The Contribution of Density Functional Theory to the Atomistic Knowledge of Electrochromic Processes

Abstract

In this review, we provide a brief overview of the contribution that computational studies can offer to the elucidation of the electronic mechanisms responsible for the electrochromism phenomenon, through the use of the density functional theory (DFT) and its time-dependent formulation (TDDFT). Although computational studies on electrochromic systems are not as numerous as those for other physico-chemical processes, we will show their reliability and ability to predict structures, excitation energies, and redox potentials. The results confirm that these methods not only help in the interpretation of experimental data but can also be used for the rational design of molecules with interesting electrochromic properties to be initiated for synthesis and experimental characterization.

Chalcogen atom effect on the intersystem crossing kinetic constant of oxygen‐ and sulfur disubstituted heteroporphyrins

“…For the N 2 O 2 ‐P derivative, the computed value for < S 1 | H SOC | T 1 > is of 0.33 cm −1 that is large enough to induce ISC on a nanosecond time scale 49 and is comparable with the value previously computed for the clinically approved Foscan (0.24 cm −1 ) 43 . The value further increases in N 2 S 2 ‐P (2.18 cm −1 ) indicating that the thionation process substantially enhances the PDT performance, as previously noted also in nonporphynoid photosensitizers 26,29 . The S 1 → T 2 channel is predicted to be inaccessible for N 4 ‐P and N 2 O 2 ‐P while it could also contribute to the S 1 deactivation pathway of N 2 S 2 ‐P being the computed value 0.24 eV.…”

“…An analogue chalcogen effect was indeed demonstrated for a series of other photosensitizers, 26–30 and is considered a promising less‐toxic way to induce the heavy atom effect on metal‐free PS.…”

“…[22][23][24][25] The substitution of the pyrrole N atom by a heavier S, Se or Te atom, are expected to induce both a red shift of the absorption band and an enhancement of the spin-orbit coupling constants, being them essential requisites for their use in photodynamic therapy (PDT). [22][23][24][25] An analogue chalcogen effect was indeed demonstrated for a series of other photosensitizers, [26][27][28][29][30] and is considered a promising less-toxic way to induce the heavy atom effect on metal-free PS. From the other side, the radicals generated through Type II reactions may further react with oxygen to produce reactive oxygen species (ROS).…”

On the antibacterial photodynamic inactivation mechanism of Emodin and Dermocybin natural photosensitizers: A theoretical investigation

“…The work was performed using the density functional theory (DFT) and its time dependent version (TDDFT) following a previously successfully applied computational protocol. [19][20][21][22][23] 2 | COMPUTATIONAL DETAILS Ground state geometries optimization and acid-base equilibria in aqueous solution of Emodin and Dermocybin have been performed at DFT level of theory by means of Gaussian 16 software. 24 The M052X exchange-correlation functional 25 and the standard 6-311+G** basis set of Pople have been used in the calculations.…”

“…With this premise, we considered useful to explore the photophysical properties of the two mentioned molecules at a theoretical level to elucidate the elementary mechanisms underlying their cytotoxic action. The work was performed using the density functional theory (DFT) and its time dependent version (TDDFT) following a previously successfully applied computational protocol 19–23 …”