Fluorescence intensities of chromophores in front of a thin metal film

The fluorescence intensity from a planar multilayered system with a chromophore separated from a gold film by a dielectric spacer is measured quantitatively. The direction of excitation and the spacer thickness are varied and the angular distribution of the emission is recorded as well as its polarization. The experimental data are compared to the predictions obtained from classical electromagnetic theory, taking into account the refractive indices of the layer system as well as the nonradiative decay rate and the relative orientation of absorption and emission dipole moments of the dye. Excellent agreement is found for a spacer thickness above 15 nm if proper values for these parameters are used. Samples with thinner spacer layers show significant deviations from classical theory.     

1-AminoTriazole Transition-Metal Complexes as Laser-Ignitable and Lead-Free Primary Explosives

This unique complex study describes two isomeric aminotriazoles as auspicious nitrogen-rich ligands for energetic coordination compounds (ECCs) to replace the commonly used highly poisonous and environmentally harmful lead-based primary explosives. The triazoles were obtained by easily scalable and convenient synthetic routes starting solely from commercially available starting materials. 1-Amino-1,2,3-triazole ( 1 , 1-ATRI) and, for the first time, 1-amino-1,2,4-triazole ( 2 , 1A-1,2,4-TRI) were employed as ligands to form highly energetic transition-metal(II) complexes. The desired characteristics could be altered successively by using various nonpoisonous metal(II) centers (Cu²⁺, Mn²⁺, Fe²⁺, and Zn²⁺) and anions (Cl⁻, NO₃⁻, ClO₃⁻, ClO₄⁻, picrate, styphnate, 2,4,6-trinitro-3-hydroxyphenolate, and 2,4,6-trinitro-3,5-dihydroxyphenolate). The 14 synthesized coordination compounds were characterized comprehensively by XRD, IR and UV/Vis spectroscopy, elemental analysis, and differential thermal and thermogravimetric analyses. Ball-drop impact, electrostatic discharge (ESD), and mechanical (impact and friction) sensitivities were determined according to BAM standard methods. In addition to laser ignition experiments, selected ECCs were evaluated in classical secondary explosive initiation tests (detonators filled with pentaerythritol tetranitrate (nitropenta)), which revealed their enormous potential and proved them to be very attractive for future applications in explosives.     

Geometrische Untersuchungen über Kurvenschwerpunkte

Ohne Zusammenfassung     

Exploring Cu/Al cluster growth and reactivity: from embryonic building blocks to intermetalloid,open-shell superatoms

Cluster growth reactions in the system [Cu₅](Mes)₅ + [Al₄](Cp*)₄ (Mes = mesitylene, Cp* = pentamethylcyclopentadiene) were explored and monitored by in situ LIFDI-MS and ¹H-NMR. Feedback into experimental design allowed for an informed choice and precise adjustment of reaction conditions and led to isolation of the intermetallic cluster [Cu₄Al₄](Cp*)₅(Mes) (1). Cluster 1 reacts with excess 3-hexyne to yield the triangular cluster [Cu₂Al](Cp*)₃ (2). The two embryonic [Cu₄Al₄](Cp*)₅(Mes) and [Cu₂Al](Cp*)₃ clusters 1 and 2, respectively, were shown to be intermediates in the formation of an inseparable composite of the closely related clusters [Cu₇Al₆](Cp*)₆ (3), [HCu₇Al₆](Cp*)₆ (3H) and [Cu₈Al₆](Cp*)₆ (4), which just differ by one Cu core atom. The radical nature of the open-shell superatomic [Cu₇Al₆](Cp*)₆ cluster 3 is reflected in its reactivity towards addition of one Cu core atom leading to the closed shell superatom [Cu₈Al₆](Cp*)₆ (4), and as well by its ability to undergo σ(C–H) and σ(Si–H) activation reactions of C₆H₅CH₃ (toluene) and (TMS)₃SiH (TMS = tris(trimethylsilyl)).

Cu/Al cluster growth reactions leading to open- and closed-shell superatoms are investigated. Therein, LIFDI-MS is presented as a powerful technique for the in situ detection of cluster identities and reactivity patterns.     

Additions to N‐Sulfinylamines as an Approach for the Metal‐free Synthesis of Sulfonimidamides: O‐Benzotriazolyl Sulfonimidates as Activated Intermediates

Sulfonimidamides are obtained in moderate to very good yields from the key intermediates O‐benzotriazolyl sulfonimidates, which are formed by reacting aryldiazonium tetrafluoroborates, N‐tritylsulfinylamine, and N‐hydroxybenzotriazole hydrate in a process mediated by a tertiary amine. The formation of the sulfonimidate proceeds in inexpensive and environmentally benign dimethyl carbonate as the solvent, it does not require anhydrous conditions, and the product yields generally exceed 70 %. The substrate scope is broad, and a wide range of sensitive organic functionalities is well tolerated. The reactions probably proceed via aryl radicals formed from diazonium cations with assistance from both the tertiary amine and the sulfinylamine.     

Cannabinoid Quinones—A Review and Novel Observations

A cannabinoid anticancer para-quinone, HU-331, which was synthesized by our group five decades ago, was shown to have very high efficacy against human cancer cell lines in-vitro and against in-vivo grafts of human tumors in nude mice. The main mechanism was topoisomerase IIα catalytic inhibition. Later, several groups synthesized related compounds. In the present presentation, we review the publications on compounds synthesized on the basis of HU-331, summarize their published activities and mechanisms of action and report the synthesis and action of novel quinones, thus expanding the structure-activity relationship in these series.