CH2Cl2 Solution Research Articles

Aromatic Fluorine-Induced One-Pot Synthesis of Ring-Perfluorinated Trimethine Cyanine Dye and Its Remarkable Fluorescence Properties.

We have developed a novel aromatic fluorine-induced one-pot synthesis of ring-perfluorinated trimethine cyanine dye without the use of a pyridine by reacting hexafluorobenzoindolenine with 5 equiv of methyl trifluoromethanesulfonate in mixed solvents of dimethylformamide and toluene. The thus-obtained ring-perfluorinated trimethine cyanine dye shows much better fluorescence properties, including intensity, quantum yield, and lifetime, than the nonfluorinated dye, not only in CH2Cl2 solution and the poly(methyl methacrylate) film but also in the powder state. Furthermore, ring-perfluorinated trimethine cyanine dye 2a shows better photostability toward white light-emitting diode irradiation than nonfluorinated dye trimethine cyanine dye 2b.

The synthesis, characterization and fluorescence properties of new benzimidazole derivatives

Abstract New ligands obtained in the reaction of o-phenylenediamine and series of aldehydes (L1-L5) were synthesized. Molecular architecture of the synthesized ligands L1-L5 has been determined by the X-ray crystal structure analysis. 1H NMR NOE diff. spectra (differential Nuclear Overhauser Effect) of ligands indicate that they have different conformation in the solution in comparison to the solid state (crystal structure). The substrates molar ratio and the reaction time allowed the controlled synthesis of mono substituted o-phenylenediamine or benzimidazole derivatives with no catalyst used. For all compounds the relatively high fluorescence efficiency was observed in the range 0.41–0.83 in MeCN and 0.48–0.96 in CH2Cl2 solution. Based on DFT calculations the fluorescence mechanism was associated with HOMO→LUMO transition between aromatic rings and benzimidazole moieties.

Facile method to fabricate poly(L-lactic acid)/C60 tetragonal single crystal composites with enhanced thermal stability

For the first time, the poly(L-lactide acid) (PLLA) composites with C60 tetragonal single crystal (C60TSC) were fabricated through facile evaporation of the CHCl3 solution containing PLLA and C60. Results showed C60TSC in composites had side length in micron scale, and their mean size decreased, their number increased with C60 content in composites. The C60TSC in composites were face-centered cubic (fcc) lattice C60 single crystal composed of monomeric C60, and displayed blueshift relative to the UV absorption bands of C60. C60TSC formation resulted in PLLA composite with higher thermal stability, higher cold crystallization temperature as well as higher melting temperature than neat PLLA.

Migratory Shift in Oxidative Cyclodehydrogenation Reaction of Tetraphenylethylenes Containing Electron-Rich THDTAP Moiety.

Four tetraphenylethylenes (2 a-d) containing an electron-rich 2,3,4,6-tetrahydro-1,6-dithia-3a-azaphenalene (THDTAP) moiety have been synthesized. The 2 a-d show aggregation-induced emission (AIE) with yellowish green photoluminescence (PL) in THF-H2 O (v/v, 1:9) solution and in the solid state. Compounds 2 a-d undergo 1,2-migratory shift in oxidative cyclodehydrogenation reactions to afford the unexpected products 3 a-d which display green PL in CH2 Cl2 solution and are non-emissive in the solid state. The PL intensities of 3 a-d are clearly enhanced in the presence of meta-chloroperoxybenzoic acid (mCPBA) owing to the oxidation of the S-atoms on the THDTAP moiety. In contrast, the PL of 2 a-d in THF-H2 O (v/v, 1:9) solution is quenched by adding mCPBA, ascribable to the oxidation of the C=C bond on the ethylene moiety. It is found that the absorption of 3 a-d is distinctly red-shifted from the UV/Vis region to the NIR region upon acidification, arising from the protonation of the N-atom on the THDTAP moiety. Furthermore, 3 a-d display nonlinear optical response (NLO) and optical limiting (OL) behaviour which is superior to that of the well-known OL material C60 .

