Poly(indenofluorene) (PIF), a novel low band gap polyhydrocarbon

This communication describes the synthesis of a novel low band gap hydrocarbon polymer, poly(indenofluorene), PIF, composed of 3,9-di-tert-butylindeno[1,2-b]fluorene building blocks. The polymer, with high degrees of polymerization (DP > 20), was generated by coupling alkylated 6,6,12,12-tetrachloro-6,12-dihydroindeno[1,2-b]fluorene monomers by means of low-valent transition metal [e.g. chromium(0) and nickel(0)] compounds as dehalogenating agents. The cross-conjugated coupling product exhibits a widely red shifted longest wavelength absorption maximum (lambda(max) of up to 799 nm). This fact can be interpreted as resulting from the contribution of quinoid states to the electronic ground state. Oligomeric products possessing similar structures were also generated by dehydrohalogenation polymerization, starting from the corresponding 6,12-dihalo-6,12-dihydroindeno[1,2-b]fluorenes.