Naslov
π-Interactions of semiquinone radicals: crystal design and tuning of the magnetic properties

Autori
Molčanov, Krešimir ; Kojić-Prodić, Biserka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
YoungChem 2001 Book of Abstracts / Brzozka, Zbigniew - Varšava : Warsaw University of Technology, 2011, 151-151

ISBN
978-83-61037-28-6

Skup
9th International Congress of Young Chemists

Mjesto i datum
Kraków, Poljska, 12.10.2011. - 16.10.2011

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
semiquinone radicals; exchange coupling; X-ray structure; single crystal-to-single crystal; phase transition

Sažetak
A series of solvates of alkali salts of tetrachlolrosemiquinone (Cl4Q, chloranil) radical anion were prepared and their crystal structures and magnetic properties were studied. The crystals display a wide range of magnetic properties: they can be paramagnetic, 1D antiferromagnetic or diamagnetic, depending on the distance between ring planes of radicals, which can be modified by different size of alkali cations and solvent molecules. Therefore, their magnetic properties can be tuned by crystal engineering. Electron spins of the contiguous rings are coupled if the interplanar separation is shorter than 3.30 Å ; they are unpaired if the distance is larger. In acetone solvates, KCl4Q∙Me2CO and RbCl4Q∙Me2CO, strongly bound radical dimers in the singlet state exist ; therefore the crystals are diamagnetic. In acetonitrile solvate, NH4Cl4Q∙MeCN, infinite stacks of equidistant anions (interplanar separation 2.227 Å) occur ; therefore the crystals are 1D antiferromagnets. The most interesting example is ethylmethylketone solvate KCl4Q∙EtMeCO which displays a continuous, reversible, single crystal-to-single crystal phase transition in the range 120 - 170 K. In the low-temperature phase (100 K), strongly bound dimers with paired electrons occur, similar to those in KCl4Q∙Me2CO. However, in the high-temperatre phase (200 K), infinite stacks of equidistant radicals are detected ; electron spins are unpaired due to greater interplanar distance. Spin coupling was also confirmed by ab initio quantum chemical calculations.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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