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Synthesis of Phenylpyridine Iridium(III) Complexes with N-Heterocyclic Carbene as Ancillary Ligands
摘要： In this study, [Ir(2,4-F2ppy)2(2-(1,2,4-triazol-1-yl)pyridine)]PF6 (C1), [Ir(2,4-F2ppy)2(2-(2-(4-dimethylbenzyl)-1,2,4-triazol-1-yl)pyridine)]PF6 (C2) and [Ir(2,4-F2ppy)2(2(2-hexyl-1,2,4-triazol-1-yl)pyridine)]PF6 (C3) complexes were successfully synthesised by refluxing the mixture of dichloro-bridged iridium(III) dimer, [Ir(2,4-F2ppy)2(μ-Cl)]2 and corresponding triazolium salt containing N-heterocyclic carbene (NHC) as ancillary ligands. 1H NMR of all complexes display well-resolved signals between 10.00-5.00 ppm assign to proton at the aromatic region for penylpyridine and pyridyltriazole. Spectra of C2 and C3 also display signals at aliphatic region (singlets) between 0.80-1.50 ppm that proved the presence of methylbenzyl and hexyl substituent on the pyridyltriazole ring. In addition, IR analysis reported the presence of C=C and C=N stretching of pyridine at range 1570-1470cm-1 and C-H stretching of aromatic pyridine at 2990-3080cm-1. Besides, UV-Vis absorption data showed that the low-energy metal-to-ligand charge-transfer (MLCT) band in C2 (364 nm) is significantly blue-shifted compared to C1 (375 nm) and C3 (381 nm). Overall, this study reported the synthesis and spectroscopic study of phenylpyridine Ir(III) complexes with various types of pyridyltriazole (NHC ancillary ligands).
关键词： Phenylpyridine Iridium(III) Complexes,Spectroscopic Study,N-Heterocyclic Carbene,Ancillary Ligands,Synthesis
更新于2025-09-23 15:21:01
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Luminescence and reactivity of a charge-transfer excited iron complex with nanosecond lifetime
摘要： Iron’s abundance and rich coordination chemistry are potentially appealing features for photochemical applications. However, the photoexcitable charge-transfer (CT) states of most Fe complexes are limited by picosecond or sub-picosecond deactivation through low-lying metal centered (MC) states, resulting in inefficient electron transfer reactivity and complete lack of photoluminescence. Here we show that octahedral coordination of Fe(III) by two mono-anionic facial tris-carbene ligands can suppress such deactivation dramatically. The resulting complex [Fe(phtmeimb)2]+, where phtmeimb is [phenyl(tris(3-methylimidazol-1-ylidene))borate]-, exhibits strong, visible, room temperature photoluminescence with a 2.0 ns lifetime and 2% quantum yield via spin-allowed transition from a ligand-to-metal charge-transfer (2LMCT) state to the ground state (2GS). Reductive and oxidative electron transfer reactions were observed for the 2LMCT state of [Fe(phtmeimb)2]+ in bimolecular quenching studies with methylviologen and diphenylamine.
关键词： charge-transfer,iron complex,electron transfer,photoluminescence,N-heterocyclic carbene
更新于2025-09-23 15:21:01
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trans-N-(Heterocyclic Carbene) Platinum(II) Acetylide Chromophores as Phosphors for OLED Applications
摘要： A family of complexes of the type trans-(NHC)2Pt(C≡C-Ar)2 (NHC = N-heterocyclic carbene and Ar = substituted phenyl or 4-pyridyl) exhibits blue or blue-green phosphorescence. The photoluminescence is 10 – 50 fold more efficient when the materials are in dispersed in a solid poly(methyl methacrylate) glass compared to in THF solution. The phosphorescence quantum efficiencies in PMMA glass range from 0.20 – 0.65, varying with the structure of the aryl acetylide ligands. Organic light emitting diodes (OLEDs) were fabricated by thermal evaporation, using bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) as the host and 15% of the trans-(NHC)2Pt(C≡C-Ar)2 complexes as the dopant/emitters. Most of the OLEDs display good performance, with EL spectra that closely match the PL in the PMMA glass. The best performing materials have peak EQE ranging from 9.6 – 14.1%, with deep blue spectral profiles (minimum CIE (0.16,0.13). Several of the complexes have deep HOMO levels and they display poor EL performance attributed to inefficient host to emitter hole transfer.
