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Orbital-free photophysical descriptors to predict directional excitations in metal-based photosensitizers

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journal contribution
posted on 22.05.2020 by Pedro Alejandro Sánchez-Murcia, Juan Jose Noguiera Perez, Felix Plasser, Leticia Gonzalez

The development of dye-sensitized solar cells, metalloenzyme photocatalysis or biological labeling heavily relies on the design of metalbased photosensitizes with directional excitations. Directionality is most often predicted characterizing manually excitations via canonical frontier orbitals. Although widespread, this traditional approach is, at the very least, cumbersome and subject to personal bias, as well as limited in many cases. Here, we demonstrate how two orbital-free photophysical descriptors allow an easy and straightforward quantification of the degree of directionality in electron excitations using chemical fragments. As proof of concept we scrutinize the effect of 22 chemical modifications on the archetype [Ru(bpy)3] 2+ with a new descriptor coined “substituent-induced exciton localization” (SIEL), together with the concept of “excited-electron delocalization length” (EEDLn). Applied to quantum ensembles of initially excited singlet and the relaxed triplet metal-to-ligand charge-transfer states, the SIEL descriptor allows quantifying how much and whereto the exciton is promoted, as well as anticipating the effect of single modifications, e.g. on C-4 atoms of bpy units of [Ru(bpy)3] 2+. The general applicability of SIEL and EDDLn is further established by rationalizing experimental trends through quantification of the directionality of the photoexcitation. We thus demonstrate that SIEL and EEDL descriptors can be synergistically employed to design improved photosensitizers with highly directional and localized electron-transfer transitions.

Funding

Austrian Science Fund (FWF, Project M 2260)

Comunidad de Madrid through the Programa de Atracción de Talento 2018, project 2018-T1/BMD-10261

History

School

  • Science

Department

  • Chemistry

Published in

Chemical Science

Volume

11

Issue

29

Pages

7685 - 7693

Publisher

Royal Society of Chemistry (RSC)

Version

VoR (Version of Record)

Rights holder

© The authors

Publisher statement

This is an Open Access Article. It is published by RSC under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

Acceptance date

14/05/2020

Publication date

2020-05-15

Copyright date

2020

ISSN

2041-6520

eISSN

2041-6539

Language

en

Depositor

Dr Felix Plasser Deposit date: 21 May 2020

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