Adducts of Zinc(II) Acetylacetonate with Various Aminoquinolines: Synthesis, Structure and Luminescence

AbstractNew adducts of zinc(II) acetylacetonate of composition [Zn(acac)2L] (where L=2‐aminoquinoline, 4‐aminoquinoline, 6‐aminoquinoline, 5‐amino‐4,6‐dimethylquinoline) were obtained and characterized by elemental analysis, IR and 1H‐NMR. The optical properties of zinc(II) adducts were investigated by UV/Vis and photoluminescence spectroscopy. In these adducts, each zinc(II) ion is coordinated with two acetylacetonate moieties and one aminoquinoline ligand through an endocyclic nitrogen atom. Adducts show thermal stability (m.p.>180 °C), good solubility in non‐polar solvents, but they easily decompose in the presence of Lewis bases. The 4‐aminoquinoline adduct does not luminesce. The emission bands of other compounds in CH2Cl2 solutions are located in the blue region of the spectrum in the range 373–460 nm with quantum yields ϕ= 0.21‐0.40.

Syntheses, characterization, and computational study of AsF5 adducts with ketones

Lewis acid-base adducts between AsF5 and the ketones, acetone, cyclopentanone, and adamantanone, were synthesized from SO2 and CH2Cl2 solutions. These adducts, which contain O---As pnictogen bonding interactions, were found to be stable in solutions at room temperature. Raman and NMR spectroscopy of the solid adducts showed a characteristic decrease in the C=O stretching frequency, as well as dramatic deshielding of the 13C resonance of the carbonyl group upon adduct formation. Fluorine-19 NMR spectroscopy showed the two fluorine environments of the O–AsF5 moiety. Optimization of the gas-phase geometry using DFT calculations yielded geometries with essentially planar CC=OAs moieties. NBO analyses of the adducts and the free ketones show the polarization of the C=O bond upon adduct formation. The lowering of the LUMO energies upon adduct formation is more dramatic than what was found for protonation of ketones and reflects the substantially enhanced electrophilicity of the adducted ketones.

Luminescence switching property of cycloplatinated(II) complexes bearing 2-phenylpyridine derivatives and the application for data security storage

Four novel cycloplatinated(II) complexes, Pt(ppy)(acac-C6H4I-4) (1), Pt(ppy)(acac-C6H4t-Bu-4) (2), Pt[dF(CF3)ppy](acac-C6H4I-4) (3) and Pt[dF(CF3)ppy](acac-C6H4t-Bu-4) (4) based on either 2-phenylpyridine (ppy) or 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine [dF(CF3)ppy] ligands were synthesized and characterized. Complex 4 has two isomers with different color and luminescence. Yellow-green 4G emits a green luminescence whereas orange 4O exhibits red luminescence. Complexes 1, 2 and 4G display mechanoluminescence with the luminescence red-shift in a range of ca. 94–135 nm. Whereas 3 and 4O exhibit no response to mechanical grinding. Systematic studies on crystal structure, TGA, luminescence spectra, and PXRD demonstrate that the mechanoluminescence of 1 and 2 is due to the formation of π-π interactions, whereas, the mechanism for 4G is the destruction of F⋯F interactions during mechanical grinding. All complexes exhibit concentration-dependent luminescence switching behaviour in CHCl3 solution. Extremely large red-shifts of their luminescence spectra suggest the formation of aggregates via PtPt interaction in high concentration solutions. Moreover, 4O don't respond to ethanol vapor, but its ground species can be converted to 4G upon exposure to ethanol vapor. Based on this unique property, a simple device was developed using 4O as starting material and successfully demonstrated potential for data security storage.

Tandem Rh(III)-Catalyzed C-H Heteroarylation of Indolyl Ketones and Cu(II)-Promoted Intramolecular Cyclization: One-Pot Access to Blue-Emitting Phenanthrone-Type Polyheterocycles.

Disclosed herein is a highly efficient one-pot synthetic strategy to phenanthrone-type polyheterocycles via tandem rhodium(III)-catalyzed ortho-C-H heteroarylation of indolyl ketones and copper(II)-promoted intramolecular cyclization. This protocol enables a library of blue-emitting fluorophores with high quantum yields and narrow full widths at half-maximum to be rapidly built from readily available substrates, among of which 6,6,7,9,12-pentamethyl-6,12-dihydro-5 H-benzofuro[2,3- a]carbazol-5-one (4a) exhibits pure blue emission with Commission Internationale de I'Eclairage coordinates of (0.15, 0.09) and a high quantum yield of 85% in CH2Cl2 solution.

