valent phenyl-unit and/or wherein one or more hydrogen atoms in each moiety X ?? and X B may be replaced by a radical selected from the group of halo, cyano, hydroxy, amino, oxo and formyl ; Y ?? and Y B each independently from each other are a radical selected from the group of ??-butyl, NR 1 R 2 and Pir ; R 1 and R 2 each independently from each other are a radical selected from the group of hyd