One‐Pot Preparation of Unsymmetrical Biaryls via Suzuki Cross‐Coupling Reaction of Aryl Halide using Phase‐Transfer Catalyst in a Biphasic Solvent System

A one‐pot synthetic method of unsymmetrical biaryls was developed via the Suzuki cross‐coupling reaction of aryl halide using a phase‐transfer catalyst in a biphasic solvent system.     

Statistical fluctuation in zeta potential distribution of nanoliposomes measured by on‐chip microcapillary electrophoresis

The zeta potential of nanoliposomes with a diameter below 100 nm has been studied by the combined use of on‐chip microcapillary electrophoresis (μCE) and sensitive fluorescence imaging. Tracking the electrophoretic migration of individual nanoliposomes has enabled the accurate evaluation of the zeta potential distribution of nanoliposomes and the first observation of its abnormal broadening due to a statistical fluctuation phenomenon specific to the “nanoscale world.” The materials used for liposome preparation were phosphocholine as the neutral lipid, phosphatidylserine as the anionic lipid, and cholesterol. The size of the liposomes encapsulating calcein, a fluorescent dye used for imaging convenience, was tailored by extrusion through polycarbonate membrane filters of different pore sizes ranging from 50 to 1000 nm. The on‐chip μCE system comprised a μCE chip, a laser source, an inverted microscope, and an electron‐multiplying charge‐coupled device camera. The electrophoresis experiment using this system revealed that the relative standard deviation of the zeta potential distribution of nanoliposomes is inversely proportional to their diameter and apparently increases below 100 nm. This abnormal broadening of zeta potential distribution of nanoliposomes is explained by prominent discreteness effect of the number of anionic lipid molecules in nanoliposomes.     

Hydrindacene‐Based Acetylenic Macrocycles with Horizontally and Vertically Ordered Functionality Arrays

The macrocyclization of 2,6‐diethynyl hydrindacenes ( 1 ) with functional groups at mutually perpendicular positions results in the formation of novel macrocycles which, as a result of the hindered rotation of the hydrindacene units, possess directionally persistent peripheral functionalities. The two hydrindacene units in the dimer macrocycle ( 2 ) have been shown to interact electronically through their respective butadiyne moieties, whereas the trimer macrocycle ( 3 ) demonstrates a moderate degree of geometrical flexibility as a result of the five‐membered hydrindacene rings. In addition, these trimer macrocycles contain a central cavity suitably sized for the inclusion of various solvent molecules. These new macrocycles can be further modified by introducing π‐conjugated side groups, such as styryl and thienyl groups, as well as by attaching a variety of peripheral ester groups.     

Heterometallic Polyhydride Complexes Containing Yttrium Hydrides with Different Cp Ligands: Synthesis,Structure, and Hydrogen‐Uptake/Release Properties

A new family of Y₄/M₂ and Y₅/M heterobimetallic rare‐earth‐metal/d‐block‐transition‐metal? polyhydride complexes has been synthesized. The reactions of the tetranuclear yttrium? octahydride complex [{Cp′′Y(μ‐H)₂}₄(thf)₄] (Cp′′=C₅Me₄H, 1‐C₅Me₄H ) with one equivalent of Group‐6‐metal? pentahydride complexes [Cp*M(PMe₃)H₅] (M=Mo, W; Cp*=C₅Me₅) afforded pentanuclear heterobimetallic Y₄/M? polyhydride complexes [{(Cp′′Y)₄(μ‐H)₇}(μ‐H)₄MCp*(PMe₃)] (M=Mo ( 2 a ), W ( 2 b )). UV irradiation of compounds 2 a , b in THF gave PMe₃‐free complexes [{(Cp′′Y)₄(μ‐H)₆(thf)₂}(μ‐H)₅MCp*] (M=Mo ( 3 a ), W ( 3 b )). Compounds 3 a , b reacted with one equivalent of [Cp*M(PMe₃)H₅] to afford hexanuclear Y₄/M₂ complexes [{Cp*M(μ‐H)₅}{(Cp′′Y)₄(μ‐H)₅}{(μ‐H)₄MCp*(PMe₃)}] (M=Mo ( 4 a ), W ( 4 b )). UV irradiation of compounds 4 a , b provided the PMe₃‐free complexes [(Cp′′Y)₄(μ‐H)₄{(μ‐H)₅MCp*}₂] (M=Mo ( 5 a ), W ( 5 b )). C₅Me₄Et‐ligated analogue [(Cp′′Y)₄(μ‐H)₄{(μ‐H)₅Mo(C₅Me₄Et)}₂] ( 5 a′ ) was obtained from the reaction of 1‐C₅Me₄H with [(C₅Me₄Et)Mo(PMe₃)H₅]. On the other hand, the reaction of pentanuclear yttrium? decahydride complex [{(C₅Me₄R)Y(μ‐H)₂}₅(thf)₂] ( 1‐C₅Me₅ : R=Me; 1‐C₅Me₄Et : R=Et) with [Cp*M(PMe₃)H₅] gave the hexanuclear heterobimetallic Y₅/M? polyhydride complexes [({(C₅Me₄R)Y}₅(μ‐H)₈)(μ‐H)₅MCp*] ( 6 a : M=Mo, R=Me; 6 a′ : M=Mo, R=Et; 6 b : M=W, R=Me). Compound 5 a released two molecules of H₂ under vacuum to give [(Cp′′Y)₄(μ‐H)₂{(μ‐H)₄MoCp*}₂] ( 7 ). In contrast, compound 6 a lost one molecule of H₂ under vacuum to yield [{(Cp*Y)₅(μ‐H)₇}(μ‐H)₄MoCp*] ( 8 ). Both compounds 7 and 8 readily reacted with H₂ to regenerate compounds 5 a and 6 a , respectively. The structures of compounds 4 a , 5 a′ , 6 a′ , 7 , and 8 were determined by single‐crystal X‐ray diffraction.     

