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Nanobelt news

15 April 2017 - The belt wars

nanobelt.PNGAn organic chemistry feat that the researchers themselves equate to the controlled synthesis of fullerene back in 2002: the synthesis of a new aromatic nanobelt that can be regarded as a nanotube segment (Povie et al. DOI). This blog has been covering loops, hoops, rings and belts before here, here and here including earlier work by one of the lead authors Kenichiro Itami.

For its size it is a complex molecule, the nomenclature has yet to be invented but it is a cyclacene and described as a belt segment of 6,6-CNT and as an isomer of 12-cyclophenacene. The final step in a 1% yield consisted of a Bis(cyclooctadiene)nickel(0) catalysed coupling reaction of the nanoring precursor shedding 12 equivalents of bromine. Main characteristics: near perfectly round with a diameter of 8.3 angstroms, two resonance structures dominate with the major one having 4 Clar sextets and the other one 2.

A nitric acid cloud

01 April 2017 - Disaster movies

nitric acid cloud.PNGNitric acid is a nasty chemical. One of those with the skull and bones logo as part of the EU classification 'very toxic' and to be handled with care in a laboratory setting. Two villages in Belgium have now first hand experience in dealing with a whole nitric acid cloud after a chemical tank accident. (nieuwsblad.be link) What to do? Run for it and evacuate! Nobody got hurt so we can be relaxed about it. The culprit was a manure processing plant, the amount of nitric acid spilled was 15,000 liters. Another news report mentions that the chemical tank had failed because the acid was eating away metal parts. It is also suggested the tank was very new and that sulfuric acid is more commonly used in this industry.

A good thing nitric acid quickly colors yellow in secondary oxidation processes otherwise it is not just lethal and yellow but lethal and colorless. And why did the cloud form? Nitric acid is known to fume, a process in which nitric acid vapor acts as an nucleation site for water condensation, according to this report.

But what does nitric acid have to do with manure in the first place? Acids are added in general to bind ammonia that is toxic and explosive. You can research it if you have to. Berg and Helleman did so back in 2008 (link). They monitored 50 Kg of manure and the effect of nitric acid for 100 days at different pH levels. By just increasing the acidity the acid also kills the biological processes responsible for forming not only ammonia but also methane. Their conclusion: do not use nitric acid but lactic acid! Lactic acid does a better job preventing nitrous oxide emissions and the amount of methane emissions is also much smaller.

02-04: article updated

Iron based photoluminescence

01 April 2017 - Organometallic chemistry

iron based photoluminescense.PNGA new iron photo-luminescent compound has been reported in Nature (doi) by a twenty-seven people strong Swedish-Danish-US team with first author Pavel Chábera. In photoluminescence a compound absorbs light and then with a delay emits light again. Many inorganic compounds are known that exhibit this property but none of then based on cheaply available iron. The competition to beat is the well-known tris(bipyridine)ruthenium(II) chloride that absorbs at 452 nm and emits at 620 nm with a lifetime of 700 nanoseconds.
The new iron compound was synthesised in a solution reaction of iron dibromide with an in-situ formed bis- NHC ligand (reaction of a bis(triazolium) bromide with potassium tert-butoxide). The bromine counterions were then replaced by hexafluorophosphate in a reaction with ammonium hexafluorophosphate. With the carbene ligands a switch is made from metal-to-ligand charge-transfer emission (usually short-lived) to ligand-to-metal emission with much better prospects. The results: absorption at 558 nm and emission at 600nm. For now the ruthenium compound mentioned earlier has no need to worry, the emission lifetime for the new iron compound is clocked at just 0,1 nanoseconds.

Rik