Synthesis and Optical and Electronic Properties of Core-Modified 21,23-Dithiaporphyrins

Core-modified 21,23-dithiaporphyrins, meso-substituted with both electron-withdrawing 4-phenylcarboxylic acids and related butyl esters, and electron-donating phenyl-dodecyl ethers were synthesized. The porphyrins displayed broad absorbance profiles that spanned from 400 to 800 nm with molar absorptivities ranging from 2500 to 200000 M-1 cm(-1). Electrochemical experiments showed the dithiaporphyrins undergo two consecutive, one-electron, quasi-reversible oxidations and reductions at -1.78, -1.43, 0.63, and 0.91 V versus a ferrocene/ferrocenium internal standard. Spectroelectrochemistry and cyclic voltammetry revealed the dithiaporphyrins are stable and can endure many cycles of oxidation and reduction without signs of decomposition. The electronics of the two dithiaporphyrins were similar, and DFT calculations showed the HOMO-LUMO energy difference was smaller than tetrapyrrolic porphyrin analogues. Overall, the combination of desirable electronics, namely: quasi-reversible oxidations and reductions as well as broad absorbance profiles, combined with stability, imply that these core-modified 21,23-dithiaporphyirns could be potentially used as an ambipolar material for organic electronic applications.