Effects of Substituents on the Blue Luminescence of Disilane-Linked Donor‒Acceptor‒Donor Triads

A series of disilane-linked donor‒acceptor‒donor triads (D‒Si‒Si‒A‒Si‒Si‒D) was synthesized to investigate the effects of substituents on the photophysical properties. The triads were prepared by metal-catalyzed diiodosilylation of aryl iodides using a Pd(P(t-Bu)3)2/(i-Pr)2EtN/toluene system that we previously developed. Optical measurements, X-ray diffraction analysis, and density functional theory calculations revealed relationships between the photophysical properties and molecular structures of these triads in solution and in the solid state. The compounds emitted blue to green fluorescence in CH2Cl2 solution and in the solid state. Notably, compound 2 showed fluorescence with an absolute quantum yield of 0.17 in the solid state but showed no fluorescence in CH2Cl2. Our findings confirmed that the substituent adjacent to the disilane moiety affects the conformations and emission efficiencies of compounds in solution and in the solid state.

Complexes of WOCl4 and WSCl4 with neutral N- and O-donor ligands: Synthesis, spectroscopy and structures

The complexes [WOCl4(L)] and [WSCl4(L)] (L = OPPh3, OPMe3, pyridine, 2,2′-bipyridyl), [{WOCl4}2(µ-L-L)] and [{WSCl4}2(µ-L-L)] (L-L = Ph2P(O)(CH2)nP(O)Ph2 (n = 1, 2)) have been prepared from WOCl4 or WSCl4 and the ligands in anhydrous CH2Cl2 solution, and characterised by microanalysis, IR and NMR (1H, 31P{1H}) spectroscopy. X-Ray crystal structures are reported for [WOCl4(OPPh3)], [{WOCl4}2(µ-Ph2P(O)(CH2)P(O)Ph2)] and [{WSCl4}2(µ-Ph2P(O)(CH2)2P(O)Ph2)]. All, except those of 2,2′-bipyridyl, are six-coordinate with the neutral donor trans to WO or WS. Spectroscopic data suggest that the [WOCl4(2,2′-bipy)] and [WSCl4(2,2′-bipy)] are seven-coordinate. Comparison of the structural and spectroscopic data for the two series of complexes indicate little difference in Lewis acidity between the two tungsten(VI) moieties. Decomposition of [WOCl4(OPMe3)] in solution gave the cyclic trimer [W3O3(µ-O)3Cl6(OPMe3)3], the structure of which revealed a six-membered W3O3 ring core with very asymmetric oxido-bridges. The structure of the tungsten(V) complex [WOCl3(2,2′-bipy)] is also reported.

Neutral and cationic phosphine and arsine complexes of tin(iv) halides: synthesis, properties, structures and anion influence.

