Spectroscopical study of bacteriopurpurinimide–naphthalimide conjugates for fluorescent diagnostics and photodynamic therapy

Two novel bis(chromophoric) dyads ABPI–NI1 and ABPI–NI2 containing 1,8-naphthalimide and bacteriopurpurinimide units linked by p-phenylene-methylene (ABPI–NI1) and pentamethylene (ABPI–NI2) spacers were prepared to test their ability to be used in the design of effective agents for both photodynamic therapy (PDT) and fluorescent tumor imaging. Photophysical studies revealed that the emission from the naphthalimide chromophore in both conjugates was partially quenched due to resonance energy transfer between the photoactive components. Compound ABPI–NI2 with more sterically flexible oligomethylene group demonstrated higher fluorescence intensity as compared with that for ABPI–NI1.