Highly Deep-Blue Luminescent Twisted Diphenylamino Terphenyl Emitters by Bromine-Lithium Exchange Borylation-Suzuki Sequence.

Four novel intensively blue luminescent chromophores were readily synthesized by bromine-lithium exchange borylation-Suzuki (BLEBS) sequence in moderate to good yields. Their electronic properties were studied by absorption and emission spectroscopy and quantum chemical calculations revealing deep-blue emission in solution as well as in the solid state and upon embedding into a PMMA (polymethylmethacrylate) matrix with small FWHM (full width at half maximum) values and CIE y values smaller than 0.1.

Linear Carbene Pyridine Copper Complexes with Sterically Demanding ,'-Bis(trityl)imidazolylidene: Syntheses, Molecular Structures, and Photophysical Properties.

The sterically demanding carbene ITr ('-bis(triphenylmethyl)imidazolylidene) was used as a ligand for the preparation of luminescent copper(I) complexes of the type [(ITr)Cu(R-pyridine/R'-quinoline)]BF (R = H, 4-CN, 4-CHO, 2,6-NH, and R' = 8-Cl, 6-Me). The selective formation of linear, bis(coordinated) complexes was observed for a series of pyridine and quinoline derivatives. Only in the case of 4-cyanopyridine a one-dimensional coordination polymer was formed, in which the cyano group of the cyanopyridine ligand additionally binds to another Cu atom in a bridging manner, thus leading to a trigonal planar coordination environment.

Correction: A tropylium annulated N-heterocyclic carbene.

Correction for 'A tropylium annulated N-heterocyclic carbene' by Sebastian Appel et al., Chem. Commun.

A tropylium annulated N-heterocyclic carbene.

Derivatives of the cationic tropylium annulated imidazolylidene ITrop are obtained by hydride abstraction from related cycloheptatriene compounds. Spectroscopic, structural and theoretical data indicate that, as a cationic relative of benzimidazolylidenes, ITrop has highly reduced σ-donor and strong π-acceptor character.

Electronic Finetuning of 8-Methoxy Psoralens by Palladium-Catalyzed Coupling: Acidochromicity and Solvatochromicity.

Differently 5-substituted 8-methoxypsoralens can be synthesized by an efficient synthetic route with various cross-coupling methodologies, such as Suzuki, Sonogashira and Heck reaction. Compared to previously synthesized psoralens, thereby promising daylight absorbing compounds as potentially active agents against certain skin diseases can be readily accessed. Extensive investigations of all synthesized psoralen derivatives reveal fluorescence in the solid state as well as several distinctly emissive derivatives in solution.

Cu-F Interactions between Cationic Linear N-Heterocyclic Carbene Copper(I) Pyridine Complexes and Their Counterions Greatly Enhance Blue Luminescence Efficiency.

A series of easily accessible linear N-heterocyclic carbene (NHC) copper(I) complexes, bearing pyridine (py) and its derivatives as chromophore ligands, are barely emissive in the single-crystalline solid state. However, their powders, neat films, and dilute doped films of poly(methyl methacrylate) (PMMA; 1-10%) show very intense blue-to-blue-green photoluminescence with remarkable quantum yields φ of up to 87% and microsecond lifetimes, indicative of triplet states being involved. These luminescence properties are similar to trigonal coordinated NHC copper(I) bis(pyridine) complexes, which we have also isolated and characterized with respect to their structures and photophysics.

Computer-Aided Design of Luminescent Linear N-Heterocyclic Carbene Copper(I) Pyridine Complexes.

Multireference configuration interaction methods including spin-orbit interactions have been employed to investigate the photophysical properties of various linear N-heterocyclic carbene (NHC) copper(I) pyridine complexes with the aim of designing performant thermally activated delayed fluorescence (TADF) emitters for use in organic-light-emitting diodes. Our theoretical results indicate that this structural motif is very favorable for generating excited triplet states with high quantum yield. The first excited singlet (S) and corresponding triplet state (T) are characterized by d → π metal-to-ligand charge-transfer (MLCT) excitations.

Flavin Monooxygenase-Generated N-Hydroxypipecolic Acid Is a Critical Element of Plant Systemic Immunity.

Following a previous microbial inoculation, plants can induce broad-spectrum immunity to pathogen infection, a phenomenon known as systemic acquired resistance (SAR). SAR establishment in Arabidopsis thaliana is regulated by the Lys catabolite pipecolic acid (Pip) and flavin-dependent-monooxygenase1 (FMO1). Here, we show that elevated Pip is sufficient to induce an FMO1-dependent transcriptional reprogramming of leaves that is reminiscent of SAR.

First N-Heterocyclic Carbenes Relying on the Triazolone Structural Motif: Syntheses, Modifications and Reactivity.

4-Phenylsemicarbazide and 1,5-diphenylcarbazide are suitable starting materials for the syntheses of N-heterocyclic carbene (NHC) compounds with new backbone structures. In the first case, cyclisation and subsequent methylation leads to a cationic precursor whose deprotonation affords the triazolon-ylidene 2, which was converted to the corresponding sulfur and selenium adducts and a range of metal complexes. In contrast, cyclisation of diphenylcarbazide affords a neutral betain-type NHC-precursor 7, which is not in equilibrium with its carbene tautomer 7a.

Tuning the electronic properties of an N-heterocyclic carbene by charge and mesomeric effects.

N-Methylation of a pyridoimidazolium salt and subsequent deprotonation afford a cationic NHC ligand. The spectroscopic characteristics of its Rh and Ir metal complexes reveal the reduced donor and enforced π-acceptor behaviour of this ligand system.

Expanding the chemistry of cationic N-heterocyclic carbenes: alternative synthesis, reactivity, and coordination chemistry.

A new synthetic route to complexes of the cationic N-heterocyclic carbene ligand 2 has been developed by the attachment of a cationic pentamethylcyclopentadienylruthenium ([RuCp*](+)) fragment to a metal-coordinated benzimidazol-2-ylidene ligand. The coordination chemistry and the steric and electronic properties of the cationic carbene were investigated in detail by experimental and theoretical methods. X-ray structures of three carbene-metal complexes were determined.

Hybrid ligands with N-heterocyclic carbene and chiral phosphaferrocene components.

N-Heterocyclic carbenes (NHCs) possessing one or two 3,4-dimethylphosphaferrocenyl substituents and either methylene or ethylene alkyl bridges have been prepared. These carbenes turned out to be remarkably stable and were characterized by NMR methods and partly by mass spectrometry. Their molybdenum and ruthenium complexes were examined in order to determine the electronic properties and the coordination behaviour of these chiral PC- and PCP-chelate ligands, which combine a NHC unit as a strong sigma-donor with pi-accepting phosphaferrocene moieties.

Chiral organometallic half-sandwich complexes with defined metal configuration.

Chiral organometallic half-sandwich complexes with stereogenic metal atoms are close relatives of chiral organic compounds with stereogenic carbon atoms. Similarities and differences between these two classes of compounds are outlined. Some representative metal complexes are discussed in an introductory section followed by a more detailed treatment of the available strategies to control the metal configuration by means of chiral auxiliaries.