A Versatile Synthesis of Long-Wavelength-Excitable BODIPY Dyes from Readily Modifiable Cyclopenta[2,1-b:3,4-b′]dithiophenes

Abstract

Knoevenagel condensation of a simple methylated borondipyrromethene (Bodipy) with 4,4′-dihexyl-4H-cyclopenta- [2,1-b:3,4-b′]dithiophenes functionalized at one end by a triphenylamine residue and at the other by a carbaldehyde fragment leads to novel dye species. These bisvinylic derivatives exhibit pronounced absorption in the visible range extending above 850 nm. Addition of other Bodipy units by coupling to a central iodophenyl entity enables filling of the gaps in absorption of the pivotal starting material. Efficient cascade energy transfer between the Bodipys is facilitated by spectral overlap between the energy donor and the energy acceptor. All photons between 350 nm and 750 nm are channeled to the distyryl centers which emit at 864 nm.The programmed synthesis of sophisticated multichromophoric dyes is challenging but has blossomed during the last few years due to the demand for energy conversion devices. 1-3 Red/near-infrared radiation (NIR, 650-1000 nm) accounts for approximately 33% of the solar energy arriving at the surface of the Earth, while visible radiation (350-650 nm) accounts for about 40%. 4,5 The key issue toward achieving efficient organic solar cells is the development of red and NIR absorbing dyes to harvest a larger fraction of the solar spectrum. We have been interested in borondipyrromethene 6 and diketopyrrolopyrrole 7 dyes as their performance can be fine-tuned by architectural alternations and molecular engineering. In this regard, various tools have been used, such as: i) the introduction of strong electron-donating subunits; ii) the increase of the conjugation pathway by construction of unsaturated vinylic or acetylenic side arms; iii) the introduction of auxiliary energy or electron acceptors in the vicinity of the central absorbing core. Many specific synthetic approaches have been found fruitful for the construction of dye molecules with strong absorption in the red or near-infra red spectral windows. 8,9 In many cases, however, the solubility of these dyes is hampered by the presence of a flat aromatic core, a situation highly favorable for undesirable aggregation process which limits their utilization in solution-processed device fabrication and biomedical applications. Thus, many structural modifications have been designed to encumber the dyes with bulky three-dimensional units. We have developed a synthetic protocol based on the 'chemistry at boron' of several borondipyrromethene (Bodipy) dyes in order to solve the problems of solubility, stability and aggregation. 10 In the present contribution, we disclose the synthesis of highly colored Bodipy dyes absorbing over a large window into the NIR and in some cases exploit the chemistry at boron to import steric bulkiness and additional energy absorbing units capable of engendering cascade energy transfer. 11 Our earlier studies have shown that the use of thiophene or bisthiophene in the construction of delocalized BODIPY dyes can provide: i) green absorbing dyes; ii) material capable of transporting equally electrons and holes...

Ullazine Donor–π bridge‐Acceptor Organic Dyes for Dye‐Sensitized Solar Cells

“…3,9‐bis(4‐(hexyloxy)phenyl) indolizino[6,5,4,3‐ija]quinoline‐5‐carbaldehyde ( 6 a ) and 3,9‐bis(4‐(hexyloxy)phenyl)indolizino[6,5,4,3‐ija]quinoline‐4‐carbaldehyde ( 7 a ) were made according to literature . 6‐Bromo‐4,4‐dihexyl‐4 H ‐cyclopenta[2,1‐b:3,4‐b′]dithiophene‐2‐carbaldehyde ( 10 ) was prepared according to literature procedure . 1‐(2,6‐Dibromophenyl)‐1 H ‐pyrrole ( 3 ) was prepared according to literature procedure .…”

“…6‐((3,9‐Bis(4‐(hexyloxy)phenyl)indolizino[6,5,4,3‐ ija ]quinolin‐5‐yl)ethynyl)‐4,4‐dihexyl‐4 H ‐cyclopenta[2,1‐ b :3,4‐ b′ ]dithiophene‐2‐carbaldehyde (11 a) : To a flame dried N 2 filled round bottom flask was added CuI (0.67 mg, 0.003 mmol, 0.04 equiv), dioxane (0.18 mL), diisopropylamine (0.03 mL, 0.211 mmol, 2.4 equiv), Pd[P( t Bu) 3 ] 2 (2.69 mg, 0.005 mmol, 0.06 equiv), 5‐ethynyl‐3,9‐bis(4‐(hexyloxy)phenyl)indolizino[6,5,4,3‐ ija ]quinoline ( 8 a ) (60 mg, 0.106 mmol, 1.2 equiv), and 6‐bromo‐4,4‐dihexyl‐4 H ‐cyclopenta[2,1‐b:3,4‐b′]dithiophene‐2‐carbaldehyde ( 10 ) (40.0 mg, 0.088 mmol, 1.0 equiv). The mixture was stirred at room temperature overnight.…”

“…6‐((3,9‐Bis(2,6‐bis(hexyloxy)phenyl)indolizino[6,5,4,3‐ ija ]quinolin‐4‐yl)ethynyl)‐4,4‐dihexyl‐4 H ‐cyclopenta[2,1‐ b :3,4 ‐b′ ]dithiophene‐2‐carbaldehyde (12 b) : To a flame dried, N 2 filled round bottom flask was added 6‐bromo‐4,4‐dihexyl‐4 H ‐cyclopenta[2,1‐ b :3,4 ‐b′ ]dithiophene‐2‐carbaldehyde ( 10 ) (34 mg, 0.075 mmol, 1.0 equiv), Pd(PPh 3 ) 4 (13.9 mg, 0.012 mmol, 0.16 equiv) and dry N , N ‐dimethylformamide (10.8 mL, 0.007 m ). A separate solution of 3,9‐bis(2,6‐bis(hexyloxy)phenyl)‐4‐((tributylstannyl)ethynyl)indolizino[6,5,4,3‐ ija ]quinoline ( 13 b ) (158 mg, 0.15 mmol, 2.0 equiv) in dry N , N ‐dimethylformamide (2.5 mL, 0.06 m ) was added dropwise followed with stirring at 110 °C and the mixture was stirred overnight.…”

Enhancing Planar Inverted Perovskite Solar Cells with Innovative Dumbbell‐Shaped HTMs: A Study of Hexabenzocoronene and Pyrene‐BODIPY‐Triarylamine Derivatives

“…The construction is supported with planar HBC and pyrene building blocks that can facilitate stability and efficient charge transport through intermolecular 𝜋-𝜋 stacking and potential self-assembly. [21][22][23]48] Since the combination of BODIPY and HBC is entirely novel and that of BODIPY-triarylamine-pyrene only occasionally covered in literature, [49,50] we examined their interaction in four, so-far unreported derivatives in a dumbbell-shaped architecture: two based on pyrene-BODIPY-triarylamine (TM-03, TM-04), the other two on HBC-BODIPY-triarylamine (TM-01, TM-02). As such, the BODIPY core was employed as a central, bridging unit (the dumbbell "bar") between one PAH moiety on either side (the dumbbell "weights").…”