Fluorescent proanthocyanidins

A proanthocyanidin condensation product comprising three or more monomers, wherein each monomer of the three or more monomers is independently selected from the group consisting of Formulas S1, S2, S3, S4, S5 and pyrylium cations thereof:

• wherein
• represents a single or double bond wherein a pyrylium cation at oxygen (O+) is formed when is a double bond;
• A1 and A2 are each independently radical or H;
• G1 is radical, H, —(C1-C6)alkyl, or —C(═O)(C1-C6)alkyl;
• G2 is H, —(C1-C6)alkyl, or —C(═O)(C1-C6)alkyl;
• R1, R2 and R3 are each independently H, —(C1-C6)alkyl, or —C(═O)(C1-C6)alkyl;
• R4 is H or ORa wherein Ra is H, —(C1-C6)alkyl or —C(═O)(C1-C6)alkyl;
• R5 and R6 are each independently radical or H;
• each Z is independently halo, —(C1-C6)alkyl, ORb, or N(Rb)2, wherein each Rb is independently H, —(C1-C6)alkyl, or —C(═O)(C1-C6)alkyl;
• and
• each n is independently 0-5;
• wherein an A-type linkage between a first monomer and a second monomer is formed when A1 and A2 of the first monomer are radical, G1 and R5 of the second monomer are radical, A1 and G1 form a bond, and A2 and R5 form a second bond;
• or
• a B-type linkage between the first monomer and the second monomer is formed when A2 of the first monomer is radical, R5 or R6 of the second monomer is radical, and A2 and R5 form a bond or A2 and R6 form a bond;
• wherein the first monomer is a monomer of Formulas S1 to S4 and the second monomer is a monomer of Formula S2, S3 or S5, and the product is an oligomer having a degree of polymerization of three or more.