Stimuli-responsive azulene-based conjugated oligomers with polyaniline-like properties

Synthesis of 2- and 6-thienylazulenes by palladium-catalyzed direct arylation of 2- and 6-haloazulenes with thiophene derivatives

Preparation of 2- and 6-thienylazulene derivatives was established by the palladium-catalyzed direct cross-coupling reaction of 2- and 6-haloazulenes with the corresponding thiophene derivatives in good yield.

Visible-light triggered photoswitching systems based on fluorescent azulenyl-substituted dithienylcyclopentenes

Novel azulenyl functionalized dithienylethenes were synthesized, and their photochromic reactivity, fluorescent and electrochemical properties were investigated.

Synthesis and acid–base properties of a proton-bridged biaryl compound based on pyridylazulene

We report the synthesis and acid–base properties of 1,1′-bi(2-pyridylazulene) and the crystal structure of its mono-protonated form in which pyridyl moieties are interacted by an intramolecular hydrogen bond.

A new aspect of cyclopentadithiophene based polymers: narrow band gap polymers upon protonation

A new aspect of CPDT based conjugated polymers that CPDT units in the polymers can be protonated with a significant change in optical and electronic properties was reported.

Synthesis of azoimidazolium dyes with nitrous oxide

A new method for the synthesis of industrially important azoimidazolium dyes is presented. The procedure is based on a reagent which is rarely used in the context of synthetic organic chemistry: nitrous oxide ("laughing gas"). N2O is first coupled to N-heterocyclic carbenes. Subsequent reaction with aromatic compounds through an AlCl3-induced C-H activation process provides azoimidazolium dyes in good yields.

Synthesis of substituted azulenes via Pt(II)-catalyzed ring-expanding cycloisomerization

Substituted azulenes, valuable structures for electronic devices and pharmaceuticals, have been synthesized by the platinum(II)-catalyzed intramolecular ring-expanding cycloisomerization of 1-en-3-yne with ortho-disubstituted benzene. This novel method provides an alternative route for the efficient synthesis of substituted azulenes. The reaction mechanism of selected catalytic transformations was explored using density functional calculations.

HOF·CH3CN: probably the best oxygen transfer agent organic chemistry has to offer

The complex HOF·CH3CN is readily obtained by bubbling dilute fluorine into aqueous acetonitrile solution. It does not have to be purified or isolated, and its solution can react as is, after the concentration has been establish by any iodometric method. It is the only reagent possessing a distinctive positive oxygen species. This enables electrophilic oxygen transfer with results no other reagent can match. HOF·CH3CN demonstrates its ability in epoxidations that either could not be performed before or could only obtained 5 orders of magnitude slower. This complex is also an excellent tool for oxygenation of compounds at the α position of a carbonyl, including the synthesis of some hard-to-come-by indanediones, which are important for fingerprint visualization on paper. HOF·CH3CN proves itself as a very efficient reagent for oxygenating tertiary nitrogen atoms both in aliphatic (including azides) and in aromatic amines, which could not be accomplished despite many attempts in the last 50 years. Oxygenation of two tertiary nitrogen atoms in the same molecule also becomes feasible as demonstrated for various phenanthrolines, bipyridines, diazafluorenones, and quinoxalines. It was also used to oxygenate primary amines, and because of the exceptionally mild conditions, it could transform vicinal aliphatic diamines to vicinal dinitro derivatives as well as amino acids to the corresponding nitro ones, practically unknown transformations before. Its ability to react with azines and hydrazones and convert them to the original carbonyls helped to establish these groups as good protecting tools for a variety of carbonyls. HOF·CH3CN excels in oxygenation of various sulfur and selenium compounds that could not be oxygenated in the past. The selectivity of the oxidation is quite good, and if there are alcohols, double bonds, and sulfides in the same molecule, usually the sulfur atom will be attacked first. Of special interest is the reaction with oligothiophenes resulting at will in either [all]-S,S-dioxooligothiophenes or in partially oxygenated ones. Some of these last derivatives have the narrowest HOMO-LUMO gap of all oligothiophenes tested, a very desirable feature. This reagent can also oxidize thiols or disulfides to either sulfonic or sulfinic acids at will, all in seconds and in very high yields. Since the oxygen atom of HOF·CH3CN originates in water, it is very easy and relatively inexpensive to introduce the heavy oxygen isotope in many sites of a variety of molecules, some of them quite important. The (18)O tirapazamine and any desirable alcohol, R(Ar)(18)OH, are two examples.

Breakdown of interference rules in azulene, a nonalternant hydrocarbon

We have designed and synthesized five azulene derivatives containing gold-binding groups at different points of connectivity within the azulene core to probe the effects of quantum interference through single-molecule conductance measurements. We compare conducting paths through the 5-membered ring, 7-membered ring, and across the long axis of azulene. We find that changing the points of connectivity in the azulene impacts the optical properties (as determined from UV-vis absorption spectra) and the conductivity. Importantly, we show here that simple models cannot be used to predict quantum interference characteristics of nonalternant hydrocarbons. As an exemplary case, we show that azulene derivatives that are predicted to exhibit destructive interference based on widely accepted atom-counting models show a significant conductance at low biases. Although simple models to predict the low-bias conductance do not hold with all azulene derivatives, we demonstrate that the measured conductance trend for all molecules studied actually agrees with predictions based on the more complete GW calculations for model systems.

Modulating structure and properties in organic chromophores: influence of azulene as a building block

The properties of isomeric azulene derivatives, substituted through the 5-membered ring, were examined using a combination of experimentation and theoretical calculations for a series of well-defined electroactive oligomers.

Conjugated oligomers incorporating azulene building blocks – seven- vs. five-membered ring connectivity

The properties of isomeric azulene derivatives based on 7- versus 5-membered ring substitution were examined by the synthesis and characterization of well-defined electroactive oligomers.

Syntheses and tunable emission properties of 2-alkynyl azulenes

Various substituted 2-azulenes have been synthesized via Sonogashira coupling. Doping with superacids allows tunable emission from 443 to 750 nm depending on the substitution. The proton doped compounds are the first azulene alkyne based systems that show emission originating only from the S(1) excited state.