Synthesis and properties of thiophene-functionalized π-extended tetrathiafulvalenes

Two molecular ensembles composed of an array of thiophene-extended tetrathiafulvalene-thiophene were synthesized using Stille coupling and Horner-Wittig reaction as the key steps. Electrochemical redox and electronic absorption properties were investigated by voltammetric and UV-vis spectroscopic analyses.     

Conformational and spectroscopic properties of π-extended, bipyrrole-fused rubyrin and sapphyrin derivatives

Two new expanded porphyrins, naphthorubyrin and naphthosapphyrin, were synthesized. The π-extended rubyrin was isolated and structurally characterized in its monoprotonated form. The sapphyrin congener undergoes pyrrole inversion as a function of the protonation state. These conformational effects are reflected in the spectroscopic features, including the excited singlet state lifetimes.     

Synthesis and properties of [9]cyclo-1,4-naphthylene: a π-extended carbon nanoring

The first synthesis of a π-extended carbon nanoring, [9]cyclo-1,4-naphthylene ([9]CN), has been achieved. Careful structure-property analyses uncovered a number of unique features of [9]CN that are quite different from those of [9]CPP, a simple carbon nanoring.     

Synthesis of π-expanded BODIPYs and their fluorescent properties in the visible-near-infrared region

A series of π-expanded boron-dipyrromethenes (BODIPYs) fused with aromatic rings at β,β-positions, such as benzene, acenaphthylene, and benzofluoranthene were prepared by the reaction of BF₃·OEt₂ with bicyclo[2.2.2]octadiene-fused dipyrromethene and the subsequent retro Diels-Alder reaction. These BODIPYs exhibited the absorptions and the fluorescence emissions over wide range of visible-near-infrared region at 500-800 nm. BODIPYs composed of two fluorantho[8,9-f]isoindoles absorbed and emitted at red-region over 750 nm with absolute fluorescence quantum yield (Φ_f) of ca. 0.3, although they are unstable under air in room light. BODIPY composed fluorantho[8,9-f]isoindole and acenaphtho[1,2-c]pyrrole was stable and showed a bright fluorescence emission at 695 nm with high Φ_f of 0.70.     

Synthesis and characterisation of photopolymerisable liquid crystals based on the π-extended fluorene core and their corresponding non-reactive analogues

We have synthesised a series of new reactive mesogens with photopolymerisable di-acrylates and their corresponding non-reactive analogues based on the π-conjugated aromatic core, fluorene (F)-di-[thiophene (T)-benzene (B)], using the Stille and Suzuki coupling reaction. The effect of lateral alkyl chains on the 9-position of the central fluorene moiety as well as α, ω- side alkyl chains attached to the π-conjugated aromatic core on the mesomorphism was investigated by utilising differential scanning calorimetry (DSC) and polarising optical microscopy (POM). A wide angle X-ray scattering (WAXS) study at the various temperatures was also carried out to reveal phase structures. Photopolymerisable di-acrylates connected directly to the rigid aromatic core showed higher phase transition temperatures, probably due to the induced dipole moment in comparison with those of a non-reactive methyl–ether counterpart.     

Synthesis and properties of conjugated oligoyne-centered π-extended tetrathiafulvalene analogues and related macromolecular systems

Alkynyl-substituted phenyldithiafulvenes have been found to act as versatile building blocks for the construction of π-conjugated molecular rods, shape-persistent macrocycles (SPMs), and conducting polymers. Through Cu(I)-catalyzed alkynyl homocoupling, a series of linear-shaped π-extended tetrathiafulvalene analogues (exTTFs) carrying conjugated oligoynes (ranging from diyne to hexayne) as the central π-bridge were readily prepared. The solid-state properties and reactivities of diyne- and tetrayne-centered exTTFs were characterized by X-ray crystallography and differential scanning calorimetry (DSC), while the electronic properties of the oligoyne-exTTFs were elucidated by UV-vis absorption spectroscopy and density functional theory (DFT) calculations. Cyclic voltammetric analysis showed that the terminal phenyldithiafulvene groups of the oligyne-exTTFs could undergo oxidative coupling to form tetrathiafulvalene vinylogue (TTFV)-linked polymer wires. Through a different synthetic route involving oxidative dimerization and Pd/Cu-catalyzed alkynyl homocoupling, the acetylenic phenyldithiafulvene precursors led to shape-persistent macrocycles where the formation of trimeric macrocycles was particularly favored due to the small ring strain incurred. Finally, spectroelectrochemical studies on these oligoyne and TTF hybrid materials disclosed electrochromic and molecular redox-controlled switching properties applicable to molecular electronic and optoelectronic devices.     

