J-Aggregates Formed by NaCl Treatment of Aza-Coating Heptamethine Cyanines and Their Application to Monitoring Salt Stress of Plants and Promoting Photothermal Therapy of Tumors.

The cationic nature of heptamethine cyanines gives them the capacity to form aggregates with salts by electrostatic interactions. In this work, NaCl promoted J-aggregate formation of aza-coating heptamethine cyanines is explored. NaCl can induce the N-benzyloxycarbonyl Cy-CO2 Bz to assemble into a J-aggregate having an absorption at 890 nm. Its excellent fluorescence response to NaCl implies that it has great potential for use as a probe for tracing salt stress in plants. Moreover, NaCl also promotes formation of J-aggregates from the N-ethyloxycarbonyl Cy-CO2 Et. The aggregate shows an intense absorption at 910 nm compared to the monomer which absorbs at 766 nm. Its J-aggregated form can serve as a photothermal agent. And the photothermal conversion efficiency is increased from 29.37 % to 57.59 %. This effort leads to the development of two applications of new cyanine J-aggregates including one for tracing salt stress of plants and the other for promoting photothermal therapy of tumors.

Near-Infrared Thienoisoindigos with Aggregation-Induced Emission: Molecular Design, Optical Performance, and Bioimaging Application.

Thienoisoindigo as a popular conjugated skeleton has been constantly applied in the construction of organic optoelectronic materials. Exploring its new applications in fluorescent sensors and bioimaging is helpful to extend its potential. In this work, a thienoisoindigo fluorophore was first selected as a building block to be applied in the construction of the near-infrared fluorescent materials with an aggregation-induced emission manner through introducing triarylamine, thiophene-bridged triarylamine, and N,N-dimethyl styrene, respectively. These fluorescent agents showed the near-infrared emission and possessed typical aggregation-induced emission behavior. Although they had low band gaps and near-infrared emission, they presented remarkable photostability. Especially, thiophene-bridged triarylamine and N,N-dimethyl styrene-coated thienoisoindigos exhibited strong lysosomal targeting capability, and they could also serve for fluorescence imaging in vivo.

Osmaindenes: Synthesis and Reversible Mechanochromism Characteristics.

A series of novel osmaindenes 1-6 bearing different substituents (CF3 , H, I, Br, OCH3 , N(Ph)2 ) has been synthesized by nucleophilic reaction of water with the corresponding aromatic osmanaphthalyne complexes. All osmaindenes 1-6 have been characterized by elemental analysis (EA) and nuclear magnetic resonance (NMR) spectroscopy, although the low solubilities of 3 and 4 precluded the accumulation of their 13 C NMR spectra. Osmaindenes 2, 3 and 5 have also been characterized by single-crystal X-ray diffraction analysis. Subsequently, through solid-state fluorescence spectroscopy, mechanochromic studies, and powder X-ray diffraction (XRD) analysis, we found that osmaindenes 1-6 fluoresce at wavelengths in the range 500-800 nm, while also displaying reversible mechanochromic properties. The solid-state fluorescence emission of 1 after grinding extends into the near-infrared region. This research provides new insight into the design and synthesis of metallic materials with excellent mechanochromic properties.

Nucleophilic Reactions of Osmanaphthalynes with PMe3 and H2 O.

Members of a new class of complexes, 2(CF3 ), 2(H), 2(Br), 2(I), and 2(OCH3 ), have been synthesized in a one-pot method involving the treatment of osmanaphthalynes bearing corresponding substituents (1(CF3 ), 1(H), 1(Br), 1(I), and 1(OCH3 )) with trimethylphosphine (PMe3 ) and water. The main reaction process involves two steps, namely a ligand-exchange with trimethylphosphine and nucleophilic addition of water to the Os≡C bond of the osmanaphthalyne. The substituents have a significant influence on the rate of the reaction, as befits a nucleophilic addition. Fortunately, the key intermediate [1(OCH3 )]' could be successfully captured, and the detailed reaction mechanism has been explored with the aid of density functional theory (DFT) calculations, which were in excellent agreement with the experimental findings. All of the target complexes have been fully characterized by 1 H, 31 P{1 H}, and 13 C{1 H} NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis.

Electronic Properties of Oxidized Cyclometalated Diiridium Complexes: Spin Delocalization Controlled by the Mutual Position of the Iridium Centers.

