A compound of formula

##STR00001## wherein V, W, X and Y represent N or CH, at least one of V, W, X and Y being N and at least two of V, W, X and Y being CH; and R.sub.1, R.sub.2 and R.sub.3 are each independently of the other hydrogen, C.sub.1-C.sub.8alkyl, C.sub.1-C.sub.8alkoxy, nitro, cyano, trifluoromethyl, halogen or hydroxy; with the proviso that the compounds of formulae

##STR00002##

are excluded, provides good lightfastness properties to textile fibre materials, in particular PES fibre materials.

A compound of formula ##STR00001##
wherein V, W, X and Y represent N or CH, at least one of V, W, X and Y being N and at least two of V, W, X and Y being CH; R.sub.1, R.sub.2 and R.sub.3 are each independently of the other hydrogen, C.sub.1-C.sub.8 alkyl, C.sub.1-C.sub.8 alkoxy, nitro, cyano, trifluoromethyl, halogen or hydroxy; and the compound provides good lightfastness properties to textile fibre materials, in particular PES fibre materials.