Enthalpies, ΔH(1) ?94.8 ± 6.0 and ΔH(6) ?57.1 ± 5.1 kJ mol?1, of the following reactions have been measured calorimetrically [Pt(trans-stilbene)(PPh3)2](s) + dpcp(g) → (PPh3)2Pt(dpcb)(s) + trans-stilbene(g) (1) [Pt(trans-stilbene)(PPh3)2](s) + bcbd(g) → (PPh3)2Pt(bcpd)(s) + trans-stilbene (g) (6) where dpcp is diphenylcyclopropenone, (PPh3)2Pt(dpcb) is (1,1-bistriphenylphosphine)platinadiphenylcyclobutenone, (PPh3)2O, bcbd is benzocyclobutene-1,2-dione and (PPh3)2Pt(bcpd) is (1,1-bistriphenylphosphine)platinabenzocyclopentanedione, . It is concluded that the five-membered platinacyclo ring system in (PPh3)2Pt(dpcb) is not heavily strained. 相似文献
We show how Khovanov's categorification of the Heisenberg algebra arises as a linearization of a discrete combinatorial structure in the bicategory of spans of groupoids. We also treat a categorification of in a similar way. 相似文献
A high-precision branching ratio measurement for the superallowed beta+ decay of 62Ga was performed at the Isotope Separator and Accelerator radioactive ion beam facility. Nineteen gamma rays emitted following beta+ decay of 62Ga were identified, establishing the dominant superallowed branching ratio to be (99.861+/-0.011)%. Combined with recent half-life and Q-value measurements, this branching ratio yields a superallowed ft value of 3075.6+/-1.4 s for 62Ga decay. These results demonstrate the feasibility of high-precision superallowed branching ratio measurements in the A>or=62 mass region and provide the first stringent tests of the large isospin-symmetry-breaking effects predicted for these decays. 相似文献
Motivated by the possibility of observing photoluminescence and electron paramagnetic resonance from the same species located within a fullerene molecule, we initiated an EPR study of Er3+ in ErSc2N@C80. Two orientations of the ErSc2N rotor within the C80 fullerene are observed in EPR, consistent with earlier studies using photoluminescence excitation (PLE) spectroscopy. For some crystal field orientations, electron spin relaxation is driven by an Orbach process via the first excited electronic state of the 4I(15/2) multiplet. We observe a change in the relative populations of the two ErSc2N configurations upon the application of 532 nm illumination, and are thus able to switch the majority cage symmetry. This photoisomerization, observable by both EPR and PLE, is metastable, lasting many hours at 20 K. 相似文献
A new class of high‐temperature dipolar polymers based on sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SO2‐PPO) was synthesized by post‐polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (Tg≈220 °C), the dipolar polarization of these SO2‐PPOs was enhanced, and thus the dielectric constant was high. Consequently, the discharge energy density reached up to 22 J cm?3. Owing to its high Tg , the SO2‐PPO25 sample also exhibited a low dielectric loss. For example, the dissipation factor (tan δ) was 0.003, and the discharge efficiency at 800 MV m?1 was 92 %. Therefore, these dipolar glass polymers are promising for high‐temperature, high‐energy‐density, and low‐loss electrical energy storage applications. 相似文献
The purpose of diversity-oriented synthesis is to drive the discovery of small molecules with previously unknown biological functions. Natural products necessarily populate biologically relevant chemical space, since they bind both their biosynthetic enzymes and their target macromolecules. Natural product families are, therefore, libraries of pre-validated, functionally diverse structures in which individual compounds selectively modulate unrelated macromolecular targets. This review describes examples of diversity-oriented syntheses which have, to some extent, been inspired by the structures of natural products. Particular emphasis is placed on innovations that allow the synthesis of compound libraries that, like natural products, are skeletally diverse. Mimicking the broad structural features of natural products may allow the discovery of compounds that modulate the functions of macromolecules for which ligands are not known. The ability of innovations in diversity-oriented synthesis to deliver such compounds is critically assessed. 相似文献