Photochemistry of electron donor-acceptor complexes of the bis(fulvalene) dicobalt mono- and dications

Addition of carbon tetrachloride or chloroform to acetonitrile solutions of the bis(fulvalene)dicobalt monocation results in the appearance of new absorption features which are attributed to formation of electron donor-acceptor complexes. The association constants of these complexes aer 2.36 /mole fraction (carbon tetrachloride) and 2.74 /mole fraction (chloroform). Excitation in the absorption bands of the donor-acceptor complexes results in oxidation of the monocation to the dication with high quantum yields. A donor-acceptor complex is also formed when sodium tetraphenylborate is added to acetonitrile solutions of the bis(fulvalene)dicobalt dication. Spectroscopic determination of the association constant of the dication with tetraphenylborate yields a value of 26.3 /mole fraction. Excitation of the absorption bands of the ion-pair results in high quantum yields for formation of the bis(fulvalene) dicobalt monocation. Biphenyl is found in photolyzed solutions as a byproduct of the oxidation of the tetraphenylborate anion.