| abstract |
A compound having Formula I n n n n n n n n n n wherein one of R 1 and R 2 is a group of the formula n n n n n n n n n n wherein R 4 is selected from H and hydrocarbyl, R 5 is a hydrocarbyl group and L is an optional linker group, or R 1 and R 2 together form a ring substituted with the group n n n n n n n n n n wherein R 3 is H or a substituent, and wherein X is selected from S, O, NR 6 and C(R 7 )(R 8 ), wherein R 6 is selected from H and hydrocarbyl groups, wherein each of R 7 and R 8 are independently selected from H and hydrocarbyl groups. |