There is provided a compound of Formula I wherein R3, R4, R5, R6 and R7 are independently selected from H and —Y—R8; wherein each R8 is independently selected from —OH, hydrocarbyl groups, oxyhydrocarbyl groups, cyano (—CN), nitro (—NO2), H-bond acceptors, and halogens; wherein at least one of R3, R4, R5, R6 and R7 is —Y—R8 wherein R8 is selected from substituted and unsubstituted heterocyclic rings and amino substituted phenyl groups, wherein X is a bond or a linker group; wherein Y is an optional linker group; and wherein ring A is optionally further substituted; wherein R9 is selected from H, —OH and —OSO2NR1R2; wherein R1 and R2 are independently selected from H and hydrocarbyl; wherein (a) X is a bond and at least one of R3, R4, R5, R6 and R7 is —Y—R8; OR (b) R9 is —OSO2NR1R2 or —OH and four of R3, R4, R5, R6 and R7 are H and one of R3, R4, R5, R6 and R7 is —Y—R8.