Solvent‐Sensitive Emitting Urea‐Bridged bis‐BODIPYs: Ready Access by a One‐Pot Tandem Staudinger/Aza‐Wittig Ureation

Abstract

Herein we describe the synthesis, and computationally aided photophysical characterization of a new set of urea-bridged bis-BODIPY derivatives. These new dyads are efficiently obtained by a one-pot tandem Staudinger/aza-Wittig ureation protocol, from easily accessible meso-phenyl ortho-azidomethyl BODIPYs. These symmetric bis-BODIPYs outstand by a high absorption probability and excellent fluorescence and laser emission in less polar media. Nevertheless, this emission ability decreases in more polar media, which is ascribed to a light-induced charge-transfer from the urea spacer to the dipyrrin core, a process that can be modulated by appropriate changes in the substitution pattern of the BODIPY core. Furthermore, this ureation protocol can also be employed for the direct conjugation of our BODIPY-azides to amine-containing compounds, thus providing access to fluorescent non-symmetric ureas.

Towards Efficient and Photostable Red‐Emitting Photonic Materials Based on Symmetric All‐BODIPY‐Triads, ‐Pentads, and ‐Hexads

“…This finding unambiguously backs up the ability of the BODIPY grafted to 3,5‐styryl groups to induce effective ICT processes. Furthermore, in cassette 10 the urea spacer linking the acceptor BODIPYs was itself able to induce an effective ICT owing to its electron donor ability, as was reported previously in symmetric bis‐BODIPYs . The viability of two pathways to induce effective ICT processes in 10 led to the lowest fluorescent quantum yield and the shortest lifetime in polar media among the cassettes herein synthetized (Table ).…”

“…Furthermore,i nc assette 10 the urea spacer linking the acceptor BODIPYsw as itself able to induce an effective ICT owing to its electron donorability,aswas reported previously in symmetric bis-BOD-IPYs. [25] The viability of two pathways to induce effective ICT processes in 10 led to the lowest fluorescent quantum yield and the shortestl ifetimei np olar media among the cassettes herein synthetized (Table 1). These resultsh ighlight the complex excited state dynamics of these multichromophoric systems in polar solvents where,b esides the ongoing intra-EET, ICT processes were also directing their emission response.…”

“…Final access to BODIPY-pentad 9,a nd -hexad 10 was straightforward from BODIPYt rimer 6a.T hus, CuAAC reaction of dialkynyl BODIPY 6a with azidomethyl BODIPY 12 [23] (Scheme 2) led to pentameric BODIPY 9.C onversely,d imerization of azidomethyl BODIPY trimer 22, [25] obtained from 6a upon treatment with 2-azido-1,3-dimethylimidazolinium hexafluorophosphate (ADMP) in the presence of DBU, [29] yieldedd imeric bisurea trimer 10.…”

“…In this way, the new ensemble of all‐BODIPY multichromophores becomes the first example of: a) a straightforward synthetic strategy for all‐BODIPY cassettes using one single BODIPY progenitor, that is, 11 (Figure ), which makes use of copper(I)‐catalyzed alkyne‐azide cycloaddition (CuAAC) reactions, chemoselective Knoevenagel condensations of 2,6‐dialkynyl BODIPYs, and an efficient ureation protocol recently described by us (synthetic disconnections A , B , C , respectively, Figure ); b) a systematic analysis of the photonic behavior of red‐emitting cassettes based on structural factors such as the number of donor and acceptor units, and the position and the spacers connecting the building blocks; and c) remarkable red‐emitting laser cassettes endowed with an effective absorption in the UV–visible spectral region, and, particularly one of the highest emission efficiencies and photostability described to date, key parameters to guarantee long‐lasting emission in any advanced applications.…”

Tuning the Photonic Behavior of Symmetrical bis-BODIPY Architectures: The Key Role of the Spacer Moiety

“…In this context, we have recently reported a straightforward synthetic approach from ortho -functionalized 8-aryl-BODIPYs, e.g., 2 and 3 (Del Río et al, 2017), to stable and luminescent urea-bridged symmetric bis-BODIPYs, i.e., 4a and 5a (López et al, 2017) (Figure 1). The fluorescence response of this covalent molecular assembly was sensible to the properties of the environment owing to the capability of the spacer moiety to induce “through-space” intramolecular charge transfer (ICT) processes.…”