Bihai Tong

A highly selective and naked-eye sensor for Hg2+ based on quinazoline-4(3H)-thione

A highly selective colorimetric and fluorescent sensor for Hg2+, TPS (TPS = 2-(4-(diphenyl-amino)phenyl)quinazoline-4(3H)-thione), based on a 2-substituted quinazoline-4(3H)-thione derivative, was designed and characterized in this paper. TPS displays relatively strong fluorescence centered at about 468 nm. When mixing with Hg2+, TPS interacts with Hg2+ in a 2 : 1(TPS-Hg2+) stoichiometry via a coordination bond interaction between the sulfur atom and Hg2+ with an association constant of 4.17 × 108 M−2 (R2 = 0.96). Upon addition of Hg2+, TPS showed a remarkable decrease in fluorescence spectra (468 nm) with a clear color change from yellow to red, so TPS could serve as a naked-eye sensor for Hg2+. The sensor allow determination of Hg2+ in the working range 2.0 μM–12.0 μM with a detection limit of 1.5 μM. Upon addition of KI to the solution of TPS-Hg2+ species, the spectra can be restored to the original spectrum in both absorption and fluorescence and indicates that this sensor could be reused. The sensor exhibited excellent reproducibility, reversibility and selectivity.

A series of selective and sensitive fluorescent sensors based on a thiophen-2-yl-benzothiazole unit for Hg2+

Different types of fluorescent probes for Hg2+ based on the 5-thiophen-2-yl-benzothiazole derivatives (TBT, 2-thiophen-2-yl-benzothiazole; CTBT, 9-(5-benzothiazol-2-yl-thiophen-2-yl)-9H-carbazole; DTBT, 2-(5-acenaphthen-5-yl-thiophen-2-yl)-benzothiazole; and NTBT, 6-(5-benzothiazol-2-yl-thiophen-2-yl)-2-hexyl-benzo[de]isoquinoline-1,3-dione) were realized by changing the subsituents. Multisignaling changes were observed through UV-vis absorption and fluorescence spectra upon addition of Hg2+. The addition of Hg2+ on TBT induced a remarkable OFF/ON-type fluorescence signaling behavior. With the introduction of electron-donating carbazole, the detection behavior of CTBT was just the reverse of what TBT displayed, while a ratiometric fluorescent probe based on DTBT for Hg2+ was prepared by introducing the weak electron-drawing group acenaphthene. Moreover, the dichloromethane solution of CTBT and DTBT showed a distinct color change from colorless to yellow with the addition of Hg2+, which indicated that these two probes would facilitate the naked-eye detection of Hg2+. However, both UV-vis absorption and fluorescence spectra of NTBT with strong electron-withdrawing substituents showed no obvious change upon addition of Hg2+. It would be concluded that the electronic properties of the molecule was one of the vital factors in designing chemosensor molecules.

Bipolar luminescent materials containing pyrimidine terminals: synthesis, photophysical properties and a theoretical study

A new series of 4-monosubstituted pyrimidine bipolar materials containing a carbazole (PM1–PM2) or a triphenylamine (PM3–PM5) moiety as the electron donor have been synthesized by a ZnCl2-catalyzed three-component coupling reaction. These 4-monosubstituted pyrimidine compounds were characterized by UV-vis and fluorescence spectroscopy, cyclic voltammetry, as well as density functional theory (DFT) calculations. It was intriguing to find that these 4-monosubstituted pyrimidine compounds exhibited bright fluorescence with excellent quantum yields (∼0.53–0.93) in the blue region. PM1 and PM2 had a lower LUMO than that of CBP (4,4′-di(9H-carbazol-9-yl)biphenyl), meaning that both of them had better electron injection and transfer abilities. The variation tendencies of energy levels and absorption spectra obtained from DFT calculations agreed well with those from experiment. Other electronic properties including ionization potentials (IP), electronic affinities (EA), and reorganization energies (λhole and λelectron) have been theoretically studied as well. These electronic properties could be tuned by introducing a different number of pyrimdin-4-yl moieties onto to the donor fragments. The incorporation of pyrimdin-4-yl can significantly decrease the λelectron and then improve the electron-accepting and hole–electron charge balance abilities. The combined theoretical and experimental studies offer insights into the nature of bipolar molecules containing 4-monosubstituted pyrimidine moieties, and provided a fertile ground for the design of appropriate ambipolar materials for optoelectronic applications.

