There is provided a compound of Formula I
wherein X, Y and Z are each independently of each other an optional linker group; R
1
is a ring system; R
2
is selected from hydrocarbyl groups, oxyhydrocarbyl groups, cyano (—CN), nitro (—NO
2
) and halogens; R
3
and R
4
are independently selected from H and hydrocarbyl, ring A and B are independently optionally further substituted.
There is provided a compound of Formula I
wherein X, Y and Z are each independently of each other an optional linker group; R
1
is a ring system; R
2
is selected from hydrocarbyl groups, oxyhydrocarbyl groups, cyano (—CN), nitro (—NO
2
) and halogens; R
3
and R
4
are independently selected from H and hydrocarbyl, ring A and B are independently optionally further substituted.