Four cyclometalated diiridium complexes, with IrCp*Cl (Cp*=η5 -C5 Me5 - ) termini bridged by 1,4- and 1,3-bis(p-tolyliminoethyl)benzene (1, 2), or 1,4- and 1,3-bis(2-pyridyl)benzene (3, 4), were prepared and characterized by nuclear magnetic resonance (NMR) spectroscopy and single-crystal X-ray diffraction (complexes 1, 2, and 4). The two iridium centers in complexes 1 and 3 are thus bound at the central benzene ring in the para-position (trans-Ir2), whereas those in complexes 2 and 4 are in the meta-position (cis-Ir2). Cyclic voltammograms of all four complexes show two consecutive one-electron oxidations. The potential difference between the two anodic steps in 1 and 3 is distinctly larger than that for 2 and 4. The visible-near-infrared (NIR)-short-wave infrared (SWIR) absorption spectra of trans-Ir2 monocations 1+ and 3+ are markedly different from those of cis-Ir2 monocations 2+ and 4+ . Notably, strong near-infrared electronic absorption appears only in the spectra of 1+ and 3+ whereas 2+ and 4+ absorb only weakly in the NIR-SWIR region. Combined DFT and TD-DFT calculations have revealed that (a) 1+ and 3+ (the diiridium-benzene trans-isomers) display the highest occupied spin-orbitals (HOSO) and the lowest unoccupied spin-orbital (LUSO) evenly delocalized over both molecule halves, and (b) their electronic absorptions in the NIR-SWIR region are attributed to mixed metal-to-ligand and ligand-to-ligand charge transfers (MLCT and LLCT). In contrast, cis-isomers 2+ and 4+ do not feature this stabilizing π-delocalization but a localized mixed-valence state showing a weak intervalence charge-transfer (IVCT) absorption in the SWIR region.

Near-infrared heptamethine cyanines (Cy7): from structure, property to application.

Heptamethine cyanine dyes (Cy7) have attracted much attention in the field of biological application due to their unique structure and attractive near infrared (NIR) photophysical properties. In this review, the influences of different modification sites on the absorption characteristics, photostability, Stokes shift, fluorescence characteristics, water solubility, and singlet oxygen generation efficiency of this class of dyes are summarized, and the application development of the corresponding dyes in the field of biological application is introduced, which will provide a reference for the optimization and improvement of heptamethine cyanine dyes in the future.

Ameliorative effects of the traditional Chinese medicine formula Qing-Mai-Yin on arteriosclerosis obliterans in a rabbit model.

CONTEXT: Qing-Mai-Yin (QMY) is a clinically used herbal formula for treating arteriosclerosis obliterans (ASO). OBJECTIVE: To evaluate the chemical constituents and effects of QMY on ASO rabbit model. MATERIALS AND METHODS: Forty-eight New Zealand rabbits were divided into six groups (n = 8): normal (normal rabbits treated with 0.5% CMC-Na), vehicle (ASO rabbits treated with 0.5% CMC-Na), positive (simvastatin, 1.53 mg/kg), and QMY treatment (300, 600, and 1200 mg/kg). ASO rabbit model was prepared by high fatty feeding, roundly shortening artery, and bovine serum albumin immune injury. QMY (300, 600 and 1200 mg/kg) was orally administered for 8 weeks. The effects and possible mechanisms of QMY on ASO rabbits were evaluated by pathological examination, biochemical assays, and immunohistochemical assays. The compositions of QMY were analysed using HPLC-Q-TOF-MS/MS analysis. RESULTS: Compared to the vehicle rabbit, QMY treatment suppressed plaque formation and intima thickness in aorta, and decreased intima thickness, whereas increased lumen area of femoral artery. Additionally, QMY treatment decreased TC, TG and LDL, decreased CRP and ET, and increased NO and 6-K-PGF1α in serum. Furthermore, the potential mechanisms studied revealed that QMY treatment could suppress expression of TNF-α, IL-6, ICAM-1 and NF-κB in endothelial tissues, and increase IκB. In addition, HPLC analysis showed QMY had abundant anthraquinones, stilbenes, and flavonoids. CONCLUSION: QMY has ameliorative effects on ASO rabbit, and the potential mechanisms are correlated to reducing inflammation and down-regulating NF-κB. Our study provides a scientific basis for the future application and investigation of QMY.

Tissue Imaging of Glutathione-Specific Naphthalimide-Cyanine Dye with Two-Photon and Near-Infrared Manners.

