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Article: Organic triplet excited states of gold(I) complexes with oligo(o- or m-phenyleneethynylene) ligands: conjunction of steady-state and time-resolved spectroscopic studies on exciton delocalization and emission pathways
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TitleOrganic triplet excited states of gold(I) complexes with oligo(o- or m-phenyleneethynylene) ligands: conjunction of steady-state and time-resolved spectroscopic studies on exciton delocalization and emission pathways
 
AuthorsLu, W1
Kwok, WM2
Ma, C1
Chan, CTL2
Zhu, MX1
Che, CM1
 
Issue Date2011
 
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html
 
CitationJournal of the American Chemical Society, 2011, v. 133 n. 35, p. 14120-14135 [How to Cite?]
DOI: http://dx.doi.org/10.1021/ja205831v
 
AbstractA series of mononuclear and binuclear gold(I) complexes containing oligo(o- or m-phenyleneethynylene) (PE) ligands, namely [PhC identical withC(C(6)H(4)-1,2-C identical withC)(n-1)Au(PCy(3))] (n = 2-4, 4a-c), [mu-{C identical withC-(1,2-C(6)H(4)C identical withC)(n)}{Au(PCy(3))}(2)] (n = 1-6, 8, 5a-g), [PhC identical withC(C(6)H(4)-1,3-C identical withC)(n-1)Au(PCy(3))] (n = 2-4, 6a-c), and [mu-{C identical withC-(1,3-C(6)H(4)C identical withC)(n)}{Au(PCy(3))}(2)] (n = 1, 2, 7a,b), were synthesized and structurally characterized. Extensive spectroscopic measurements have been performed by applying combined methods of femtosecond transient absorption (fs-TA), fs time-resolved fluorescence (fs-TRF), and nanosecond time-resolved emission (ns-TRE) coupled with steady-state absorption and emission spectroscopy at both ambient and low (77 K) temperatures to directly probe the temporal evolution of the excited states and to determine the dynamics and spectral signatures for the involved singlet (S(1)) and triplet (T(1)) excited states. The results reveal that S(1) and T(1) both feature ligand-centered electronic transitions with pipi* character associated with the phenyl and acetylene moieties. The (3)pipi* emission of the PE ligands is switched on by the attachment of [Au(PCy(3))](+) fragment(s) due to the heavy-atom effect. T(1)((3)pipi*) was found to form with nearly unity efficiency through intersystem crossing (ISC) from S(1)((1)pipi*). The ISC time constants were determined to be approximately 50, 35, and 40 ps for 4b and 6a,b, respectively. Dual emission composed of fluorescence from S(1) and phosphorescence from T(1) were observed for most of the complexes except 5a and 7a, where only phosphorescence was found. The fluorescence at ambient temperature is accounted for by both the short-lived prompt fluorescence (PF) and long-lived delayed fluorescence (DF, lifetime on microsecond time scale). Explicit evidence was presented for a triplet-triplet annihilation mechanism for the generation of DF. Ligand length and substitution-dependent dynamics of T(1) are the key factors governing the dual emission character of the complexes. By extrapolation from the plot of emission energy against the PE chain length of the [Au(PCy(3))](+) complexes with oligo(o-PE) or oligo(m-PE) ligands, the triplet emission energies were estimated to be approximately 530 and approximately 470 nm for poly(o-PE) and poly(m-PE), respectively. Additionally, we assign the unusual red shifts of 983 cm(-1) from [PhC identical withCAu(PCy(3))] (1) to [mu-{1,3-(C identical withC)(2)C(6)H(4)}{Au(PCy(3))}(2)] (7a) and 462 cm(-1) from 7a to [mu(3)-{1,3,5-(C identical withC)(3)C(6)H(3)}{Au(PCy(3))}(3)] (8) in the phosphorescence energies to excitonic coupling interactions between the C identical withCAu(PCy(3)) arms in the triplet excited states. These complexes, together with those previously reported [Au(PCy(3))](+) complexes containing oligo(p-PE) ligands ( J. Am. Chem. Soc. 2002 , 124 , 14696 - 14706 ), form a collection of oligo(phenyleneethynylene) complexes exhibiting organic triplet emission in solution under ambient conditions. The remarkable feature of these complexes in exhibiting TTA prompted DF in conjunction with high formation efficiency of T(1)((3)pipi*) affords an opportunity for emission spectra to cover a wide range of wavelengths. This may have implication in the development of PE-based molecular materials for future optical applications.
 
