Crystal structures of noble gas compounds

Procesom kristalizacije nastaju krutine zvane kristalima koje su građene od atoma ili molekula periodično ponavljanih u prostoru. Razlikujemo ionske, molekulske, metalne i kovalentne kristale koji se razlikuju prema vrsti čestica koje ih grade te vrsti veza između njih. Svrstavaju se u prostorne i točkaste grupe, Bravaisove rešetke te osnovne kristalne sustave. U 18. skupini periodnog sustava elemenata smješteni su plemeniti plinovi, helij, neon, argon, kripton, ksenon i na kraju radon. Plemeniti plinovi su plinovi bez boje, mirisa i okusa te u pravilu ne stvaraju spojeve s drugim elementima, odnosno inertni su. Industrijski se dobivaju na način na koji su i prvi put dobiveni, frakcijskom destilacijom tekućeg zraka. Neil Bartlett, kanadski kemičar, je prvi proučavao njihovo svojstvo inertnosti i otkrio prve spojeve plemenitih plinova, fluoride. Helij u uvjetima visokog tlaka ulazi u strukturu spoja 4-hidroksi cijanobenzena koji pod tlakom rotira u prostoru čime se stvaraju nove interakcije pogodne za ulazak helija. Nadalje, svi plemeniti plinovi mogu pri određenim uvjetima ući u strukture nešto kompleksnijih spojeva. Bilo da se radi o istraživanju iz znatiželje ili radi općeg dobra, kao što je to slučaj kod ksenona, rezultati su nadasve zanimljivi. U svrhu zarobljavanja plinova najviše se koriste tzv. MOF-ovi, tj. metaloorganske mreže.The crystallization proces produces solids, crystals, which are made of atoms and molecules periodically repeated in space. There are ionic, covalent, metal and molecular crystals and the difference between them is in the type of particles of which they are made and in the type of bonds. We can classify them into space groups, crystallographic point groups, Bravais lattices and finally into main crystal systems. In the 18th group of the Periodic Tablet of Elements are noble gases, helium, neon, argon, krypton, xenon and radon. Noble gases are colorless, tasteless, with no smell and in general, they do not make compounds with other elements, so basically they are inactive. In industry, noble gases are obtained by fractional distillation of liquid air, just in the way they were first isolated. Canadian, Neil Bartlett, was the first scientist who studied the inactivity of noble gases and the first who discovered noble gas compounds, fluorides. Under high pressure conditions, helium can enter into the structure of compound 4-hydroxy cyanobenzene, which rotates under the pressure and creates new interactions and the entrance for helium is allowed. Today, it is known that noble gases can fit into complex compounds. Whether it is research out of curiosity or for the common good, as is the case with xenon, the results are interesting. For the purpose of capturing noble gases, the most used are MOFs or metal organic frameworks