Synthesis and fluorescence properties of DMCX+—a stable oxygen-bridged [4]helicenium dye

A one-step synthesis of the stable [4]helicenium dye, 1,13-dimethoxy-chromeno[2,3,4-kl]xanthenium hexafluorophosphate (DMCX⁺) from the readily available tris(2,6-dimethoxyphenyl)carbenium ion is reported. The crystal structure, the chemical stability, and dye properties of the DMCX⁺ helicenium system are described.     

Synthesis and photochemical reactivity of caged glutamates with a π-extended coumarin chromophore as a photolabile protecting group

‘Caging’ and ‘uncaging’ bioactive substrates are key techniques in studying a wide variety of biological processes. In the present study, two-types of novel caged glutamates with a two-photon absorption (TPA) core, that is, π-extended coumarin, were synthesized and their photochemical release of glutamate was analyzed. The high yields of glutamate (>92%) were observed in the photolysis of compounds 1 and 10, respectively.     

Redox-active π-conjugated polymer nanotubes with viologen for encapsulation and release of fluorescent dye in the nanospace

We report the encapsulation of negatively charged Au nanoparticles and anionic fluorescent (FL) dye in the inner cavity of redox-active cationic polymer nanotubes with viologen via electrostatic interaction and the release of the FL dye from the FL dye confined in the cavity of the polymer nanotubes by electrochemical and chemical reduction.     

Enhancement of fluorescence and lasing properties of covalent bridged fluorescent dye in organic–inorganic hybrid materials

Fluorescent dye (DCM-OH) is covalently bridged to organic–inorganic hybrid material to prevent molecular stacking and to get high fluorescence efficiency and laser property. Novel DCM-OH is synthesized to have hydroxyl functional groups and is bridged to trialkoxysilane as a sol–gel precursor. It participates in sol–gel process to synthesize dye-bridged organic–inorganic hybrid material (dye-bridged hybrimer) and solid-state dye laser sample is ready through polymerization. Fluorescence property of dye-bridged hybrimer is compared with DCM-doped hybrimer that is simple mixture of DCM-OH and hybrimer matrix. The covalently bridged structure of hybrimer with DCM-OH prevented the stacking of fluorescent molecules and enhanced concentration stability. The dye-bridged hybrimer shows much higher fluorescence intensity and low color-shift until it reached high concentration in comparison with DCM-doped system. And the proper lasing property is observed in dye-bridged hybrimer samples.     

Synthesis and optical properties of C3-ethynylated chlorin and π-extended chlorophyll dyads

A C3-ethynylated chlorophyll derivative was prepared from methyl pyropheophorbide-d possessing a 3-formyl group by treatment of Bestmann-Ohira reagent. The mono-substituted acetylene was subjected to coupling reactions at the terminal acetylenic carbon atom to form a series of π-extended chlorophyll derivatives. Replacement of the terminal hydrogen to phenyl, phenylethynyl and C3-chlorin-ethynyl caused red-shifts of their Q_y (0,0) maxima from 675 to 679, 686, and 696 nm, respectively. Optical properties of C3²-substituted 3-ethynyl-chlorophyll derivatives including chlorophyll dyads were investigated in comparison with those of their related compounds. Partial quenching of the fluorescence emission (Φ_flu=0.14) was observed for ortho-substituted dyad, compared to meta- (Φ=0.27) and para-dyads (Φ=0.29), suggesting a through-space interaction between the two chlorin macrocycles in a molecule.     