ISSN0002-7863
2012 Impact Factor: 10.677
2012 SCImago Journal Rankings: 5.182
 
DOIhttp://dx.doi.org/10.1021/ja205831v
 
ReferencesReferences in Scopus
 
DC FieldValue
dc.contributor.authorLu, W
 
dc.contributor.authorKwok, WM
 
dc.contributor.authorMa, C
 
dc.contributor.authorChan, CTL
 
dc.contributor.authorZhu, MX
 
dc.contributor.authorChe, CM
 
dc.date.accessioned2012-08-16T05:49:10Z
 
dc.date.available2012-08-16T05:49:10Z
 
dc.date.issued2011
 
dc.description.abstractA series of mononuclear and binuclear gold(I) complexes containing oligo(o- or m-phenyleneethynylene) (PE) ligands, namely [PhC identical withC(C(6)H(4)-1,2-C identical withC)(n-1)Au(PCy(3))] (n = 2-4, 4a-c), [mu-{C identical withC-(1,2-C(6)H(4)C identical withC)(n)}{Au(PCy(3))}(2)] (n = 1-6, 8, 5a-g), [PhC identical withC(C(6)H(4)-1,3-C identical withC)(n-1)Au(PCy(3))] (n = 2-4, 6a-c), and [mu-{C identical withC-(1,3-C(6)H(4)C identical withC)(n)}{Au(PCy(3))}(2)] (n = 1, 2, 7a,b), were synthesized and structurally characterized. Extensive spectroscopic measurements have been performed by applying combined methods of femtosecond transient absorption (fs-TA), fs time-resolved fluorescence (fs-TRF), and nanosecond time-resolved emission (ns-TRE) coupled with steady-state absorption and emission spectroscopy at both ambient and low (77 K) temperatures to directly probe the temporal evolution of the excited states and to determine the dynamics and spectral signatures for the involved singlet (S(1)) and triplet (T(1)) excited states. The results reveal that S(1) and T(1) both feature ligand-centered electronic transitions with pipi* character associated with the phenyl and acetylene moieties. The (3)pipi* emission of the PE ligands is switched on by the attachment of [Au(PCy(3))](+) fragment(s) due to the heavy-atom effect. T(1)((3)pipi*) was found to form with nearly unity efficiency through intersystem crossing (ISC) from S(1)((1)pipi*). The ISC time constants were determined to be approximately 50, 35, and 40 ps for 4b and 6a,b, respectively. Dual emission composed of fluorescence from S(1) and phosphorescence from T(1) were observed for most of the complexes except 5a and 7a, where only phosphorescence was found. The fluorescence at ambient temperature is accounted for by both the short-lived prompt fluorescence (PF) and long-lived delayed fluorescence (DF, lifetime on microsecond time scale). Explicit evidence was presented for a triplet-triplet annihilation mechanism for the generation of DF. Ligand length and substitution-dependent dynamics of T(1) are the key factors governing the dual emission character of the complexes. By extrapolation from the plot of emission energy against the PE chain length of the [Au(PCy(3))](+) complexes with oligo(o-PE) or oligo(m-PE) ligands, the triplet emission energies were estimated to be approximately 530 and approximately 470 nm for poly(o-PE) and poly(m-PE), respectively. Additionally, we assign the unusual red shifts of 983 cm(-1) from [PhC identical withCAu(PCy(3))] (1) to [mu-{1,3-(C identical withC)(2)C(6)H(4)}{Au(PCy(3))}(2)] (7a) and 462 cm(-1) from 7a to [mu(3)-{1,3,5-(C identical withC)(3)C(6)H(3)}{Au(PCy(3))}(3)] (8) in the phosphorescence energies to excitonic coupling interactions between the C identical withCAu(PCy(3)) arms in the triplet excited states. These complexes, together with those previously reported [Au(PCy(3))](+) complexes containing oligo(p-PE) ligands ( J. Am. Chem. Soc. 2002 , 124 , 14696 - 14706 ), form a collection of oligo(phenyleneethynylene) complexes exhibiting organic triplet emission in solution under ambient conditions. The remarkable feature of these complexes in exhibiting TTA prompted DF in conjunction with high formation efficiency of T(1)((3)pipi*) affords an opportunity for emission spectra to cover a wide range of wavelengths. This may have implication in the development of PE-based molecular materials for future optical applications.
 
