Compound of formula (I-A') wherein a is 0 or 1; R 1, R 2 and R 3 are at each occurrence independently selected from the group consisting of H, F, Cl, Br, I, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, aryl and heteroaryl; one or both of R 4 and R 5 is a group of formula and, if only one group of R 4 and R 5 is of formula, the other of R 4 and R 5 is selected from the group consisting of H, F, Cl, Br, I, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, aryl, heteroaryl, and R 6 -Sp-[X 1] a -*; R 6 is a group of formula (IV-A) Sp is selected from the group consisting of alkanediyl, alkenediyl and alkyndiyl, wherein at least one hydrogen has been replaced with OH; X 1 is O; X 2 and X 3 are independently of each other selected from the group consisting of O, S and N-R 17; R 10, R 11, R 12, R 13 and R 14 are at each occurrence independently of each other selected from the group consisting of H, F, CI, Br, I, R 6 -Sp-[X 1] a -* and R 15, wherein any two adjacent groups of R 10, R 11, R 12, R 13 and R 14 that are R 15 may also form a ring system; R 15 is at each occurrence independently selected from the group consisting of alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, alkoxy having from 1 to 20 carbon atoms, partially or completely halogenated alkoxy having from 1 to 20 carbon atoms, thioalkyl having from 1 to 20 carbon atoms, and partially or completely halogenated thioalkyl having from 1 to 20 carbon atoms; and R 17 is at each occurrence independently selected from the group consisting of H, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms and aryl, X 4 is selected from the group consisting of O, S, C(=O), C(=O)O and N-R 17; c is 0 or 1; and R 20, R 21 and R 22 are at each occurrence independently of each other selected from the group consisting of H, F, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, aryl and heteroaryl. a is 0 or 1; R 1, R 2 and R 3 are at each occurrence independently selected from the group consisting of H, F, Cl, Br, I, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, aryl and heteroaryl; one or both of R 4 and R 5 is a group of formula and, if only one group of R 4 and R 5 is of formula, the other of R 4 and R 5 is selected from the group consisting of H, F, Cl, Br, I, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, aryl, heteroaryl, and R 6 -Sp-[X 1] a -*; R 6 is a group of formula (IV-A) Sp is selected from the group consisting of alkanediyl, alkenediyl and alkyndiyl, wherein at least one hydrogen has been replaced with OH; X 1 is O; X 2 and X 3 are independently of each other selected from the group consisting of O, S and N-R 17; R 10, R 11, R 12, R 13 and R 14 are at each occurrence independently of each other selected from the group consisting of H, F, CI, Br, I, R 6 -Sp-[X 1] a -* and R 15, wherein any two adjacent groups of R 10, R 11, R 12, R 13 and R 14 that are R 15 may also form a ring system; R 15 is at each occurrence independently selected from the group consisting of alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, alkoxy having from 1 to 20 carbon atoms, partially or completely halogenated alkoxy having from 1 to 20 carbon atoms, thioalkyl having from 1 to 20 carbon atoms, and partially or completely halogenated thioalkyl having from 1 to 20 carbon atoms; and R 17 is at each occurrence independently selected from the group consisting of H, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms and aryl, X 4 is selected from the group consisting of O, S, C(=O), C(=O)O and N-R 17; c is 0 or 1; and R 20, R 21 and R 22 are at each occurrence independently of each other selected from the group consisting of H, F, alkyl having from 1 to 20 carbon atoms, partially or completely halogenated alkyl having from 1 to 20 carbon atoms, aryl and heteroaryl.