ROOM-TEMPERATURE STABLE GROUND-STATE TRIPLET CARBENE AS MODELS FOR ORGANIC HIGH-SPIN UNITS WITH ROBUST PI-SPIN POLARIZATION - ESR STUDY ANDX-RAY-ANALYSIS
K. Furukawa et al., ROOM-TEMPERATURE STABLE GROUND-STATE TRIPLET CARBENE AS MODELS FOR ORGANIC HIGH-SPIN UNITS WITH ROBUST PI-SPIN POLARIZATION - ESR STUDY ANDX-RAY-ANALYSIS, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 306, 1997, pp. 185-190
we report the first room-temperature stable triplet pi-aryl based carb
ene, 2,2',4,4',6,6',-hexabromodiphenylmethylene 2 in both crystals and
fluid solutions. This paper describes ESR detection of 2 in the cryst
al of the diazo precursor 1 and the molecular and crystal structure of
1 obtained by X-ray diffraction at room temperature. ESR spectroscopy
showed that 2 was a tripler molecule in the ground state and survived
up to room temperature in the crystal state. The crystal of 1 is mono
clinic with cell dimensions, a=9.933 Angstrom, b=13.261 Angstrom, c=12
.743 Angstrom, beta=91.88 degrees, Z = 4 and the space group P2(1)/n.
The two 2,4,6-bromo-substituted phenyl rings make bent perpendicular c
onformation with 139 degrees of the bond angle at the diazo methane. N
on-bonded contacts shorter than the van der Waals radii were found bet
ween the nitrogen and bromine atoms of the nearest neighboring molecul
es. The correlation between the chemical stability and the molecular s
tructure of 2 is discussed.