Boron Difluoride Complexes of Expanded N‐Confused Calix[n]phyrins That Demonstrate Unique Luminescent and Lasing Properties

Complexation of novel multiply N‐confused expanded calix[n]phyrins with boron difluoride afforded a new class of cyclic BODIPY (boron‐dipyrromethene) arrays. The structures of circularly arranged BODIPY subunits linked in an N‐confused fashion give rise to such photophysical properties unique to the macrocycles as redshifted emission wavelengths along with apparent large Stokes shifts, long emission lifetimes, and solid‐state lasing. The DFT calculations support the size‐dependent excited‐state dynamics of the macrocycles.     

ortho‐Phenylene‐Bridged Cyclic Oligopyrroles: Conformational Flexibilities and Optical Properties

ortho‐Phenylene‐bridged cyclic trimeric oligopyrrole C3 and hexameric oligopyrrole C6 were synthesized by Suzuki–Miyaura coupling reactions. The twisted structures of C3 and C6 were unambiguously revealed by X‐ray diffraction analysis. The optical properties of these cyclic oligopyrroles were compared with linear oligopyrrole L3 and cyclic tetramer C4 . The cyclic oligopyrroles exhibited large Stokes shifts and blue fluorescence with high quantum yields in solution and in the solid state. In addition, selective N‐methylation and N‐tolylation of C3 were used to tune the optical and electrochemical properties by changing the molecular twists and conformational flexibilities. Throughout these studies, the structure–property relationship of these cyclic strained oligopyrroles has been illustrated as an interesting molecular motif for novel cyclic π‐conjugated systems.     

Doubly N‐Fused [24]Pentaphyrin Silicon Complex and Its Fluorosilicate: Enhanced Möbius Aromaticity in the Fluorosilicate

Treatment of nonaromatic N‐fused [24]pentaphyrin with trichloromethylsilane in the presence of a base afforded doubly N‐fused [24]pentaphyrin and its silicon complex. Addition of fluoride ion to the silicon complex led to the formation of its fluorosilicate as an unprecedented monoanionic six‐coordinated Si^IV complex of porphyrinoid. Treatment of the fluorosilicate with acid led to the recovery of the silicon complex. The doubly N‐fused pentaphyrin, the silicon complex, and the fluorosilicate were all characterized as distinct Möbius aromatic molecules by spectroscopic measurements and X‐ray crystallographic analyses. Importantly, the second N‐fusion reaction, Si‐incorporation and fluoride addition to the Si‐atom enhanced the aromaticity of doubly N‐fused [24]pentaphyrins in this order. Tamao–Fleming oxidation of the silicon complex gave β‐keto doubly N‐fused pentaphyrin and triply fused [24]pentaphyrin, which were nonaromatic and Hückel anti‐aromatic, respectively.     

Trimeric and Tetrameric Electron‐Deficient Porphyrin Tapes

New hybrid porphyrin tapes comprising meso‐3,5‐di‐tert‐butylphenyl‐substituted Zn^II‐porphyrins ( D ) and meso‐pentafluorophenyl‐substituted Zn^II‐porphyrins ( A ) were synthesized via cross‐condensation of meso‐formyl porphyrins 1 , 5 , and 9 with oligopyrromethanes 2 and 6 as key steps. These hybrid tapes exhibit improved solubilities and enhanced chemical stability as compared with original Dn porphyrin tapes, and all display remarkably coplanar structures favorable for π‐conjugation. The absorption spectrum of ADDA displays Q‐like bands at 1400 and 1657 nm with a vibronic structure characteristic of porphyrinoids. The cyclic voltammograms exhibited positively shifted oxidation and reduction waves in the order of DDD < DAD < ADA < AAA . Tetrameric tape ADDA displays five reversible waves in a narrow range of 1.13 V. Two‐photon absorption (TPA) measurement confirmed that the π‐conjugation path is extended from 12 to ADDA and the molecular polarizability of ADA is larger than that of AAA .     

Centrosome amplification and multinuclear phenotypes are Induced by hydrogen peroxide

Multinucleated cells resulted from mitosis defect have been noted in pathophysiological states of the cells such as inflammation, senescence and cancer. Since oxidative stress has been known to correlate with these pathophysiological conditions, we tested the effect of H2O2 on the cell cycle progression and formation of multinucleated cells. H2O2 induced a significant delay in cell cycle progression in Chang liver cells. Interestingly, H2O2 actively induced hyperamplification of centrosomes (n>or=3) and multipolar spindle formation during mitosis and subsequently increased the generation of multinucleated cells. A significant increase of the phospho-ERK level was observed upon H2O2 treatment but PD98059, an MEK1/2 inhibitor, didn't reduce the frequency of cells with hyperamplified centrosomes. On the other hand, treatment of either H2O2 or adriamycin increased intracellular ROS levels and multinucleated cells, which were significantly suppressed by antioxidants, N-acetylcysteine and PDTC. Thus, our results suggest that oxidative stress can trigger centrosome hyperamplification and multinucleated cell formation, which may promote pathophysiological progression.     

Large two-photon absorption (TPA) cross-section of directly linked fused diporphyrins

The excited state dynamics and two-photon absorption properties of four novel triply linked porphyrin dimers in toluene have been investigated. The fused porphyrin dimers exhibit extremely increased two-photon absorption cross-section values (12,000-15,000 GM) compared with porphyrin monomers owing to much enhanced pi-electron delocalization throughout the porphyrin dimer ring.     

Image recording material based on the polymeric photobase generator containing oxime‐urethane groups

A polymeric photobase generator containing oxime‐urethane groups was prepared from copolymerization of MMA with N‐[4‐(benzophenoneoximino‐carbonylamino)phenyl]maleimide, a maleimide monomer containing oxime‐urethane group, and its properties as an image recording material were studied. The irradiation of this copolymer with UV light dissociates the urethane linkage to result in the formation of aromatic amino groups, which can be developed by the diazo‐coupling reaction. Various colors could be developed depending on the phenolic coupling reagents as the developer.     

Thermal curing reaction of poly(glycidyl methacrylate) using photogenerated amines from oxime-urethane derivatives

Two oxime-urethane derivatives, benzophenone oxime N-cyclohexylurethane (1 ) and dibenzophenone oxime N,N′-hexamethylenediurethane (2 ), were used as photobase generators. Photolysis of these derivatives results in the formation of amines which induce cross-linking of poly(glycidyl methacrylate) (PGMA) upon heating. The bifunctional derivative 2 is more efficient than the monofunctional derivative 1 in inducing thermal cross-linking of PGMA, with a maximum degree of insolubilization increasing up to ca. 90%.