Organoplatinum‐Mediated Synthesis of Cyclic pi‐Conjugated Molecules

Considerable interest has been recently focused on hoop‐shaped π‐conjugated molecules because of their great potentials in molecular electronics. In particular, cycloparaphenylenes (CPPs), consist of para‐linked phenylene unit in a cyclic manner, have become the subject of recent interest in this area.1 We report here the synthesis of CPPs,2) their derivatives,3 and a cage‐like three‐dimensional molecule4 based on the platinum‐mediated assembly of ‐units and subsequent reductive elimination of platinum (Scheme 1). Several unique properties of the prepared compounds are also reportedConsiderable interest has been recently focused on hoop‐shaped π‐conjugated molecules because of their great potentials in molecular electronics. In particular, cycloparaphenylenes (CPPs), consist of para‐linked phenylene unit in a cyclic manner, have become the subject of recent interest in this area.1 We report here the synthesis of CPPs,2) their derivatives,3 and a cage‐like three‐dimensional molecule4 based on the platinum‐mediated assembly of ‐units and subsequent reductive elimination of platinum (Scheme 1). Several unique properties of the prepared compounds are also reportedUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Stochastic Simulation of Controlled Radical Polymerization Forming Dendritic Hyperbranched Polymers

Stochastic simulation of the formation process of hyperbranched polymers (HBPs) based on the reversible deactivation radical polymerization (RDRP) using a branch-inducing monomer, evolmer, has been carried out. The simulation program successfully reproduced the change of dispersities (Đs) during the polymerization process. Furthermore, the simulation suggested that the observed Đs (=1.5–2) are due to the distribution of the number of branches instead of undesired side reactions, and that the branch structures are well controlled. In addition, the analysis of the polymer structure reveals that the majority of HBPs have structures close to the ideal one. The simulation also suggested the slight dependence of branch density on molecular weight, which was experimentally confirmed by synthesizing HBPs with an evolmer having phenyl group

A donor-acceptor 10-cycloparaphenylene and its use as an emitter in an organic light-emitting diode

We thank JSPS Core-to-Core Program and International Joint Usage/Research Program of Institute for Chemical Research, Kyoto University (grant #2020-37 and 2021-37) for financial support. The St Andrews team would also like to thank EPSRC (EP/P010482/1) for financial support. D.C. thanks the China Scholarship Council (No. 201603780001). The Kyoto team would like to thank JSPS KAKENHI Grant Numbers JP20H05840 (Grant-in-Aid for Transformative Research Areas, “Dynamic Exciton”).Here, we explored the possibility of using cycloparaphenylenes (CPP) within a donor–acceptor TADF emitter design. 4PXZPh-[10]CPP contains four electron-donating moieties connected to a [10]CPP. In the 15 wt % doped in CzSi film, 4PXZPh-[10]CPP showed sky-blue emission with λPL = 475 nm, ΦPL = 29%, and triexponential emission decays with τPL of 4.4, 46.3, and 907.8 ns. Solution-processed OLEDs using 4PXZPh-[10]CPP exhibited sky-blue emission with an λEL of 465 nm and an EQEmax of 1.0%.Publisher PDFPeer reviewe

Recent progress in the use of photoirradiation in living radical polymerization

The effects of photoirradiation in controlled and living radical polymerization (LRP), namely nitroxide-mediated polymerization (NMP), atom-transfer radical polymerization (ATRP), cobalt-mediated radical polymerization (CMRP), reversible addition-fragmentation chain transfer polymerization (RAFT), organoiodine-mediated radical polymerization (IRP), and organotellurium-mediated radical polymerization (TERP), are summarized. As in the conventional radical polymerization, photoirradiation has been used for generating radicals under mild conditions in LRP methods. In addition to this use, photoirradiation is also used to overcome the difficulties characteristic to each method, such as activation of catalysis, generation of controlling agents, and increasing the polymer-end structure. The most-recent developments in the use of photochemistry in LRP are summarized in this review

One-Step Synthesis of Dendritic Highly Branched Polystyrenes by Organotellurium-Mediated Copolymerization of Styrene and a Dienyl Telluride Monomer

Dendritic highly branched polystyrenes (HB‐PSts) were prepared by a one‐step copolymerization of dienyl telluride 6 and St in the presence of organotellurium chain transfer agent 2. The molecular weight (MW), dendritic generation, and branching density were easily controlled by the ratio of 2 to 6 to styrene (St) with maintaining monodispersity. The branching efficiency estimated by a deuterium‐labeling experiment showed that 6 quantitatively (>95 %) served as the branching point. The end group fidelity was high (ca. 90 %) as determined by the end group transformation to pyrene‐derivative. Intrinsic viscosity of the HP‐polystyrenes was significantly lower than that of linear polystyrenes and were easily tuned by the branching number and branching density. The method is compatible of various functional groups and chloro and acetoxy‐substituted styrenes were also used as a comonomer. A tadpole block copolymer was also synthesized starting from linear PSt as a macroinitiator

Role of Lewis Acids in Preventing the Degradation of Dithioester-Dormant Species in the RAFT Polymerization of Acrylamides in Methanol to Enable the Successful Dual Control of Molecular Weight and Tacticity

Reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylamide in methanol using dithioester RAFT chain-transfer agents was unsuccessful due to degradation of the end group. However, this degradation was completely suppressed by the addition of rare-earth metal triflates (RMTs). As RMTs are effective for the stereoselective polymerization of acrylamides, RAFT polymerization in the presence of RMTs afforded the corresponding poly(acrylamide)s with controlled molecular weight and tacticity. The conditions allowed the synthesis of high-molecular-weight polyacrylamides with molecular weights up to 168,000, low dispersity (meso diad selectivity). The degradation mechanism initiated by nucleophilic attack of acrylamide on the dithioester group was experimentally clarified for the first time. As RMT is a Lewis acid, its coordination to the amide group of acrylamide reduces its nucleophilicity

Synthesis of Structurally Controlled, Highly Branched Polymethacrylates) by Radical Polymerization Through the Design of a Monomer Having Hierarchical Reactivity

The controlled synthesis of highly branched (HB) poly(methyl methacrylate) (PMMA) with a molecular weight of up to 88 × 103 gmol and low dispersity (Ð 2C=CHTePh (4cD), and MMA in the presence of the organotellurium chain transfer agent 6cI at 30 °C. Control of the branching structure was suggested by the Mark-Hauwink-Khun-Sakurada plots corresponding to samples in solution and trapped ion mobility spectroscopy-time of flight mass spectrometry in the gas phase. The mechanism of 4cD for the structural control of HB-PMMA synthesis comes from the hierarchical reactivity of the C-Te bond of 4cD, which serves as the branching point only after 4cD reacts and is incorporated into the polymer chain. In contrast, copolymerization using previously reported vinyltellurides 4aA (H2C=C(Me)TeMe) and 4aB (H2C=C(Me)-CH=CHTeMe) could not control the branching structure due to the b-carbon fragmentation reaction from the intermediate radicals generated from 4aA and 4bB. The theoretical calculations suggest that the suppression of the undesired fragmentation reaction when using 4cD is due to the acceleration of the desired propagation reaction forming a branched structure instead of decelerating the fragmentation reaction. Due to the versatility of radical polymerization, methacrylates with bulky substituents, such as t-butyl methacrylate, and polar functional groups, such as N,N-dimethylethyl methacrylate (DMAEM), were also used as monomers to afford structurally controlled corresponding HB polymers. These studies clearly open a new possibility for the use of HB polymers in macromolecular engineering