The reaction of trans-[SnCl4(PR3)2] (R = Me or Et) with trimethylsilyltriflate (TMSOTf) in CH2Cl2 solution substitutes one chloride to form [SnCl3(PR3)2(OTf)]; addition of excess TMSOTf does not substitute further chlorides. The complexes have been fully characterised by microanalysis, IR and multinuclear NMR (1H, 13C{1H}, 19F{1H}, 31P{1H}, 119Sn) spectroscopy. The crystal structure of [SnCl3(PMe3)2(OTf)] revealed mer-chlorines and trans-phosphines. In contrast, trans-[SnBr4(PR3)2], [SnCl4{Et2P(CH2)2PEt2}], [SnCl4{o-C6H4(PMe2)2}] and [SnCl4{o-C6H4(AsMe2)2}] did not react with TMSOTf in CH2Cl2 solution even after 3 days. The arsine complexes, [SnX4(AsEt3)2] (X = Cl, Br), were confirmed as trans-isomers by similar spectroscopic and structural studies, while attempts to isolate [SnI4(AsEt3)2] were unsuccessful and reaction of SnX4 with SbR3 (R = Et, iPr) resulted in reduction to SnX2 and formation of R3SbX2. trans-[SnCl4(AsEt3)2] is converted by TMSOTf into [SnCl3(AsEt3)2(OTf)], whose X-ray structure reveals the same geometry found in the phosphine analogues, with the triflate coordinated. The salts, [SnCl3(PEt3)2][AlCl4] and [SnCl2(PEt3)2][AlCl4]2 were made by treatment of [SnCl4(PEt3)2] with one and two mol. equivalents, respectively, of AlCl3 in anhydrous CH2Cl2, whereas reaction of [SnCl4(AsEt3)2] with AlCl3 produced a mixture including Et3AsCl2 and [Et3AsCl][Sn(AsEt3)Cl5] (the latter identified crystallographically). In contrast, using Na[BArF] (BArF = [B{3,5-(CF3)2C6H3}4]-) produced [SnCl3(PEt3)2][BArF] and also allowed clean isolation of the arsine analogue, [SnCl3(AsEt3)2][BArF]. [SnCl4{o-C6H4(PMe2)2}] also reacts with AlCl3 in CH2Cl2 to form [SnCl3{o-C6H4(PMe2)2}][AlCl4] and [SnCl2{o-C6H4(PMe2)2}][AlCl4]2. Multinuclear NMR spectroscopy on the [AlCl4]- salts show that δ31P and δ119Sn move progressively to high frequency on conversion from the neutral complex to the mono- and the di-cations, whilst 1J(119Sn-31P) follow the trend: [SnCl3{o-C6H4(PMe2)2}]+ > [SnCl4{o-C6H4(PMe2)2}] > [SnCl2{o-C6H4(PMe2)2}]2+. DFT studies on selected complexes show only small changes in ligand geometries and bond lengths between the halide and triflate complexes, consistent with the X-ray crystallographic data reported and the HOMO and LUMO energies are relatively unperturbed upon the introduction of (coordinated) triflate, whereas the energies of both are ca. 4 eV lower in the cationic species and reveal significant hybridisation across the pnictine ligands.

Polynuclear Cu(i) and Ag(i) phosphine complexes containing multi-dentate polytopic ligands: syntheses, crystal structures and photoluminescence properties.

A series of polynuclear metal complexes, [Cu2(L1)(PPh3)4](ClO4)2 (1), [Cu3(L2)(PPh3)6](ClO4) (2), [Cu3(L3)(PPh3)6] (3), [Ag2(L1)(PPh3)4](BF4)2 (4), [Ag4(L2)2(PPh3)6] (5) and [Ag3(L3)(PPh3)5] (6), have been obtained from the reactions of the highly conjugated bridging ligands 2,3-bis(2-pyridyl)pyrazine (L1), 2,3-bis(2-tetrazoyl)pyrazine (H2L2) and 2,3-bis(2-tetrazoyl)imidazole (H3L3) with [Cu(MeCN)4]ClO4 and AgBF4, respectively. Their crystal structures have been determined by X-ray crystallography and their photophysical properties have been investigated in detail. Complexes 1 and 3 show photoluminescence in CH2Cl2 solution, while all the complexes exhibit obvious luminescence in the solid state; detailed photophysical studies and density functional theory calculations of these complexes have revealed that their lowest energy absorptions and emissions are predominantly derived from either metal-to-ligand charge-transfer (MLCT) or intraligand (IL) excited states.

Evidence of proton-coupled mixed-valency by electrochemical behavior on transition metal complex dimers bridged by two Ag+ ions.

H-Bonded metal complex dimers with reversible redox behaviour, which are connected by a low-barrier hydrogen bond (LBHB) with a very low energy barrier for proton transfer, can provide a unique mixed-valency state stabilized by the proton-coupled electron transfer (PCET) phenomenon. Using cyclic voltammetry measurements, newly prepared [ReIIICl2(PnPr3)2(Hbim)]2 (2) and [OsIIICl2(PnPr3)2(Hbim)]2 (3) existing as H-bonded dimers in a CH2Cl2 solution showed a four-step and four-electron transfer containing two mixed-valency states of ReIIReIII and ReIIIReIV, and OsIIOsIII and OsIIIOsVI, respectively. Furthermore, [ReIIICl2(PnPr3)2(Agbim)]2 (4) and [OsIIICl2(PnPr3)2(Agbim)]2 (5), bridged by two Ag+ ions instead of two H-bonding protons, were prepared, and their electrochemical behaviours changed to a two-step and four-electron transfer. It is clear that the H-bonded complex dimers 2 and 3, connected by an LBHB, can be electrochemically stabilized into unique pairs of mixed-valency states by PCET, and the H-bonding proton transfer also controls the electrochemical redox behaviour.

