Porphyrinoids decorated at their periphery with various number of nitro groups have been extensively investigated for wide range of applications such as in redox catalytic activity, nonlinear optical materials, theranostics, and in artificial solar energy harvesting devices. The substitution of a nitro group onto a porphyrin compound has a large effect on the photophysical properties and potential applications of these dye. We present here the spectroscopic studies of a series of nitrated porphyrinoids in polar (DMSO) and non polar (toluene) solvents. The nitro group on the porphyrins shown to decrease the fluorescence quantum yield as well as reduces the lifetime of the porphyrinoids. The amount of fluorescence quenching depends on the number and position of the nitro groups appended on the porphyrinoid macrocycle. The low fluorescence quantum yield is complementary of their high triplet quantum yield, makes these chromophores a potential platform to develop new photosensitizer for photodynamic therapeutic treatment of cancers. Nitro groups when present at the <i>β</i>-pyrrole position significantly affect the electronic properties and can interact with a nearby bulky meso substituent to significantly distort the porphyrin macrocycle compared to corresponding un-substituted porphyrin. We propose that molecular distortion due to steric hindrance is the prevailing cause behind all of the anomalous photophysics.<br/>

Effect of nitro group on the photophysical properties of porphyrin dyes

256th National Meeting (2018)

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