CRYSTAL-STRUCTURE AND MAGNETIC-SUSCEPTIBILITY OF A HYDROCARBON FREE-RADICAL - TRIS(3,5-DI-TERT-BUTYLPHENYL)METHYL

The magnetic susceptibility and crystal structure of the toluene solva te of tris(3,5-di-tertbutylphenyl)methyl (1) were determined. Crystals Of 1.C7H8 are monoclinic, space group C2/c: a = 11.476(4) angstrom, b = 17.312(6) angstrom, c = 22.216(7) angstrom, beta = 100.87(3)-degree s, Z = 4. The molecules have C2 site symmetry and approximate D3 symme try in the lattice; the methyl carbon is planar in its coordination. P henyl ring twists out of the mean molecular plane are comparable to ot her meta- or para-substituted triarylmethyls. The X-ray structure is i n substantial agreement with the molecular structure calculated with t he AM1 Hamiltonian. The magnetic susceptibility of the crystals is cha racteristic of a paramagnet; SQUID magnetometry shows no measurable ex change interaction above 2.6 K. This is consistent with a solvated lat tice in which there is no appreciable pi-overlap between adjacent radi cals. A comparison with other known triarylmethyl crystal structures i s reported.