dc.description.natureLink_to_subscribed_fulltext
 
dc.identifier.citationJournal of the American Chemical Society, 2011, v. 133 n. 35, p. 14120-14135 [How to Cite?]
DOI: http://dx.doi.org/10.1021/ja205831v
 
dc.identifier.doihttp://dx.doi.org/10.1021/ja205831v
 
dc.identifier.eissn1520-5126
 
dc.identifier.epage14135
 
dc.identifier.hkuros205442
 
dc.identifier.issn0002-7863
2012 Impact Factor: 10.677
2012 SCImago Journal Rankings: 5.182
 
dc.identifier.issue35
 
dc.identifier.pmid21846130
 
dc.identifier.scopuseid_2-s2.0-80052326952
 
dc.identifier.spage14120
 
dc.identifier.urihttp://hdl.handle.net/10722/159411
 
dc.identifier.volume133
 
dc.languageeng
 
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html
 
dc.publisher.placeUnited States
 
dc.relation.ispartofJournal of the American Chemical Society
 
dc.relation.referencesReferences in Scopus
 
dc.titleOrganic triplet excited states of gold(I) complexes with oligo(o- or m-phenyleneethynylene) ligands: conjunction of steady-state and time-resolved spectroscopic studies on exciton delocalization and emission pathways
 
dc.typeArticle
 
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<contributor.author>Kwok, WM</contributor.author>
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<contributor.author>Zhu, MX</contributor.author>
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<description.abstract>A series of mononuclear and binuclear gold(I) complexes containing oligo(o- or m-phenyleneethynylene) (PE) ligands, namely [PhC identical withC(C(6)H(4)-1,2-C identical withC)(n-1)Au(PCy(3))] (n = 2-4, 4a-c), [mu-{C identical withC-(1,2-C(6)H(4)C identical withC)(n)}{Au(PCy(3))}(2)] (n = 1-6, 8, 5a-g), [PhC identical withC(C(6)H(4)-1,3-C identical withC)(n-1)Au(PCy(3))] (n = 2-4, 6a-c), and [mu-{C identical withC-(1,3-C(6)H(4)C identical withC)(n)}{Au(PCy(3))}(2)] (n = 1, 2, 7a,b), were synthesized and structurally characterized. Extensive spectroscopic measurements have been performed by applying combined methods of femtosecond transient absorption (fs-TA), fs time-resolved fluorescence (fs-TRF), and nanosecond time-resolved emission (ns-TRE) coupled with steady-state absorption and emission spectroscopy at both ambient and low (77 K) temperatures to directly probe the temporal evolution of the excited states and to determine the dynamics and spectral signatures for the involved singlet (S(1)) and triplet (T(1)) excited states. The results reveal that S(1) and T(1) both feature ligand-centered electronic transitions with pipi* character associated with the phenyl and acetylene moieties. The (3)pipi* emission of the PE ligands is switched on by the attachment of [Au(PCy(3))](+) fragment(s) due to the heavy-atom effect. T(1)((3)pipi*) was found to form with nearly unity efficiency through intersystem crossing (ISC) from S(1)((1)pipi*). The ISC time constants were determined to be approximately 50, 35, and 40 ps for 4b and 6a,b, respectively. Dual emission composed of fluorescence from S(1) and phosphorescence from T(1) were observed for most of the complexes except 5a and 7a, where only phosphorescence was found. The fluorescence at ambient temperature is accounted for by both the short-lived prompt fluorescence (PF) and long-lived delayed fluorescence (DF, lifetime on microsecond time scale). Explicit evidence was presented for a triplet-triplet annihilation mechanism for the generation of DF. Ligand length and substitution-dependent dynamics of T(1) are the key factors governing the dual emission character of the complexes. By extrapolation from the plot of emission energy against the PE chain length of the [Au(PCy(3))](+) complexes with oligo(o-PE) or oligo(m-PE) ligands, the triplet emission energies were estimated to be approximately 530 and approximately 470 nm for poly(o-PE) and poly(m-PE), respectively. Additionally, we assign the unusual red shifts of 983 cm(-1) from [PhC identical withCAu(PCy(3))] (1) to [mu-{1,3-(C identical withC)(2)C(6)H(4)}{Au(PCy(3))}(2)] (7a) and 462 cm(-1) from 7a to [mu(3)-{1,3,5-(C identical withC)(3)C(6)H(3)}{Au(PCy(3))}(3)] (8) in the phosphorescence energies to excitonic coupling interactions between the C identical withCAu(PCy(3)) arms in the triplet excited states. These complexes, together with those previously reported [Au(PCy(3))](+) complexes containing oligo(p-PE) ligands ( J. Am. Chem. Soc. 2002 , 124 , 14696 - 14706 ), form a collection of oligo(phenyleneethynylene) complexes exhibiting organic triplet emission in solution under ambient conditions. The remarkable feature of these complexes in exhibiting TTA prompted DF in conjunction with high formation efficiency of T(1)((3)pipi*) affords an opportunity for emission spectra to cover a wide range of wavelengths. This may have implication in the development of PE-based molecular materials for future optical applications.</description.abstract>
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Author Affiliations
  1. The University of Hong Kong
  2. Hong Kong Polytechnic University