Triarylmethyl and Related Radicals - Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds - page 12

Figure1.1 Calculatedstructureof 54a .(ReproducedbypermissionofProfessorMathiasTacke.)

diradical structure, with some attraction between the two radical sites. 20b Later computational studies
agreed with this conclusion, and also found that the diradical was a ground state singlet. 20c

Ph

Ph

C

C•

Ph

Ph

Fe

Fe Ph

Ph

C•

C

Ph

Ph

54a 54b

1.8 Tris(heteroaryl)methyl and related triarylmethyl radicals

Tris(2-thienyl)methyl and tris(3-thienyl)methyl radicals generated by zinc reduction of the corresponding
carbocations were directly observed by EPR and characterized by their distinctive spectra. 21a Tris(2-
thienyl)methyl radical 55 generated by reduction of the corresponding cation with zinc dimerizes to a
mixture of the tail to tail dimer 56 and head to tail dimer 57 (Equation 1.18). 21b

S

S

S

S

S

H

S

H

Zn

S C

+ C •

C S S

+

S

DME
65 ° C

S S

S

S S

S

S

H

S

55 56 57

(1.18)