Emissive osmium(II) complexes supported by N-heterocyclic carbene-based C^C^C-pincer ligands and aromatic diimines

Lai-Hon Chung; Siu-Chung Chan; Wing-Chun Lee; Chun-Yuen Wong

doi:10.1021/ic202726g

Emissive osmium(II) complexes supported by N-heterocyclic carbene-based C^C^C-pincer ligands and aromatic diimines

Lai-Hon Chung, Siu-Chung Chan, Wing-Chun Lee, Chun-Yuen Wong^*

^*Corresponding author for this work

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

63 Citations (Scopus)

Abstract

Osmium(II) complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-methylimidazolin-2-ylidene)phenyl anion (C ¹^C^C ¹) or 1,3-bis(3-methylbenzimidazolin-2-ylidene)phenyl anion (C ²^C^C ²) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,4'-diphenyl-2,2'-bipyridine (Ph ₂bpy)) in the form of [Os(C^C^C)(N^N)(CO)] ⁺ have been prepared. Crystal structures for these complexes show that the Os-C _NHC bonds are essentially single (Os-C _NHC distances = 2.079(5)-2.103(7) Å). Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes ( _max = 493-536 nm, μ _max = (5-10)×10 ³ dm ³ mol ^-1 cm ^-1, solvent = CH ₃CN) originate from a d _π(Os ^II) → π*(N^N) metal-to-ligand charge transfer transition, where the d _π(Os ^II) and π*(N^N) levels contain significant contribution from the C^C^C ligands. All these complexes are emissive in the red-spectral region (674-731 nm) with quantum yields of 10 ^-4-10 ^-2 and emission lifetimes of around 1-6 μs. Transient absorption spectroscopy and spectroelectrochemical measurements have also been used to probe the nature of the emissive excited-states. Overall, this joint experimental and theoretical investigation reveals that the C^C^C ligands can be used to modulate the photophysical properties of a [Os(N^N)] core via the formation of the hybrid [Os + C^C^C] frontier orbitals.

Original language	English
Pages (from-to)	8693-8703
Journal	Inorganic Chemistry
Volume	51
Issue number	16
Online published	8 Aug 2012
DOIs	https://doi.org/10.1021/ic202726g
Publication status	Published - 20 Aug 2012

Funding

The work described in this paper was supported by grants from the Hong Kong Research Grants Council (Project No. CityU 103911) and City University of Hong Kong (Project No. 7002757), and the Special Equipment Grant from the University Grants Committee of Hong Kong (SEG_CityU02). We are grateful to Dr. Shek-Man Yiu for X-ray diffraction data collection, and Dr. Chun-Yu Ho for giving constructive comments on NMR experiments.

Research Keywords

TRANSITION-METAL-COMPLEXES
SOLAR-ENERGY CONVERSION
COORDINATION-COMPOUNDS
NHC LIGANDS
POLYPYRIDYL COMPLEXES
IRIDIUM COMPLEXES
EXCITED-STATES
ORGANOMETALLIC CATALYSIS
PHOTOPHYSICAL PROPERTIES
ALLENYLIDENE COMPLEXES

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@article{5349bc160d5a4f478dfb690b5118d1d9,

title = "Emissive osmium(II) complexes supported by N-heterocyclic carbene-based C^C^C-pincer ligands and aromatic diimines",

abstract = "Osmium(II) complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-methylimidazolin-2-ylidene)phenyl anion (C 1^C^C 1) or 1,3-bis(3-methylbenzimidazolin-2-ylidene)phenyl anion (C 2^C^C 2) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,4'-diphenyl-2,2'-bipyridine (Ph 2bpy)) in the form of [Os(C^C^C)(N^N)(CO)] + have been prepared. Crystal structures for these complexes show that the Os-C NHC bonds are essentially single (Os-C NHC distances = 2.079(5)-2.103(7) {\AA}). Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes ( max = 493-536 nm, μ max = (5-10)×10 3 dm 3 mol -1 cm -1, solvent = CH 3CN) originate from a d π(Os II) → π*(N^N) metal-to-ligand charge transfer transition, where the d π(Os II) and π*(N^N) levels contain significant contribution from the C^C^C ligands. All these complexes are emissive in the red-spectral region (674-731 nm) with quantum yields of 10 -4-10 -2 and emission lifetimes of around 1-6 μs. Transient absorption spectroscopy and spectroelectrochemical measurements have also been used to probe the nature of the emissive excited-states. Overall, this joint experimental and theoretical investigation reveals that the C^C^C ligands can be used to modulate the photophysical properties of a [Os(N^N)] core via the formation of the hybrid [Os + C^C^C] frontier orbitals. ",

