Synthesis and photoluminescence properties of π-extended fluorene derivatives: the first example of a fluorescent solvatochromic nitro-group-containing dye with a high fluorescence quantum yield
methoxycarbonyl, cyano, and nitro groups, were synthesized. Except for the nitro group, the resulting compounds exhibited extremely highfluorescencequantumyields (ΦF >0.85 in chloroform). The diphenylfluorene containing nitro groups have higher fluorescencequantumyield (ΦF = 0.31 in N,N’-dimethyl-formamide) than other nitro-group-containing fluorophores which were previously reported (ΦF <0.1). Furthermore