Evolution of lowest singlet and triplet excited states with electronic structure of fluorene group in metal polyyne polymers

The design of metal acetylide complexes and polymers with unusual optoelectronic properties has aroused growing research interests. An identified problem in organic light-emitting diodes is the ratio of 3:1 for the generation of nonemissive triplet to emissive singlet excitons on the basis of spin statistics. In view of this, conjugated polymers containing transition metal atoms have been widely studied as model systems to explain aspects of the photophysics of excited states in such polymers and obtain a clear picture of the spatial extent of the singlet and triplet manifolds. The strong spin-orbit coupling associated with these heavy metals renders the spin-forbidden triplet emission (phosphorescence) partially allowed. Very recently, a comprehensive program was launched in our laboratory on the study of some novel organometallic polyyne polymers with fluorene-based auxiliaries. One of the merits here is that the 9-fluorenyl positions can be functionalized easily so that the solubility, the emission and electronic properties as well as the bandgaps of these materials can be chemically tuned. In this chapter, we report our investigations on the synthesis, characterization, structural, redox and photoluminescent properties of a series of transition metal polyyne polymers containing 9-functionalized fluorene units.