ROOM-TEMPERATURE STABLE GROUND-STATE TRIPLET CARBENE AS MODELS FOR ORGANIC HIGH-SPIN UNITS WITH ROBUST PI-SPIN POLARIZATION - ESR STUDY ANDX-RAY-ANALYSIS

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.