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postgraduate thesis: Luminescent cyclometalated gold (III) complexes with ancillary N-heterocyclic carbene and alkynyl ligands : from design, synthesis, photophysics to supramolecular assembly and functions
Title | Luminescent cyclometalated gold (III) complexes with ancillary N-heterocyclic carbene and alkynyl ligands : from design, synthesis, photophysics to supramolecular assembly and functions |
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Authors | |
Advisors | Advisor(s):Yam, VWW |
Issue Date | 2012 |
Publisher | The University of Hong Kong (Pokfulam, Hong Kong) |
Citation | Au, K. [區嘉雯]. (2012). Luminescent cyclometalated gold (III) complexes with ancillary N-heterocyclic carbene and alkynyl ligands : from design, synthesis, photophysics to supramolecular assembly and functions. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4775268 |
Abstract | A library of luminescent cyclometalated gold(III) complexes containing
various bis-cyclometalating R-C^N^C ligands derived from 2,6-diphenylpyridine
and ancillary alkynyl ligands, [Au(R-C^N^C)(C≡CR’)], has been synthesized.
Some of the complexes have been structurally determined by X-ray
crystallography. These complexes were found to exhibit intense emission in
dichloromethane solution at 298 K, originating from metal-perturbed triplet
intraligand (IL) excited states of the R-C^N^C ligand, with substantial charge
transfer character from the aryl moiety to the pyridyl ring. In the presence of
electron-rich alkynyl ligands, the emission origin could be switched to an
alkynyl-to-cyclometalating ligand ligand-to-ligand charge transfer (LLCT) excited
state. This class of complexes was also demonstrated to show rich
electroluminescence properties as emitters in organic light-emitting devices. In
addition, the supramolecular assembly of this class of complexes has also been
revealed in gelation studies.
N-Heterocyclic carbenes have been incorporated into the gold(III) metal
center to prepare a series of luminescent mononuclear and dinuclear gold(III)
complexes, [{Au(C^N^C)}n(NHC)](PF6)n and [{Au(tBuC^N^CtBu)}n(NHC)]-
(PF6)n
(n = 1, 2). The X-ray crystal structures of most of the complexes have been
determined. The emissions of these complexes were assigned to originate from the
metal-perturbed intraligand excited state of the bis-cyclometalating ligand. One of
the C2-bridged dinuclear complexes was found to exhibit two distinct reduction
couples, tentatively correlated to the presence of significant intramolecular π-π
interaction in the complex.
Two novel series of luminescent mononuclear alkynylgold(III) complexes,
[Au(C^N)(C≡CR)2] (HC^N = 2-phenylpyridine (Hppy) and derivatives) and
[Au(C^N^N)(C≡CR)]PF6 (HC^N^N = 6-phenyl-2,2’-bipyridine and derivatives),
have been synthesized. Some of the X-ray crystal structures have been determined.
The former class of complexes with bidentate C^N ligands has been observed to
show tunable emission spanning across the visible spectrum from 462 to 697 nm.
