" the group consisting of alkoxy and halide, and R3 is selected from the group consisting of alkoxy, halide and alkyl; wherein L1 and L2 are both ???(CH2)n???, wherein n=2 to 10; and wherein A1 is a moiety comprising one or more derivatizable functional groups selected from the group consisting of hydroxyl, amino, carboxyl, thio, halo and sulfonate. 6." . . . .