Theoretical modelling of photoactive molecular systems: insights using the Density Functional Theory

Abstract

An account of the performance of a modern and efficient approach to Density Functional Theory (DFT) for the prediction of the photophysical behavior of a series of Ru(II) and Os(II) complexes is given. The time-dependent-DFT method was used to interpret their electronic spectra. Two different types of compounds have been analyzed: (1) a complex undergoing a light induced isomerization of one of its coordination bonds; (2) an inorganic dyads expected to undergo intramolecular photoinduced electron transfer to form a charge separated (CS) sate. Besides the noticeable quantitative agreement between computed and experimental absorption spectra, our results allow to clarify, by first principles, both the nature of the excited states and the photochemical behavior of these complex systems, thus underlying the predictive character of the theoretical approach. RésuméNous rendons compte ici des performances d'une approche moderne et opérante de la théorie de la fonctionnelle de la densité (DFT) pour la prédiction du comportement photophysique de composés du ruthénium (II) et de l'osmium(II). Pour interpréter leurs propriétés d'absorption électronique, l'approche DFT dépendante du temps a été utilisée. Nous illustrons notre propos par l'analyse des deux systèmes suivants : (1) un complexe qui présente une isomérisation photo-induite de la liaison de coordination impliquant l'un de ses ligands ; (2) une molécule bipartite composée d'un complexe photosensibilisateur lié à un accepteur d'électron, conçue pour être le siège d'un transfert d'électron photo-induit conduisant à la formation d'un état de « charges séparées » (CS). Au-delà du remarquable accord quantitatif constaté entre les caractéristiques calculées et expérimentales des spectres d'absorption, nos résultats ont permis de clarifier, ab initio, la nature des états excités impliqués, illustrant ainsi les vertus prédictives de l'approche théorique employée.

Theoretical study on the influence of ancillary and cyclometalated ligands on the electronic structures and optoelectronic properties of heteroleptic iridium(iii) complexes

“…Calculations on electronic singlet and triplet states of all studied complexes were carried out by using density functional theory (DFT) 23 with the hybrid-type Perdew-Burke-Ernzerhof exchange correlation functional (PBE0) and the unrestricted PBE0 (UPBE0), respectively, [24][25][26] which has been proven to be particularly efficient and accurate for the calculation of transition metal complexes and organic dyes. [27][28][29][30][31] Furthermore, we found PBE0 is more precise for the optimization of complexes with sulfur atoms (Table S1 †). There were no symmetry constraints on these complexes.…”

A TD-DFT investigation of ground and excited state properties in indoline dyes used for dye-sensitized solar cells

“…To this end we made use of density functional theory (DFT) 17 and time dependent DFT (TD-DFT), 18 nowadays standard tools for investigating and predicting electronic properties of molecular dyes in both the ground and the excited states, [19][20][21] whether concerning purely organic species [22][23][24][25][26][27][28][29] or metal-containing complexes. [30][31][32][33][34][35][36][37] In particular, we refer the reader to the rather extensive literature on the performance of TD-DFT for the calculation of UV-visible spectra of organic dyes, [19][20][21][23][24][25][26][27][28][29] proving the efficiency of such computational methods. Well-performing and cheap computational approaches, mainly based on the use of hybrid exchange correlation functionals in conjunction with medium size basis sets (containing both diffuse and polarization functions on non hydrogen atoms), have proven to provide valence excitations of organic dyes with an average error of a few tenths of eV, 21 while slightly larger errors are expected for Rydberg bands.…”

Theoretical Insights into Branched and Fused Expanded Pyridiniums by the Means of Density Functional Theory

“…Nevertheless, it is for their electrochemical properties that pyridiniums have mostly been exploited . These species have been largely used not only as main components of zwitterionic solvatochromic dyes and other biologically active mesomeric betaines but also as subunits of push−pull dyads showing NLO properties. – Focusing on the field of artificial photosynthesis, pyridiniums have been recently employed as full building blocks of multicomponent functional assemblies, either purely organic , and inorganic, – designed to undergo photoinduced electron transfers (PET) to form charge-separated states (CSS).…”

“…Nowadays, a combined use of DFT and TD-DFT has become a reliableand extensively benchmarkedtool for the analysis and prediction of ground state properties as well as of vertical absorption spectra of organic chromophores. – In particular, this computational protocol is able to provide valence excitations of organic dyes with an average error of a few tenths of an electronvolt, when solvent effects are also properly taken into account (for instance, using a simple, yet efficient, polarizable continuum model, PCM). ,– More recently, a similar computational protocol has been validated in the case of emission energies – …”