Color centers in poly(arylenesulfophthalides) and the ground state of Muller's hydrocarbon molecule

Published data on the properties of Muller's hydrocarbon are analyzed. The total energies of several hydrocarbon biradicals with p-phenylene bridges, including Thiele's, Chichibabin's, and Muller's hydrocarbons in the singlet and tripler states were calculated by the AMI and PM3 semiempirical quantu m-chemical methods. Contrary to popular opinion, our calculations revealed that the Muller's hydrocarbon molecule has a triplet rather than singlet gr ound state. The results obtained make it possible to explain the fact that quinoid color centers do not form in the course of reduction of poly(terphe nylsulfophthalide). The calculated parameters of electronic spectra for sin glet states of some related biradicals are reported.