Stable Red‐Emissive Cationic Dithienotropylium Dyes

A series of thiophene‐fused tropylium ions, containing various electron‐donating amino groups at the terminal positions, was synthesized. The fusion of the thiophene rings, as well as the presence of the terminal amino groups endows the cationic tropylium ion with excellent stability and high pK_R⁺ values. X‐ray crystallographic analysis of these compounds revealed a pronounced quinoidal character for the amino‐substituted dithienotropylium skeletons. These compounds exhibit attractive photophysical properties such as strong absorption in the visible region combined with red fluorescence. Theoretical calculations suggested that the 3,3′‐bithiophene substructure should be crucial for attaining these photophysical properties.     

Synthesis and Exploration of Ladder‐Structured Large Aromatic Dianhydrides as Organic Cathodes for Rechargeable Lithium‐Ion Batteries

Compared to anode materials in Li‐ion batteries, the research on cathode materials is far behind, and their capacities are much smaller. Thus, in order to address these issues, we believe that organic conjugated materials could be a solution. In this study, we synthesized two non‐polymeric dianhydrides with large aromatic structures: NDA‐4N (naphthalenetetracarboxylic dianhydride with four nitrogen atoms) and PDA‐4N (perylenetetracarboxylic dianhydride with four nitrogen atoms). Their electrochemical properties have been investigated between 2.0 and 3.9 V (vs. Li⁺/Li). Benefiting from multi‐electron reactions, NDA‐4N and PDA‐4N could reversibly achieve 79.7 % and 92.3 %, respectively, of their theoretical capacity. Further cycling reveals that the organic compound with a relatively larger aromatic building block could achieve a better stability, as an obvious 36.5 % improvement of the capacity retention was obtained when the backbone was switched from naphthalene to perylene. This study proposes an opportunity to attain promising small‐molecule‐based cathode materials through tailoring organic structures.     

Investigation of collision‐induced dissociations involving odd‐electron ion formation under positive electrospray ionization conditions using accurate mass

Collision induced dissociation (CID) has been extensively used for structure elucidation. CID in the electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) modes has been found to generate mostly even‐electron fragment ions while it has been occasionally reported to form odd‐electron free radical ions. However, the structural requirements and the fragmentation mechanisms for free‐radical CIDs have not been well characterized in the literature. For this purpose, we studied a series of aromatic and non‐aromatic compounds such as sulfonamides, N‐aryl amides, tert‐butyl‐substituted aromatic compounds, aryl alkyl ethers, and O‐alkyl aryl oximes using the LTQ? and LTQ Orbitrap? linear ion trap mass spectrometers. The accurate measurement of the fragment ion masses established the unambiguous assignment of the fragment structures resulting from the test compounds. Our results showed that free radical fragmentation is structure dependent and is to a large extent correlated with the neighboring groups in the structures that stabilize the newly formed free radical ions. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and chirooptical properties of optically active poly(ester imide)s based on axially asymmetric 1,1′‐binaphthyls

A series of optically active poly(ester imide)s (PEsI's) has been synthesized by the polycondensation reactions of new axially asymmetric dianhydrides, that is, (R)‐2,2′‐bis(3,4‐dicarboxybenzoyloxy)‐1,1′‐binaphthyl dianhydride and (S)‐2,2′‐bis(3,4‐dicarboxybenzoyloxy)‐1,1′‐binaphthyl dianhydride, and various diamines with aromatic, semiaromatic, and aliphatic structures. The polymers have inherent viscosities of 0.45–0.70 dL/g, very good solubility in common organic solvents, glass‐transition temperatures of 124–290 °C, and good thermal stability. Wide‐angle X‐ray crystallography of these polymers shows no crystal diffraction. In comparison with model compounds, an enhanced optical rotatory power has been observed for the repeat unit of optically active PEsI's based on aromatic diamines, and it has been attributed to a collaborative asymmetric perturbation of chiral 1,1′‐binaphthyls along the rigid backbones. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4318–4326, 2004     

