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The Effect of tert-Butyl Functionalization on the Photoexcited Decay of a Fe(II)-N-Heterocyclic Carbene Complex

Lookup NU author(s): Professor Thomas Penfold



This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).


Understanding, and subsequently, being able to manipulate the excited state decay pathways of functional transition metal complexes, is of utmost importance in order to solve grand challenges in solar energy conversion and data storage. Herein we perform quantum chemical calculations and spin-vibronic quantum dynamics simulations on the Fe-N-heterocyclic carbene (NHC) complex, [Fe(btbip)2]2+ (btbip = 2,6-bis(3-tert-butyl-imidazole-1-ylidene)pyridine). The results demonstrate that a relatively minor structural change compared to its parent complex, [Fe(bmip)2]2+ (bmip = 2,6-bis(3-methyl-imidazole-1-ylidene)pyridine), completely alters the excited state relaxation. Ultrafast deactivation of the initially excited metal-to-ligand charge transfer (1,3MLCT) states occur within 350 fs. In contrast to the widely adopted mechanism of Fe(II) photophysics, these states decay into close-lying singlet metal-centered (1MC) states. This occurs because the t-butyl functionalization stabilises the 1MC states, enabling the 1,3MLCT→1MC population transfer to occur close to the Franck-Condon geometry, making the conversion very efficient. Subsequently, a spin cascade occurs within the MC manifold leading to the population of triplet and quintet MC states. These results will inspire highly-involved ultrafast experiments performed at X-ray Free Electron Lasers (XFELs) and shall pave the way for the design of novel high efficiency transition metal-based functional molecules.

Publication metadata

Author(s): Pápai M, Penfold TJ, Moller KB

Publication type: Article

Publication status: Published

Journal: Journal of Physical Chemistry C

Year: 2016

Volume: 120

Issue: 31

Pages: 17234-17241

Print publication date: 11/08/2016

Online publication date: 20/07/2016

Acceptance date: 20/07/2016

Date deposited: 20/07/2016

ISSN (print): 1932-7447

ISSN (electronic): 1932-7455

Publisher: American Chemical Society


DOI: 10.1021/acs.jpcc.6b05023


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Funder referenceFunder name
609405People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme under REA (COFUNDPostdocDTU)