Synthesis, characterization and spectroscopic studies of luminescent<scp>l</scp>-valine modified alkynyl-based cyclometalated gold(<scp>iii</scp>) complexes with gelation properties driven by π–π stacking, hydrogen bonding and hydrophobic–hydrophobic interactions

Siu, Steven Kin-Lok; Po, Charlotte; Yim, King-Chin; Au, Vonika Ka‐Man; Yam, Vivian Wing‐Wah

doi:10.1039/c5ce01136a

Cited by 21 publications

(8 citation statements)

References 86 publications

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“…Considering first the complexes with two pincer chains, 16a–18a , they each display vibrationally structured emission spectra in solution at 295 K, in which the 0,0 component is of highest intensity, indicative of high rigidity and little distortion in the excited state compared to the ground state (Figures a and S11). The spectra are typical of the many reported complexes of type 2 , − ,,, where the emission is assigned to a metal-perturbed π → π* intraligand transition based on the cyclometallating ligand. Not surprisingly, the λ max values and the spectral profiles are rather similar to those of 16aH – 18aH under the same conditions, just as the absorption spectra were identical, reflecting the “insulation” of the fluorinated chains from the spectroscopically active parts of the molecule.…”

Section: Photophysical Propertiesmentioning

confidence: 77%

“…More than 15 years ago, Yam and co-workers reported the observation of room-temperature phosphorescence in gold(III) complexes ligated by a 2,6-diphenylpyridine pincer ligand and a phenyl acetylide (Figure ). A great deal of work has since been published describing many structural variants with impressive results, − including high values for both molecular photoluminescence quantum yields (PLQYs) in solution and external quantum efficiencies (EQEs) , for devices employing such complexes as emitters. Further, by using 3,4,5-trialkoxyphenylacetylide co-ligands (=R, Figure ), complexes were realized that showed the ability to gelate .…”

Section: Introductionmentioning

confidence: 99%

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Synthesis, Mesomorphism, Photophysics, and Device Properties of Liquid-Crystalline Pincer Complexes of Gold(III) Containing Semiperfluorinated Chains

et al. 2022

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Gold(III) complexes of C ∧ N ∧ C -coordinating 2,6-diphenylpyridine pincer ligands with arylacetylide co-ligands are known triplet emitters at room temperature. We have reported previously that by functionalizing both the pincer ligand and the phenylacetylene with alkoxy chains, liquid crystallinity may be induced, with the complexes showing columnar mesophases. We now report new derivatives in which the phenylacetylene incorporates one, two, or three 1 H ,1 H ,2 H ,2 H -perfluoroalkyl chains. In terms of intermolecular interactions, solution 1 H NMR experiments suggest that the semiperfluoroalkyl chains promote a parallel, head-to-head arrangement of neighboring molecules relative to one another, rather than the anti-parallel, head-to-tail orientation found for the all-hydrocarbon materials. In terms of the liquid crystal properties, the complexes show columnar phases, with the addition of the more rigid fluorocarbon chains leading to a stabilization of both the crystal and liquid crystal mesophases. Mesophase temperature ranges were also wider. Interestingly, the amphiphilic nature of these complexes is evident through the observation of a frustrated columnar nematic phase between a Col r and a Col h phase, an observation recently reported in detail for one compound ( Liq. Cryst. , 2022, doi: 10.1080/02678292.2021.1991017 ). While calculation shows that, despite the “electronic insulation” provided by the dimethylene spacer group in the semiperfluoroalkyl chains, a small hypsochromic shift in one component of the absorption band is anticipated, experimentally this effect is not observed in the overall absorption envelope. Complexes with substituents in the 3,3′,4,4′-positions of the phenyl rings of the pincer ligand once more show higher-luminescence quantum yields than the analogues with substituents in the 4,4′-positions only, associated with the lower-energy-emissive state in the former. However, in contrast to the observations with all-hydrocarbon analogues, the luminescence quantum yield of the complexes with 3,3′,4,4′-substitution on the pincer increases as the number of semiperfluoroalkyl chains on the phenylacetylide increases, from 20% (one chain) to 34% (three chains). External quantum efficiencies in fabricated OLED devices are, however, low, attributed to the poor dispersion in the host materials on account of the fluorinated chains.

