All-nitrogen solids, if successfully synthesized, are ideal high-energy-density materials because they store a great amount of energy and produce only harmless N2 gas upon decomposition. Currently, the only method to obtain all-nitrogen solids is to apply high pressure to N2 crystals. However, products such as cg-N tend to decompose upon releasing the pressure. Compared to covalent solids, molecular crystals are more likely to remain stable during decompression because they can relax the strain by increasing the intermolecular distances. The challenge of such a route is to find a molecular crystal that can attain a favorable phase under elevated pressure. In this work, we show, by designing a novel N16 molecule (tripentazolylamine) and examining its crystal structures under a series of pressures, that the aromatic units and high molecular symmetry are the key factors to achieving an all-nitrogen molecular crystal. Density functional calculations and structural studies reveal that this new all-nitrogen molecular crystal exhibits a particularly slow enthalpy increase with pressure due to the highly efficient crystal packing of its highly symmetric molecules. Vibration mode calculations and molecular dynamics (MD) simulations show that N16 crystals are metastable at ambient pressure and could remain inactive up to 400 K. The initial reaction steps of the decomposition are calculated by following the pathway of the concerted excision of N2 from the N5 group as revealed by the MD simulations.

We report a convenient single-flask methodology for the preparation of polyazatriaryl products with relevance to luminescence, catalysis, and pharmacology. The diborylation of 1,3-dibromobenzenes and double Suzuki–Miyaura coupling produces 1,3-diheteroarylbenzenes. Similarly, borylation of heteroaryl halides and double coupling to 2,6-dichloropyridine produces 2,6-diheteroarylpyridines. This methodology appears general in producing challenging polyheteroaryl targets as long as the boronic esters have no ortho heteroatoms and coupling avoids adjacent oxygens.

AbstractAn optimized single‐flask method is developed.

AbstractOctanol‐(2) (I) und Decahydroanacardol werden mit verschiedenen Raney‐Metallen und Adkin‐Kupferchromit in flüssiger Phase zu den entsprechenden Ketonen dehydriert.

The FTIR spectra of six argon-matrix-isolated flavonols were measured. Carbonyl stretching frequencies for the following compounds were the following: flavone, 1669 cm(-1); chromone, 1676 cm-1; 5-hydroxyflavone (5HF), 1660 cm(-1); 3-hydroxyflavone (3HF), 1652 cm(-1); 5-methoxyflavone (5MF), 1672 cm(-1); and 3-methoxyflavone (3MF), 1658 cm(-1). The 3HF carbonyl stretching frequency assignment represents a correction to the literature values: (1628.6 cm(-1) in an argon matrix and 1621 cm(-1) in the liquid phase). 1,2-5 The hydroxyl stretch modes for 5HF and 3HF were observed at 2935 and 3320 cm(-1), respectively, in agreement with the literature values.2-5 While the hydroxyl stretch modes predict that the 5HF intramolecular-hydrogen bond to the carbonyl is stronger than that of 3HF, the carbonyl stretch frequency of 3HF is red-shifted more than that of 5HF. In analogy to hydroxyl-substituted flavones, methoxyl substitution at the flavone 3 position also results in a greater carbonyl red-shift than at the 5 position. Relative to the methoxyflavones, the effect of hydroxyl substitution on the carbonyl is clearly greater in 5HF than in 3HF. Density functional calculations at the B3LYP/6-3 1 G(d) level are consistent with the experimental findings. Calculated OH (. . .) O intramolecular hydrogen bond distances and C-H... 0 angles were 1.70 Angstrom and 149degrees for 5HF and 1.94degrees and 122degrees for 3HF, consistent with greater hydrogen-bonding in 5HF than in 3HF. Changes in the bond distances from 5MF to 5HF are consistent with hydrogen bonding, encouraging a resonance form resembling the excited-state proton-transfer tautomer of 5HF that weakens the carbonyl. Similarly, changes in the bond distances from 3MF to 3HF suggest that hydrogen bonding stabilizes a zwitterionic resonance form that also weakens its carbonyl. This zwitterionic resonance form of 3HF resembles the excited state proposed for its unusual fluorescence and could be responsible for the facile energy transfer to this state.

The aldehyde moiety in the title complex, chloro(2-pyridinecarboxaldehyde-N,O)(2,2':6',2"-terpyridine-kappa(3)N)ruthenium(II)-chloro(2-pyridinecarboxylic acid-N,O)(2,2':6',2"-terpyridine-kappa(3)N)ruthenium(II)-perchlorate-chloroform-water (1.8/0.2/2/1/1), [RuCl(C6H5NO)(C15H11N3)](1.8)[RuCl(C6H5NO2)(C15H11N3)](0.2)(ClO4)2-CHCl3-H2O, is a structural model of substrate coordination to a transfer hydrogenation catalyst. The title complex features two independent Ru(II) complex cations that display very similar distorted octahedral coordination provided by the three N atoms of the 2,2':6',2"-terpyridine ligand, the N and O atoms of the 2-pyridinecarboxaldehyde (pyCHO) ligand and a chloride ligand. One of the cation sites is disordered such that the aldehyde group is replaced by a 20 (1)% contribution from a carboxylic acid group (aldehyde H replaced by carboxyl O-H). Notable dimensions in the non-disordered complex cation are Ru-N 2.034 (2) A and Ru-O 2.079 (2) A to the pyCHO ligand and O-C 1.239 (4) A for the pyCHO carbonyl group.

Photography is one of the few sources available that can demon- strate the scientific validity of UFO phenomena. The Heflin photos, taken in Santa Ana, California, in 1965 were regarded as most probably genuine until 1968. Then questions arose from scientists and other UFO researchers that remained unanswered until the 1990s, mainly because the four original pho- tos had been taken by unidentified persons posing as government personnel. In 1993, Heflin' s Polaroid originals surfaced unexpectedly under mysterious circumstances, and reanalysis was resumed by a three-member team, includ- ing two scientists and a veteran UFO investigator. State-of-the-art computer enhancement has revealed new data that answer all prior doubts and ques- tions and discloses additional information that could not have been available at the time they were taken. In this article, we address the validity of the ob- jections as originally put forth and the results of the computer-enhancement analysis. A second article, to follow, details more technical aspects of the computer-enhancement analysis performed.

The preparation of trans-[(terpy)Ru(NC5H4O-kappaN)(2)(OH2)] 1 provides the first structurally characterized example of monodentate kappaN bound 2-pyridonato ligands on ruthenium(II) and a new catalyst for the transfer hydrogenation of ketones featuring a saturated hard donor ligand set.

The complex (Trpy)RuCl3 (Trpy = 2,2′:6′,2″-terpyridine) reacts with alkaline hexacyanoferrate(III) to form a terpyridyl ruthenium(IV)-oxo complex that catalyzes the oxidation of 2-propanol and benzyl alcohol by alkaline hexacyanoferrate(III). The reaction kinetics of this catalytic oxidation have been studied photometrically. The reaction rate shows a first-order dependence on [RU(IV)], a zero-order dependence on [hexacyanoferrate(III)], a fractional order in [substrate], and a fractional inverse order in [HO−]. The kinetic data suggest a reaction mechanism in which the catalytic species and its protonated form oxidize the uncoordinated alcohol in parallel slow steps. Isotope effects, substituent effects, and product studies suggest that both species oxidize alcohol through similar pericyclic processes. The reduced catalytic intermediates react rapidly with hexacyanoferrate(III) and hydroxide to reform the unprotonated catalytic species. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 760–770, 2000