The intermolecular or intramolecular asymmetric benzoin reaction was catalyzed by a small amount of N-heterocyclic carbene (NHC) (0.2-1 mol %) under solvent-free conditions. The solvent-free intramolecular asymmetric Stetter reaction also proceeded efficiently with NHC (0.2-1 mol %). In some cases, even solid-to-solid or solid-to-liquid conversions took place with low catalyst loading (0.2-1 mol %).

Flapping fluorophores (FLAP) with a flexible 8π ring are rapidly gaining attention as a versatile photofunctional system. Here we report a highly photostable “flapping peryleneimide” with an unprecedented fluorogenic mechanism based on a bent‐to‐planar conformational change in the S1 excited state. The S1 planarization induces an electronic configurational switch, almost quenching the inherent fluorescence (FL) of the peryleneimide moieties. However, the FL quantum yield is remarkably improved with a prolonged lifetime upon a slight environmental change. This fluorogenic function is realized by sensitive π‐conjugation design, as a more π‐expanded analogue does not show the planarization dynamics. With strong visible‐light absorption, the FL lifetime response synchronized with the flexible flapping motion is useful for the latest optical techniques such as FL lifetime imaging microscopy (FLIM).

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Transparent lanthanum-doped lead zirconate titanate (PLZT) ceramics with high density were fabricated using spark plasma sintering (SPS), a recently developed hot-pressing method. A wet-dry combination method was used to prepare the fine PLZT powders. The average grain size of the PLZT ceramics was less than 1 lm, because of a relatively low sintering temperature and a very short sintering time. The transmittance of PLZT ceramics increased with an increase of calcination temperature up to 7001C and then it slightly decreased with further increase of calcination temperature. The transmittance strongly depended on the SPS temperature and heat-treatment temperature. The pellet sintered at 9001C for 10 min and heat treated at 8001C for 1 h with a thickness of 0.5 mm showed a transmittance of 31% at a wavelength of 700 nm. The relationships between the transmittance and the microstructure were investigated.

Ad endrimeric trimer undergoes folding and unfolding in response to ac hemical stimulus. The trimer of interest contains ac entral dendrimer with ab utadiynelinked zinc porphyrin dimer ((ZnP) 2 )c ore, in addition to two terminal dendrimers with zinc porphyrin (ZnP) cores. The obtaineda bsorption spectra indicate that the unfolded form is the exclusive conformer in chloroform, while the addition of 1,4-diazabicyclo[2.2.2]octane (DABCO) in chloroform leads to transformation from the unfolded to the folded structure containing two DABCO units per trimer;t he folded structure originates from the cross-linking of (ZnP) 2 and ZnP with DABCO. Moreover,t he addition of excess DABCO promotes the generation of the unfolded structure containing four DABCO units.The folding of proteinsi sk nown to create organized three-dimensional structurest hat are essential for imparting aw ide range of biological functions. This process can also be simulated by the cross-linkage of single-chain polymers to produce discrete nanoscale macromolecules, such as organic nanoparticles (ONPs).[1] However,t he application of such methods to the construction of organized arrays of functional units is challenging due to structural diversity at the molecular level. To date, dendrimers have attracted attention as building blocks for ONPs, as the well-defineds tructures of dendrimers allow the precise arrangemento ff unctional units.[2] Indeed,w ep reviously reported au nique method for the construction of ONPs using dendrimers with rigid backbones. [3] In this method, dendrimersw ere linearly connected using alkyl chains and the self-folding of the resulting assembly produced ONPs with rigid backbones. Although such rigid backbonesa ppear to be au seful framework for the precise arrangement of functional units in ONPs,t he random aggregation of these backbones limits their utility.In contrast, folding of the dendrimer assembly through the cross-linking of rigid backbones is am ore sophisticated approach to create ONPs since the rigid cross-linkers can produce an extended backbone with ap redictable structure (Figure 1a). Thus, we herein report the preparation of at rimer of dendrimers containing ab utadiyne-linked zinc porphyrin dimer( (ZnP) 2 ) as the core of the central dendrimer,i na ddition to two terminal dendrimers containing zinc porphyrin (ZnP) cores (Figure 1b). Such porphyrins are considered particularly valuable for the formation of noncovalentc ross-linkages.[4] We expect that upon the addition of suitable bidentate ligands as crosslinkers, the trimer will undergo folding and unfolding as shown in Figure 1a.I na ddition, ZnP and (ZnP) 2 can be independently monitored by spectroscopicm easurements, thereby allowing the folding and unfolding processes to be disclosed. [5] As such, we will employ spectroscopic techniques to examine trimerf olding and unfolding in response to ac hemical stimulus.Trimer 1 andd endrimers 2 and 3 were synthesized as outlined in Scheme1.F ollowing the initial reaction of two hydroxyl groups in 2a wi...