A compound has Formula I: A, B, C, D, W, X, Y, and Z are independently selected from hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C1-C6 alkoxy, aryl, aldehyde, protected aldehyde, CH, N, O, S, null, and bond; Q is selected from aldehyde, protected aldehyde, and null, at least one of A, B, C, D, W, X, Y, Z, or Q is an aldehyde or protected aldehyde; the bonds between each of A-B, B-C, C-D, W-X, X-Y, and Y-Z are selected from single bond, double bond, triple bond, and no bond; L is a linker selected from a C1-C12 alkyl, aralkyl, and aryl, any of which is optionally substituted; one or more methylene unit (CH2) of the C1-C12 alkyl is optionally replaced by any combination of oxygen, carbonyl(C═O), and NH; and R1 and R2 are independently selected from —NR3R4, halogen, C1-C8 alkoxy, aralkoxy, alkenyloxy, alkynyloxy, and OCH2CH2CN; R3 and R4 are independently a C1-C4, straight chain or branched alkyl group.