关键词： OLED,blue emission,platinum acetylide,platinum N-heterocyclic carbene,phosphor
更新于2025-09-23 15:19:57
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Tuning the electrochemiluminescent properties of iridium complexes of N-heterocyclic carbene ligands
摘要： A series of five heteroleptic Ir(III) complexes of the general form Ir(dfppy)2(C^C) have been prepared (where dfppy represents 2-(2,4-difluorophenyl)pyridine and C^C represents a bidentate cyclometalated phenyl substituted imidazolylidene ligand). The cyclometalated phenyl ring of the imidazolylidene ligand was either unsubstituted or substituted with electron donating (OMe and Me) or electron withdrawing (Cl and F) groups in the 2 and 4 positions. The synthesised Ir(III) complexes have been characterised by elemental analysis, NMR spectroscopy, cyclic voltammetry and electronic absorption and emission spectroscopy. The molecular structures for four Ir(III) complexes were determined by single crystal X-ray diffraction. Each of the Ir(III) complexes exhibited intense photoluminescence in acetonitrile solution at room temperature with quantum yields (ΦPL) ranging from 58% to 86%. Cyclic voltammetry experiments revealed one oxidation process (formally ascribed to the metal centre), and two ligand-based reductions for each complex. Complexes 1–5 gave moderate to intense annihilation and co-reactant electrochemiluminescence (ECL). Consideration of the electrochemical, spectroscopic and theoretical investigations provide insights into the electrochemiluminescence behaviour.
关键词： iridium complexes,electrochemiluminescence,cyclic voltammetry,photoluminescence,N-heterocyclic carbene ligands
更新于2025-09-19 17:15:36
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Ratiometric fluorescence probe for hydrazine vapor detection and biological imaging
摘要： A series of four new mononuclear cationic gold(I) complexes containing nitrogen functionalized N-heterocyclic carbenes (NHCs) was synthesized and fully characterized by spectroscopic methods. The X-ray structures of three complexes are presented. These lipophilic gold(I) complexes originate from a pharmacomodulation of previously described gold(I)-NHC complexes, by replacing an aliphatic spacer with an aromatic one. The Log P values of the resulting complexes increased by 0.7e1.5, depending on the substituents in comparison to the aliphatic-linker systems. The new series of complexes has been investigated in vitro for their anti-cancer activities in PC-3 (prostate cancer) and T24 (bladder cancer) cell lines and in the non-cancerous MC3T3 (osteoblast) cell line. All tested complexes show high activities against the cancer cell lines with GI50 values lower than 500 nM. One complex (11) has been selected for further investigations. It has been tested in vitro in six cancer cell lines from different origins (prostate, bladder, lung, bone, liver and breast) and two non-cancerous cell lines (osteoblasts, ?broblasts). Moreover, cellular uptake measurements were indicative of a good bioavailability. By various biochemical assays, this complex was found to effectively inhibit the thioredoxin reductase (TrxR) and its cytotoxicity towards prostate PC-3, bladder T24 and liver HepG2 cells was found to be ROS-dependent.
