### Abstract

The series of complexes [Ru(bpy) _{3-n}(btz) _{n}][PF _{6}] _{2} (bpy = 2,2′-bipyridyl, btz = 1,1′-dibenzyl-4,4′-bi-1,2,3-triazolyl, 2n = 1, 3n = 2, 4n = 3) have been prepared and characterised, and the photophysical and electronic effects imparted by the btz ligand were investigated. Complexes 2 and 3 exhibit MLCT absorption bands at 425 and 446 nm respectively showing a progressive blue-shift in the absorption on increasing the btz ligand content when compared to [Ru(bpy) _{3}][Cl] _{2} (1). Complex 4 exhibits a heavily blue-shifted absorption spectrum with respect to those of 1-3, indicating that the LUMO of the latter are bpy-centred with little or no btz contribution whereas that of 4 is necessarily btz-centred. DFT calculations on analogous complexes 1′-4′ (in which the benzyl substituents are replaced by methyl) show that the HOMO-LUMO gap increases by 0.3 eV from 1′-3′ through destabilisation of the LUMO with respect to the HOMO. The HOMO-LUMO gap of 4′ increases by 0.98 eV compared to that of 3′ due to significant destabilisation of the LUMO. Examination of TDDFT data show that the S _{1} states of 1′-3′ are ^{1}MLCT in character whereas that of 4′ is ^{1}MC. The optimisation of the T _{1} state of 4′ leads to the elongation of two mutually trans Ru-N bonds to yield [Ru(κ ^{2}-btz)(κ ^{1}-btz) _{2}] ^{2+}, confirming the ^{3}MC character. Thus, replacement of bpy by btz leads to a fundamental change in the ordering of excited states such that the nature of the lowest energy excited state changes from MLCT in nature to MC.

Original language | English |
---|---|

Pages (from-to) | 7637-7646 |

Number of pages | 10 |

Journal | Dalton Transactions |

Volume | 41 |

Issue number | 25 |

DOIs | |

Publication status | Published - 7 Jul 2012 |

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_{1}and T

_{1}states from MLCT to MC.

*Dalton Transactions*,

*41*(25), 7637-7646. https://doi.org/10.1039/c2dt30510k

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_{1}and T

_{1}states from MLCT to MC',

*Dalton Transactions*, vol. 41, no. 25, pp. 7637-7646. https://doi.org/10.1039/c2dt30510k

**Synthesis, characterisation and theoretical study of ruthenium 4,4′-bi-1,2,3-triazolyl complexes : Fundamental switching of the nature of S _{1} and T _{1} states from MLCT to MC.** / Welby, Christine E.; Grkinic, Stev; Zahid, Adam; Uppal, Baljinder S.; Gibson, Elizabeth A.; Rice, Craig R.; Elliott, Paul I.P.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Synthesis, characterisation and theoretical study of ruthenium 4,4′-bi-1,2,3-triazolyl complexes

T2 - Fundamental switching of the nature of S 1 and T 1 states from MLCT to MC

AU - Welby, Christine E.

AU - Grkinic, Stev

AU - Zahid, Adam

AU - Uppal, Baljinder S.

AU - Gibson, Elizabeth A.

AU - Rice, Craig R.

AU - Elliott, Paul I.P.

PY - 2012/7/7

Y1 - 2012/7/7

N2 - The series of complexes [Ru(bpy) 3-n(btz) n][PF 6] 2 (bpy = 2,2′-bipyridyl, btz = 1,1′-dibenzyl-4,4′-bi-1,2,3-triazolyl, 2n = 1, 3n = 2, 4n = 3) have been prepared and characterised, and the photophysical and electronic effects imparted by the btz ligand were investigated. Complexes 2 and 3 exhibit MLCT absorption bands at 425 and 446 nm respectively showing a progressive blue-shift in the absorption on increasing the btz ligand content when compared to [Ru(bpy) 3][Cl] 2 (1). Complex 4 exhibits a heavily blue-shifted absorption spectrum with respect to those of 1-3, indicating that the LUMO of the latter are bpy-centred with little or no btz contribution whereas that of 4 is necessarily btz-centred. DFT calculations on analogous complexes 1′-4′ (in which the benzyl substituents are replaced by methyl) show that the HOMO-LUMO gap increases by 0.3 eV from 1′-3′ through destabilisation of the LUMO with respect to the HOMO. The HOMO-LUMO gap of 4′ increases by 0.98 eV compared to that of 3′ due to significant destabilisation of the LUMO. Examination of TDDFT data show that the S 1 states of 1′-3′ are 1MLCT in character whereas that of 4′ is 1MC. The optimisation of the T 1 state of 4′ leads to the elongation of two mutually trans Ru-N bonds to yield [Ru(κ 2-btz)(κ 1-btz) 2] 2+, confirming the 3MC character. Thus, replacement of bpy by btz leads to a fundamental change in the ordering of excited states such that the nature of the lowest energy excited state changes from MLCT in nature to MC.

AB - The series of complexes [Ru(bpy) 3-n(btz) n][PF 6] 2 (bpy = 2,2′-bipyridyl, btz = 1,1′-dibenzyl-4,4′-bi-1,2,3-triazolyl, 2n = 1, 3n = 2, 4n = 3) have been prepared and characterised, and the photophysical and electronic effects imparted by the btz ligand were investigated. Complexes 2 and 3 exhibit MLCT absorption bands at 425 and 446 nm respectively showing a progressive blue-shift in the absorption on increasing the btz ligand content when compared to [Ru(bpy) 3][Cl] 2 (1). Complex 4 exhibits a heavily blue-shifted absorption spectrum with respect to those of 1-3, indicating that the LUMO of the latter are bpy-centred with little or no btz contribution whereas that of 4 is necessarily btz-centred. DFT calculations on analogous complexes 1′-4′ (in which the benzyl substituents are replaced by methyl) show that the HOMO-LUMO gap increases by 0.3 eV from 1′-3′ through destabilisation of the LUMO with respect to the HOMO. The HOMO-LUMO gap of 4′ increases by 0.98 eV compared to that of 3′ due to significant destabilisation of the LUMO. Examination of TDDFT data show that the S 1 states of 1′-3′ are 1MLCT in character whereas that of 4′ is 1MC. The optimisation of the T 1 state of 4′ leads to the elongation of two mutually trans Ru-N bonds to yield [Ru(κ 2-btz)(κ 1-btz) 2] 2+, confirming the 3MC character. Thus, replacement of bpy by btz leads to a fundamental change in the ordering of excited states such that the nature of the lowest energy excited state changes from MLCT in nature to MC.

UR - http://www.scopus.com/inward/record.url?scp=84862198675&partnerID=8YFLogxK

U2 - 10.1039/c2dt30510k

DO - 10.1039/c2dt30510k

M3 - Article

C2 - 22609688

AN - SCOPUS:84862198675

VL - 41

SP - 7637

EP - 7646

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 25

ER -

_{1}and T

_{1}states from MLCT to MC. Dalton Transactions. 2012 Jul 7;41(25):7637-7646. https://doi.org/10.1039/c2dt30510k