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Alkhaibari I, Zhang X, Zhao J, Stonelake TM, Knighton RC, Horton PN, Coles SJ, Buurma NJ, Richards E, Pope SJA. Tuning Excited State Character in Iridium(III) Photosensitizers and Its Influence on TTA-UC. Inorg Chem 2024; 63:9931-9940. [PMID: 38738860 PMCID: PMC11134496 DOI: 10.1021/acs.inorgchem.4c01003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/25/2024] [Accepted: 04/26/2024] [Indexed: 05/14/2024]
Abstract
A series of mixed ligand, photoluminescent organometallic Ir(III) complexes have been synthesized to incorporate substituted 2-phenyl-1H-naphtho[2,3-d]imidazole cyclometalating ligands. The structures of three example complexes were categorically confirmed using X-ray crystallography each sharing very similar structural traits including evidence of interligand hydrogen bond contacts that account for the shielding effects observed in the 1H NMR spectra. The structural iterations of the cyclometalated ligand provide tuning of the principal electronic transitions that determine the visible absorption and emission properties of the complexes: emission can be tuned in the visible region between 550 and 610 nm and with triplet lifetimes up to 10 μs. The nature of the emitting state varies across the series of complexes, with different admixtures of ligand-centered and metal-to-ligand charge transfer triplet levels evident. Finally, the use of the complexes as photosensitizers in triplet-triplet annihilation energy upconversion (TTA-UC) was investigated in the solution state. The study showed that the complexes possessing the longest triplet lifetimes showed good viability as photosensitizers in TTA-UC. Therefore, the use of an electron-withdrawing group on the 2-phenyl-1H-naphtho[2,3-d]imidazole ligand framework can be used to rationally promote TTA-UC using this class of complex.
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Affiliation(s)
- Ibrahim
S. Alkhaibari
- School
of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K.
- Department
of Chemistry, College of Science, Qassim
University, Buraydah 52571, Saudi Arabia
| | - Xue Zhang
- State
Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart
Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, PR China
| | - Jianzhang Zhao
- State
Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart
Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, PR China
| | - Thomas M. Stonelake
- School
of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K.
| | - Richard C. Knighton
- School
of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K.
| | - Peter N. Horton
- UK
National Crystallographic Service, Chemistry, Faculty of Natural and
Environmental Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, U.K.
| | - Simon J. Coles
- UK
National Crystallographic Service, Chemistry, Faculty of Natural and
Environmental Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, U.K.
| | - Niklaas J. Buurma
- School
of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K.
| | - Emma Richards
- School
of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K.
| | - Simon J. A. Pope
- School
of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K.
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Knighton RC, Pope SJA. Synthesis and luminescent properties of hetero-bimetallic and hetero-trimetallic Ru(II)/Au(I) or Ir(III)/Au(I) complexes. Dalton Trans 2024; 53:4165-4174. [PMID: 38318847 DOI: 10.1039/d3dt03690a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
A series of Ru(II) and Ir(III) based photoluminescent complexes were synthesised that incorporate an ancillary 2,2'-bipyridine ligand adorned with either one or two pendant N-methyl imidazolium groups. These complexes have been fully characterised by an array of spectroscopic and analytical techniques. One Ir(III) example was unequivocally structurally characterised in the solid state using single crystal X-ray diffraction confirming the proposed formulation and coordination sphere. These complexes were then transformed into their heterometallic, Au(I)-containing, analogues in two steps to yield either bi- or trimetallic complexes that integrate {Au(PPh3)}+ units. X-ray diffraction was used to corroborate the solid state structure of the hetero bimetallic complex, based upon a Ru(II)-Au(I) species. The heterometallic complexes all displayed red photoluminescent features (λem = 616-629 nm) that were consistent with the parent Ru(II) or Ir(III) lumophores in each case. The modulation of the emission from the Ru(II)-Au(I) complexes was much more strongly evident than for the Ir(III)-Au(I) analogues, which is ascribed to the inherent differences in the specific triplet excited state character of the emitting states within each heterometallic species.
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Affiliation(s)
- Richard C Knighton
- School of Chemistry, Cardiff University, Main Building, Cardiff, CF10 3AT, UK.
| | - Simon J A Pope
- School of Chemistry, Cardiff University, Main Building, Cardiff, CF10 3AT, UK.
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Stokes EC, Shoetan IO, Gillman AM, Horton PN, Coles SJ, Woodbury SE, Fallis IA, Pope SJA. Alkyl chain functionalised Ir(iii) complexes: synthesis, properties and behaviour as emissive dopants in microemulsions. RSC Adv 2024; 14:6987-6997. [PMID: 38414995 PMCID: PMC10897649 DOI: 10.1039/d3ra06764e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 02/16/2024] [Indexed: 02/29/2024] Open
Abstract
Six iridium(iii) complexes of the general form [Ir(C^N)2(N^N)]X (where C^N = cyclometalating ligand; N^N = disubstituted 2,2'-bipyridine), and incorporating alkyl chains of differing lengths (C8, C10, C12), have been synthesised and characterised. The complexes have been characterised using a variety of methods including spectroscopies (NMR, IR, UV-Vis, luminescence) and analytical techniques (high resolution mass spectrometry, cyclic voltammetry, X-ray diffraction). Two dodecyl-functionalised complexes were studied for their behaviour in aqueous solutions. Although the complexes did not possess sufficient solubility to determine their critical micelle concentrations (CMC) in water, they were amenable for use as emissive dopants in a N-methyl C12 substituted imidazolium salt microemulsion carrier system with a CMC = 36.5 mM. The investigation showed that the metal doped microemulsions had increased CMCs of 40.4 and 51.3 mM and luminescent properties characterised by the dopant.
