An N^N Platinum(II) Bis(acetylide) Complex with Naphthalimide and Pyrene Ligands: Synthesis, Photophysical Properties, and Application in Triplet–Triplet Annihilation Upconversion

Zhong, Fangfang; Zhao, Jianzhang

doi:10.1002/ejic.201700656

Cited by 24 publications

(11 citation statements)

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“…Specifically, upon excitation of a deaerated solution of 1 codissolved with a certain concentration of unattached, free DBP (as an intermolecular ET acceptor) with a pulsed laser of 450 nm as the pump source, two transient absorption bands were clearly observable around 420 and 540 nm in microsecond time scale (Figure a). Both peaks were characteristic and assignable to the T 1 → T n transitions of DBP. ,,, Prior to the examination of the intermolecular ET process, the intramolecular ET kinetics was first elucidated by the TA spectra. By selectively exciting the Ir-complex moiety with a 450 nm laser, the absorption peak at 425 nm was observed to rise continuously within the first 20 ns or so (Figure S3).…”

Section: Resultsmentioning

confidence: 99%

Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism

et al. 2018

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The photodynamic properties involving both intra- and intermolecular triplet energy transfers (ET) of a bichromophoric photosensitizer having a tris-cyclometalated Ir(III) tethered with a pyrene derivative are studied. Due to the triplet energy gap of the two chromophores, a reversible intramolecular triplet ET equilibrium is quickly established upon photoexcitation, with the triplet exciton mainly residing on the acceptor side in the photostationary state. By virtue of the very small decay rate of triplet pyrene, a considerably extended triplet lifetime (2 ms) is observed. Next, the intermolecular triplet-triplet ET properties are investigated. Using steady-state and time-resolved spectroscopy, the ET rate constants from the Ir complex and pyrene unit in the sensitizer to an external triplet acceptor (unattached, free pyrene derivative) in solution are found to be around 10 s and 10 M s, respectively. In spite of a lower ET rate constant, the tethered pyrene serves as the main intermolecular ET channel because of the large, favorable intramolecular ET equilibrium ( K ∼ 10). Importantly, this cascade ET process, from Ir complex to linked pyrene, and then to free pyrene, offers an overall improved ET efficiency than a direct ET from Ir complex to free pyrene, by virtue of the much smaller spontaneous decay rate compared to that of the metal complex. Finally, the more efficient ET ability is demonstrated experimentally by applying the molecule as sensitizer in a triplet-triplet annihilation upconversion. The bichromophoric sensitizer achieved upconverted emission intensity 5 times higher than a monochromophoric Ir-complex analogue.

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Section: Resultsmentioning

confidence: 99%

Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism

et al. 2018

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“…Dichloromethane was dried and degassed with an Innovative Technologies solvent purification system before use. The Pt precursors, ( t ‑Bu2 bpy)PtCl 2 , ( Ph2 bpy)PtCl 2 , and (phbpy)PtCl , were prepared according to literature procedures. All reactions were carried out under air-free conditions using standard Schlenk techniques.…”

Section: Methodsmentioning

confidence: 99%

“…16,18,33 The high-field anionic carbanion ligands raise the energy of the 3 MC states well above that of the emissive state, thus increasing photoluminescence quantum yields (Φ PL ). 21,39 Emission in such systems may occur from a metal-to-ligand charge-transfer ( 3 MLCT) state, 23,32,40 a ligand-to-ligand charge-transfer ( 3 LL'CT) state, 33 a ligand-centered ( 3 LC) state such as 3 π−π* state, 18,27,40 or a state of mixed origin, 33 depending on which of these states is lowest in energy (Figure 1a).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Emissive Pt II complexes are typically square-planar complexes involving combinations of substituted bipyridyl ligands, − cyclometallating (C^N) or (C^N^N) ligands, − alkynyl ligands, ,,,,− and N-heterocyclic carbene (NHC) ligands. ,, The high-field anionic carbanion ligands raise the energy of the 3 MC states well above that of the emissive state, thus increasing photoluminescence quantum yields (Φ PL ). , Emission in such systems may occur from a metal-to-ligand charge-transfer ( 3 MLCT) state, ,, a ligand-to-ligand charge-transfer ( 3 LL’CT) state, a ligand-centered ( 3 LC) state such as 3 π–π* state, ,, or a state of mixed origin, depending on which of these states is lowest in energy (Figure a).…”

Section: Introductionmentioning

confidence: 99%

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Role of the Trifluoropropynyl Ligand in Blue-Shifting Charge-Transfer States in Emissive Pt Diimine Complexes and an Investigation into the PMMA-Imposed Rigidoluminescence and Rigidochromism

