Theoretical Illumination of Highly Original Photoreactive 3MC States and the Mechanism of the Photochemistry of Ru(II) Tris(bidentate) Complexes

Isabelle M. Dixon, Jean-Louis Heully, Fabienne Alary, Paul Elliott

Research output: Contribution to journalArticle

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Abstract

We have identified highly novel photoreactive 3MC states of ruthenium(II) 4,4’-bi-1,2,3-triazolyl (btz) complexes of the form [Ru(N^N)(btz)2]2+ and have elucidated the mechanism of the highly unusual experimental observations of photochemical ligand dechelation and concomitant ligand rearrangement reactivity to form unusual photoproducts trans-[Ru(N^N)(2-btz)(1-btz)(solvent)]2+. The 3MLCT states and classical Jahn-Teller type 3MC states of the series of complexes [Ru(N^N)3-n(btz)n]2+ (btz = 4,4’-bi-1,2,3-triazolyl; N^N = 2,2’bipyridyl (bpy), n = 0 (1), 1 (2), 2 (3), 3 (5); N^N = 4-{pyrid-2-yl)-1,2,3-triazole (pytz), n = 1 (4)) have been optimised by DFT and characterised. There is a gradual and significant destabilisation of the 3MLCT states as the triazole content of the complexes increases, which occurs with a slight stabilisation of the 3MC states. Whilst consistent with the promotion of photochemical reactivity in the heteroleptic complexes of the series relative to 1, these classical 3MC states fail to account for the extraordinary ligand rearrangement processes that accompany ligand ejection. Thorough theoretical exploration of the lowest excited triplet potential energy surface (3PES) here reveals the existence of a new type of 3MC state and the role it plays in the photochemical reactivity of the complexes. This newly discovered state, called MC(F), displays a flattened geometry which makes it clearly on the path to achieving the coplanarity of the bidentate ligands in the experimentally observed trans-photoproduct. Further novel ‘pentacoodinate’ 3MC states with coplanar bidentate ligands, called MC(P), were then identified and optimised. The energy barriers between the different triplet states were confirmed to be small which makes all triplet states accessible. Solvent trapping, which occurs on the singlet PES according to Wigner’s rules, is finally achieved by a singlet pentacoordinate species to yield the monosolvento photoproduct. Thus, our calculations not only reveal highly novel 3MC states but more significantly demonstrate their crucial role in the formation of the experimentally observed photoproducts.
Original languageEnglish
Pages (from-to)27765-27778
Number of pages14
JournalPhysical Chemistry Chemical Physics
Volume19
Issue number40
Early online date25 Sep 2017
DOIs
Publication statusPublished - 2017

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Photochemical reactions
photochemical reactions
Lighting
illumination
Ligands
ligands
Triazoles
reactivity
atomic energy levels
coplanarity
Potential energy surfaces
Ruthenium
Energy barriers
destabilization
F region
promotion
Discrete Fourier transforms
ejection
ruthenium
Stabilization

Cite this

@article{6271bbd222af4ecfa5173ea8b7c0364e,
title = "Theoretical Illumination of Highly Original Photoreactive 3MC States and the Mechanism of the Photochemistry of Ru(II) Tris(bidentate) Complexes",
abstract = "We have identified highly novel photoreactive 3MC states of ruthenium(II) 4,4’-bi-1,2,3-triazolyl (btz) complexes of the form [Ru(N^N)(btz)2]2+ and have elucidated the mechanism of the highly unusual experimental observations of photochemical ligand dechelation and concomitant ligand rearrangement reactivity to form unusual photoproducts trans-[Ru(N^N)(2-btz)(1-btz)(solvent)]2+. The 3MLCT states and classical Jahn-Teller type 3MC states of the series of complexes [Ru(N^N)3-n(btz)n]2+ (btz = 4,4’-bi-1,2,3-triazolyl; N^N = 2,2’bipyridyl (bpy), n = 0 (1), 1 (2), 2 (3), 3 (5); N^N = 4-{pyrid-2-yl)-1,2,3-triazole (pytz), n = 1 (4)) have been optimised by DFT and characterised. There is a gradual and significant destabilisation of the 3MLCT states as the triazole content of the complexes increases, which occurs with a slight stabilisation of the 3MC states. Whilst consistent with the promotion of photochemical reactivity in the heteroleptic complexes of the series relative to 1, these classical 3MC states fail to account for the extraordinary ligand rearrangement processes that accompany ligand ejection. Thorough theoretical exploration of the lowest excited triplet potential energy surface (3PES) here reveals the existence of a new type of 3MC state and the role it plays in the photochemical reactivity of the complexes. This newly discovered state, called MC(F), displays a flattened geometry which makes it clearly on the path to achieving the coplanarity of the bidentate ligands in the experimentally observed trans-photoproduct. Further novel ‘pentacoodinate’ 3MC states with coplanar bidentate ligands, called MC(P), were then identified and optimised. The energy barriers between the different triplet states were confirmed to be small which makes all triplet states accessible. Solvent trapping, which occurs on the singlet PES according to Wigner’s rules, is finally achieved by a singlet pentacoordinate species to yield the monosolvento photoproduct. Thus, our calculations not only reveal highly novel 3MC states but more significantly demonstrate their crucial role in the formation of the experimentally observed photoproducts.",
author = "Dixon, {Isabelle M.} and Jean-Louis Heully and Fabienne Alary and Paul Elliott",
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language = "English",
volume = "19",
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journal = "Physical Chemistry Chemical Physics",
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Theoretical Illumination of Highly Original Photoreactive 3MC States and the Mechanism of the Photochemistry of Ru(II) Tris(bidentate) Complexes. / Dixon, Isabelle M.; Heully, Jean-Louis; Alary, Fabienne; Elliott, Paul.

