Method for making schiff base

A method for making a Schiff base of formula (I)

• or a salt, solvate, tautomer, or stereoisomer thereof;
• wherein R1 is an optionally substituted alkyl, optionally substituted cycloalkyl, or optionally substituted aryl;
• R2 an R3 are independently —OH, —NH2, —OR5, —NHR5, —NR5R5;
• R4 is —H, —F, —Cl, —Br, —CN, —OH, —OR5, —NO2, —NH2, —NHR5, —NR5R5;
• and
• each R5 is independently an optionally substituted alkyl, optionally substituted cycloalkyl, or optionally substituted aryl, said method comprising:
• refluxing a fluorescein or rhodamine based compound with hydrazine to form a fluorescein or rhodamine based hydrazide;
• and
• refluxing the fluorescein or rhodamine based hydrazide with a N-alkylimidazole-2-carboxaldehyde to form the Schiff base.