Naslov
Structural characterization of p-benzosemiquinone radical in a solid state: the radical stabilisation by a low-barrier hydrogen bond

Autori
Molčanov, Krešimir ; Kojić-Prodić, Biserka ; Roboz, Mario

Izvornik
Acta crystallographica. Section B, Structural science (0108-7681) 62 (2006), 6; 1051-1060

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
semiquinone ; radical ; low-barrier hydrogen bond ; EPR spectroscopy ; variable-temperature X-ray diffraction

Sažetak
Semiquinone (p-benzosemiquinone), a transient organic radical, was detected in the solid state by EPR spectroscopy revealing four symmetrically equivalent protons. A variable-temperature X-ray diffraction analysis (293 and 90 K) and EPR data support a dynamical disorder of proton. A low-barrier O-H...O hydrogen bond stabilises the radical. The C-O bond length is 1.297(4) A, corresponding to bond order of about 1.5. The geometry of the radical implies an electron delocalisation throughout a benzenoid ring. Two polymorphs of semiquinone, monoclinic and triclinic, were observed and their structures determined. Their crystal packings were compared with those of quinhydrone polymorphs.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA