Directly Connected AzaBODIPY–BODIPY Dyad: Synthesis, Crystal Structure, and Ground- and Excited-State Interactions

Abstract

Directly connected, strongly interacting sensitizer donor-acceptor dyads mimic light-induced photochemical events of photosynthesis. Here, we devised a dyad composed of BF2-chelated dipyrromethene (BODIPY) directly linked to BF2-chelated tetraarylazadipyrromethene (azaBODIPY) through the β-pyrrole position of azaBODIPY. Structural integrity of the dyad was arrived from two-dimensional NMR spectral studies, while single-crystal X-ray structure of the dyad provided the relative orientation of the two macrocycles to be ∼62°. Because of direct linking of the two entities, ultrafast energy transfer from the (1)BODIPY* to azaBODIPY was witnessed. A good agreement between the theoretically estimated Förster energy transfer rate and experimentally determined rate was observed, and this rate was found to be higher than that reported for BODIPY-azaBODIPY analogues connected with spacer units. In agreement with the free-energy calculations, the product of energy transfer, (1)azaBODIPY* revealed additional photochemical events such as electron transfer leading to the creation of BODIPY(•+)-azaBODIPY(•-) radical ion pair, more so in polar benzonitrile than in nonpolar toluene, as evidenced by femtosecond transient spectroscopic studies. Additionally, the spectral, electrochemical, and photochemical studies of the precursor compound azaBODIPY-dipyrromethane also revealed occurrence of excited-state events. In this case, electron transfer from the (1)azaBODIPY* to dipyrromethane (DPM) yielded DPM(•+)-azaBODIPY(•-) charge-separated state. The study described here stresses the role of close association of the donor and acceptor entities to promote ultrafast photochemical events, applicable of building fast-response optoelectronic and energy-harvesting devices.

Covalently Linked meso‐BODIPYnyl Dithiahomoporphyrins: Synthesis and Properties

“…[5] Synthesis of Tetrapyrrane 7: The required tripyrrane, 7 as E/Z mixture (pale yellow semi solid) was synthesized from diol 6 and excess pyrrole by following our previously reported procedure. [8][9][10][11] The spectroscopic data is in good agreement with the reported data for the BODIPY precursors (8-10). [8][9][10][11] The spectroscopic data is in good agreement with the reported data for the BODIPY precursors (8-10).…”

“…Different formyl-BODIPY precursors (8)(9)(10)(11) and -dipyrromethanyl aza-BODIPY (12) were synthesized by following the reported protocols. [8][9][10][11][12] As shown in Scheme 1a, the appropriate formyl-BODIPY such as meso-(4formyl phenyl) BODIPY (8), -formyl meso-anisyl BODIPY (9), meso-(2-formyl pyrrolyl) BODIPY (10) and α-(2-formyl-pyrrolyl) BODIPY (11) was treated with equimolar tetrapyrrane 7 in CH 2 Cl 2 in the presence of catalytic amount of BF 3 .OEt 2 at room temperature under inert atmosphere for 15-20 min followed by oxidation with 2 equiv. of DDQ for additional 15-20 min in open air.…”

Azadipyrromethenes: from traditional dye chemistry to leading edge applications

“…Under similar conditions, 29g was formylated and aldehyde 50b converted to the azadipyrromethene-BODIPY dyad 51 (Scheme 24). 67 This reaction sequence is a good illustration of the complexity of sequential transformations that can be carried out on azadipyrromethenes.…”

Panchromatic Light Capture and Efficient Excitation Transfer Leading to Near‐IR Emission of BODIPY Oligomers

“…Thus, a wide variety of BODIPYs have been synthesized and explored for their novel optical properties and energy‐harvesting applications . We recently reported a facile route for the synthesis of BF 2 complexes of meso ‐aryl pyrrolyldipyrrins (3‐pyrrolyl BODIPYs), which were not easily accessible before. The 3‐pyrrolyl BODIPYs have better photophysical properties than meso ‐aryl BODIPYs.…”