 150 , 151 , 152 , 153 ].…”