keywords = "TRANSITION-METAL-COMPLEXES, SOLAR-ENERGY CONVERSION, COORDINATION-COMPOUNDS, NHC LIGANDS, POLYPYRIDYL COMPLEXES, IRIDIUM COMPLEXES, EXCITED-STATES, ORGANOMETALLIC CATALYSIS, PHOTOPHYSICAL PROPERTIES, ALLENYLIDENE COMPLEXES",

author = "Lai-Hon Chung and Siu-Chung Chan and Wing-Chun Lee and Chun-Yuen Wong",

year = "2012",

month = aug,

day = "20",

doi = "10.1021/ic202726g",

language = "English",

volume = "51",

pages = "8693--8703",

journal = "Inorganic Chemistry",

issn = "0020-1669",

publisher = "American Chemical Society",

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TY - JOUR

T1 - Emissive osmium(II) complexes supported by N-heterocyclic carbene-based C^C^C-pincer ligands and aromatic diimines

AU - Chung, Lai-Hon

AU - Chan, Siu-Chung

AU - Lee, Wing-Chun

AU - Wong, Chun-Yuen

PY - 2012/8/20

Y1 - 2012/8/20

N2 - Osmium(II) complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-methylimidazolin-2-ylidene)phenyl anion (C 1^C^C 1) or 1,3-bis(3-methylbenzimidazolin-2-ylidene)phenyl anion (C 2^C^C 2) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,4'-diphenyl-2,2'-bipyridine (Ph 2bpy)) in the form of [Os(C^C^C)(N^N)(CO)] + have been prepared. Crystal structures for these complexes show that the Os-C NHC bonds are essentially single (Os-C NHC distances = 2.079(5)-2.103(7) Å). Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes ( max = 493-536 nm, μ max = (5-10)×10 3 dm 3 mol -1 cm -1, solvent = CH 3CN) originate from a d π(Os II) → π*(N^N) metal-to-ligand charge transfer transition, where the d π(Os II) and π*(N^N) levels contain significant contribution from the C^C^C ligands. All these complexes are emissive in the red-spectral region (674-731 nm) with quantum yields of 10 -4-10 -2 and emission lifetimes of around 1-6 μs. Transient absorption spectroscopy and spectroelectrochemical measurements have also been used to probe the nature of the emissive excited-states. Overall, this joint experimental and theoretical investigation reveals that the C^C^C ligands can be used to modulate the photophysical properties of a [Os(N^N)] core via the formation of the hybrid [Os + C^C^C] frontier orbitals.

AB - Osmium(II) complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-methylimidazolin-2-ylidene)phenyl anion (C 1^C^C 1) or 1,3-bis(3-methylbenzimidazolin-2-ylidene)phenyl anion (C 2^C^C 2) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,4'-diphenyl-2,2'-bipyridine (Ph 2bpy)) in the form of [Os(C^C^C)(N^N)(CO)] + have been prepared. Crystal structures for these complexes show that the Os-C NHC bonds are essentially single (Os-C NHC distances = 2.079(5)-2.103(7) Å). Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes ( max = 493-536 nm, μ max = (5-10)×10 3 dm 3 mol -1 cm -1, solvent = CH 3CN) originate from a d π(Os II) → π*(N^N) metal-to-ligand charge transfer transition, where the d π(Os II) and π*(N^N) levels contain significant contribution from the C^C^C ligands. All these complexes are emissive in the red-spectral region (674-731 nm) with quantum yields of 10 -4-10 -2 and emission lifetimes of around 1-6 μs. Transient absorption spectroscopy and spectroelectrochemical measurements have also been used to probe the nature of the emissive excited-states. Overall, this joint experimental and theoretical investigation reveals that the C^C^C ligands can be used to modulate the photophysical properties of a [Os(N^N)] core via the formation of the hybrid [Os + C^C^C] frontier orbitals.

KW - TRANSITION-METAL-COMPLEXES

KW - SOLAR-ENERGY CONVERSION

KW - COORDINATION-COMPOUNDS

KW - NHC LIGANDS

KW - POLYPYRIDYL COMPLEXES

KW - IRIDIUM COMPLEXES

KW - EXCITED-STATES

KW - ORGANOMETALLIC CATALYSIS

KW - PHOTOPHYSICAL PROPERTIES

KW - ALLENYLIDENE COMPLEXES

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U2 - 10.1021/ic202726g

DO - 10.1021/ic202726g

M3 - RGC 21 - Publication in refereed journal

SN - 0020-1669

VL - 51

SP - 8693

EP - 8703

JO - Inorganic Chemistry

JF - Inorganic Chemistry

IS - 16

ER -

Emissive osmium(II) complexes supported by N-heterocyclic carbene-based C^C^C-pincer ligands and aromatic diimines

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