Extended Benzene‐Fused Oligo‐BODIPYs: In Three Steps to a Series of Large, Arc‐Shaped, Near‐Infrared Dyes

Abstract

We present a straightforward, three‐step synthesis engaging an oligomerization and subsequent one‐pot oxidation step to form fully conjugated, benzene‐fused oligo‐BODIPYs from simple BODIPY precursors. FeCl3 serves as an efficient, bifunctional oxidant for a (multiple) cyclization/desaturation process, applied to ethylene‐bridged dimeric, trimeric and oligomeric species to transform linking ethano units into stiff benzene fusions between unsubstituted β‐positions of each BODIPY unit. The structural integrity was verified by X‐ray crystallography, and all target compounds were studied in detail by photophysical, electrochemical and computational means. The main S1 excited state gradually converges to a structure‐specific excitation limit, displaying a strong shift of the absorption event from about 500 nm (BODIPY monomer) to 955 nm (octamer) with attenuation coefficients up to ca. 500 000 M−1 cm−1.

Facile and Convergent Synthesis of Highly Fused Oligosiloles by Rhodium‐Catalyzed Stitching Reaction

“…In fact, CV analysis of Si2x2 showed four reduction waves and the process was reversible up to the third reduction (Table 3). [7] Similarly, Si2x3 showed five reversible reduction waves and Si2x4 showed six reduction waves and the process was reversible up to the fifth reduction [4,10,11] . These electron‐accepting properties are complementary to recently reported ladder‐type π‐conjugated compounds with similar lengths that can donate multiple electrons reversibly under oxidizing conditions [2a,3] …”

“…Hence the synthesis can often become tedious for long ladder‐type π‐conjugated compounds. As notable recent examples, highly emissive carbon‐bridged oligo(phenylenevinylenes)s with up to 19 fused rings by Tsuji and Nakamura (2012), [2a] multi‐electron‐donating thienoacenes with up to 21 fused rings by Goodson, III and Yu (2016), [3] and NIR‐absorbing oligo‐BODIPYs with up to 31 fused rings by Werz (2021) were reported [4] . Although they exhibited unique and promising physical properties, they all required long synthetic schemes and the chemical yields became lower for the longer derivatives (e. g., 19–32 % yield in the final ladder‐forming steps).…”

Ausgedehnte, benzanellierte Oligo‐BODIPYs: In nur drei Schritten zu einer Serie planarer, bogenförmiger Nahinfrarot‐Farbstoffe

“…Mit optimierten Reaktionsbedingungen konnten die benzanellierten Trimere 3 T1 und 3 T2 so in Ausbeuten von 62 % und 51 % erhalten werden, was den meso-Substituenten als weitgehend uninvolviertes Strukturmerkmal auswies. [20] Der meso-Substituent Ar 2 wurde zwecks Veranschaulichung vereinfacht. Zur Einsicht in die Geometrie des Dimers 2 CyD2 siehe Hintergrundinformationen.…”

NIR-emitting benzene-fused oligo-BODIPYs for bioimaging

“…biological labelling, photodynamic therapy, organic photovoltaics, etc. 38,39 Recently, a novel three-step synthetic protocol to yield fully conjugated, benzene-fused oligo-BODIPYs from BODIPY precursors was presented 38 . With this procedure consisting in oligomerization and one-pot oxidation steps, a full series of oligomers ranging from dimers to octamers was synthesized.…”