The synthesis,X‐ray structure analysis,and photophysical characterization of 4‐[(E)‐2‐(4‐cyanophenyl)diazenyl]‐morpholine

A novel triazene, 4‐[(E)‐2‐(4‐cyanophenyl)diazenyl]‐morpholine ( 1 ) was prepared via a diazonium ion coupling reaction between 4‐aminobenzonitrile and morpholine. The x‐ray structure of 1 was determined and evidenced π delocalization in the triazene subunit. The room temperature absorption spectrum of 1 in acetonitrile was dominated by an intense triazene‐centered π→π* transition at 325 nm. Compound 1 was observed to be luminescent, with an emission maximum at 434 nm in room temperature acetonitrile solution. The emission spectrum of 1 in propionitrile glass at 77K exhibited a narrowed emission band with a maximum at 449 nm. Broad emission from 400–700 nm with poorly resolved vibrational structure was observed from solid 1 at room temperature. J. Heterocyclic Chem., 2011.     

(±)-trans,cis-4-Hydroxy-5,6-di-O-isopropylidenecyclohex-2-ene-1-one: synthesis and facile dimerization to decahydrodibenzofurans

An efficient synthesis of (±)-trans,cis-4-hydroxy-5,6-di-O-isopropylidenecyclohex-2-ene-1-one (3) has been developed from acetonide-protected meso-1,2-dihydrocatechol derivative 1 via photooxygenation, then Kornblum-DeLaMare rearrangement. The product is unstable unless its 4-hydroxy group is protected, as it undergoes facile dimerization in solution to a 1:1 mixture of diastereoisomeric decahydrodibenzofurans 8 and 9. A new synthesis of the dihydrocatechol 1 from 1,3-cyclohexadiene has also been developed.     

Do Metric Standards Contract?—A reply to Cantoni

The Ehrenfest paradox is reviewed in order to categorize classes of “resolution” that are logically at least semiconsistent. Cantoni's candidate is analyzed with reference to such a taxonomy of resolutions.     

Laser-driven micro-rocket

We have developed a new type of miniature rocket motor for pointing and positioning microsatellites. A specially prepared tape with a transparent layer, through which the laser light passes, and an absorbing layer produce the thrust by the laser ablation process. We have achieved a specific impulse of 1800 s (greater than possible with chemistry), and laser momentum coupling coefficients of up to 50 dyn/W. The preprototype achieved 68 dyn of thrust. We discuss the target interaction physics and some of our measurements with the preprototype thruster. Received: 7 October 2002 / Accepted: 8 February 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +1-505/4663-877, E-mail: crphipps@aol.com     

Hydrogen-deuterium exchange reactions catalyzed by zerovalent phosphinepalladium complexes

Complexes of the type [Pd(PR₃)_n] (n = 3 or 4), which may be conveniently generated in situ, catalyze hydrogen-deuterium exchange reactions between D₂O and various organic substrates, at ambient temperature. The reactions are most rapid for nitroalkanes, where exchange occurs exclusively at the C(1) position and allows the isolation of specifically deuterium-labeled compounds.     

A spectral study of tautomerism in 4-arylamino-1,2-naphthoquinones

The tautomerism of 4-arylamino-1,2-naphthoquinones in aqueous solutions has been investigated by UV-visible absorption spectroscopy. It has been demonstrated that in strongly acidic solutions (Ph 0·8), protonation of the 2-keto group leads to 2-hydroxy-1,4-naphthoquinone-4-arylimine as the more stable tautomer. However, weakly acidic or alkaline solutions (Ph 4–13) contain 4-arylamino-1,2-naphthoquinone as the more stable tautomer.     

Apparent spin polarization decay in Cu-dusted Co/Al2O3/Co tunnel junctions

Co/Al2O3/Co magnetic tunnel junctions with an interfacial Cu layer have been investigated with in situ growth characterization and ex situ magnetotransport measurements. Cu interlayers grown on Co give an approximately exponential decay of the tunneling magnetoresistance with xi approximately 0.26 nm while those grown on Al2O3 have a decay length of 0.70 nm. The difference in decay lengths can be explained by different growth morphologies, and in this way clarifies a present disagreement in the literature. For monolayer coverage of Cu, we show that the tunneling spin polarization is suppressed by at least a factor of 2 compared to Co and beyond approximately 5 ML it becomes vanishingly small.