Evidence that protons can be the active catalysts in Lewis acid mediated hetero-Michael addition reactions

The mechanism of Lewis acid catalysed hetero‐Michael addition reactions of weakly basic nucleophiles to α,β‐unsaturated ketones was investigated. Protons, rather than metal ions, were identified as the active catalysts. Other mechanisms have been ruled out by analyses of side products and of stoichiometric enone–catalyst mixtures and by the use of radical inhibitors. No evidence for the involvement of π‐olefin–metal complexes or for carbonyl–metal‐ion interactions was obtained. The reactions did not proceed in the presence of the non‐coordinating base 2,6‐di‐tert‐butylpyridine. An excellent correlation of catalytic activities with cation hydrolysis constants was obtained. Different reactivities of mono‐ and dicarbonyl substrates have been rationalised. A ¹H NMR probe for the assessment of proton generation was established and Lewis acids have been classified according to their propensity to hydrolyse in organic solvents. Brønsted acid‐catalysed conjugate addition reactions of nitrogen, oxygen, sulfur and carbon nucleophiles are developed and implications for asymmetric Lewis acid catalysis are discussed.     

Synthesis and properties of all members of methylated tropylium ions

An members of the methylated tropylium perchlorates have been synthesized and their properties (UV absorptions, ¹H NMR spectra, and charge-transfer spectra with pyrene) determined. The methylated tropylium ions other than the hexa- and hepta-methyl homologues have been prepared by abstracting a hydride ion with trityl perchlorate from the corresponding methylated tropilidenes. The preparation of the hexa- and hepta-methyltropylium ions has been effected by utilizing phosphorus pentachloride as the hydride-abstraction reagent. The methylated tropilidenes have been prepared via one of the three known routes, i.e. the ring expansion of methylated benzenes with diazomethane (Route 1) or with ethyl diazoacetate (Route 2), and the cycloaddition of cyclopropene or methylcyclopropenes with methylated thiophene 1,1-dioxides accompanied with the exclusion of sulfur dioxide (Route 3). The methyl ¹H NMR chemical-shift values have been assigned, partly with the aid of the Me ¹³C NMR chemical-shift data for the tropylium ions containing the Me groups on contiguous ring-carbons (3a, 4a, 5a, 6 and 7). The transition energy for the charge-transfer band of the tropylium ions with pyrene increases with the increase in the number of the Me group, indicating that the more methylated the tropylium ion, the more stable is the ion.     

Noncovalent complex formation of tetratosylated resorcarene with aromatic,aliphatic, and cyclic alkyl ammonium ions: a mass spectrometric study of complex properties

The ability of tetratosylated resorcarene to form complexes with aromatic ammonium ions was investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The formation of noncovalent complexes, [1+guest]⁺ and [1 · 1+guest]⁺, as observed with singly charged aromatic anilinium and phenylene aminoammonium guests. Comparison of the complexation efficiencies of the aromatic and aliphatic ammonium ions showed the importance of proton affinity of conjugate amines in complex formation. In collision‐induced dissociation experiments, gas‐phase stability was found to be lower for complexes formed with aromatic ions and this behavior was not found to depend on the proton affinity of conjugate amines. Fast oxidation of the para and ortho aminoammonium ions and complexation of these ions with tetratosylated resorcarene was observed. Copyright © 2005 John Wiley & Sons, Ltd.     

Heterocyclic fused tropylium ions VII. On the synthesis of 9H-dithieno[2,1 -b:4,5-c′]tropylium fluoborate and 4H-dithieno[1,2-b:4,5-c′]tropylium fluoborate

9H-Dithieno[2,1 -b:4,5-c′]tropylium ion (III) and 4ii-dithieno[1,2-b:4,5-c′]tropylium ion (IV) have been synthesized by ring-closure of 1-(4-carboxy-3-thienyl)-2-(3′-thienyl)ethane (IX) and 1-(4-carboxy-3-thienyl)-2-(2′-thienyl)ethane (XVI), respectively, followed by bromination-debrom-ination to 9H-cyclohepta[2,1-b:4,5-c′] dithiophen-9-one (XI) and 4H-cyclohepta[1,2-b:4,5-c′]-dithiophen-4-one (XVIII), and finally by reduction and hydride transfer. The tropylium ions III and IV were less stable than the [b,b′]-fused isomers previously studied.     

