Density Functional Theory Based Analysis of Photoinduced Electron Transfer in a Triazacryptand Based K⁺ Sensor

Abstract

A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. The electronic structure and photoinduced electron transfer processes in a K + fluorescent sensor that comprises a 4-amino-naphthalimide derived fluorophore with a triazacryptand ligand is investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) in order to rationalise the function of the sensor. The absorption and emission energies of the intense electronic excitation localised on the fluorophore are accurately described using a ∆SCF Kohn-Sham DFT approach, which gives excitation energies closer to experiment than TDDFT. Analysis of the molecular orbital diagram arising from DFT calculations for the isolated molecule or with implicit solvent cannot account for the function of the sensor and it is necessary to consider the relative energies of the electronic states formed from the local excitation on the fluorophore and the lowest fluorophore→chelator charge transfer state. The inclusion of solvent in these calculations is critical since the strong interaction of the charge transfer state with the solvent lowers it energy below the local fluorophore excited state making a reductive photoinduced electron transfer possible in the absence of K + , while no such process is possible when the sensor is bound to K + . The rate of electron transfer is quantified using Marcus theory, which gives a rate of electron transfer of k ET =5.98 x 10 6 s −1 .

Quantum chemical elucidation of the turn-on luminescence mechanism in two new Schiff bases as selective chemosensors of Zn2+: synthesis, theory and bioimaging applications

“…13 This interaction can lead to a series of transduction mechanisms that need to be understood to achieve efficiency and selectivity in the sensors. The most frequent sensing mechanisms shown by shown are Photoinduced Electron Transfer (PET), 14,15 intramolecular charge transfer (ICT), 9 Energy Transfer (ET), 14,16 Metal-Ligand Charge Transfer (MLCT or LMCT), 17 Excited State Intramolecular Proton Transfer (ESIPT), 18 excimer and exciplex formation. 19,20 The Schiff bases have been widely studied because of their biological and structural importance, mainly for their specic and selective reactions with metal ions.…”

Solution Structure and Ultrafast Vibrational Relaxation of the PtPOP Complex Revealed by ΔSCF-QM/MM Direct Dynamics Simulations

“…With this perspective in mind, we have extended the capabilities of the code by coupling it to a single-determinant DFT description of the excited states based on the ∆SCF approach, 40 which carries no extra computational cost with respect to ground-state DFT. ∆SCF is gaining increasing popularity in the study of the excited states of both organic chromophores [41][42][43][44] and transition metal complexes. 45,46 This renewed interest is motivated in part by the growing demand for computationally cheap strategies for simulating with sufficient accuracy the excited-state structure and dynamics of large systems, for which high-level multireference methods are not yet a viable choice.…”

Quantum chemical calculations of tryptophan → heme electron and excitation energy transfer rates in myoglobin

“…requires excited state electronic structure methods, including structural optimization of the relevant states. This is commonly done using methods such as single excitation configuration interaction (CIS) or TDDFT . The study of large biological systems is challenging, as the size of the system usually precludes a full treatment with quantum chemical methods, necessitating some further approximations.…”

“…This is commonly done using methods such as single excitation configuration interaction (CIS) or TDDFT. [19,[33][34][35][36][37][38][39] The study of large biological systems is challenging, as the size of the system usually precludes a full treatment with quantum chemical methods, necessitating some further approximations. Despite this inherent complexity, several studies have reported calculations of ET in proteins based on Marcus theory.…”