Synthesis of polymers possessing tetraphenylethylene units by three‐component coupling reactions of poly(p‐phenylene ethynylene) derivative with aryl halides and phenylboronic acid

A derivative of poly(p‐phenylene ethynylene) was subjected to the palladium‐catalyzed three‐component coupling reactions with aryl halides and phenylboronic acid to obtain polymers having tetrasubstituted cis‐vinylene units. For example, 69% of the acetylene units in the prepolymer were converted to cis‐vinylene (i.e., tetrasubstituted cis‐vinylene) units using iodobenzene and phenylboronic acid (5 equiv each with respect to acetylene units). In the UV–vis absorption spectra of the resulting polymers, clear hypsochromic shifts of the absorption maxima were observed, while bathochromic shifts and suppression of the efficiency were observed in their photoluminescence spectra. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 787–791     

Molecularly Dispersed Donors in Acceptor Molecular Crystals for Photon Upconversion under Low Excitation Intensity

For real‐world applications of photon upconversion based on the triplet–triplet annihilation (TTA‐UC), it is imperative to develop solid‐state TTA‐UC systems that work effectively under low excitation power comparable to solar irradiance. As an approach in this direction, aromatic crystals showing high triplet diffusivity are expected to serve as a useful platform. However, donor molecules inevitably tend to segregate from the host acceptor crystals, and this inhomogeneity results in the disappointing performance of crystalline state TTA‐UC. In this work, a series of cast‐film‐forming acceptors was developed, which provide both regular acceptor alignment and soft domains of alkyl chains that accommodate donor molecules without segregation. A typical triplet sensitizer, Pt^II octaethylporphyrin (PtOEP), was dispersed in these acceptor crystals without aggregation. As a result, efficient triplet energy transfer from the donor to the acceptor and diffusion of triplet excitons among regularly aligned anthracene chromophores occurred. It resulted in TTA‐UC emission at low excitation intensities, comparable to solar irradiance.     

π‐Electron Systems That Form Planar and Interlocked Anion Complexes and Their Ion‐Pairing Assemblies

Interactions between designed charged species are important for the ordered arrangements of π‐electron systems in assembled structures. As precursors of π‐electron anion units, new arylethynyl‐substituted dipyrrolyldiketone boron complexes, which showed anion‐responsive behavior, were synthesized. They formed a variety of receptor–anion complexes ([1+1] and [2+1] types) in solution, and the stabilities of these complexes were discussed in terms of their thermodynamic parameters. Solid‐state ion‐pairing assemblies of [1+1]‐ and [2+1]‐type complexes with countercations were also revealed by single‐crystal X‐ray analysis. In particular, a totally charge‐segregated assembly was constructed based on negatively and positively charged layers fabricated from [2+1]‐type receptor–anion complexes and tetrabutylammonium cations, respectively. Furthermore, the [1+1]‐type anion complex of the receptor possessing long alkyl chains exhibited mesophases based on columnar assembled structures with contributions from charge‐by‐charge and charge‐segregated arrangements, which exhibited charge‐carrier transporting properties.     

Visible-to-UV Photon Upconversion in Nanostructured Chromophoric Ionic Liquids

Visible-to-ultraviolet (vis-to-UV) triplet-triplet annihilation based photon upconversion (TTA-UC) is achieved in a non-volatile chromophoric ionic liquid (IL) for the first time. A novel IL is synthesized by combining UV-emitting anion 4-(2-phenyloxazol-5-yl)benzenesulfonate (PPOS) and trihexyltetradecylphosphonium cation (P₆₆₆₁₄). The nanostructured organization of chromophoric anions is demonstrated by synchrotron X-ray and optical measurements. When the IL is doped with a triplet sensitizer tris(2-phenylpyridinato)iridium(III) (Ir(ppy)₃), the visible-to-UV TTA-UC with a relatively low threshold excitation intensity of 61 mW cm⁻² is achieved. This is due to a large triplet diffusion coefficient in the IL (1.4×10⁻⁷ cm² s⁻¹) as well as a high absorption coefficient 15 cm⁻¹ and a long PPOS triplet lifetime of 1.55 ms, all implemented in the condensed IL system. This work demonstrates the unique potential of ILs to control chromophore arrangements for desired functions.     

Ultrasonic separation of a suspension for in situ spectroscopic imaging

Optical Review - Application of spectroscopic techniques to suspensions is difficult because optical scattering caused by solid particles reduces the accuracy. At the extreme, dense suspensions...     

Enantioselective Direct Alkynylation of Ketones Catalyzed by Chiral CCN Pincer RhIII Complexes

A direct asymmetric alkynylation of ketones with new chiral CCN Rh catalysts containing N‐heterocyclic carbene and oxazoline hybrid ligands is described. The catalytic reaction of fluoroalkyl‐substituted ketones, ArCOCF₂X (X=F, Cl, H), with aromatic and aliphatic alkynes yielded the corresponding chiral propargyl alcohols with high enantioselectivity. Control and kinetic experiments suggested a bis(alkynyl) Rh intermediate as the active species for the C?C bond‐forming step.