Mono- and Dinitro-BN-Naphthalenes: Formation and Characterization.

Mono- and dinitro-BN-naphthalenes, i.e., 1-nitro-, 3-nitro-, 1,6-dinitro-, 3,6-dinitro-, and 1,8-dinitro-BNN, were generated in the nitration of 9,10-BN-naphthalene (BNN), a boron-nitrogen (BN) bond-embedded naphthalene, with AcONO2 and NO2BF4 in acetonitrile. The nitrated products were isolated and characterized by NMR, GC-MS, IR, and X-ray single crystallography. The effects of the nitration on the electron density and aromaticity of BNN were evaluated by B-11 NMR analysis and HOMA calculations.

Effect of counter-ion on packing and crystal density of 5,5'-(3,3'-bi[1,2,4-oxa-diazole]-5,5'-di-yl)bis-(1H-tetra-zol-1-olate) with five different cations.

In energetic materials, the crystal density is an important parameter that affects the performance of the material. When making ionic energetic materials, the choice of counter-ion can have detrimental or beneficial effects on the packing, and therefore the density, of the resulting energetic crystal. Presented herein are a series of five ionic energetic crystals, all containing the dianion 5,5'-(3,3'-bi[1,2,4-oxa-diazole]-5,5'-di-yl)bis-(1H-tetra-zol-1-olate), with the following cations: hydrazinium (1) (2N2H5+·C6N12O42-), hydroxyl-ammonium (2) 2NH4O+·C6N12O42- [Pagoria et al.. (2017). Chem. Heterocycl. Compd, 53, 760-778; included for comparison], di-methyl-ammonium (3) (2C2H8N+·C6N12O42-), 5-amino-1H-tetra-zol-4-ium (4) (2CH4N5+·C6N12O42-·4H2O), and amino-guanidinium (5) (2CH7N4+·C6N12O42-). Both the supra-molecular inter-actions and the sterics of the cation play a role in the density of the resulting crystals, which range from 1.544 to 1.873 Mg m-1. In 5, the tetra-zolate ring is disordered over two positions [occupancy ratio 0.907 (5):0.093 (5)] due to a 180° rotation in the terminal tetra-zole rings.

Structural determination of NSC 670224, synthesis of analogues and biological evaluation.

Follow my lead! NSC 670224, previously shown to be toxic to Saccharomyces cerevisiae at low micromolar concentrations, potentially acts via a mechanism of action related to that of tamoxifen (NSC 180973), breast cancer drug. The structure of NSC 670224, previously thought to be a 2,4-dichloro arene, was established as the 3,4-dichloro arene, and a focused library of analogues were synthesized and biologically evaluated.

Manipulation of intraparticle charge delocalization by selective complexation of transition-metal ions with histidine moieties.

Ruthenium nanoparticles were cofunctionalized with pyrene and histidine moieties through Ru═carbene π bonds. The selective complexation of the histidine moiety with transition-metal ions led to a marked diminishment of the emission peak at 490 nm which arose from the nanoparticle-bridged pyrene moieties that behaved analogously to pyrene dimers with a conjugated spacer. This is accounted for by the polarization of the core electrons by the added positive charge that impacted the intraparticle charge delocalization between the particle-bound pyrene moieties. This electronic interaction was likely facilitated by the π interactions between the metal ions and the imidazole ring as well as by the conjugated molecular backbone that linked the imidazole ring to the nanoparticle cores. Within the present experimental context, of all the metal ions tested, the impacts were much more drastic with Pb(2+), Co(2+), and Hg(2+) than with Li(+), K(+), Rb(+), Mg(2+), Ca(2+), and Zn(2+) ions, with the most sensitive variation observed with Pb(2+). This is ascribed to the enhanced π interactions of the histidine moiety with the Pb(2+), Co(2+), and Hg(2+) ions because of their capability of donating d electrons, a behavior consistent with prior studies based on conventional histidine-metal ion complexes.

Alkyne-functionalized ruthenium nanoparticles: ruthenium-vinylidene bonds at the metal-ligand interface.

Stable ruthenium nanoparticles were prepared by the self-assembly of 1-dodecyne onto the "bare" Ru colloid surface. The formation of a Ru-vinylidene (Ru═C═CH-R) interfacial bonding linkage was confirmed by the specific reactivity of the nanoparticles with imine derivatives to form a heterocyclic complex at the metal-ligand interface, as manifested in (1)H and (13)C NMR, photoluminescence, and electrochemical measurements in which a ferrocenyl imine was used as the labeling probe. Notably, the resulting nanoparticles could also undergo olefin metathesis reactions with vinyl-terminated molecules, as exemplified by the functionalization of the nanoparticles with 1-vinylpyrene. In sharp contrast, no reactvity was observed with 1-dodecynide-stabilized ruthenium nanoparticles with either imine or vinyl derivatives, indicating that these (deprotonated) nanoparticles were stabilized instead by the formation of a Ru-C≡ dπ bond at the metal-ligand interface.

