Stable organomercury compounds containing an o-iminosemiquinone radical ligand

A series of stable paramagnetic organomercury compounds containing the 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinone ligand (imSQ) with the general formula imSQHgR (R = Ph, Et, Prⁿ, Buⁿ, Prⁱ, Hex^c, CH₂SiMe₃, p-FPh, Fc, p-Me₂NPh) were synthesized. The molecular and electronic structures of the synthesized compounds were investigated by EPR spectroscopy and X-ray diffraction. The o-iminosemiquinone ligand shows the unusual amidophenoxy-type coordination mode. In the EPR spectra of the compounds imSQHgR, the hyperfine coupling constant of magnetic mercury isotopes (^199,201Hg) depends on the nature of the substituent R, the temperature, and the nature of the solvent. Voltammetric investigations showed that the complex imSQHgFc undergoes three reversible one-electron redox steps related to the redox transformations of both the o-iminoquinone ligand and the metallocene moiety of the molecule.     

The Structurally Regular trans-1,4-Poly(chloroprene)

Radiation polymerization of large crystals of chloroprene formed within the temperature range -130 to -180°C has yielded the stereoregular trans-1,4-poly(2-chloro-1,3-butadiene). The monomer was found to have a glass transition temperature of ca. -180°C. Polymerization of monomer rapidly cooled to below -180°C was difficult and gave only structurally irregular polymer in low yield.     

Synthesis and tautomerism of spiro-pyrazolines

An experimental study on the synthesis, tautomerism, and acid promoted structural changes of spiro-pyrazolines is described. The target was achieved through a [3+2]-dipolar cycloaddition of an alkene with nitrile imines generated in situ and was isolated in high yield. The synthesized cycloadduct displayed a tendency to exhibit an imine–enamine type of tautomerism as evidenced by X-ray crystal and NMR studies. Furthermore, addition of an acid resulted in the transformation of an imine tautomer to an enamine. The current report constitutes a first formal observation of this kind of tautomerism observed in spiro-indoline pyrazolines.     

The structure and helicity of perfluorooctanonitrile, CF3–(CF2)6–CN

New molecular structural data is presented for a cyanide terminated oligomer of polytetrafluoroethene. The target molecule, CF₃–(CF₂)₆–CN, has been seeded within a pulsed supersonic expansion of argon. The result of this action is to cool the species to rotational temperatures below 4 K. Within this state, the pure rotational spectrum of the oligomer has been recorded using two types of Fourier transform microwave spectroscopy. A total of 111 transitions have been identified involving rotational J levels between 6 and 40. Only a- and b-type transitions were observed. The spectrum has been analyzed using a Hamiltonian containing all three rotational constants and one centrifugal distortion constant, D_J. The experimental spectroscopic constants have been used to develop an effective molecular structure by scaling the quantum chemical calculated structure. The data shows that the seven carbon perfluorinated chain for the isolated oligomer twists ≈104°. This compares well to the C₇F₁₃-twist of ≈97° anticipated from the X-ray structure of phase II polytetrafluoroethene.     

BKP方程族的Pfaffian解

本文从约化的角度考虑BKP方程族的Pfaffian形式的解.证明了通过施加适当的微分约束,KP方程族的格拉姆行列式的解很自然的约化为BKP方程族的解.     

Ruthenium‐Grafted Vinylhelicenes: Chiroptical Properties and Redox Switching

The properties of mono‐ and bis‐Ru–vinyl[6]helicene complexes ( 2 a and 2 b , respectively), recently synthesized by using molecular engineering of helicenes based on the grafting of lateral organometallic substituents on the π‐helical backbone through a vinyl bridge, are presented. These helicene derivatives are thoroughly characterized, with special attention given to their chiroptical properties and redox switching activity. The UV/Vis and electronic circular dichroism (ECD) spectra of P and M enantiopure species, both in the neutral and oxidized states ([ 2 a ] ^{. +}, [ 2 b ] ^{. +}, and [ 2 b ]²⁺), are analyzed with the aid of quantum‐chemical calculations. The extended π‐conjugation facilitated by the vinyl moiety, clearly visible in the electronic structures of 2 a , b , introduces new active bands in the ECD spectra that consequently lead to a significant increase in optical rotation of Ru–vinylhelicenes compared with the organic precursors. The vibrational circular dichroism (VCD) spectra were measured and calculated for both the organic and organometallic species and constitute the first examples of VCD for metal‐based helicene derivatives. Finally, the redox‐triggered chiroptical switching activity of 2 a , b is examined in detail by using ECD spectroscopy. The modifications of the ECD spectra in the UV/Vis and NIR region are well reproduced and rationalized by calculations.     

DNA Damage Checkpoint Responses in the S Phase of Synchronized Diploid Human Fibroblasts

We investigated the hypothesis that the strength of the activation of the intra‐S DNA damage checkpoint varies within the S phase. Synchronized diploid human fibroblasts were exposed to either 0 or 2.5 J m^?2 UVC in early, mid‐ and late‐S phase. The endpoints measured were the following: (1) radio‐resistant DNA synthesis (RDS), (2) induction of Chk1 phosphorylation, (3) initiation of new replicons and (4) length of replication tracks synthesized after irradiation. RDS analysis showed that global DNA synthesis was inhibited by approximately the same extent (30 ± 12%), regardless of when during S phase the fibroblasts were exposed to UVC. Western blot analysis revealed that the UVC‐induced phosphorylation of checkpoint kinase 1 (Chk1) on serine 345 was high in early and mid S but 10‐fold lower in late S. DNA fiber immunostaining studies indicated that the replication fork displacement rate decreased in irradiated cells at the three time points examined; however, replicon initiation was inhibited strongly in early and mid S, but this response was attenuated in late S. These results suggest that the intra‐S checkpoint activated by UVC‐induced DNA damage is not as robust toward the end of S phase in its inhibition of the latest firing origins in human fibroblasts.     

Hydrophobic Cysteine Poly(disulfide)‐based Redox‐Hypersensitive Nanoparticle Platform for Cancer Theranostics

Selective tumor targeting and drug delivery are critical for cancer treatment. Stimulus‐sensitive nanoparticle (NP) systems have been designed to specifically respond to significant abnormalities in the tumor microenvironment, which could dramatically improve therapeutic performance in terms of enhanced efficiency, targetability, and reduced side‐effects. We report the development of a novel L ‐cysteine‐based poly (disulfide amide) (Cys‐PDSA) family for fabricating redox‐triggered NPs, with high hydrophobic drug loading capacity (up to 25 wt % docetaxel) and tunable properties. The polymers are synthesized through one‐step rapid polycondensation of two nontoxic building blocks: L ‐cystine ester and versatile fatty diacids, which make the polymer redox responsive and give it a tunable polymer structure, respectively. Alterations to the diacid structure could rationally tune the physicochemical properties of the polymers and the corresponding NPs, leading to the control of NP size, hydrophobicity, degradation rate, redox response, and secondary self‐assembly after NP reductive dissociation. In vitro and in vivo results demonstrate these NPs’ excellent biocompatibility, high selectivity of redox‐triggered drug release, and significant anticancer performance. This system provides a promising strategy for advanced anticancer theranostic applications.