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Affiliation(s)
- Emily C Stokes
- School of Chemistry, Cardiff University Main Building Cardiff CF10 3AT UK
| | - Ibrahim O Shoetan
- School of Chemistry, Cardiff University Main Building Cardiff CF10 3AT UK
| | - Alice M Gillman
- School of Chemistry, Cardiff University Main Building Cardiff CF10 3AT UK
| | - Peter N Horton
- Chemistry, UK National Crystallographic Service, Faculty of Natural and Environmental Sciences, University of Southampton Highfield Southampton SO17 1BJ England UK
| | - Simon J Coles
- Chemistry, UK National Crystallographic Service, Faculty of Natural and Environmental Sciences, University of Southampton Highfield Southampton SO17 1BJ England UK
| | - Simon E Woodbury
- National Nuclear Laboratory, Central Laboratory Sellafield, Seascale Cumbria CA20 1PG UK
| | - Ian A Fallis
- School of Chemistry, Cardiff University Main Building Cardiff CF10 3AT UK
| | - Simon J A Pope
- School of Chemistry, Cardiff University Main Building Cardiff CF10 3AT UK
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Fitzgerald SA, Payce EN, Horton PN, Coles SJ, Pope SJA. 2-(Thienyl)quinoxaline derivatives and their application in Ir(III) complexes yielding tuneable deep red emitters. Dalton Trans 2023; 52:16480-16491. [PMID: 37874197 DOI: 10.1039/d3dt02193a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The synthesis and characterisation of eleven different 2-(thienyl)quinoxaline species that incorporate different points of functionality, including at the thiophene or quinoxaline rings, are described. These species display variable fluorescence properties in the visible region (λem = 401-491 nm) depending upon the molecular structures and extent of conjugation. The series of 2-(thienyl)quinoxaline species were then investigated as cyclometalating agents for Ir(III) to yield [Ir(C^N)2(bipy)]PF6 (where C^N = the cyclometalated ligand; bipy = 2,2'-bipyridine). Eight complexes were successfully isolated and fully characterised by an array of spectroscopic and analytical techniques. Two Ir(III) examples were structurally characterised in the solid state using single crystal X-ray diffraction; both structures confirmed the proposed formulations and coordination spheres in each case showing that the thiophene coordinates via a Ir-C bond. The photophysical properties of the complexes revealed that each complex is luminescent under ambient conditions with a range of emission wavelengths observed (665-751 nm) indicating that electronic tuning can be achieved via both the thienyl and quinoxaline moieties.
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Affiliation(s)
- Sophie A Fitzgerald
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK.
| | - Ellie N Payce
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK.
| | - Peter N Horton
- UK National Crystallographic Service, Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Simon J Coles
- UK National Crystallographic Service, Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Simon J A Pope
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK.
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Owen Bonello R, Pitak MB, Tizzard GJ, Coles SJ, Fallis IA, Pope SJ. Aryl, bi-functionalised imidazo[4,5-f]-1,10-phenanthroline ligands and their luminescent rhenium(I) complexes. Polyhedron 2022. [DOI: 10.1016/j.poly.2022.116179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Otaif HY, Adams SJ, Horton PN, Coles SJ, Beames JM, Pope SJA. Bis-cyclometalated iridium( iii) complexes with terpyridine analogues: syntheses, structures, spectroscopy and computational studies. RSC Adv 2021; 11:39718-39727. [PMID: 35494133 PMCID: PMC9044569 DOI: 10.1039/d1ra07213g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/02/2021] [Indexed: 12/28/2022] Open
Abstract
Two ligands based upon a 2,6-disubstituted pyridine bridge introduce bis-quinoxalinyl units in a fashion that yields analogues to the archetypal terdentate ligand, 2,2′:6′,2′′-terpyridine. The ligands were synthesised from the key intermediate 2,6-bis(bromoacetyl)pyridine: a new, high-yielding route is described for this reagent. Two ligand variants (differentiated by H/Me substituents on the quinoxaline ring) were explored as coordinating moieties for iridium(iii) in the development of luminescent complexes. Computational studies (DFT approaches employing B3LYP, B3LYP/LANL2DZ, and M062X/LANL2DZ levels) were used to investigate the geometric and coordination mode preferences of the new ligands and two possibilities arose from theoretical investigations: [Ir(N^N^N)2]3+ and [Ir(N^N^C)2]+, with the former predicted to be more energetically favourable. Upon synthesis and isolation of the Ir(iii) complexes, X-ray crystallographic studies revealed coordination spheres that were cyclometalated, the structures both showing a [Ir(N^N^C)2]PF6 arrangement. Further spectroscopic characterization via NMR confirmed the ligand arrangements in the complexes, and photophysical studies, supported by DFT, showed that a mixture of metal-to-ligand charge transfer (MLCT) and intra-ligand charge transfer (ILCT) character is likely to contribute to the emission features of the complexes, which phosphoresce orange-red (λem = 580–618 nm). The emission wavelength was influenced by the substituents on the quinoxaline ring (H vs. Me), thereby implying further tuneability is possible with future ligand iterations. Bis-terdentate Ir(iii) complexes incorporate two cyclometalated N^N^C bis-quinoxalinyl type ligands derived from the condensation of 2,6-bis(bromoacetyl)pyridine and different o-phenylenediamines.![]()
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Affiliation(s)
- Haleema Y. Otaif
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK
| | - Samuel J. Adams
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK
| | - Peter N. Horton
- UK National Crystallographic Service, Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, England
| | - Simon J. Coles
- UK National Crystallographic Service, Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, England
| | - Joseph M. Beames
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK
| | - Simon J. A. Pope
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK
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