Abstract: A mixture comprising a molecule of formula (I); in which A1, A2, A3, A4, A5 and A6, which may be the same or different, are each N or —CH; Y1, Y2, Y3, Y4, Y5 and Y6, which may be the same or different, are each hydrogen or C1 to C12 alkoxy; X1, X2, X3, X4, X5 and X6, which may be the same or different, are each hydrogen, C1 to C12 alkoxy or alkyl C1 to C12; and R7, R8, R9, R10, R11 and R12 are each hydrogen, or each of R7 and R8, R9 and R10 and R11 and R12 may form a bond; and a molecule of formula (II); in which R1, R2, R3, R4, R5 and R6, which may be the same or different, are each alkyl or substituted (and/or chiral) alkyl C1 to C16, acyl C1 to C16, polyethyleneoxy, a flexible connection to a polymer backbone or part of a polymer backbone in homopolymers, copolymers or block copolymers; and B1, B2, B3, B4, B5 and B6a, which may be the same or different, are each, hydrogen, alkyl C1 to C16, alkoxy C1 to C16, nitro, halogeno, cyano, amido, diazo or ester, e.g. alkyl C1 to C16 ester.