Effect of pH on the photophysical properties of two new carboxylic-substituted iridium(III) complexes.

Two cyclometalated iridium(III) complexes have been prepared based on 2-(4-diphenylamino-phenyl)-quinoline and incorporating carboxylic acid ethyl ester (–COOC(2)H(5), (TPAQCE)(2)Irpic and carboxylic acid (–COOH, (TPAQCOOH)(2)Irpic) substituents at the 4-position of the quinoline ligand, respectively. The absorption, emission and (1)H NMR spectra of (TPAQCE)(2)Irpic and (TPAQCOOH)(2)Irpic under alkaline or acidic conditions demonstrate that they respond to the pH of the surrounding solvent environment. The deprotonation of the carboxylic acid group significantly blue-shifts the metal-to-ligand charge transfer absorption band of (TPAQCOOH)(2)Irpic by 48 nm and enhances the emission quantum-yield in DMSO. In addition, (1)H-NMR titration reveals that (TPAQCOOH)(2)Irpic is deprotonated into negatively charged (TPAQCOO(−))(2)Irpic in free DMSO-d(6) solution, and the acid-induced N^O ancillary ligands cleavage or replacement in (TPAQCOOH)(2)Irpic could be ignored. A water-soluble near-neutral optical pH probe (TPAQCOOH)(2)Irpic with pK(a) of ~7 is also reported. In aqueous buffer, (TPAQCOOH)(2)Irpic possesses an obvious emission response with an excellent linearity in the pH range of 6.50–8.00, showing a promising application in bioprocessing.

Synthesis, Crystal Structure and Luminescence Properties of a Cyclometalated Ir(III) Complex of 3,4-Diphenylcinnoline

An iridium(III) complex, [(dpci-H)2Ir(dafo)](PF6) (dpci-H = deprotonated 3,4-diphenylcinnoline, dpci; dafo = 4,5-diazafluoren-9-one), was synthesized from the reaction of the iridium complex [Ir(dpci-H)2(Cl)]2 and dafo in methanol, and characterized by single-crystal X-ray diffraction along with FT-IR, UV/Vis, 1H NMR and mass spectroscopy. The luminescence properties and the decay of the cyclometalated iridium(III) complex were also investigated. Excitation at the absorption wavelength (469 nm) resulted in a strong emission band centered at 591 nm with a lifetime of 0.9 μs. Graphical Abstract Synthesis, Crystal Structure and Luminescence Properties of a Cyclometalated Ir(III) Complex of 3,4-Diphenylcinnoline

Heteroleptic ruthenium(II)/(III) 2,2′-bipyridine/1,10-phenanthroline complexes incorporating bidentate Schiff base N,O-ligands

Abstract Eight substituted bidentate Schiff base ligands HOC6H4CH=N-R (HL) (HL1: R = 4-ClC6H4, HL2: R = 2-ClC6H4, HL3: R = 4-NO2C6H4, HL4: R = 4-MeC6H4, HL5: R = 2,6-Me2C6H3, HL6: R = 2,46-Me3C6H2, HL7: R = CH2C6H5, and HL8: R = n-Pr) were synthesized by the typical condensation reaction. Interaction of cis-[Ru(bpy)2Cl2]⋅2H2O (bpy = 2,2′-bipyridine) with one equivalent of HL ligand in the presence of KPF6 afforded the cationic ruthenium(II) complexes of the type [Ru(bpy)2(L)](PF6) (1–8). The reaction of cis-[Ru(phen)2Cl2]⋅2H2O (phen = 1,10-phenanthroline) and HL1 under similar condition gave complex [(phen)2Ru(L)](PF6) (1a). Treatment of cis-[Ru(phen)2Cl2]⋅2H2O with two equivalents of HL in the presence of KPF6 resulted in isolation of the cationic ruthenium(III) complexes of the type [Ru(phen)(L)2](PF6) (9-16). All complexes have been spectroscopically characterized. The structures of 1a⋅CH2Cl2, 2⋅½CH2Cl2, 3⋅CH3CN, 5⋅½H2O, 6, 12⋅½HOCH2CH2OH, 13⋅CH3CN, 15⋅H2O, and 16 have been determined by single-crystal X-ray diffraction.