A Novel Thin‐Film Copper Array Based on an Organic/Inorganic Sensor Hybrid: Microfabrication,Potentiometric Characterization,and Flow‐Injection Analysis Application

A first step towards the microfabrication of a thin‐film array based on an organic/inorganic sensor hybrid has been realized. The inorganic microsensor part incorporates a sensor membrane based on a chalcogenide glass material (Cu‐Ag‐As‐Se) prepared by pulsed laser deposition technique (PLD) combined with an PVC organic membrane‐based organic microsensor part that includes an o‐xylyene bis(N,N‐diisobutyl‐dithiocarbamate) ionophore. Both types of materials have been electrochemically evaluated as sensing materials for copper(II) ions. The integrated hybrid sensor array based on these sensing materials provides a linear Nernstian response covering the range 1×10^?6–1×10^?1 mol L^?1 of copper(II) ion concentration with a fast, reliable and reproducible response. The merit offered by the new type of thin‐film hybrid array includes the high selectivity feature of the organic membrane‐based thin‐film microsensor part in addition to the high stability of the inorganic thin‐film microsensor part. Moreover, the thin‐film sensor hybrid has been successfully applied in flow‐injection analysis (FIA) for the determination of copper(II) ions using a miniaturized home‐made flow‐through cell. Realization of the organic/inorganic thin‐film sensor hybrid array facilitates the development of a promising sophisticated electronic tongue for recognition and classification of various liquid media.     

Synthesis and characterization of N‐benzoylated wholly aromatic polyamides from 4,4′‐oxydianilinobis(benzimidoyl) chloride and aromatic dicarboxylic acids

A novel type of polyamides, N‐benzoylated wholly aromatic polyamides, were synthesized by low‐temperature solution polycondensation of a new aromatic bis(imidoyl) chloride, 4,4′‐oxydianilinobis(benzimidoyl) chloride, with aromatic dicarboxylic acids, 4,4′‐oxydibenzoic acid and isophthalic acid. Compared with the conventional all aromatic polyamides and also N‐phenylated wholly aromatic polyamides, these N‐benzoylated aramides exhibit better solubility in organic solvents, lower glass transition temperatures and thermal stability.     

Dicyclohepta[ijkl,uvwx]rubicene with Two Pentagons and Two Heptagons as a Stable and Planar Non‐benzenoid Nanographene

Polycyclic aromatic hydrocarbons with hexagons/pentagons or hexagons/heptagons have been intensively investigated in recent years, but those with simultaneous presence of hexagons, pentagons and heptagons remain rare. In this paper, we report dicyclohepta[ijkl,uvwx]rubicene ( DHR ), a non‐benzenoid isomer of dibenzo[bc,kl]coronene with two pentagons and two heptagons. We developed an efficient and scalable synthetic method for DHR by using Scholl reaction and dehydrogenation. Crystal structure of DHR shows that the benzenoid rings, two pentagons and two heptagons are coplanar. The bond lengths analysis and the ICSS(1)zz and LOL‐π calculations indicate that the incorporation of two formal azulene moieties has an effect on the conjugated structure. The π‐electrons of benzenoid and pentagon rings are more delocalized. Cyclic voltammetry studies indicate that DHR shows multiple oxidation and reduction potentials. Interestingly, DHR exhibits unusual S₀ to S₂ absorption and abnormal anti‐Kasha S₂ to S₀ emission. Moreover, crystals of DHR exhibit semiconducting behaviour with hole mobility up to 0.082 cm² V^?1 s^?1.     