In: Physical Chemistry Chemical Physics, Vol. 19, No. 40, 2017, p. 27765-27778.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Theoretical Illumination of Highly Original Photoreactive 3MC States and the Mechanism of the Photochemistry of Ru(II) Tris(bidentate) Complexes

AU - Dixon, Isabelle M.

AU - Heully, Jean-Louis

AU - Alary, Fabienne

AU - Elliott, Paul

PY - 2017

Y1 - 2017

N2 - We have identified highly novel photoreactive 3MC states of ruthenium(II) 4,4’-bi-1,2,3-triazolyl (btz) complexes of the form [Ru(N^N)(btz)2]2+ and have elucidated the mechanism of the highly unusual experimental observations of photochemical ligand dechelation and concomitant ligand rearrangement reactivity to form unusual photoproducts trans-[Ru(N^N)(2-btz)(1-btz)(solvent)]2+. The 3MLCT states and classical Jahn-Teller type 3MC states of the series of complexes [Ru(N^N)3-n(btz)n]2+ (btz = 4,4’-bi-1,2,3-triazolyl; N^N = 2,2’bipyridyl (bpy), n = 0 (1), 1 (2), 2 (3), 3 (5); N^N = 4-{pyrid-2-yl)-1,2,3-triazole (pytz), n = 1 (4)) have been optimised by DFT and characterised. There is a gradual and significant destabilisation of the 3MLCT states as the triazole content of the complexes increases, which occurs with a slight stabilisation of the 3MC states. Whilst consistent with the promotion of photochemical reactivity in the heteroleptic complexes of the series relative to 1, these classical 3MC states fail to account for the extraordinary ligand rearrangement processes that accompany ligand ejection. Thorough theoretical exploration of the lowest excited triplet potential energy surface (3PES) here reveals the existence of a new type of 3MC state and the role it plays in the photochemical reactivity of the complexes. This newly discovered state, called MC(F), displays a flattened geometry which makes it clearly on the path to achieving the coplanarity of the bidentate ligands in the experimentally observed trans-photoproduct. Further novel ‘pentacoodinate’ 3MC states with coplanar bidentate ligands, called MC(P), were then identified and optimised. The energy barriers between the different triplet states were confirmed to be small which makes all triplet states accessible. Solvent trapping, which occurs on the singlet PES according to Wigner’s rules, is finally achieved by a singlet pentacoordinate species to yield the monosolvento photoproduct. Thus, our calculations not only reveal highly novel 3MC states but more significantly demonstrate their crucial role in the formation of the experimentally observed photoproducts.

AB - We have identified highly novel photoreactive 3MC states of ruthenium(II) 4,4’-bi-1,2,3-triazolyl (btz) complexes of the form [Ru(N^N)(btz)2]2+ and have elucidated the mechanism of the highly unusual experimental observations of photochemical ligand dechelation and concomitant ligand rearrangement reactivity to form unusual photoproducts trans-[Ru(N^N)(2-btz)(1-btz)(solvent)]2+. The 3MLCT states and classical Jahn-Teller type 3MC states of the series of complexes [Ru(N^N)3-n(btz)n]2+ (btz = 4,4’-bi-1,2,3-triazolyl; N^N = 2,2’bipyridyl (bpy), n = 0 (1), 1 (2), 2 (3), 3 (5); N^N = 4-{pyrid-2-yl)-1,2,3-triazole (pytz), n = 1 (4)) have been optimised by DFT and characterised. There is a gradual and significant destabilisation of the 3MLCT states as the triazole content of the complexes increases, which occurs with a slight stabilisation of the 3MC states. Whilst consistent with the promotion of photochemical reactivity in the heteroleptic complexes of the series relative to 1, these classical 3MC states fail to account for the extraordinary ligand rearrangement processes that accompany ligand ejection. Thorough theoretical exploration of the lowest excited triplet potential energy surface (3PES) here reveals the existence of a new type of 3MC state and the role it plays in the photochemical reactivity of the complexes. This newly discovered state, called MC(F), displays a flattened geometry which makes it clearly on the path to achieving the coplanarity of the bidentate ligands in the experimentally observed trans-photoproduct. Further novel ‘pentacoodinate’ 3MC states with coplanar bidentate ligands, called MC(P), were then identified and optimised. The energy barriers between the different triplet states were confirmed to be small which makes all triplet states accessible. Solvent trapping, which occurs on the singlet PES according to Wigner’s rules, is finally achieved by a singlet pentacoordinate species to yield the monosolvento photoproduct. Thus, our calculations not only reveal highly novel 3MC states but more significantly demonstrate their crucial role in the formation of the experimentally observed photoproducts.

UR - http://pubs.rsc.org/en/journals/journalissues/cp#!recentarticles

U2 - 10.1039/C7CP05532C

DO - 10.1039/C7CP05532C

M3 - Article

VL - 19

SP - 27765

EP - 27778

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 40

ER -