Synthesis and NIR photoluminescence studies of novel Yb(III) complexes of asymmetric perfluoryl β-diketone

The four new NIR emitting Yb3+ complexes using, perfluorinated β-diketone (5,5,6,6,7,7,7-heptafluoro-2,2-dimethyl-3,5-octanedione, Hfod) as main chromophore and N- / O- containing neutral heterocyclic bases namely: trispyridyl triazine (tptz) (1), indazole (2), triphenyl phosphine oxide (tppo) (3) and 4,4′-bipyridyl (4,4′ -bpy) (4) as ancillary ligands have been successfully designed. The complexes, [Yb(fod)3(L)n] (n = 1 for tptz, 4,4′-bpy and indazole and 2 for tppo) have been thoroughly characterized by elemental analysis, TGA-DTA, IR and UV–Vis spectroscopy. The complexes display efficient ligand-sensitized near-infrared luminescence from ytterbium at 925–1075 nm with lifetimes and quantum yields as high as 13 μs and 0.65%, in the solid state, and 12.35 μs and 0.62% in CHCl3 solution, respectively. The effect of ancillary ligand triplet states on the emission intensity of Yb3+ is discussed.

Regioisomeric synthesis of chlorin-e6 dimethyl esters and their optical properties

Chlorin-[Formula: see text] dimethyl esters possessing a single carboxy group at the 13-, 151-, or 172-position were prepared by chemically modifying chlorophyll-[Formula: see text]. These three synthetic regioisomers were fully characterized by their mass, NMR, and visible absorption spectra. Their molecular structures were unambiguously identified by the specific 1H–[Formula: see text]C correlation at the 13-, 15-, and/or 17-substituents in their respective HMBC spectra. Methyl esterification of 13/151-COOH and hydrolysis of 13/151-COOMe affected small shifts of the Qy absorption and fluorescence emission maxima in a diluted CH2Cl2 solution, while no substitution effect of 172-COOH/Me was observed.

Iridium(III) complexes adopting thienylpyridine derivatives for yellow-to-deep red OLEDs with low efficiency roll-off

By introduction of trifluoromethyl and phenyl groups to 2-(2-thienyl)pyridine (thp), four new phosphorescent bis-cyclometalated iridium(III) complexes, (thp)2Ir(tpip), (cf3thp)2Ir(tpip), (cf3btp)2Ir(tpip) and (3-cf3btp)2Ir(tpip) (cf3thp = 2-(thiophen-2-yl)-4-(trifluoromethyl)pyridine, cf3btp = 2-(benzo[b]thiophen-2-yl)-4- (trifluoromethyl)pyridine, 3-cf3btp = 2-(benzo[b]thiophen-3-yl)-4-(trifluoromethyl)pyridine, tpip = tetraphenylimidodiphosphinate), were synthesized and fully characterized. The density functional theory and time-dependent DFT calculations show that the frontier orbitals are mainly localized in the Ir(III) ion and the cyclometalated ligands. Thus, the photophysical properties were dominated by the cyclometalated C∧N ligand, attributed to 3MLCT and 3ILCT transition. These Ir(III) complexes emit in the yellow-to-deep red region with photoluminescence quantum yields in the range 40.5–86.4% in CH2Cl2 solutions at 298 K. The organic light-emitting diodes (OLEDs) using (thp)2Ir(tpip), (cf3thp)2Ir(tpip) and (cf3btp)2Ir(tpip) as yellow, orange and deep red emitters display good electroluminescent performance with low efficiency roll-off. Notably, the device based on (cf3thp)2Ir(tpip) possesses very high EL efficiencies with the maximum luminance efficiency and external quantum efficiency (EQE) of 53.9 cd A−1 and 17.9%, respectively. Furthermore, the EQE for this complex could be still retained as 15.4% at a luminance of 1000 cd m−2.

Quantitative Sensitization Efficiencies in NIR-Emissive Homoleptic Ln(III) Complexes Using 2-(5-Methylpyridin-2-yl)-8-hydroxyquinoline.