关键词： Glutathione,Thioredoxin reductase,Lipophilicity,N-heterocyclic carbene,Gold,ROS,Cancer
更新于2025-09-19 17:15:36
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Neutral Cyclometalated Iridium(III) Complexes Bearing Substituted N-Heterocyclic Carbene (NHC) Ligands for High-Performance Yellow OLED Application
摘要： The synthesis, crystal structure, and photophysics of a series of neutral cyclometalated iridium(III) complexes bearing substituted N-heterocyclic carbene (NHC) ancillary ligands ((C∧N)2Ir(R-NHC), where C∧N and NHC refer to the cyclometalating ligand benzo[h]quinoline and 1-phenylbenzimidazole, respectively) are reported. The NHC ligands were substituted with electron-withdrawing or -donating groups on C4′ of the phenyl ring (R = NO2 (Ir1), CN (Ir2), H (Ir3), OCH3 (Ir4), N(CH3)2 (Ir5)) or C5 of the benzimidazole ring (R = NO2 (Ir6), N(CH3)2 (Ir7)). The configuration of Ir1 was confirmed by a single-crystal X-ray diffraction analysis. The ground- and excited-state properties of Ir1?Ir7 were investigated by both spectroscopic methods and time-dependent density functional theory (TDDFT) calculations. All complexes possessed moderately strong structureless absorption bands at ca. 440 nm that originated from the C∧N ligand based 1π,π*/1CT (charge transfer)/1d,d transitions and very weak spin?forbidden 3MLCT (metal-to-ligand charge transfer)/3LLCT (ligand-to-ligand charge transfer) transitions beyond 500 nm. Electron-withdrawing substituents caused a slight blue shift of the 1π,π*/1CT/1d,d band, while electron-donating substituents induced a red shift of this band in comparison to the unsubstituted complex Ir3. Except for the weakly emissive nitro-substituted complexes Ir1 and Ir6 that had much shorter lifetimes (≤160 ns), the other complexes are highly emissive in organic solutions with microsecond lifetimes at ca. 540?550 nm at room temperature, with the emitting states being predominantly assigned to 3π,π*/3MLCT states. Although the effect of the substituents on the emission energy was insignificant, the effects on the emission quantum yields and lifetimes were drastic. All complexes also exhibited broad triplet excited-state absorption at 460?700 nm with similar spectral features, indicating the similar parentage of the lowest triplet excited states. The highly emissive Ir2 was used as a dopant for organic light-emitting diode (OLED) fabrication. The device displayed a yellow emission with a maximum current efficiency (ηc) of 71.29 cd A?1, a maximum luminance (Lmax) of 32747 cd m?2, and a maximum external quantum efficiency (EQE) of 20.6%. These results suggest the potential of utilizing this type of neutral Ir(III) complex as an efficient yellow phosphorescent emitter.
关键词： cyclometalated iridium(III) complexes,phosphorescent emitter,OLED,photophysics,N-heterocyclic carbene (NHC) ligands
更新于2025-09-19 17:13:59
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There Is a Future for N-Heterocyclic Carbene Iron(II) Dyes in Dye-Sensitized Solar Cells: Improving Performance through Changes in the Electrolyte
摘要： By systematic tuning of the components of the electrolyte, the performances of dye-sensitized solar cells (DSCs) with an N-heterocyclic carbene iron(II) dye have been significantly improved. The beneficial effects of an increased Li+ ion concentration in the electrolyte lead to photoconversion efficiencies (PCEs) up to 0.66% for fully masked cells (representing 11.8% relative to 100% set for N719) and an external quantum efficiency maximum (EQEmax) up to approximately 25% due to an increased short-circuit current density (JSC). A study of the effects of varying the length of the alkyl chain in 1-alkyl-3-methylimidazolium iodide ionic liquids (ILs) shows that a longer chain results in an increase in JSC with an overall efficiency up to 0.61% (10.9% relative to N719 set at 100%) on going from n-methyl to n-butyl chain, although an n-hexyl chain leads to no further gain in PCE. The results of electrochemical impedance spectroscopy (EIS) support the trends in JSC and open-circuit voltage (VOC) parameters. A change in the counterion from I? to [BF4]? for 1-propyl-3-methylimidazolium iodide ionic liquid leads to DSCs with a remarkably high JSC value for an N-heterocyclic carbene iron(II) dye of 4.90 mA cm?2, but a low VOC of 244 mV. Our investigations have shown that an increased concentration of Li+ in combination with an optimized alkyl chain length in the 1-alkyl-3-methylimidazolium iodide IL in the electrolyte leads to iron(II)-sensitized DSC performances comparable with those of containing some copper(I)-based dyes.
关键词： N-heterocyclic carbene,iron,dye-sensitized solar cell,ionic liquid,lithium ion,electrolyte
更新于2025-09-12 10:27:22
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A Second-Generation Chameleon N-Heterocyclic Carbene–Borane Coinitiator for the Visible-Light Oxygen-Resistant Photopolymerization of Both Organic and Water-Compatible Resins
摘要： N-Heterocyclic carbene?boranes (NHC-boranes, NHCBs) were recently described as efficient coinitiators for the visible light photopolymerization of hydroxyethyl methacrylate (HEMA) in the presence of water. In this work, a new, more water-soluble, NHC-borane—2,4-dimethyl-1,2,4,5-tetrazol-3-ylidene borane—has been synthesized, and its efficiency in three-component systems (dye (Acridine Orange), disulfide, and NHC-borane coinitiators) for the polymerization of methacrylate resins under visible light under air has been studied. In fluid resins this new photoinitiating system (PIS) gives better results than the one previously studied. More importantly, this system is competitive with the widely used type II system—camphorquinone/4-(dimethylamino)benzonitrile (DMABN)—for the polymerization of methacrylate resins but better for the photopolymerization of poly(2-hydroxyethyl methacrylate) leading to hydrogels, where the former PIS fails. The excellent ability of the NHC-boranes, and especially the new one, to be used as photopolymerization coinitiators has been analyzed by laser flash photolysis (LFP). The rate constants for elementary reactions of the three boranes and their derived NHC-boryl radicals obtained by LFP correlated well with the molecular modeling data and show that the key for the observed reactivity is the ability of the tetrazolydinyl NHC-borane to repair the peroxyl radicals formed by the reactions of the macroradicals with oxygen.
