A systematic characterization of chemically reduced Parasexiphenyl (empty set(6)) by radical anions such as biphenyl and naphthylsodium or potassium in tetrahydrofuran (THF) is presented, and the vibrational properties of this phenylene oligomer have been studied. Resonance Raman scattering coupled with a theoretical vibrational analysis leads to the conclusion that a quinoid structure takes place in the sexiphenyl molecules upon reduction with an enhancement of the external phenyl polarizability as compared to neutral molecules. However, this enhancement as well as the quinoid character of (empty set(6)) is strongly dependent on the presence or absence of THF.