Intraparticle charge delocalization of carbene-functionalized ruthenium nanoparticles manipulated by selective ion binding.

Olefin metathesis reactions of carbene-stabilized ruthenium nanoparticles were exploited for the incorporation of multiple functional moieties onto the nanoparticle surface. When the nanoparticles were cofunctionalized with 4-vinylbenzo-18-crown-6 and 1-vinylpyrene, the resulting particles exhibited fluorescence characteristics that were consistent with dimeric pyrene with a conjugated chemical bridge, with three peaks observed in the emission spectra at 391, 410, and 485 nm. The behaviors were ascribed to intraparticle charge delocalization between the pyrene moieties afforded by the conjugated Ru═carbene interfacial linkages. Notably, upon the binding of metal ions in the crown ether cavity, the emission intensity of the nanoparticle fluorescence was found to diminish at 485 nm and concurrently increase at 391 and 410 nm rather markedly, with the most significant effects observed with K(+). This was accounted for by the selective binding of 18-crown-6 to potassium ions, where the positively charged ions led to the polarization of the nanoparticle core electrons that was facililated by the conjugated linkage to the metal surface and hence impeded intraparticle charge delocalization. Control experiments with a pyrene-crown ether conjugate (2) and with ruthenium nanoparticles cofunctionalized with 4-vinylbenzo-18-crown-6 and 1-allylpyrene suggested that the through-bond pathway played a predominant role in the manipulation of intraparticle electronic communication whereas the contributions from simple electrostatic interactions (i.e., through-space pathway) were minimal.

Ferrocene-functionalized carbon nanoparticles.

Carbon nanoparticles were synthesized from natural gas soot and functionalized with ferrocenyl moieties by using 4-ferrocenylphenyldiazonium as the reactive precursor. The incorporation of the ferrocenyl units onto the carbon nanoparticle surface was confirmed by varied spectroscopic measurements. For instance, in FTIR measurements the characteristic vibrational bands of the ferrocenyl and phenyl moieties could be clearly identified. XPS measurements showed that there were approximately 31.9 ferrocenyl units per nanoparticle. UV-vis spectroscopic measurements displayed an absorption band at ca. 465 nm which was consistent with the optical characteristics of ferrocenyl derivatives. Furthermore, with surface functionalization by the ferrocenyl moieties, the photoluminescence of the carbon nanoparticles was found to diminish in intensity and red-shift in energy with the addition of NOBF(4). This was accounted for by the formation of varied electron-accepting moieties on the particle surface, such as positively charged ferrocenium, quinone-like derivatives, and nitrosation of the aromatic rings of the graphitic cores. Interestingly, in electrochemical studies the nanoparticle-bound ferrocenyl moieties were found to exhibit two pairs of voltammetric waves with a difference of their formal potentials at about 78 mV, suggesting nanoparticle-mediated intraparticle charge delocalization at mixed valence as a result of the strong core-ligand covalent bonds and the conductive sp(2) carbon matrix of the graphitic cores. Consistent behaviors were observed in near-infrared measurements, indicating that the particles behaved analogously to a Class I/II mixed-valence compound.

Pyrene-functionalized ruthenium nanoparticles as effective chemosensors for nitroaromatic derivatives.

Pyrene-functionalized Ru nanoparticles were synthesized by olefin metathesis reactions of carbene-stabilized Ru nanoparticles with 1-vinylpyrene and 1-allylpyrene (the resulting particles were denoted as Ru=VPy and Ru=APy, respectively) and examined as sensitive chemosensors for the detection of nitroaromatic compounds, such as 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), 1-chloro-nitrobenzene (CNB), and nitrobenzene (NB), by their effective quenching of the nanoparticle fluorescence. It was found that the detection sensitivity increased with increasing nitration of the molecules. Additionally, in comparison to monomeric pyrene derivatives, both Ru=VPy and Ru=APy nanoparticles exhibited markedly enhanced performance in the detection of nitroaromatic explosives, most probably as a result of the enhanced collision frequency between the fluorophores and the quencher molecules. Furthermore, Ru=VPy nanoparticles displayed much higher sensitivity (down to the nanomolar regime for TNT) than Ru=APy in the detection of these nitroaromatic explosives, which was ascribed to the extended intraparticle conjugation that provided efficient pathways for energy/electron transfer and consequently amplified the analyte binding events.