et al. 2022

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Square-planar Pt II complexes are of interest as dopants for the emissive layer of organic light-emitting diodes. Herein, the photophysics of three Pt bipyridyl complexes with the strongly e − withdrawing, high-field, 3,3,3-trifluoropropynyl ligand has been investigated. One complex, (phbpy)PtC 2 CF 3 (phbpy = 6phenyl-2,2′-dipyridyl), has also been characterized by single-crystal X-ray diffraction. All complexes reported are emissive in both RT CH 2 Cl 2 solution (Φ PL = 0.007 to 0.027) and PMMA film (Φ PL = 0.25 to 0.42). The trifluoropropynyl ligand elevates the energy of the MLCT and LL'CT states above that of the IL π−π* state, resulting in IL emission in all cases. The emission energies of the trifluoropropynyl compounds are also blue-shifted relative to the analogous pentafluorophenylethynyl compounds, suggesting that the trifluoropropynyl ligand is one of the most electron-withdrawing alkynyl ligands. Rate constants for radiative and nonradiative deactivation were determined from experimentally determined values of Φ PL and excited-state lifetimes in both solution and PMMA films. The increase in Φ PL upon incorporation into PMMA film (rigidoluminescence) results from a decrease in the rate constant for non-radiative relaxation. Experimental activation energies for excited-state decay in combination with TDDFT are consistent with the rigidoluminescence resulting from an increase in the energy of the non-emissive triplet metal-centered state. Two of the complexes investigated, ( Ph2 bpy)Pt(C 2 CF 3 ) 2 and ( t-Bu2 bpy)Pt(C 2 CF 3 ) 2 , where t-Bu2 bpy = 4,4′-di-tert-butyl-2,2′-dipyridyl and Ph2 bpy = 4,4′-diphenyl-2,2′-dipyridyl, exhibit concentration-dependent excimer emission (orange) along with monomer emission (blue), enabling fine-tuning of the emission color. However, excimer emission was absent in cured PMMA films up to the solubility limit for solution processing of ( Ph2 bpy)Pt(C 2 CF 3 ) 2 in CH 2 Cl 2 , demonstrating the diffusional nature of excimer formation.

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“…This is against the general intuition that the fully π-conjugated ligand should be without distinct 3 MLCT and 3 LE states in the platinum(II) bis(acetylide) complexes. This scenario is different from the N^N platinum(II) bis(acetylide) ligands with heteroleptic acetylide ligands, for which the existence of two closel-lying triplet excited states is understandable because the two ligands are not in π conjugation. − The examples showing this close-lying triplet excited state with fully π-conjugated ligands are very limited.…”

Section: Introductionmentioning

confidence: 95%

Effect of Molecular Conformation Restriction on the Photophysical Properties of N^N Platinum(II) Bis(ethynylnaphthalimide) Complexes Showing Close-Lying ³MLCT and ³LE Excited States

Zhong

Zhao

Hayvalı³

et al. 2019

Inorg. Chem.

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Using naphthalimide (NI), complexes (Pt-PhNI and Pt-PhMeNI) based on the N^N platinum(II) bis-(phenylacetylide) coordination framework were prepared, in which there are two close-lying triplet states, i.e., the metal-toligand-charge-transfer ( 3 MLCT) and the NI localized emissive state ( 3 LE). Pt-PhNI has better electronic communication between the Pt coordination center and the NI moiety, whereas in Pt-PhMeNI, they are more isolated by orthogonal geometry. For Pt-PhMeNI, the S 0 → 1 MLCT and S 0 → 1 LE absorption bands are separated by 5655 cm −1 , while they are more overlapped in Pt-PhNI. The 3 MLCT → S 0 and 3 LE → S 0 dual phosphorescence emissions were observed for both Pt-PhNI (in toluene) and Pt-PhMeNI (in benzonitrile). The molecular conformation tunes the 3 MLCT/ 3 LE state population ratio, and the orthogonal geometry makes the 3 LE state in Pt-PhMeNI basically a dark state (in toluene). Switching of the relative energy levels of the 3 MLCT/ 3 LE states by variation of the solvent polarity and temperature was achieved. For Pt-PhMeNI, the energy level of 3 MLCT state is higher in a polar solvent; thus, the 3 MLCT emission decreases, while the phosphorescence lifetime is prolonged from 9.5 μs (in toluene) to 58 μs (in benzonitrile) because of the different equilibria with the nonemissive 3 LE state. Conversely, increasing the temperature enhances the upward transition from the nonemissive 3 LE state to the emissive 3 MLCT state; as such, the phosphorescence of Pt-PhMeNI was intensified at higher temperature (which is unusual), and the phosphorescence lifetime decreased from 58 μs (298 K) to ca. 5 μs (348 K). The ultrafast intersystem crossing (ca. 0.5 ps) and intramolecular triplet−triplet energy transfer (3−11 ps) were studied by femtosecond transient absorption spectroscopy. These results are useful for an in-depth understanding of the photophysics of multichromophore transition-metal complexes and for the design of external stimuli-responsive sensing materials, for instance, temperature or microenvironment sensing materials.

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An N^N Platinum(II) Bis(acetylide) Complex with Naphthalimide and Pyrene Ligands: Synthesis, Photophysical Properties, and Application in Triplet–Triplet Annihilation Upconversion

Cited by 24 publications

References 51 publications

Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism

Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism

Role of the Trifluoropropynyl Ligand in Blue-Shifting Charge-Transfer States in Emissive Pt Diimine Complexes and an Investigation into the PMMA-Imposed Rigidoluminescence and Rigidochromism

Effect of Molecular Conformation Restriction on the Photophysical Properties of N^N Platinum(II) Bis(ethynylnaphthalimide) Complexes Showing Close-Lying ³MLCT and ³LE Excited States

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An N^N Platinum(II) Bis(acetylide) Complex with Naphthalimide and Pyrene Ligands: Synthesis, Photophysical Properties, and Application in Triplet–Triplet Annihilation Upconversion

Cited by 24 publications

References 51 publications

Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism

Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism

Role of the Trifluoropropynyl Ligand in Blue-Shifting Charge-Transfer States in Emissive Pt Diimine Complexes and an Investigation into the PMMA-Imposed Rigidoluminescence and Rigidochromism

Effect of Molecular Conformation Restriction on the Photophysical Properties of N^N Platinum(II) Bis(ethynylnaphthalimide) Complexes Showing Close-Lying 3MLCT and 3LE Excited States

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Effect of Molecular Conformation Restriction on the Photophysical Properties of N^N Platinum(II) Bis(ethynylnaphthalimide) Complexes Showing Close-Lying ³MLCT and ³LE Excited States