Pi-Extended Ethynyl 21,23-Dithiaporphyrins: A Synthesis and Comparative Study of Electrochemical, Optical, and Self-Assembling Properties

Abstract

21,23-Dithiaporphyrins were synthesized containing pi-extending ethynyl substituents at the meso positions. These porphyrins displayed highly bathochromic and broadened absorbance profiles spanning 400-900 nm with molar absorptivities ranging from 2500 to 300,000 M(-1) cm(-1). Electrochemically, these ethynyl dithiaporphyrins undergo a single oxidation at 0.44 or 0.57 V and reduction at -1.17 or -1.08 V versus a ferrocene/ferrocenium internal standard depending on the type of functionalization appended to the ethynyl group. DFT calculations predict that the delocalization of the frontier molecular orbitals should expand onto the meso positions of the ethynyl 21,23-dithiaporphyrins; shrinking the HOMO-LUMO energy gap by destabilizing the HOMO energy. Indeed, the DFT results agree with our optical and electrochemical assessments. Finally, differential scanning calorimetry combined with cross-polarized optical microscopy and powder X-ray diffraction was used to assess the ability of these porphyrins for long-range order. For the ethynylphenyl alkoxy 21,23-dithiaporphyin, birefringent, soft-crystalline-like domains were observed by polarized microscopy, which are marginally sustained by a low-level of crystallinity detected in the XRD, suggesting that long-range ordering is possible. Overall, ethynyl 21,23-dithiaporphyrins are able to harvest much lower energy light and possess lower oxidation and reduction potentials compared to their pyrrolic analogues, which are desirable properties for applications in organic electronics.

Phenyl dialkynylcarbinols, a Bioinspired Series of Synthetic Antitumor Acetylenic Lipids

“…The silylated alkyne 2.12a (1.57 g, 57% yield) was isolated as a yellow oil. All analyses agreed with data reported in the literature …”

“…All analyses agreed with data reported in the literature. 62 ((3-Fluoro-4-octylphenyl)ethynyl)trimethylsilane (2.8b). The crude mixture was purified by flash column chromatography using 100% pentane.…”

Long alkoxy substituted N2S2 porphyrins for liquid crystalline property

“…However, recently Bromby et al reported a series of novel N 2 S 2 porphyrins with meso‐phenyl substituted long alkoxy groups that shows interesting optical and electrical properties and could behave as ambipolar materials for organic electronic devices [ 19–22 ] . However, to the best of our knowledge, there are only one reports of self‐assembled 21,23‐dithiaporphyrin having decyl or dodecyl chains that shows columnar liquid crystalline phases (Figure 2).…”

“…[17] Nowak-Kr ol et al mentioned N 4 systems with 12 long alkyloxy groups showing low melting point and showed that the melting point of octyloxy derivative is 55.1 C that is comparable with the porphyrin 3 (54.5 C) with N 2 S 2 system reported in this article. [18] However, recently Bromby et al reported a series of novel N 2 S 2 porphyrins with meso-phenyl substituted long alkoxy groups that shows interesting optical and electrical properties and could behave as ambipolar materials for organic electronic devices [19][20][21][22] . However, to the best of our knowledge, there are only one reports of selfassembled 21,23-dithiaporphyrin having decyl or dodecyl chains that shows columnar liquid crystalline phases (Figure 2).…”