Molecular probes suitable for different fluorescence imaging technologies can meet the requirements of different scientific research in biological applications. In this work, a naphthalimide-cyanine-based sulfonamide was used to specifically visualize the glutathione of mouse tissues with a two-photon manner for the naphthalimide moiety and a near-infrared manner for the cyanine moiety, respectively. The results showed that this probe served as a dual-model tissue-imaging agent for visualization of glutathione with around 200 µm imaging depth in a two-photon manner and 120 µm imaging depth in a near-infrared manner, which provided a model for tissue imaging in the visible and near-infrared channels.

Fluorophore-Labeling Tetraphenylethene Dyes Ranging from Visible to Near-Infrared Region: AIE Behavior, Performance in Solid State, and Bioimaging in Living Cells.

Functional molecules with aggregation-induced emission (AIE) have lately received the most attention due to their versatile functions in many fields. In this work, tetraphenylethene (TPE) as one of the most discussed AIE system was installed on different fluorophores including dansyl, naphthalimide, 4-nitro-1,2,3-benzoxadiazole (NBD), borondipyrromethene, and hemicyanine to afford a series of new fluorescent dyes, whose spectra covered the fluorescence region of the visible to near-infrared emission. Especially, these tetraphenylethene-containing compounds all exhibited AIE behavior. In solid state, they presented multiple colors including blue, orange, red, crimson, and NIR (near-infrared emission). It was worth mentioning that the dansyl- and NBD-coated TPEs exhibited obvious mechanoresponsive luminescence phenomena. Moreover, these AIE-based TPEs displayed a good bioimaging performance in living cells. This work will be helpful for designing functional AIE dyes with different fluorescence emission.

Anion-Binding-Induced Electrochemical Signal Transduction in Ferrocenylimidazolium: Combined Electrochemical Experimental and Theoretical Investigation.

Five ferrocene alkymethylimidazolium cations 1a⁻1d and 2 with different alkyl spacer lengths were reinvestigated using voltammetry and density functional theory (DFT) calculations. The voltammetric responses of ligand 2 toward various anions are described in detail. An interesting and unprecedented finding from both experimental and theoretical studies is that coupled electron and intramolecular anion (F-) transfer may be present in these molecules. In addition, it was also observed that, in these studied molecules, the electrostatic attraction interaction toward F- would effectively vanish beyond 1 nm, which was previously reported only for cations.

A Visible-Light-Induced Strategy To Construct Osmanaphthalynes, Osmaanthracyne, and Osmaphenanthryne.

Herein, we describe a novel, green, and efficient synthesis of a series of different substituted osmanaphthalynes (including -H, -Br, -I, -CH3 and -CF3 ) and the first examples of the preparation of α-osmaanthracyne and α-osmaphenanthryne by means of a visible light-induced intramolecular cyclization reaction of their corresponding osmium hydrido alkenylcarbyne complexes. This visible-light-driven method provides an efficient and straightforward approach to afford the desired fused metal heterocyclic complexes constructed with an Os atom as the metal center in high yield under mild conditions.

Diphenylamine-Substituted Osmanaphthalyne Complexes: Structural, Bonding, and Redox Properties of Unusual Donor-Bridge-Acceptor Systems.

Diarylamine-substituted osmanaphthalyne complexes that feature two redox centers linked by the rigid skeleton of the metallacycle (C^C+ ), specifically, [OsCl2 (PPh3 )2 {(C^C+ )NAr2 }][BF4 - ] (Ar=Ph (1 a), p-MeOPh (1 b)) and their open-ring precursors [OsHCl2 (PPh3 )2 {(≡C-C(PPh3 + )=CHPh)NR2 }][BF4 - ] (Ar=Ph (2 a), p-MeOPh (2 b)), were successfully synthesized and characterized by 1 H, 13 C, and 31 P NMR spectroscopy, ESI-MS, and elemental analysis. The solid-state molecular structures of complexes 1 a and 2 a were ascertained by single-crystal X-ray diffraction. The Os≡C bond length in both complexes 1 a and 2 a fell within the range reported for similar osmanaphthalynes and osmium carbyne complexes, respectively. The structural parameters determined for complex 1 a, which were successfully reproduced by theoretical calculations, point to a π-delocalized metallacycle structure. The purple color of compounds 1 a and b was explained by the diarylamine→Os(metallacycle) charge-transfer absorption in the visible region. The neutral, one-electron-oxidized and one-electron-reduced states of compounds 1 a, b, and a reference complex that lacked the diarylamine substituent, [OsCl2 (PPh3 )2 {(C^C+ )}][BF4 - ] (1'), were investigated by cyclic and square-wave voltammetry, UV/Vis/NIR spectroelectrochemistry, and DFT calculations. The spin density in singly oxidized complexes [1 a]+ and [1 b]+ predominantly resided on the aminyl segment, with osmium involvement controlled by the diphenylamine substitution. Spin density in stable, singly-reduced [1']- was distributed mainly over the osmanaphthalyne metallacycle.

