686746-87-2

There is provided a compound having Formula (I): wherein one of R1 and R2 is a group of the Formula (a), wherein R4 is selected from H and hydrocarbyl, R5 is a hydrocarbyl group and L is an optional linker group, or R1 and R2 together form a ring substituted with the group (Formula (a)) wherein R3 is H or a substituent, and wherein X is selected from S, O, NR6 and C(R7)(R8), wherein R6 is selected from H and hydrocarbyl groups, wherein each of R7 and R8 are independently selected from H and hydrocarbyl groups.