Synthesis and Investigation of Solar‐Cell Photosensitizers Having a Fluorazone Backbone

Abstract

A synthetic sequence for the preparation of fully conjugated 2,7-disubstituted fluorazone (9H-pyrrolo[1,2--a]indol-9-one) derivatives has been developed comprising an Elming–Clauson–Kaas-type pyrrole formation, POCl3-mediated ring closure, selective halogenation and elongation of the conjugated backbone through cross-coupling reactions. As a proof of principle, this methodology was used to prepare for the first time two organic D–π–A dyes containing the fluorazone moiety. The new compounds display broad absorption bands in the visible-light region when adsorbed on nanocrystalline TiO2 and electrochemical properties compatible with their employment as photosensitizers in dye-sensitized solar cells. Small-scale photovoltaic devices fabricated with the fluorazone dyes yielded power conversion efficiencies in the range of 2.1–2.4 %, which correspond to approximately 70 % of the efficiency obtained with the reference organic dye DF15 under the same conditions

Synthesis of 3H‐Pyrrolo‐(1,2‐a) Indole‐based Fluorophore Macrocycles and their Stable Cation Radicals

“…[39] Further, fluorazone, a derivative of pyrrolo [1,2-a]indole has been used as a dye sensitizers for photovoltaics and dye-sensitized solar cell (DSSC) applications. [40,41] Depending upon conjugation and place of sp 3 carbon, pyrrolo [1,2-a]indole scaffold has three structural isomers namely, 9Hpyrrolo [1,2-a]indole V, 1H-pyrrolo [1,2-a]indole VI and 3H-pyrrolo [1,2-a]indole VII. [28] Owing to their diverse applications, many synthetic protocols for the synthesis of pyrrolo [1,2-a]indoles have been developed.…”

“…Pyrrolo[1,2‐ a ]indoles have been used as anticancer, [31,32] antiparasitic, [34] antimalarial, [33] anti‐HIV, [35] and central nervous system (CNS) stimulating agents [39] . Further, fluorazone, a derivative of pyrrolo[1,2‐ a ]indole has been used as a dye sensitizers for photovoltaics and dye‐sensitized solar cell (DSSC) applications [40,41] . Depending upon conjugation and place of sp 3 carbon, pyrrolo[1,2‐ a ]indole scaffold has three structural isomers namely, 9 H ‐pyrrolo[1,2‐ a ]indole V , 1 H ‐pyrrolo[1,2‐ a ]indole VI and 3 H ‐pyrrolo[1,2‐ a ]indole VII [28] .…”

Synthesis of the 4,7‐Dibromo Derivative of Highly Electron‐Deficient [1,2,5]Thiadiazolo[3,4‐d]pyridazine and Its Cross‐Coupling Reactions

“…General Information: The reagents were purchased from commercial sources and used as received. 5,6‐Dihydro[1,2,5]thiadiazolo[3,4‐ d ]pyridazine‐4,7‐dione ( 3 ) (for details see Supporting Information), [5‐(1,3‐dioxolan‐2‐yl)thiophen‐2‐yl]boronic acid ( 5b ), (9‐hexyl‐9 H ‐carbazol‐3‐yl)boronic acid ( 5d ), [4‐(diphenylamino)phenyl]boronic acid ( 5l ), [4‐( p ‐tolyl)‐1,2,3,3a,4,8b‐hexahydrocyclopenta[ b ]indol‐7‐yl]boronic acid ( 5m ), [5‐(1,3‐dioxolan‐2‐yl)thiophen‐2‐yl]tributylstannane ( 8b ), [2,2′‐bithiophen]‐5‐yltributylstannane ( 8j ), tributyl(thiophen‐3‐yl)stannane ( 8k ), tributyl(4‐methoxyphenyl)stannane ( 8i ), tributyl( p ‐tolyl)stannane ( 8h ) were prepared according to the published methods and characterized by NMR spectra. All synthetic operations were performed under a dry argon atmosphere.…”

Synthesis and Applications of 9H‐Pyrrolo[1,2‐a]indole and 9H‐Pyrrolo[1,2‐a]indol‐9‐one Derivatives

“…Indeed, in 1994, Bauer et al evaluated the properties as photosensitizers of fluorazone and 5 H ‐pyrido[4,3‐ b ]pyrrolizin‐5‐one 187 – 188 . Later, Faigl, Mordini et al described the synthesis of solar‐cell photosensitizers 189 – 190 , possessing a fluorazone structure (Scheme ) . The donor‐acceptor‐type dyes 189 – 190 showed broad absorption bands in the visible‐light region, after absorption on a nanocrystalline TiO 2 film.…”

“…[73] Later, Faigl, Mordini et al described the synthesis of solar-cell photosensitizers 189-190, possessing a fluorazone structure (Scheme 46). [74] The donor-acceptor-type dyes 189-190 showed broad absorption bands in the visible-light region, after absorption on a nanocrystalline TiO 2 film. The donor part was the HexO-substituted triarylamine and the 2-cyanoacrylic acid functionality the anchoring group.…”