Small molecule dye for molecular imaging and photothermal therapy

A method of synthesizing a near-infrared-II fluorophore, comprising:

• a) synthesizing a dialkyl 3,3′((arylazanediyl)bis(4,1-phenylene))diacrylate with a reagent of formula Ph3PCHCO2(alkyl);
• b) synthesizing a dialkyl 3,3′((arylazanediyl)bis(4,1-phenylene))propionate from the compound of step a) using hydrogen and a catalyst;
• c) halogenating the arylazanediyl group of the compound of step b);
• d) protecting two propionate groups of the compound of step c) with a protecting reagent comprising a trimethylsilyl (TMS) group;
• e) substituting the halogen of the compound of step d) with a coupling group;
• f) reacting a 2,1,3-benzothiodiazole-containing compound with the coupling group of the compound of step e) such that in the resulting compound a 2,1,3-benzothiodiazole-containing group is coupled to two protected dialkyl 3,3′((arylazanediyl)bis(4,1-phenylene))propionate groups;
• g) reacting the compound of step f) such that the 2,1,3-benzothiodiazole-containing group of the resulting compound has one more ring than the 2,1,3-benzothiodiazole-containing group of the compound of step f);
• h) deprotecting the two protected propionate groups of the compound of step g).