Photophysical characteristics of 4,4′-bis(N-carbazolyl)tolan derivatives and their application in organic light emitting diodes

4,4′-bis(N-carbazolyl)tolan (BCT) and 4,4′-bis[N-(3,6-di-t-butyl)carbazolyl]tolan (BCT-t-Bu) were synthesized as π-expanded analogs of 4,4′-bis(N-carbazolyl)biphenyl. Their photophysical characteristics both in solution and films were thoroughly investigated. Interestingly, the phosphorescence spectrum of BCT was significantly medium-dependent, and the emission maximum was red-shifted by 131 nm from 489 nm in solution at 77 K to 620 nm in a deposited film at 5 K, suggesting the presence of strong intermolecular interactions in the film. BCT and BCT-t-Bu were found to be useful as host materials for fluorescence-based organic light emitting diodes (OLEDs). However, their low triplet energy levels in films negated their potential to act as hosts in phosphorescence-based OLEDs.     

Switching of Redox Properties Triggered by a Thermal Equilibrium between Closed‐Shell Folded and Open‐Shell Twisted Species

Thermally switchable redox properties have been reported to be due to a change in the spin state of newly designed overcrowded ethylenes, which can adopt closed‐shell folded and open‐shell twisted forms. In this study, tetrathienylanthraquinodimethane derivatives were designed to be in thermal equilibrium between a more stable folded form and less stable but more donating twisted diradical in solution, so that the oxidation potential can be controlled by heating/cooling. This is the first example of a switching of redox properties based on a thermally equilibrated twisted diradical, which can be more readily oxidized to the twisted dication.     

Effect of Alkyl Groups in Pyrene Chromophore on the Mechanical Response of Pyrene‐Octafluoronaphthalene Co‐Crystals

Changes in the photophysical properties of pyrene ( Py )‐octafluoronaphthalene ( OFN ) co‐crystals ( Py ? OFN ) upon mechanical stimuli are described herein. The Py ? OFN co‐crystal showed a mechano‐induced bathochromic shift in emission, and a similar tendency was observed for the 1,3,6,8‐tetramethylpyrene‐ OFN co‐crystal. These shifts are due to disruption of the microscopic molecular orientation in the co‐crystal, which allows for excimer formation. In sharp contrast to the parent Py ? OFN and methyl‐substituted Py ‐ OFN co‐crystals, no mechano‐induced bathochromic shift was observed when longer alkyl chains were introduced to the 1‐, 3‐, 6‐, and 8‐positions of the Py chromophore. This photophysical opposability against mechanical stimuli could be explained by the orthogonally oriented alkyl groups on the Py ring, which existed between two Py cores like pillars. This fixed OFN to maintain the face‐to‐face alternatively stacked structure of the co‐crystal and thus prevented the formation of the Py excimer. The pillar effect demonstrated herein provides a rational design for co‐crystalline systems that are photophysically stable against mechanical stresses.     

Intercalation and staging behavior in super-oxygenated La2CuO4 + δ

A high temperature electrochemical oxidation process has been used to produce large single crystals of La₂CuO_{4 + δ} suitable for neutron scattering experiments. Below room temperature the oxygen-rich phases have structural superlattice scattering peaks which indicate new periodicities ranging from 2 to 6.6 layers perpendicular to the copper oxide planes. A model structure originally proposed for La₂NiO_{4 + δ} can account for the superlattice peaks as a result of anti-phase domain boundaries between different tilt directions of the CuO₆ octahedra. Within this model, the changes in CuO₆ tilt directions are induced by segregated layers of interstitial oxygen which order in a manner similar to intercalants in graphite. This structural model thus clarifies previous work and establishes La₂CuO_{4 + δ} as a unique lamellar superconducting system with annealed disorder.