A Highly Reversible Mechanochromic Difluorobenzothiadiazole Dye with Near-Infrared Emission.

A difluorobenzothiadiazole-based fluorescent material with a D-π-A-π-D structure exhibits a reversible mechanofluorochromic characteristic in the solid state. Its red fluorescent emission switches to near-infrared fluorescence upon mechanical stimulation, but recover after fuming the ground solid powder with dichloromethane.

Excited-State Electronic Asymmetry Prevents Photoswitching in Terthiophene Compounds.

The diarylethene moiety is one of the most extensively used switches in the field of molecular electronics. Here we report on spectroscopic and quantum chemical studies of two diarylethene-based compounds with a non- C3-symmetric triethynyl terthiophene core symmetrically substituted with RuCp*(dppe) or trimethylsilyl termini. The ethynyl linkers are strong IR markers that we use in time-resolved vibrational spectroscopic studies to get insight into the character and dynamics of the electronically excited states of these compounds on the picosecond to nanosecond time scale. In combination with electronic transient absorption studies and DFT calculations, our studies show that the conjugation of the non- C3-symmetric triethynyl terthiophene system in the excited state strongly affects one of the thiophene rings involved in the ring closure. As a result, cyclization of the otherwise photochromic 3,3″-dimethyl-2,2':3',2″-terthiophene core is inhibited. Instead, the photoexcited compounds undergo intersystem crossing to a long-lived triplet excited state from which they convert back to the ground state.

Regulating glutathione-responsiveness of naphthalimide-based fluorescent probes by an oxidation strategy.

Two naphthalimide-based fluorescent probes containing a thiomorpholine (Np-NS) or a sulfoxide-morpholine (Np-NSO) component are reported. The morpholine unit of non-fluorescent Np-NS and Np-NSO can transform into sulphone-morpholine and be accompanied by blue fluorescence upon oxidative stress, ascribed to the formation of sulphone-morpholine on probes. This sensing behavior displays that they can selectively respond to glutathione to generate a green emission by a sulfonamide-based detection moiety both in vitro and in living cells. Interestingly, the different oxidation states of a sulphur atom on a thiomorpholine ring can be utilized to regulate responsiveness of these probes towards glutathione. Such an oxidation strategy would provide a possibility for enhancing the response rate.

The Role of Through-Space Interactions in Modulating Constructive and Destructive Interference Effects in Benzene.

Quantum interference effects, whether constructive or destructive, are key to predicting and understanding the electrical conductance of single molecules. Here, through theory and experiment, we investigate a family of benzene-like molecules that exhibit both constructive and destructive interference effects arising due to more than one contact between the molecule and each electrode. In particular, we demonstrate that the π-system of meta-coupled benzene can exhibit constructive interference and its para-coupled analog can exhibit destructive interference, and vice versa, depending on the specific through-space interactions. As a peculiarity, this allows a meta-coupled benzene molecule to exhibit higher conductance than a para-coupled benzene. Our results provide design principles for molecular electronic components with high sensitivity to through-space interactions and demonstrate that increasing the number of contacts between the molecule and electrodes can both increase and decrease the conductance.

Bonding and Electronic Properties of Linear Diethynyl Oligothienoacene-Bridged Diruthenium Complexes and Their Oxidized Forms.