How constant are Ritchie's "constant selectivity relationships"? A general reactivity scale for n-, pi-, and sigma-nucleophiles

The kinetics of 82 reactions of benzhydrylium ions (Ar(2)CH(+)) with n-nucleophiles has been determined at 20 degrees C. Evaluation by the equation log k = s(N + E) delivered the reactivity parameters N and s for 15 n-nucleophiles (water, hydroxide, amines, etc.). All nucleophiles except water (s = 0.89) and (-)SCH(2)CO(2)(-) (s = 0.43) have closely similar slope parameters (0.52 < s < 0.71), indicating that the reactions of most n-nucleophiles approximately follow Ritchie's constant selectivity relationship (s = constant). The different slope parameter for water is recognized as the main reason for the deviations from the Ritchie relationship reported in 1986. Correlation analysis of the rate constants for the reactions of benzhydrylium ions with the n-nucleophiles (except H(2)O) on the basis of Ritchie's equation log k = N(+) + log k(0) yields a statistically validated set of N(+) parameters for Ritchie-type nucleophiles and log k(0) parameters for benzhydrylium ions. The N and s parameters of the n-nucleophiles derived from their reactions with benzhydrylium ions were combined with literature data for the reactions of these nucleophiles with other carbocations to yield electrophilicity parameters E for tritylium, tropylium, and xanthylium ions. While the E parameters for tropylium and xanthylium ions appear to be generally applicable, it is demonstrated that the E parameters of tritylium ions can be used to predict reactivities toward n-nucleophiles as well as hydride transfer rate constants but not rates for the reactions of tritylium ions with pi-nucleophiles. It is now possible to merge the large data sets determined by Ritchie and others with our kinetic data and present a nucleophilicity scale comprising n- (e.g., amines), pi- (e.g., alkenes and arenes), and sigma-nucleophiles (e.g., hydrides).     

A green method for the synthesis of thiochromene derivatives in ionic liquids

Controlling the pH value by changing the negative ion of ionic liquids, the same reactions of aromatic aldehyde, 2‐(2,3‐dihydrothiochromen‐4‐ylidene) malononitrile and malononitrile product unaromatized and aromatized 6H‐benzo[c]thiochromene derivatives in high yields. The nice features of these procedures include mild reactions condition, simple operations, high yields, and environmentally benign. J. Heterocyclic Chem., (2011).     

Chemical and thermal stability of N‐heterocyclic ionic liquids in catalytic C–H activation reactions

¹H‐NMR spectrum analyses are applied to study the chemical and thermal stability of selected N‐heterocyclic ionic liquids within the reaction system that can highly efficiently activate a C–H bond of methane and convert it into the C–O bond in methanol. Our results indicate that under such reaction conditions involving using a powerful Pt‐based catalyst and strong acidic solvent, the aromatic ring of an imidazolium cation becomes unstable generating an ammonium ion (NH₄⁺). Our results also suggest that the instability of the imidazolium ring is more chemically (participation in reactions) than thermally based. Modifications of the aromatic ring structure such as pyrazolium and triazolium cations can increase the chemical/thermal stability of ionic liquids under these reaction conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Formation and stability of gaseous tolyl ions

Collisional activation mass spectra confirm that tolyl ions can be produced from a variety of CH₃C₆H₄Y compounds. High purity o-, m- and p-tolyl ions are prepared by chemical ionization of the corresponding fluorides (Y=F) as proposed by Harrison. In electron ionization of CH₃C₆H₄Y formation of the more stable tropylium and benzyl ionic isomers usually accompanies that of the o-, m- and p-tolyl ions. Isomerization of low energy [CH₃C₆H₄Y]⁺? to [Y–methylenecyclohexadiene]⁺? is proposed to account for most [benzyl]⁺ formation, while the tropylium ion appears to arise from the isomerization of tolyl ions formed with higher internal energies, [o-, m-, p-tolyl]⁺→ [benzyl]⁺→ [tropylium]⁺, consistent with Dewar's predictions from MINDO/3 calculations.     