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Section: Photophysical Propertiesmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Synthesis, Mesomorphism, Photophysics, and Device Properties of Liquid-Crystalline Pincer Complexes of Gold(III) Containing Semiperfluorinated Chains

et al. 2022

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“…[12,16] Gold (I) and gold (III) complexes, known for their wide range of applications in catalysis, [17][18][19] optoelectronic materials [20,21] and bioconjugation methodologies, [22][23][24] have been extensively developed due to their unique luminescence properties and aqueous stability. Pioneering amphiphilic molecular design of cyclometalated gold (III) complexes, [25][26][27][28][29] a system, featured with polyethene glycol (PEG), has provided micellar assemblies with good biocompatibility and aqueous solubility in exhibiting activity towards in vitro phototoxicity, reported by Che. [30] In 2018, Besenius and co-workers reported gold (I) metalloamphiphile with a kinetically controlled stepwise nanofibre assembly in buffered aqueous solution.…”

Section: Introductionmentioning

confidence: 99%

Controlled Supramolecular Assembly of Gold (III) Amphiphiles in Aqueous Media

et al. 2022

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Supramolecular assemblies of gold complex‐based amphiphiles in aqueous media are highly structural sensitive to external environments, providing an attractive prospect for its application in soft functional materials. Notably, the development of a supramolecular assembly transformation of gold (III) amphiphiles directly controlled by counterion exchange is of fundamental importance for exerting the full potential of dynamic supramolecular assembly by external stimuli. Here we present a reversible supramolecular assembly of gold (III) amphiphiles controlled by counterions in aqueous media and their co‐assembly with gold nanoparticles.

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“…[31] Additional weak interactions, e. g. hydrogen bonds, could further promote the aggregation properties of Pt(II) complexes at the condition that a convenient balance takes place between these interactions within the nanostructure. [13] Recent work has been devoted towards the construction of supramolecular assemblies of molecular Pt [32][33][34][35][36][37][38][39][40] or other metal [41][42][43][44] complexes and hydrogenbonding moieties. Yam and co-workers reported that a Lglutamine-derived dialkynylplatinum(II) bipyridine complex aggregated through a combination of hydrogen bonding, πÀ π stacking and Pt•••Pt interactions leading to the formation of a metallogel.…”

Section: Introductionmentioning

confidence: 99%

Cyclometallated Pt(II) Complexes Containing a Functionalized Bis‐Urea Alkynyl Ligand: Probing Aggregation Mediated by Hydrogen BondsversusPt⋅⋅⋅Pt and π−π Interactions

et al. 2021

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Neutral cyclometallated Pt(II) complexes [(C^N tÀ Bu^NtÀ Bu )PtÀ R] (4-5) containing a bis-urea alkynyl (R) ligand have been prepared and fully characterized. The dichotomous nature of 4-5 makes it difficult to anticipate which interactions (hydrogen bonds, πÀ π stacking and Pt•••Pt) will dominate their assembly process. The aggregation properties of 4-5 were thus probed by multifarious analytical (UV/Vis, FT-IR, NMR, MS, CD, emission) and computational (DFT, TD-DFT) techniques. CD analyses of sergeants-and-soldiers type mixtures between 4 and an enantiopure Pt-free monomer (S,S)-3 reveal that no amplification of supramolecular helicity occurs in this system. In fact, complex 4 acts as competitor or chain capper, likely through hydrogen bonding, of the homochiral assemblies formed by (S,S)-3. In DMSO, 1 H NMR and DOSY analyses indicate that 4 and 5 form aggregates. Likewise, the aggregation is promoted by the addition of H 2 O as suggested by red shift of the lowest energy emission band, which might originate from a 3 MMLCT excited state. TD-DFT calculations confirm that self-aggregation occurs through Pt•••Pt and πÀ π interactions yielding head-to-tail aggregates in DMSO and DMSO/H 2 O mixtures. Our study therefore suggests a (condition dependent) competitive rather than a cooperative mode of action of the different types of interactions present in aggregates of 4-5.

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Synthesis, characterization and spectroscopic studies of luminescentl-valine modified alkynyl-based cyclometalated gold(iii) complexes with gelation properties driven by π–π stacking, hydrogen bonding and hydrophobic–hydrophobic interactions

Cited by 21 publications

References 86 publications

Synthesis, Mesomorphism, Photophysics, and Device Properties of Liquid-Crystalline Pincer Complexes of Gold(III) Containing Semiperfluorinated Chains

Synthesis, Mesomorphism, Photophysics, and Device Properties of Liquid-Crystalline Pincer Complexes of Gold(III) Containing Semiperfluorinated Chains

Controlled Supramolecular Assembly of Gold (III) Amphiphiles in Aqueous Media

Cyclometallated Pt(II) Complexes Containing a Functionalized Bis‐Urea Alkynyl Ligand: Probing Aggregation Mediated by Hydrogen BondsversusPt⋅⋅⋅Pt and π−π Interactions

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