Synthesis and photophysical properties of novel quinoxalinochlorins as photosensitizers

A class of novel quinoxalinochlorin compounds bearing different substituents at quinoxaline ring used as photosensitizers for photodynamic therapy (PDT) were designed and synthesized along with the optimization of the reaction conditions of the last reduction step. The UV-visible spectra of these compounds displayed a chlorin-characteristically sharp Q[Formula: see text] band (the fourth Q-band at the longest wavelength) but significantly red-shifted ([Formula: see text] > 687 nm). The fluorescence emission spectra also experienced a significant red-shift. The fluorescence and singlet oxygen quantum yields were measured using zinc 5,10,15,20-tetraphenylporphyrin (ZnTPP) as a standard ([Formula: see text] = 0.033 and [Formula: see text] = 0.73 in toluene). All the quinoxalinochlorin compounds reported showed good photostability and those compounds bearing substituent with electron-donating conjugated effect at quinoxaline ring could produce high yield of singlet oxygen under light.