A series of isostructural lanthanide complexes [Ln(MPQ)3] (Ln = Nd, Gd, Er, Yb, Lu) using a monoanionic tridentate methylpyridyl-substituted 8-hydroxyquinoline ligand (MPHQ = 2-(5-methylpyridin-2-yl)-8-hydroxyquinoline) have been prepared and characterized using elemental analysis (CHN), single-crystal X-ray diffraction (XRD), and 1H NMR spectroscopy. This ligand forms homoleptic charge-neutral lanthanide complexes with three coordinated ligands arranged in an "up-up-down" fashion around the metal center. The photophysical properties of the Nd, Er, and Yb complexes were investigated using absorption and emission spectroscopy, with the latter species displaying efficient sensitization in the Near Infra-Red (NIR) region and a photoluminescence quantum yield (PLQY) as high as 1.0% in CH2Cl2 solution. The intersystem crossing and energy-transfer processes involved in the antenna effect were further investigated using transient absorption techniques, which revealed essentially quantitative sensitization efficiencies for the NIR-emitting cations.

Luminescent Electropolymerizable Ruthenium Complexes and Corresponding Conducting Metallopolymers

Tris(2,2′-bipyridyl)ruthenium(II) dichloride [Ru(bpy)3Cl2] and analogous complexes have been studied extensively in the literature due to their luminescent and photochemical properties as well as their excited-state lifetimes. Conducting polymers with similar ruthenium groups have also been investigated for various applications. In this study, syntheses of four ruthenium complexes with a polymerizable tridentate ligand, bis[4-[2-(3,4-diethylenedioxy)thiophene]pyrazol-1-yl]pyridine (EDOT2NNN), and with bidentate ligands, two of which were anionic (hfac: 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; dbm: dibenzoylmethane) and two of which were neutral (bpy: 2,2′-bipyridyl; phen: 1,10-phenanthroline), were achieved for potential OLED/PLED applications. Saturated CH2Cl2 solutions of monomers were oxidatively and electrochemically polymerized, and the scan rate dependences of the polymers were measured. UV–vis spectroscopic characterizations of the complexes and the EDOT-functionalized ligand were obtained. [Ru(EDO...

Methoxy‐Substituted Difluoroboron Benzoylacetonate Complexes with Color‐Tunable Phosphorescence

AbstractDifluoroboron β‐diketonates (BF2bdks) exhibit fluorescence (F) and room‐temperature phosphorescence (RTP) in a poly(lactic acid) (PLA) matrix. Fluorescence color tuning has been achieved by dye loading or bdk ligand modification, namely substituent effects or extended conjugation. In this study, color‐tunable RTP (450–570 nm) is achieved with 1‐benzoylacetonate derivatives by varying the number and position of methoxy groups on the benzene ring. The methoxy groups can be used to alter the energy levels of the dye or induce geometry changes (e. g. twisting) to disrupt π‐conjugation. The dyes were evaluated theoretically with density functional theory (DFT) and spectroscopy (absorbance and fluorescence) in CH2Cl2 solution and dilute PLA blends. These findings inform future boron‐based lighting devices and oxygen‐sensing bioprobe designs.

Organic Salts Suppress Aggregation and Enhance the Hyperpolarizability of a π-Twisted Chromophore.

Twisted intramolecular charge-transfer (TICT) chromophores exhibit extraordinary hyperpolarizabilities, β, and are therefore promising for electro-optic technologies. Nevertheless, centrosymmetric aggregate formation severely diminishes β in concentrated solutions or in polymer matrices. Herein, the remarkable effects of organic salts on the linear and nonlinear optical response of a high β benzimidazolium-based TICT chromophore, B2TMC-2, are reported. Addition of Bu4 P+ Br- to B2TMC-2 solution in CHCl3 induces a halochromic blueshift, primarily reflecting interactions between Bu4 P+ Br- and the B2TMC-2 cationic portion. DC electric-field induced second-harmonic generation (EFISH) measurements on B2TMC-2+Bu4 P+ Br- solution reveal a large μβ=-22,160×10-48 esu, unprecedented for any chromophore with such a broad optical transparency window. Moreover, Bu4 P+ Br- is shown to suppress B2TMC-2 aggregation, thereby preserving high μβ in concentrated solutions. This phenomenon should be applicable to many other NLO chromophores.