Ketoheterocyclic derivatives

The 1,5-di(benzoheterocyclic)-3-oxopentane compound of the formula ##STR15## wherein R is aromatic of up to 30 carbon atoms and from 1 to 2 aromatic rings, inclusive, R' is R or aliphatic of up to 10 carbon atoms inclusive, r independently is 0 or 1, Y' is imino, alkylimino, oxy or thio, X is a direct valence bond, alkylene of up to 8 carbon atoms inclusive, oxy, thio, sulfonyl, carbonyl, dioxyphenylene, 2,2-dioxyphenyl)propane, di(oxyphenyl) sulfone or dioxydiphenylene and Z independently is >C(Z').sub.2 in which Z' independently is hydrogen, lower alkyl, lower halogen or phenyl, or Z is such that adjacent Z moieties form a ring system Z" of from 5 to 7 ring atoms, up to two of which are heteroatoms selected from nitrogen, oxygen or sulfur with the remainder of the ring atoms being carbon atoms, there being up to 15 carbon atoms in each Z", two of which form a bridge between the carbon atoms connected by the adjacent Z moieties, with the proviso that N and Y' are substituted on adjacent carbon atoms of R.