A versatile palladium catalyst system for Suzuki-Miyaura coupling of alkenyl tosylates and mesylates

A general and effective palladium system for Suzuki-Miyaura coupling of alkenyl electrophiles under mild reaction conditions is reported. With the Pd(OAc)(2)/CM-phos system, a variety of alkenyl tosylates are coupled well with ArB(OH)(2). Moreover, the first successful examples of using alkenyl mesylates in alkenylation are also described.     

Tunable Linear and Nonlinear Optical Properties from Room Temperature Phosphorescent Cyclic Triimidazole-Pyrene Bio-Probe

Organic materials with multiple emissions tunable by external stimuli represent a great challenge. TTPyr, crystallizing in different polymorphs, shows a very rich photophyisics comprising excitation-dependent fluorescence and phosphorescence at ambient conditions, and mechanochromic and thermochromic behavior. Transformation among the different species has been followed by thermal and X-ray diffraction analyses and the emissive features interpreted through structural results and DFT/TDDFT calculations. Particularly intriguing is the polymorph TTPyr(HT), serendipitously obtained at high temperature but stable also at room temperature, whose non-centrosymmetric structure guarantees an SHG efficiency 10 times higher than that of standard urea. Its crystal packing, where only the TT units are strongly rigidified by π-π stacking interactions while the Pyr moieties possess partial conformational freedom, is responsible for the observed dual fluorescence. The potentialities of TTPyr for bioimaging have been successfully established.     

Dual pH‐ and Temperature‐Responsive Metallosupramolecular Block Copolymers with Tunable Critical Micelle Temperature by Modulation of the Self‐Assembly of NIR‐Emissive Alkynylplatinum(II) Complexes Induced by Changes in Hydrophilicity and Electrostatic Effects

Terpyridylplatinum(II)‐based metallosupramolecular triblock copolymers with hydrophilic alkynyl ligands have been synthesised and characterised. As a result of the intrinsic properties of Pluronics, reversible temperature‐induced micellisation occurred at high temperature leading to aggregation of the platinum(II) complex moieties through Pt???Pt and π–π interactions, resulting in significant UV/Vis absorption and near‐infrared (NIR) emission spectral changes. The critical micelle temperatures of the complexes were found to vary from 21 to 30 °C due to differences in the hydrophilicity of the alkynyl ligands and the electrostatic repulsions between the positively charged platinum(II) complex moieties. One of the complexes with pH‐responsive CH₂NMe₂ groups on the alkynyl ligand was found to show NIR emission that is sensitive to both pH and temperature. Such dual‐responsive behaviour has been ascribed to the modulation of the self‐assembly of the complex moieties by temperature‐induced micellisation and the changes in the hydrophilicity as well as electrostatic interactions upon protonation/deprotonation of the CH₂NMe₂ groups on the alkynyl ligand.     

Efficient synthesis of bromocyclopenta[b] indoles via a bromination ‐ reduction sequence

Substituted cyclopenta[b]indoles are selectively brominated in good yields with excess pyridine ‐ Br₂ charge‐transfer complex (PyBr₂) in a one‐pot reaction to provide 5 and/or 7‐bromoindoles. The mechanism involves the formation of an adduct (addition of bromine on the central double bond) which is subsequently reduced in situ with Zn and AcOH. A variety of functional groups in the cyclopentyl and the benzenoid rings are tolerated.     

Direct Visualization of Atomic Structure in Multivariate Metal-Organic Frameworks (MOFs) for Guiding Electrocatalysts Design

The direct utilization of metal–organic frameworks (MOFs) for electrocatalytic oxygen evolution reaction (OER) has attracted increasing interests. Herein, we employ the low-dose integrated differential phase contrast-scanning transmission electron microscopy (iDPC-STEM) technique to visualize the atomic structure of multivariate MOFs (MTV-MOFs) for guiding the structural design of bulk MOFs for efficient OER. The iDPC-STEM images revealed that incorporating Fe³⁺ or 2-aminoterephthalate (ATA) into Ni-BDC (BDC: benzenedicarboxylate) can introduce inhomogeneous lattice strain that weaken the coordination bonds, which can be selectively cleaved via a mild heat treatment to simultaneously generate coordinatively unsaturated metal sites, conductive Ni@C and hierarchical porous structure. Thus, excellent OER activity with current densities of 10 and 100 mA cm⁻² are achieved over the defective MOFs at small overpotentials of 286 mV and 365 mV, respectively, which is superior to the commercial RuO₂ catalyst and most of the bulk MOFs.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXXII . The synthesis of 2-azathianthrene and selected analogs

The synthesis of 2-azathianthrene ([1,4]benzodithiino[2,3-c]pyridine), the only remaining monoazathianthrene yet to be reported, is described. Attempts at the direct condensation of disubstituted pyridines with the dianion of 1,2-dimercaptobenzene were generally unsuccessful requiring that the alternative condensation of the dianion with disubstituted pyridine 1-oxides be employed. The title compound was characterized by physical means including ¹³C-nmr spectroscopy. One analog, 4-nitro-2-azathianthrene was also studied by X-ray crystallographic means; the molecule crystallized with two molecules in the asymmetric unit P2₁/n, a = 20.712(3), b = 7.8109(13), c = 13.720(2)Å, β = 107.880(11)°, Z = 8, the data refined to a final R = 0.051 for 3061 reflections. Dihedral angles between the planes of the phenyl rings were 135.00(13) and 132.52(13)° for the two independent molecules contained in the crystal. Close non? bonded S ?O intramolecular contacts were observed in both molecules between the sulfur and nitro-group oxygens. Both nitro groups are twisted out of the plane of the pyridine ring and are oriented at angles of 28.75 and 38.82° respectively.     

Highly Emissive Fused Heterocyclic Alkynylgold(III) Complexes for Multiple Color Emission Spanning from Green to Red for Solution‐Processable Organic Light‐Emitting Devices

A new class of fused heterocyclic tridentate ligand‐containing alkynylgold(III) complexes with tunable emission color has been successfully designed and synthesized. Structural modification of the σ‐donating fused heterocyclic alkynyl ligands, including substituted fluorene, carbazole, and triphenylamine, enables a large spectral shift of about 110 nm (ca. 3310 cm^?1) that covers the green to red region to be realized with the same tridentate ligand‐containing alkynylgold(III) complexes in solid‐state thin films. Interestingly, the energy of the excimeric emission can be controlled by the rational design of the fused heterocyclic alkynyl ligands. Superior solution‐processable organic light‐emitting devices (OLEDs) with high external quantum efficiencies (EQEs) of 12.2, 13.5, 9.3, and 5.2 % were obtained with green, yellow, orange, and red emission. These high EQE values are comparable to those of the vacuum‐deposited OLEDs based on structurally related alkynylgold(III) complexes.     

Enantioselective Allylic Oxidation of Olefins Using Chiral Quinolinyl‐oxazoline Copper Complex Catalysts

Copper complexes of chiral quinolinyl‐oxazoline have been studied as the catalysts for enantioselective allylic oxidation of cycloalkenes with tert‐butyl perbenzoate. Using 5 mol% of these chiral catalysts, optical active allylic benzoates were obtained in moderate enantiomeric excesses. CuOTf prepared in situ, CuClO₄ and CuPF₆ were found to be good precatalysts in acetone.