A pharmaceutical composition comprising: (i) a conjugate containing a phthalocyanine dye linked to a targeting molecule; and (ii) a pharmaceutically acceptable excipient; wherein the targeting molecule binds to a cell surface target molecule on a surface of a cell or pathogen, wherein the phthalocyanine dye comprises the formula: wherein: L is a linker; Q is a reactive group for attachment of the dye to the targeting molecule; R 2 , R 3 , R 7 , and R 8 are each independently selected from among optionally substituted alkyl and optionally substituted aryl; R 4 , R 5 , R 6 , R 9 , R 10 , and R 11 are each independently selected from among hydrogen, optionally substituted alkyl, optionally substituted alkanoyl, optionally substituted alkoxycarbonyl, optionally substituted alkylcarbamoyl, and a chelating ligand, wherein at least one of R 4 , R 5 , R 6 , R 9 , R 10 , and R 11 comprises a water soluble group; R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 and R 23 are each independently selected from among hydrogen, halogen, optionally substituted alkylthio, optionally substituted alkylamino and optionally substituted alkoxy; and X 2 and X 3 are each independently C 1 -C 10 alkylene, optionally interrupted by a heteroatom; and wherein greater than 90% or greater than 95% of the conjugate is present as a main monomer component. (i) a conjugate containing a phthalocyanine dye linked to a targeting molecule; and (ii) a pharmaceutically acceptable excipient; wherein the targeting molecule binds to a cell surface target molecule on a surface of a cell or pathogen, wherein the phthalocyanine dye comprises the formula: wherein: L is a linker; Q is a reactive group for attachment of the dye to the targeting molecule; R 2 , R 3 , R 7 , and R 8 are each independently selected from among optionally substituted alkyl and optionally substituted aryl; R 4 , R 5 , R 6 , R 9 , R 10 , and R 11 are each independently selected from among hydrogen, optionally substituted alkyl, optionally substituted alkanoyl, optionally substituted alkoxycarbonyl, optionally substituted alkylcarbamoyl, and a chelating ligand, wherein at least one of R 4 , R 5 , R 6 , R 9 , R 10 , and R 11 comprises a water soluble group; R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 and R 23 are each independently selected from among hydrogen, halogen, optionally substituted alkylthio, optionally substituted alkylamino and optionally substituted alkoxy; and X 2 and X 3 are each independently C 1 -C 10 alkylene, optionally interrupted by a heteroatom; and wherein greater than 90% or greater than 95% of the conjugate is present as a main monomer component. L is a linker; Q is a reactive group for attachment of the dye to the targeting molecule; R 2 , R 3 , R 7 , and R 8 are each independently selected from among optionally substituted alkyl and optionally substituted aryl; R 4 , R 5 , R 6 , R 9 , R 10 , and R 11 are each independently selected from among hydrogen, optionally substituted alkyl, optionally substituted alkanoyl, optionally substituted alkoxycarbonyl, optionally substituted alkylcarbamoyl, and a chelating ligand, wherein at least one of R 4 , R 5 , R 6 , R 9 , R 10 , and R 11 comprises a water soluble group; R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 and R 23 are each independently selected from among hydrogen, halogen, optionally substituted alkylthio, optionally substituted alkylamino and optionally substituted alkoxy; and X 2 and X 3 are each independently C 1 -C 10 alkylene, optionally interrupted by a heteroatom; and wherein greater than 90% or greater than 95% of the conjugate is present as a main monomer component. <EOS>