Too Short-Lived or Not Existing Species: N-Azidoamines Reinvestigated

Enhanced cation interaction in perovskites for efficient tandem solar cells with silicon

To achieve the full potential of monolithic perovskite/silicon tandem solar cells, crystal defects and film inhomogeneities in the perovskite top cell must be minimized. We discuss the use of methylenediammonium dichloride as an additive to the perovskite precursor solution, resulting in the incorporation of in situ-formed tetrahydrotriazinium (THTZ-H+) into the perovskite lattice upon film crystallization. The cyclic nature of the THTZ-H+ cation enables a strong interaction with the lead octahedra of the perovskite lattice through the formation of hydrogen bonds with iodide in multiple directions. This structure improves the device power conversion efficiency (PCE) and phase stability of 1.68 electron volts perovskites under prolonged light and heat exposure under 1-sun illumination at 85°C. Monolithic perovskite/silicon tandems incorporating THTZ-H+ in the perovskite photo absorber reached a 33.7% independently certified PCE for a device area of 1 square centimeter.

Treatment of Substandard Rocket Fuel 1,1-Dimethylhydrazine via Its Methylene Derivative into Heterocycles Based on Pyrrolo-[3,4c]Quinolines, Cyclododeca[b]piran and Pyrrole

1,1-Dimethylhydrazine (Heptil, rocket fuel (UDMH)) is characterized by extremely high toxicity, teratogenicity and the ability to constantly absorb water from the atmosphere, losing its energy characteristics. In this regard, as well as due to the alternative fuel ("Angara") transition, there is a need for UDMH utilization in huge amounts. A more benign approach involves its immediate reaction with a formalin solution to form 1,1-dimethyl-2-methylene hydrazone (MDH), which is significantly less toxic by an order of magnitude. MDH can then be polymerized under acidic conditions, and the resulting product can be burned, yielding a substantial amount of nitrogen oxides. We propose an alternative to incineration by involving MDH in organic synthesis. We studied the reactions of MDH and its analog N,N-dimethyl-2-(methylenamino)ethane-1-amine (MDEA) with available CH-acids: tetracyanoethylated ketones (TCEKs) based on cyclohexanone, 4-propylcyclohexanone, 2-methylcyclohexanone, cyclododecanone and tetracyanoethane. The structures synthesized were confirmed by IR, 1H, 13C NMR and mass spectroscopy methods. MDH-based adducts were also identified by X-ray structural analysis. TCEKs and MDH, as well as TCEK based on cyclohexanone and MDEA, form bi- and tricyclic structures: pyrrolo [3,4c]-quinolines (using TCEKs based on cyclohexanone and 4-propylcyclohexanone), epiminomethanoquinoline-3,4-dicarbonitrile (using TCEK based on 2-methylcyclohexanone) and cyclododec[b]pyran-3,4-dicarbonitrile (using TCEK based on cyclododecanone). MDH and TCNEH2 formed a pyrrole derivative. Thus, we synthesized the structures that are of interest for molecular design and pharmaceutical chemistry.

Aerosol-Assisted Chemical Vapor Deposition of MoS2 with a Thiourea Sulfur Source: Single-Source Precursors vs Coreactant Mixtures

Aerosol-assisted chemical vapor deposition of MoS2 from solutions containing the single-source precursors cis-Mo(CO)4(TMTU)2 and Mo(CO)5(TMTU) in toluene was compared to depositions from the coreactant solution containing Mo(CO)6 and uncoordinated TMTU in toluene. The results were used to assess the significance of ligand precoordination on the properties of the deposited films. Raman spectra and GI-XRD patterns of the films show that the single-source precursors produced more intense and sharper signals for 2H-MoS2 as compared to the coreactant system of Mo(CO)6 and TMTU, which is indicative of improved crystallinity. SEM and XPS were also used to assess morphology and film composition. Thermolysis of cis-Mo(CO)4(TMTU)2 and analysis of the pyrolysis products by GC-MS and 1H NMR suggested a decomposition mechanism of the TMTU ligand where a terminal sulfido is generated on the molybdenum center with loss of a heteroatom stabilized carbene.

Nucleophilic Attack of Azide at Electrophilic Azides: Formation of N6 Units in Hexazene and Aminopentazole Derivatives

With the help of selective 15 N labeling experiments, it has been confirmed that nucleophilic attack of azide at iminium-activated organic azides leads to short-lived hexazene intermediates. Such species do not only tend to a cleavage reaction with formation of N-azido compounds, but also undergo ring closure to generate unprecedented amidino-functionalized pentazoles. Thus, treatment of the parent Vilsmeier reagent with two equivalents of sodium azide creates an aminopentazole derivative as the main product, which is easily characterized by NMR spectroscopy.