Poly(2,5-diphenylgermole): Incorporation of a germole ring into a conjugated polymer

The intramolecular zirconocene coupling of 4,4-bis(hexyloxymethyl)-1,7-bis-p-halophenyl-1,6-heptadiynes provides 2,5-bis-p-halophenylzirconocyclopentadienes (bromo and chloro derivatives), which undergo efficient transmetalation reactions with GeBr(4). Methylation of the resulting dihalogermoles with MeLi provided bis-p-halophenyl-2,5-germole monomers. These functionalized germoles were polymerized via nickel coupling to give oligo- and poly(2,5-diphenylgermole) materials (7). Investigations of optical properties reveal that the monomers and a model 2,5-bisphenylgermole are somewhat photoluminescent (Phi = 0.018-0.12), while the high molecular weight polymer (M(n) approximate to 20 000) exhibits very efficient photoemission (Phi = 0.79). Electrochemical studies indicate that delocalization in 7 is accompanied by a modest lowering of the LUMO level relative to that of the monomer.