Synthesis and properties of new π-conjugated pyridine ligands with tetrathiafulvalene derivatives and the rhenium(I) tricarbonyl complexes

Three new π-conjugated pyridine ligands with redox-active tetrathiafulvalene (TTF) derivatives, L₁-L₃, have been synthesized and characterized. The Diels-Alder reaction is the key step for this multistep synthetic strategy. The crystal structures of L₁ and L₃ have been studied. The electrochemical and spectroscopic properties of these new ligands, as well as the corresponding tricarbonyl rhenium(I) complexes (ReL₁(CO)₃X, X = Cl, 5; X = Br, 6) have also been investigated.     

Synthesis,liquid crystalline properties and fluorescence of polycatenar 1,3,4‐oxadiazole derivatives

A series of hexacatenar liquid crystals containing the 1,3,4‐oxadiazole group as rigid core, i.e. 1,4‐bis[(3,4,5‐trialkoxyphenyl)‐1,3,4‐oxadiazolyl]‐ benzene (P‐P‐oxd‐n), were designed and synthesised. Based on a detailed study of their thermotropic phase behaviour and mesophase structures, it was revealed that columnar phases are generated in these materials. Furthermore, combination of experimental and calculated results enabled a proposal for the molecular packing in the mesophase. The photoluminescent properties of these materials were examined using P‐P‐oxd‐8 as an example. A strong blue light emission (λ_max = 456 nm) was observed in P‐P‐oxd‐8 and a higher quantum yield was obtained in dilute chloroform solution.     

Synthesis and characterization of π-extended thienoacenes with up to 13 fused aromatic rings

π-Extended thienoacenes that comprise alternatively arranged anthracene and thieno[3,2-b]thiophene moieties and have 8 or 13 aromatic rings were synthesized. The delocalization of their HOMO and LUMO orbitals is over the entire molecules, and low-lying HOMO levels endow them good stability.     

Synthesis and properties of the first Möbius annulenes

Heilbronner in 1964 predicted that annulenes with ".. a planar perimeter of N=4r AO's, which would yield an open shell configuration when occupied by 4r electrons, can be twisted into a closed shell M?bius strip perimeter without loss in pi electron energy". We have been able to synthesize the first [4n]annulene with such a M?bius topology and now present further M?bius isomers and the details of their preparation as stable compounds. To address the question whether the twist in the pi system has an effect on the properties we systematically investigate energy, geometry and magnetic parameters of a large number isomers of [16]annulenes. The M?bius twisted annulenes are consistently more aromatic than the non-twisted isomers. This is true for the parent as well as our benzoannelated systems. Our results are in contrast to those published recently by C. Castro, W. L. Karney, P. von R. Schleyer et al.     

Synthesis of highly soluble fluorescent π-extended 2-(2-thienyl)benzothiazole derivatives via oxidative cyclization of 2-thienylthioanilide as the key step

In this Letter, we synthesize highly soluble push–pull type fluorescent 2-(2-thienyl)benzothiazole dyes and evaluate their photophysical properties. The key step is the synthesis of 2-(5′-bromothien-2′-yl)-6-alkoxybenzothiazole (2) via oxidative cyclization of 2-thienylthioanilide using PhI(OAc)₂ as the oxidant. The target dyes could be easily synthesized by the Suzuki–Miyaura cross-coupling reaction of 2 and an appropriate π-donor. The photophysical properties of the 2-thienylbenzothiazole chromophore were controlled by the π-donor moiety. It was found that 2 exhibited large Stokes shifts (5345 cm⁻¹) and a high quantum efficiency for fluorescence (Φ_F = 0.94 in CH₂Cl₂). Therefore, it can be expected to be a useful photofunctional material in liquid crystal laser dyes and nonlinear optical materials.     

