Experimental determination of the alpha and beta C--H bond dissociation energies in naphthalene

The acidities of the two different sites in naphthalene (1alpha and 1beta) and the electron affinities of the alpha- and beta-naphthyl radicals were measured using a Fourier transform mass spectrometer. Both carbon-hydrogen bond dissociation energies for naphthalene also were obtained, in this case via the application of a thermodynamic cycle. The final results are DeltaH(o)acid (1alpha) = 394.2+/-1.2 kcal mol(-1), DeltaH(o)acid (1beta) = 395.5+/-1.3 kcal mol(-1), EA(alpha) = 31.6+/-0.5 kcal mol(-1), EA(beta) = 31.6+/-0.5 kcal mol(-1), BDE(1alpha) = 112.2+/-1.3 kcal mol(-1) and BDE(1alpha) = 111.9+/-1.4 kcal mol(-1), and they are compared to benzene and phenyl radical as well as ab initio and density functional theory (B3LYP) calculations.     

Energy release in the reaction of metal powders with fluorine containing polymers

Fluorine and its derivatives have been used as a substitute to oxygen-containing oxidizers in higher performing propellants and other energetic materials. They typically react rapidly with metals or thin oxide layers of the metals to produce metal fluorides, generally in the gaseous state.Thermal reactions of stoichiometric mixtures of metal (M=Al, Ti) -F containing polymers have been studied using thermal analyzers and their energetics are compared with the metals in other halogen element containing oxidizers. The experimental results indicated that thermal reaction becomes more exothermic as the bond strength between Al-X (X=F, Br, I) becomes stronger. It was also found that oxidation of metal powders is largely affected by the size of metal powders as well as the nature of existing oxide layer.     

New family of aminophenalenyl-based neutral radical molecular conductors: synthesis, structure, and solid state properties

We report the preparation, crystallization, and solid-state characterization of the first members of a new family of spiro-bis-(1,9-diamino-substituted-phenalenyl)boron neutral radicals. The crystal structures show that the three radicals are monomeric and without close contacts in the crystal lattice. In all cases magnetic susceptibility measurements confirm the presence of free radicals with one unpaired spin per molecule. Two of the new radical compounds are among the most highly conducting neutral organic solids, with room-temperature conductivities reaching sigma(RT) = 4 x 10(-2) S/cm. The measured conductivities correlate with the closest intermolecular contacts in the solid state and with the calculated band dispersions, even though the bandwidths are much smaller than those found in other organic conductors.     

Time delays in lead-salt semiconductor diode lasers

Time delays of typically 15–17 have been measured directly for PbS_1–xSe_x, Pb_1–xSn_xSe and Pb_1–xSn_xTe diode lasers at injection levels just above threshold in each case. The corresponding minority carrier lifetimes, as determined using the one-carrier injection model, were typically 2–4.     

Preparation of crown compounds containing allyloxymethyl or butenyl groups for attachment to silica gel or containing long chain lipophilic groups for use in liquid membrane systems

Several new macrocyclic polyether ligands have been prepared for use in the separation of metal ions from aqueous solutions. Four of the crown ethers reported contain 1,2,4-triazole or 4-pyridone protonionizable subcyclic units and lipophilic groups. The remaining crown ethers are not proton-ionizable but contain alkene groups and were prepared for attachment to silica gel. The crowns were prepared by reacting the appropriate glycols with the appropriate ditosylates or dichloride in the case of the 1,2,4-triazole subcyclic unit. The crowns with proton-ionizable and lipophilic substituents were tested in liquid membrane transport systems and some of the crowns with alloxymethyl or butenyl substituents were attached to silica gel. The log K values for the interaction of these silica gel-bound macrocycles with certain metal ions were nearly the same (± 10%) as those for the association of the unbound macrocycles with the same metal ions.     

Chiral Pyridine-Based Macrobicyclic Clefts: Synthesis and Enantiomeric Recognition of Ammonium Salts

An achiral (3) and two chiral pyridine-based macrobicyclic clefts (4 and 5) have been prepared by treating 2,6-bis[[2',6'-bis(bromomethyl)-4'-methylphenoxy]methyl]pyridine (2) with the appropriate achiral and chiral glycols. Starting 2 was prepared by first treating 2,6-bis(hydroxymethyl)-4-methylphenol with 2,6-[(tosyloxy)methyl]pyridine followed by phosphorus tribromide. Achiral macrobicyclic cleft 3 formed a complex at 25 degrees C in 50% CH(3)OH/50% CHCl(3) (v/v) with a primary ammonium salt (log K = 3.15) as evidenced by a significant change in the (1)H NMR spectrum. Highly organized (S,S,S,S)-4, prepared by treating 2 with (1S,5S)-3-oxapentane-1,5-diol, exhibited recognition at 25 degrees C in 20% C(2)H(5)OH/80% 1,2-C(2)H(4)Cl(2) (v/v) for the (S)-enantiomer of alpha-(1-naphthyl)ethylammonium perchlorate (NapEt) over its (R)-form (Delta log K = 0.85). This high recognition factor probably reflects an increase in molecular rigidity by the introduction of a second macro ring on the monocyclic pyridinocrown ligand.     

Transition Metal Complexes with Bidentate Ligands Spanning trans-Positions. Part XIII. Preparation,properties and crystal and molecular structures of chlorocarbonyl-2,11-bis(diphenylphosphinophenyl) benzo[c]phenanthreneiridium (I) and trichlorocarbonyl-2,11-bis(diphenylphosphinomethyl) benzo[c]phenanthreneiridium(III)

The complex [IrCl₃(CO)( 1 )]( 4,1 =2,11-bis (diphenylphosphinomethyl)benzo[c]phenanthrene) has been prepared by CuCl₂-oxidation of [IrCl(CO)( 1 )]( 2a ). It is shown that the chlorine oxidation of 2a gives a mixture of products whose composition depends on the reaction conditions. The X-ray crystal structures of 2a and 4 have been determined. The small conformational differences observed for the trans-spanning ligand 1 in the two complexes are likely to be caused by the difference in Ir-P bond lengths in square planar 2a and octahedral 4 (2.310(4) and 2.411(3) Å, respectively).