A series of five diruthenium diethynyl complexes based on α,ß-fused oligothienoacenes in the core of the bridging ligands [{Ru(dppe)Cp*}2(µ-C≡C-L-C≡C)] [dppe = 1,2-bis(diphenylphosphino)ethane, Cp* = η5-C5Me5; L = thieno[3,2-b]thiophene (4), thieno[2,3-b]thiophene (5), 3,4-dimethylthieno[2,3-b]thiophene (6), dithieno[3,2-b:2',3'-d]thiophene (7), and thieno[3,2-b]thieno[2',3':4,5]thieno[2,3-d]thiophene (8)] have been synthesized and fully characterized electrochemically and spectroscopically. Elongation of the redox noninnocent oligothienoacene bridge core causes a smaller potential difference between the initial two anodic steps, not seen for free dialkyl oligothienoacenes, and increased positive charge delocalization over the conjugated bridge backbone. The highest occupied molecular orbital of the parent complexes resides predominantly on the oligothienoacene core, with strong participation of the ethynyl linkers and slightly smaller contribution from the metallic termini. This bonding character makes the initial one-electron oxidation symmetrical, as revealed by combined voltammetric and spectroscopic (IR, UV-vis-near-IR, and electron paramagnetic resonance) methods as well as density functional theory (DFT) and time-dependent DFT calculations of truncated and selected nontruncated models of the studied series. The remarkable gradual appearance of two C≡C stretching absorptions in the IR spectra of the monocationic diethynyl complexes is ascribed to increasing vibronic coupling of the IR-forbidden νs(C≡C) mode of the oxidized -[C≡C-core-C≡C]+- bridge with a low-lying π-π*(intrabridge)/metal-to-ligand charge-transfer electronic transition in the near-to-mid-IR spectral region.

Multistep Oxidation of Diethynyl Oligophenylamine-Bridged Diruthenium and Diiron Complexes.

Homo-dinuclear nonlinear complexes [{M(dppe)Cp*}2{µ-(-C≡C)2X}] (dppe = 1,2-bis(diphenylphosphino)ethane; Cp* = η5-C5Me5; X = triphenylamine (TPA), M = Ru (1a) and Fe (1b); X = N,N,N',N'-tetraphenylphenylene-1,4-diamine (TPPD), M = Ru (2a)) were prepared and characterized by 1H, 13C, and 31P NMR spectroscopy and single-crystal X-ray diffraction (1a, 2a). Attempts to prepare the diiron analogue of 2a were not successful. Experimental data obtained from cyclic voltammetry, square wave voltammetry, UV-vis-NIR (NIR = near-infrared) spectro-electrochemistry, and very informative IR spectro-electrochemistry in the C≡C stretching region, combined with density functional theory calculations, afford to make an emphasizing assessment of the close association between the metal-ethynyl termini and the oligophenylamine bridge core as well as their respective involvement in sequential one-electron oxidations of these complexes. The anodic behavior of the homo-bimetallic complexes depends strongly both on the metal center and the length of the oligophenylamine bridge core. The poorly separated first two oxidations of diiron complex 1b are localized on the electronically nearly independent Fe termini. In contrast, diruthenium complex 1a exhibits a significantly delocalized character and a marked electronic communication between the ruthenium centers through the diethynyl-TPA bridge. The ruthenium-ethynyl halves in 2a, separated by the doubly extended and more flexible TPPD bridge core, show a lower degree of electronic coupling, resulting in close-lying first two anodic waves and the NIR electronic absorption of [2a]+ with an indistinctive intervalence charge transfer character. Finally, the third anodic waves in the voltammetric responses of the homo-bimetallic complexes are associated with the concurrent exclusive oxidation of the TPA or TPPD bridge cores.

An active catalytic system for Suzuki-Miyaura cross-coupling reactions using low levels of palladium loading.

An easily available Pd(OAc)2/(2-(anthracen-9-yl)-1H-inden-3-yl) dicyclohexylphosphine/toluene/iPrOH/water catalytic system was developed, which shows high catalytic activity in the Suzuki-Miyaura cross-coupling reactions of a diverse array of aryl and heteroaryl chlorides with Pd loadings down to 0.01 mol%.

Synthesis of rotaxanes and catenanes using an imine clipping reaction.

Supramolecular chemistry and self-assembly provide a valuable chance to understand the complicated topological structures on a molecular level. Two types of classical mechanically interlocked molecules, rotaxanes and catenanes, possess non-covalent mechanical bonds and have attracted more attention not only in supramolecular chemistry but also in the fields of materials science, nanotechnology and bioscience. In the past decades, the template-directed clipping reaction based on imine chemistry has become one of the most efficient methods for the construction of functionalized rotaxanes and catenanes. In this review, we outlined the main progress of rotaxanes and catenanes using the template-directed clipping approach of imine chemistry. The review contains the novel topological structures of rotaxanes and catenanes, functions and applications.