Synthesis and spectral properties of π-extended rhodamine hydrazide probe for the detection of Hg2+EI北大核心CSCD

The π-extended rhodamine derivative aminobenzopyranoxanthene ABPX was synthesized by condensation of 2-4-diethylamino-2-hydroxybenzoylbenzoic acid with resorcinol in H2 SO4 solutionthen the derivative reacted with hydrazine monohydrate to obtain ABPX-hydrazideABPX-hyand its structure was characterized by ESI-MSFT-IR and NMR spectroscopy. The UV-Vis adsorption spectra at 500-600 nm tended to increase in the presence of Hg2+ in ABPX-hy ethanol solutionand the color of the solution changed from colorless to pink and gradually deepenedenabling visual colorimetric detection of Hg2+ by naked eye. Under the coexistence of 10 common metal ionsthe recognition of Hg2+ at 533 nm showed good anti-interference sensing performance. The absorption intensity of ABPX-hy had a good exponential relationship with the addition of Hg2+. The continuous coordination of Hg2+ to the N and O binding sites of ABPX-hy formed 21 stoichiometry of the ABPX-hy-Hg2+ complex. The orbital energy and spatial distribution levels of the closed-cycle to the open-cycle form were obtained by density functional theoryDFTcalculation. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Spectroscopic and electrochemical sensing of lanthanides with π-extended chromophores incorporating ferrocenes and a coordinative end

In this study, we report the synthesis and characterization of three novel "push-pull" chromophores, in which multiple phenylenevinylene units are endcapped by ferrocene as donor units and malonate moieties as acceptor units. These chromophores have spectroscopic and electrochemical characteristics which consistently change according to the extension of the conjugated bridge, thus to the variation of the HOMO-LUMO band gap. The 1,3-dicarbonyl units, directly incorporated into the conjugated molecular structures, are able to coordinate Lewis acid-like cations, such as lanthanides, as confirmed by UV/Vis, (1)H NMR and cyclic voltammetry studies. The UV/Vis spectroscopic response upon complexation with Sc(3+) or Eu(3+) as the triflate salts is rather unselective and nonlinear in going from the least to the most π-extended chromophore. Binding studies in MeCN, analyzed via equilibrium-restricted factor analysis, give values between log K(a) = 1.21 and 3.07 and affirm a 1?:?1 stoichiometry of the host:guest complexes in all cases. On the other hand, cyclic voltammetry reveals a selectivity in the response to Sc(3+) coordination over Ln(3+) (Eu(3+), but also Lu(3+) and Er(3+) were tested) for the two shorter chromophores, whereas the ligand with the longest π-bridge is able to sense Er(3+) (ΔE(1/2) complexed/uncomplexed chromophore = 20 mV) selectively over the other lanthanides.     

Synthesis of a flavonoid fluorescent probe for the detection of sulfur dioxide derivatives and cell imagingEI北大核心CSCD

A novel fluorescent probe HMQC was synthesized for HSOf detection by coupling flavonoid derivatives with 3-quinoline salt. In PBS buffer solution, the probe showed high selectivity, good sensitivity (58 nmol/L) and rapid response (150 s) for the detection of HSO3−. The possible sensing mechanism of the probe was discussed by nuclear magnetic hydrogen spectroscopy, mass spectrometry and theoretical calculation, indicating that the addition reaction between HSO3− and the C=C bond of the probe led to the fluorescence enhancement. The probe HMQC could be used for the detection of HSO3− in living cells, making it to be a promising tool for delecting HSO3−. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Comparison of fluorescence and QCM technologies: Example of explosives detection with a π-conjugated thin film

A π-conjugated compound was synthesized as a sensitive material for explosives detection. The detection of vapors of 2,4-dinitrotoluene was demonstrated with quartz crystal microbalance (QCM) and fluorescence transduction methods. The fluorescence intensity monitoring shows a higher sensitivity and selectivity than the monitoring of the QCM frequency. Both methods appear to be synergic when used simultaneously as the sensor helps to discriminate interferent vapors from nitroaromatics.