High-brightness solution-processed phosphorescent OLEDs with pyrimidine-based iridium(III) complexes

Two heteroleptic cyclometalated iridium(III) complexes, Ir(ppm)2(pic) and Ir(ppm)2(taz), using 4,6-diphenyl pyrimidine (Hppm) as a cyclometalating ligand, were successfully synthesized and characterized. Strong emission at 555 and 532 nm with high photoluminescence quantum yields of 83% and 86% in PMMA at 298 k were obtained for Ir(ppm)2(pic) and Ir(ppm)2(taz), respectively. Solution-processed organic light-emitting diodes (OLEDs) based on Ir(ppm)2(pic) and Ir(ppm)2(taz) showed high-brightness of 112 233 and 125 072 cd m−2, peak current efficiencies of 30.6 and 40.4 cd A−1 and maximum external quantum efficiencies of 10.4 and 17.3%, respectively, accompanied by very low efficiency roll-off values. The ancillary ligand taz tuned the emission to saturated green, and more importantly, it can significantly increase the spectral stability and device efficiency.

Highly efficient orange phosphorescent organic light-emitting diodes based on an iridium(III) complex with diethyldithiocarbamate (S^S) as the ancillary ligand

A novel iridium(III) complex Ir(dpp)2(dta) (dppH = 4,6-diphenyl pyrimidine; dta = diethyldithiocarbamate) was synthesized and characterized. The complex displayed strong emissions at 575 nm with high photoluminescence quantum yields of 86% in the doped poly(methyl methacrylate) (PMMA) film at 1% doping concentration. The orange-yellow polymer light-emitting devices (PLEDs) based on Ir(dpp)2(dta) as a triplet emitter with different concentrations (x = 1%, 3%, 5%, 7% and 10%) doped in a polymeric host 70% poly(N-vinylcarbazole) (PVK) + 30% 2,2′-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-7) were fabricated with high luminance and efficiency. The device achieved an ideal turn-on voltage (<4 V) and superior luminance (81 918 cd m−2) as well as electroluminescence efficiency (30.12 cd A−1) at 3% doping concentration.

Phosphorescent chemosensor for Hg2+ based on an iridium(III) complex coordinated with 4-phenylquinazoline and carbazole dithiocarbamate

A highly selective and colorimetric phosphorescent turn-on chemosensor for Hg2+ based on an iridium(III) complex Ir(pqz)2(cdc) (pqzH = 4-phenylquinazoline, Nacdc = sodium carbazole dithiocarbamate) was realized. The photograph of Ir(pqz)2(cdc)under ultraviolet light exhibited an emitting color change from red to yellow without and with Hg2+ in an acetonitrile (MeCN) solution, and it can also serve as a highly selective chemosensor for Hg2+ with naked-eye detection. Upon addition of a tetrahydrofuran (THF) solution of Hg2+, the dichloromethane (DCM) solution of Ir(pqz)2(cdc) gave a visual color change and significant luminescent quenching. When MeCN was added, a new emission peak at 562 nm emerged, which constituted a selective MeCN phosphorescent chemosensor.

Syntheses, crystal structures and phosphorescence properties of cyclometalated iridium(III) bis(pyridylbenzaldehyde) complexes with dithiolate ligands

Abstract The synthesis of three neutral bis-cyclometalated iridium(III) complexes [Ir(pba)2(S^S)] (pbaH=4-(2-pyridyl)benzaldehyde; S^S=Et2NCS2− (1), iPrOCS2− (2), (nPrO)2PS2− (3)) from [{Ir(μ-Cl)(pba)2}2] and the corresponding sodium or potassium dithiolates in methanol-dichloromethane is described. The composition of complexes 1–3 is discussed on the basis of 1H NMR, 13C NMR, IR, and mass spectroscopy, and the crystal structures of 1 and 3 were determined by X-ray crystallography. The absorption and emission spectra show that the [Ir(pba)2(S^S)] complexes may be effective candidates as green-emitting phosphorescent materials. The stability of the three cyclometalated iridium(III) complexes towards different transition metal ions was also investigated in acetonitrile-water solvent.