A compound having the general the general structure I is provided: (Formula I), wherein Z is a substituent selected from a group consisting of S and O; X is a substituent selected from a group consisting of Cl, Br, I, OH and NH2; each of R1 and R2 is a substituent independently selected from a group consisting of H, a linear, cyclic or branched, substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted aryl, and a substituted or unsubstituted heteroaryl; and each of Y and Y1 is a substituent independently selected from a group consisting of H and C(O)—C6H4—Br.