Modulation of the Physicochemical Properties of Donor–Spiro–Acceptor Derivatives through Donor Unit Planarisation: Phenylacridine versus Indoloacridine—New Hosts for Green and Blue Phosphorescent Organic Light‐Emitting Diodes (PhOLEDs)

This work reports a detailed structure–property relationship study of a series of efficient host materials based on the donor–spiro–acceptor (D‐spiro‐A) design for green and sky‐blue phosphorescent organic light‐emitting diodes (PhOLEDs). The electronic and physical effects of the indoloacridine (IA) fragment connected through a spiro bridge to different acceptor units, namely, fluorene, dioxothioxanthene or diazafluorene moiety, have been investigated in depth. The resulting host materials have been easily synthesised through short, efficient, low‐cost, and highly adaptable synthetic routes by using common intermediates. The dyes possess a very high triplet energy (E_T) and tuneable HOMO/LUMO levels, depending on the strength of the donor/acceptor combination. The peculiar electrochemical and optical properties of the IA moiety have been investigated though a fine comparison with their phenylacridine counterparts to study the influence of planarisation. Finally, these molecules have been incorporated as hosts in green and sky‐blue PhOLEDs. For the derivative SIA‐TXO₂ as a host, external quantum efficiencies as high as 23 and 14 % have been obtained for green and sky‐blue PhOLEDs, respectively.     

Octahedral Chiral‐at‐Metal Iridium Catalysts: Versatile Chiral Lewis Acids for Asymmetric Conjugate Additions

Octahedral iridium(III) complexes containing two bidentate cyclometalating 5‐tert‐butyl‐2‐phenylbenzoxazole ( IrO ) or 5‐tert‐butyl‐2‐phenylbenzothiazole ( IrS ) ligands in addition to two labile acetonitrile ligands are demonstrated to constitute a highly versatile class of asymmetric Lewis acid catalysts. These complexes feature the metal center as the exclusive source of chirality and serve as effective asymmetric catalysts (0.5–5.0 mol % catalyst loading) for a variety of reactions with α,β‐unsaturated carbonyl compounds, namely Friedel–Crafts alkylations (94–99 % ee), Michael additions with CH‐acidic compounds (81–97 % ee), and a variety of cycloadditions (92–99 % ee with high d.r.). Mechanistic investigations and crystal structures of an iridium‐coordinated substrates and iridium‐coordinated products are consistent with a mechanistic picture in which the α,β‐unsaturated carbonyl compounds are activated by two‐point binding (bidentate coordination) to the chiral Lewis acid.     

Protein Staining Agents from Cationic and Neutral Luminescent Iridium(III) Complexes

Seven luminescent iridium(III) complexes were prepared to investigate the relationships between chemical structures and properties of protein staining. For the first time, the effect of the main ligand, the π conjugation effect of the ancillary ligand, and the charge effect of organometallic complexes on protein staining has been revealed. Most importantly, this study gives the first experimental evidence of the potential applications of charge‐neutral organometallic complexes in protein staining, which could open an avenue of exploiting novel protein staining agents in the future.     

Bis(N‐Confused Porphyrin) as a Semirigid Receptor with a Chirality Memory: A Two‐Way Host Enantiomerization through Point‐to‐Axial Chirality Transfer

The adduct formation of protonated bis(N‐confused porphyrin) (BNCP, 3,3′‐bis(meso‐tetratolyl‐2‐aza‐21‐carbaporphyrin) with chiral anions, carboxylic acids, and alcohols was studied in solution by means of ¹H NMR and circular dichroism (CD) spectroscopic analysis and DFT methods. The addition of enantiopure guests to the acidified BNCP resulted in optical activity that vanished after neutralization. Pairs of the ¹H NMR‐distinguishable diastereomers were formed when enantiopure guests were applied, although a single form was observed upon the addition of the racemic mixtures in each case. Unidirectional configuration change that led to diastereomeric excess was observed in several instances. Such an excess was memorized by metalation of the adducts with AgBF₄, thus resulting in optically active silver(III) complexes of BNCP with some enantiomeric excess. Absolute configurations of BNCP cations and bis(zinc) and bis(silver(III)) complexes were determined on the basis of time‐dependent (TD)‐DFT calculations of their CD spectra. It was shown that some of the chiral carboxylates induced opposite directions of enantiomerization of di‐ and tetracations or di‐/tetracation and bis(zinc) complexes. The source of the optical activity of the equimolar diastereomeric mixture of adducts is discussed.     

