| Title
| - Incorporation of Stable Organic Radicals of theTris(2,4,6-trichlorophenyl)methyl Radical Series to Pyrrole Unitsas Models for Semiconducting Polymers with High SpinMultiplicity. 1. [2,6-Dichloro-4-[2,5-bis(5-methyl-2-thienyl)-1-pyrrolyl]phenyl]bis(2,4,6-trichlorophenyl)methyl Radical as aPrecursor of a Disjoint Heterospin Diradical with a Triplet or aNearly Degenerate Singlet−Triplet Ground State
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| Abstract
| - The condensation reactions between (4-amino-2,6-dichlorophenyl)bis(2,4,6-trichlorophenyl)methylradical and acetylacetone or 1,4-bis(5-methyl-2-thienyl)-1,4-butanedione yield [2,6-dichloro-4-(2,5-dimethyl-1-pyrrolyl)phenyl]bis(2,4,6-trichlorophenyl)methyl radical (3•) and [2,6-dichloro-4-[2,5-bis(5-methyl-2-thienyl)-1-pyrrolyl]phenyl]bis(2,4,6-trichlorophenyl)methyl radical (4•), respectively. EPRstudies of both radicals 3• and 4• in CH2Cl2 solution suggest a weak electron delocalization withcoupling constant values of 1.25 and 1.30 G, respectively, with the six aromatic hydrogens. Theirelectrochemical behavior was analyzed by cyclic voltammetry. Both radicals show reversiblereduction processes at E° = −0.69 V and −0.61 V versus SSCE, respectively, and anodic peakpotentials at Epa = 1.10 and 0.72 V, respectively, versus SSCE at a scan rate (ν) of 200 mV s-1,being reversible for radical 4•. X-ray analysis of radical 3• shows a high value (65°) of the dihedralangle between the 2,5-dimethylpyrrolidyl moiety and the phenyl ring. Smooth oxidation of radical4• in CH2Cl2 containing trifluoroacetic acid gives an ionic diradical species with a weak electroninteraction (|D/hc| = 0.0047 cm-1). A Curie plot of the Δms = ±2 signal intensity versus the inverseof the absolute temperature in the range between 4 and 70 K suggests a triplet or a nearlydegenerate singlet−triplet ground state.
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