关键词： laser flash photolysis,methacrylate resins,N-Heterocyclic carbene?boranes,hydrogels,visible light photopolymerization
更新于2025-09-09 09:28:46
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Selective Photocatalytic C-F Borylation of Polyfluoroarenes by Rh/Ni Dual Catalysis Providing Valuable Fluorinated Arylboronate Esters
摘要： A highly selective and general photocatalytic C-F borylation protocol that employs a rhodium biphenyl complex as a triplet sensitizer and the nickel catalyst [Ni(IMes)2] (IMes = 1,3-dimesitylimidazolin-2-ylidene) for the C-F bond activation and defluoroborylation process is reported. This tandem catalyst system operates with visible (blue, 400 nm) light and achieves borylation of a wide range of fluoroarenes with B2pin2 at room temperature in excellent yields and with high selectivity. Direct irradiation of the intermediary C-F bond oxidative addition product trans-[NiF(ArF)(IMes)2] leads to very fast decomposition when B2pin2 is present. This destructive pathway can be bypassed by indirect excitation of the triplet states of the nickel(II) complex via the photoexcited rhodium biphenyl complex. Mechanistic studies suggest that the exceptionally long-lived triplet excited state of the Rh biphenyl complex used as the photosensitizer allows for efficient triplet energy transfer to trans-[NiF(ArF)(IMes)2], which leads to dissociation of one of the NHC ligands. This contrasts with the majority of current photocatalytic transformations, which employ transition metals as excited state single electron transfer agents. We have previously reported that C(arene)-F bond activation with [Ni(IMes)2] is facile at room temperature, but that the transmetalation step with B2pin2 is associated with a high energy barrier. Thus, this triplet energy transfer ultimately leads to a greatly enhanced rate constant for the transmetalation step and thus for the whole borylation process. While addition of a fluoride source such as CsF enhances the yield, it is not absolutely required. We attribute this yield-enhancing effect to (i) formation of an anionic adduct of B2pin2, i.e. FB2pin2-, as an efficient, much more nucleophilic {Bpin-} transfer reagent for the borylation/transmetalation process, and/or (ii) trapping of the Lewis acidic side product FBpin by formation of [F2Bpin]- to avoid the formation of a significant amount of NHC-FBpin and consequently of decomposition of {Ni(NHC)2} species in the reaction mixture.
关键词： C-F Bond Activation,Nickel Complex,N-Heterocyclic Carbene,Borylation,Aryl Boronate,Photocatalysis,Rhodium Complex,Fluoroarene
更新于2025-09-09 09:28:46
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Dinuclear N-heterocyclic carbene silver complexes: Synthesis, luminescence and catalytic studies
摘要： A new dibenzimidazole compound (1) and three dibenzimidazolium salts (2a-2c) were prepared. Reactions of these salts with silver(I) oxide in methanol led to dinuclear N-heterocyclic carbene silver complexes (3a-3c). All of the compounds were characterized by 1H NMR, 13C NMR and elemental analyses. Molecular weights of the silver complexes were confirmed by MALDI-TOF mass spectrometry. Preliminary catalytic studies using all the silver complexes were performed on three-component coupling reaction of p-formaldehyde, piperidine and phenylacetylene. Complexes 3a and 3c exhibited good catalytic activities under neat conditions. The silver complexes showed luminescence properties in CH3CN at room temperature.
关键词： luminescence,coupling reaction,silver,N-heterocyclic carbene
更新于2025-09-09 09:28:46