Homo‐double helix formation of an optically active conjugated polymer bearing carboxy groups and amplification of the helicity upon complexation with achiral and chiral amines

An optically active, m‐terphenyl‐based π‐conjugated polymer bearing carboxy groups was synthesized by the copolymerization of the diethynyl monomer bearing a carboxy group with (S,S)‐2,5‐bis(2‐methylbutoxy)‐1,4‐dibromobenzene using Sonogashira reaction. The copolymer showed a weak circular dichroism (CD) in the main‐chain chromophore region due to a homo‐double helix formation with an excess helical handedness biased by the chiral alkoxy substituents through self‐association. However, upon complexation with achiral amines, such as piperidine, the CD intensity of the polymer significantly increased resulting in the formation of a greater excess one‐handed homo‐double helix via hydrogen‐bonded inclusion complexation with the achiral amines between each strand, leading to the amplification of the helicity. A preferred‐handed homo‐double helix was also induced in the polymer in the presence of nonracemic amines. The effect of the achiral and chiral amines on the homo‐double helix formation was investigated by comparing the CD spectra of the polymer to those of its model dimer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 990–999     

Palladium‐Catalyzed N‐Arylation of Iminodibenzyls and Iminostilbenes with Aryl‐ and Heteroaryl Halides

Compounds containing the iminodibenzyl and iminostilbene ring systems are prevalent in medicinal targets and functional materials. Herein, we report palladium‐catalyzed conditions for the N‐arylation of these ring systems. This protocol could be applied to a variety of (hetero)aryl chloride and bromide substrates, including ones, which are sterically hindered or those containing a variety of functional groups. Use of the fourth‐generation palladacycle precatalyst gave good to excellent yields by using low palladium‐catalyst loadings (0.1 to 1 mol %).     

Rational Design and Application of a Redox‐Active,Photoresponsive, Discrete Metallogelator

A photoresponsive discrete metallogelator was rationally designed by incorporating a photochromic azobenzene subunit in the structure of a redox‐active ferrocene–peptide conjugate. The target molecule was purposefully equipped with a dipeptide unit capable of self‐assembly in response to sonication. The designed molecule was shown to undergo supramolecular self‐assembly and achieve organogelation in response to ultrasound, light, heat, and redox signals. The sol–gel phase transition of the designed gelator was found to be sensitive to a plethora of input stimuli, allowing the application of the sol–gel transition behavior in basic logic gate operations. A gel‐based NOT logic gate operation was realized when the redox‐active property of the organogel was examined by using different oxidizing agents. The smart response of the gelator was further exploited in designing XOR operations under oxidizing or non‐oxidizing conditions.     

Air‐Stable Spirofluorene‐Containing Ladder‐Type Bis(alkynyl)borane Compounds with Readily Tunable Full Color Emission Properties

A series of air‐stable spiro‐fused ladder‐type boron(III) compounds has been designed, synthesized, and the electrochemistry and photophysical behavior have been characterized. By simply varying the substituents on the pyridine ring and extending the π‐conjugation of the spiro framework, the emission color of these compounds can be easily fine‐tuned spanning the visible spectrum from blue to red. All compounds exhibit a broad and structureless emission band across the entire visible region, assigned as an intramolecular charge‐transfer transition originating from the thiophene of the spiro framework to the pyridine‐borane moieties. In addition, these compounds demonstrate high photoluminescence quantum yields of up to 0.81 in dichloromethane solution and 0.86 in doped thin films. Some of the compounds have also been employed as emissive materials, in which solution‐processed organic light‐emitting devices (OLEDs) with tunable emission colors spanning the visible spectrum from blue, green to red have been realized, demonstrating the potential applications of these boron compounds in OLEDs.     

Dual Palladium(II)/Tertiary Amine Catalysis for Asymmetric Regioselective Rearrangements of Allylic Carbamates

The streamlined catalytic access to enantiopure allylic amines as valuable precursors towards chiral β‐ and γ‐aminoalcohols as well as α‐ and β‐aminoacids is desirable for industrial purposes. In this article an enantioselective method is described that transforms achiral allylic alcohols and N‐tosylisocyanate in a single step into highly enantioenriched N‐tosyl protected allylic amines via an allylic carbamate intermediate. The latter is likely to undergo a cyclisation‐induced [3,3]‐rearrangement catalysed by a planar chiral pentaphenylferrocene palladacycle in cooperation with a tertiary amine base. The otherwise often indispensable activation of palladacycle catalysts by a silver salt is not required in the present case and there is also no need for an inert gas atmosphere. To further improve the synthetic value, the rearrangement was used to form dimethylaminosulfonyl‐protected allylic amines, which can be deprotected under non‐reductive conditions.