With the exception of [Au(ppy)(C≡C-C6H4-NH2-p)2] which showed a low-energy
band originated from a 3LLCT [π(C≡C-C6H4-NH2)→π*(C^N)] excited state, all
complexes exhibited vibronic-structured emission bands originated from the
intraligand transition of the cyclometalating C^N ligand in dichloromethane
solution at 298 K. On the other hand, most of the complexes with the tridentate
C^N^N-type ligand have been observed to exhibit vibronic-structured emission
bands attributed to the intraligand transition of the C^N^N ligand in
low-temperature butyronitrile glass. |
Degree | Doctor of Philosophy |
Subject | Organogold compounds - Synthesis Carbenes (Methylene compounds) Heterocyclic compounds Ligands |
Dept/Program | Chemistry |
Persistent Identifier | http://hdl.handle.net/10722/207995 |
HKU Library Item ID | b4775268 |
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | Yam, VWW | - |
dc.contributor.author | Au, Ka-man | - |
dc.contributor.author | 區嘉雯 | - |
dc.date.accessioned | 2015-02-06T14:19:32Z | - |
dc.date.available | 2015-02-06T14:19:32Z | - |
dc.date.issued | 2012 | - |
dc.identifier.citation | Au, K. [區嘉雯]. (2012). Luminescent cyclometalated gold (III) complexes with ancillary N-heterocyclic carbene and alkynyl ligands : from design, synthesis, photophysics to supramolecular assembly and functions. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4775268 | - |
dc.identifier.uri | http://hdl.handle.net/10722/207995 | - |
dc.description.abstract | A library of luminescent cyclometalated gold(III) complexes containing various bis-cyclometalating R-C^N^C ligands derived from 2,6-diphenylpyridine and ancillary alkynyl ligands, [Au(R-C^N^C)(C≡CR’)], has been synthesized. Some of the complexes have been structurally determined by X-ray crystallography. These complexes were found to exhibit intense emission in dichloromethane solution at 298 K, originating from metal-perturbed triplet intraligand (IL) excited states of the R-C^N^C ligand, with substantial charge transfer character from the aryl moiety to the pyridyl ring. In the presence of electron-rich alkynyl ligands, the emission origin could be switched to an alkynyl-to-cyclometalating ligand ligand-to-ligand charge transfer (LLCT) excited state. This class of complexes was also demonstrated to show rich electroluminescence properties as emitters in organic light-emitting devices. In addition, the supramolecular assembly of this class of complexes has also been revealed in gelation studies. N-Heterocyclic carbenes have been incorporated into the gold(III) metal center to prepare a series of luminescent mononuclear and dinuclear gold(III) complexes, [{Au(C^N^C)}n(NHC)](PF6)n and [{Au(tBuC^N^CtBu)}n(NHC)]- (PF6)n (n = 1, 2). The X-ray crystal structures of most of the complexes have been determined. The emissions of these complexes were assigned to originate from the metal-perturbed intraligand excited state of the bis-cyclometalating ligand. One of the C2-bridged dinuclear complexes was found to exhibit two distinct reduction couples, tentatively correlated to the presence of significant intramolecular π-π interaction in the complex. Two novel series of luminescent mononuclear alkynylgold(III) complexes, [Au(C^N)(C≡CR)2] (HC^N = 2-phenylpyridine (Hppy) and derivatives) and [Au(C^N^N)(C≡CR)]PF6 (HC^N^N = 6-phenyl-2,2’-bipyridine and derivatives), have been synthesized. Some of the X-ray crystal structures have been determined. The former class of complexes with bidentate C^N ligands has been observed to show tunable emission spanning across the visible spectrum from 462 to 697 nm. With the exception of [Au(ppy)(C≡C-C6H4-NH2-p)2] which showed a low-energy band originated from a 3LLCT [π(C≡C-C6H4-NH2)→π*(C^N)] excited state, all complexes exhibited vibronic-structured emission bands originated from the intraligand transition of the cyclometalating C^N ligand in dichloromethane solution at 298 K. On the other hand, most of the complexes with the tridentate C^N^N-type ligand have been observed to exhibit vibronic-structured emission bands attributed to the intraligand transition of the C^N^N ligand in low-temperature butyronitrile glass. | - |
dc.language | eng | - |
dc.publisher | The University of Hong Kong (Pokfulam, Hong Kong) | - |
dc.relation.ispartof | HKU Theses Online (HKUTO) | - |
dc.rights | The author retains all proprietary rights, (such as patent rights) and the right to use in future works. | - |
dc.rights | This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. | - |
dc.subject.lcsh | Organogold compounds - Synthesis | - |
dc.subject.lcsh | Carbenes (Methylene compounds) | - |
dc.subject.lcsh | Heterocyclic compounds | - |
dc.subject.lcsh | Ligands | - |
dc.title | Luminescent cyclometalated gold (III) complexes with ancillary N-heterocyclic carbene and alkynyl ligands : from design, synthesis, photophysics to supramolecular assembly and functions | - |
dc.type | PG_Thesis | - |
dc.identifier.hkul | b4775268 | - |
dc.description.thesisname | Doctor of Philosophy | - |
dc.description.thesislevel | Doctoral | - |
dc.description.thesisdiscipline | Chemistry | - |
dc.description.nature | published_or_final_version | - |
dc.identifier.doi | 10.5353/th_b4775268 | - |
dc.date.hkucongregation | 2012 | - |
dc.identifier.mmsid | 991033465579703414 | - |