Field ionization mass spectrometry as a facile method for the study of the thermal formation of radicals

Electron impact spectra of thermolysis products of organic salts heated in the ion source of a mass spectrometer may give rise to organic ions corresponding to the cation of the salt. Field ionization mass spectrometry has been used as a facile method for detemining whether such an ion is due to ionization of the corresponding radical present in the gas phase, or to an electron impact induced fragmentation of a reaction product of higher mass. By comparison of the electron impact and field ionization spectra of a series of N-methyl pyridinium, tropylium and 1,2-dithiolylium salts it has been found possible to identify the radicals formed thermolytically, when present.     

Electrospray ionization mass spectrometry studies of cyclodextrin‐carboxylate ion inclusion complexes

Aqueous solutions containing simple model aliphatic and alicyclic carboxylic acids (surrogates 1–4) were studied using negative ion electrospray mass spectrometry (ESI‐MS) in the presence and absence of α‐, β‐, and γ‐cyclodextrin. Molecular ions were detected corresponding to the parent carboxylic acids and complexed forms of the carboxylic acids; the latter corresponding to non‐covalent inclusion complexes formed between carboxylic acid and cyclodextrin compounds (e.g., β‐CD, α‐CD, and γ‐CD). The formation of 1:1 non‐covalent inclusion cyclodextrin‐carboxylic complexes and non‐inclusion forms of the cellobiose‐carboxylic acid compounds was also observed. Aqueous solutions of Syncrude‐derived mixtures of aliphatic and alicyclic carboxylic acids (i.e. naphthenic acids; NAs) were similarly studied using ESI‐MS, as outlined above. Molecular ions corresponding to the formation of CD‐NAs inclusion complexes were observed whereas 1:1 non‐inclusion forms of the cellobiose‐NAs complexes were not detected. The ESI‐MS results provide evidence for some measure of inclusion selectivity according to the 'size‐fit' of the host and guest molecules (according to carbon number) and the hydrogen deficiency (z‐series) of the naphthenic acid compounds. The relative abundances of the molecular ions of the CD‐carboxylate anion adducts provide strong support for differing complex stability in aqueous solution. In general, the 1:1 complex stability according to hydrogen deficiency (z‐series) of naphthenic acids may be attributed to the nature of the cavity size of the cyclodextrin host compounds and the relative lipophilicity of the guest. Copyright © 2009 John Wiley & Sons, Ltd.     

Halide Anion Triggered Reactions of Michael Acceptors with Tropylium Ion

Tropylium bromide undergoes noncatalyzed, regioselective additions to a large variety of Michael acceptors. In this way, acrylic esters are converted into β‐bromo‐α‐cycloheptatrienylpropionic esters. The reactions are interpreted as nucleophilic attack of bromide ions at the electron‐deficient olefins and the approach of the tropylium ion to the incipient carbanion. Quantum chemical calculations were performed to elucidate the analogy to the amine‐ or phosphine‐catalyzed Rauhut–Currier reactions. Subsequent synthetic transformations of the bromo‐cycloheptatrienylated adducts are reported.     

Zinc–Organic Battery with a Wide Operation‐Temperature Window from −70 to 150 °C

Aqueous zinc (Zn) batteries have been considered as promising candidates for grid‐scale energy storage. However, their cycle stability is generally limited by the structure collapse of cathode materials and dendrite formation coupled with undesired hydrogen evolution on the Zn anode. Herein we propose a zinc–organic battery with a phenanthrenequinone macrocyclic trimer (PQ‐MCT) cathode, a zinc‐foil anode, and a non‐aqueous electrolyte of a N,N‐dimethylformamide (DMF) solution containing Zn²⁺. The non‐aqueous nature of the system and the formation of a Zn²⁺–DMF complex can efficiently eliminate undesired hydrogen evolution and dendrite growth on the Zn anode, respectively. Furthermore, the organic cathode can store Zn²⁺ ions through a reversible coordination reaction with fast kinetics. Therefore, this battery can be cycled 20 000 times with negligible capacity fading. Surprisingly, this battery can even be operated in a wide temperature range from ?70 to 150 °C.