Bathochromically shifted absorption and near IR emission in bismuth(III) porphyrins with meso-fluorophenyl and methoxyphenyl substitutions

A series of bismuth(III) porphyrins with varying degrees of electron-donating and electron-withdrawing groups in their meso-positions have been synthesized. All the porphyrins were synthesized successfully and characterized spectroscopically. The absorption studies reveal bathochromically shifted spectra, up to ~60 nm, compared to their corresponding free-base porphyrins which is common for p-type hyperporphyrins. Interestingly, all the samples exhibited broad near-IR phosphorescence at room temperature. The spectroscopic studies indicate that the demetallation occurs in both solution and solid states to form corresponding free-base porphyrin and this process is much faster in mesotrimethoxyphenyl substituted bismuth(III) porphyrin. Nevertheless, the study reveals interesting optical properties of bismuth(III) porphyrins, particularly red-shifted absorption and near IR emission bands.