Solid nitrogen

Summary

Solid nitrogen is a number of solid forms of the element nitrogen, first observed in 1884. Solid nitrogen is mainly the subject of academic research, but low-temperature, low-pressure solid nitrogen is a substantial component of bodies in the outer Solar System and high-temperature, high-pressure solid nitrogen is a powerful explosive, with higher energy density than any other non-nuclear material. Generation Karol Olszewski first observed solid nitrogen in 1884, by first liquefying hydrogen with evaporating liquid nitrogen, and then allowing the liquid hydrogen to freeze the nitrogen. By evaporating vapour from the solid nitrogen, Olszewski also generated the extremely low temperature of 48K, at the time a world record. Modern techniques usually take a similar approach: solid nitrogen is normally made in a laboratory by evaporating liquid nitrogen in a vacuum. The solid produced is porous. Occurrence in nature Solid nitrogen forms a lar

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Isolation and characterization of diazoolefins

Zhaowen Dong, Farzaneh Fadaei Tirani, Rosario Scopelliti, Kay Severin, Paul Varava

Diazoolefins tend to be highly reactive compounds that rapidly lose dinitrogen. So far, most experimental evidence for diazoolefins is indirect, via trapping experiments. Here we show that diazoolefins are observed to form in reactions of N-heterocyclic olefins with nitrous oxide. The products benefit from resonance stabilization, which enables isolation on a preparative scale, and comprehensive characterization, which includes crystallographic analyses. N-heterocyclic diazoolefins show a strong ylidic character, with a high charge density at the carbon atom next to the diazo group. Despite the presence of terminal N2 groups, N-heterocyclic diazoolefins display a good thermal stability, which surpasses that observed for most diazoalkanes. N-heterocyclic diazoolefins can bind transition and main group metal complexes without the liberation of dinitrogen, and spectroscopic data show that they are strong electron donors. They can also undergo reactions that involve the N2 group, as evidenced by cycloaddition reactions.

2021

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The symbiosis between dinoflagellate microalgae and their cnidarian host represents the fundamental mechanism that allows zooxanthellate corals to access the inorganic nutrient pool of the surrounding seawater and conserve and recycle nutrients within their tissues. Experiments have shown that colony symbiont density is strongly affected by ambient nitrogen levels and the nitrogen status of the host. Under oligotrophic conditions, the symbiont population is N- and potentially DIC-limited. Here, we investigated how a feeding-induced increase in colony symbiont density modulates the phototrophic assimilation of individual symbionts. Using stable isotopes in combination with NanoSIMS-imaging of fixed coral coenosarc tissue, we quantified in hospite C and N assimilation of individual symbionts and related these values to the local tissue density. Stylophora pistillata displayed a general negative correlation between colony symbiont density and symbiont carbohydrate and protein content, independent of feeding state. Under unfed conditions, cell-specific assimilation rates for C and N were not affected by local symbiont density. However, when the colony symbiont density was increased by regular feeding, we observed a significant negative effect: Individual autotrophic assimilation of C and N declined on average by 26% for a local density range from one to ten Symbiodinium cells. Thus, the increase in global symbiont density created conditions where symbionts in some microhabitats might be subject to competition, governed by individual performance, local host supply or light microenvironment.

2017

Synthesis of Four-Membered BN3 Heterocycles by the Borylation of Triazenes

Rosario Scopelliti, Kay Severin, Abdusalom Suleymanov

Borylated triazenes were synthesized by the dehydrocoupling of triazenes with 9-borabicyclo(3.3.1)nonane, by the condensation of triazenes with BEt3, or by the reaction of sodium triazenides with dialkyl- or diarylboron halides. The structures of the products were found to depend on the size of the substituents. Sterically demanding mesityl groups at boron or nitrogen gave rise to open-chain structures, whereas smaller substituents led to the formation of novel BN3 heterocycles.

2022