Multichromophore Integrated Panchromatic Azaborondipyrromethenes: Synthesis, Characterization, and Exploring the Role of AzaBODIPY as an Energy and Electron Relay in Photoinduced Processes

Abstract

Panchromatic azaborondipyrromethenes directly connected with N,N‐ditolylaniline (TPA) and naphthalene (Naph) at 1,7‐ and/or 3,5‐positions of the azaBODIPY platform, 1, 2, and 3, were synthesized and the roles of the individual chromophore constituents in the photo‐induced energy and electron transfer processes have been investigated. Optical absorption studies have indicated that integrating the complementary absorbers, naphthalene and TPA moieties, into the azaBODIPY core yielded broad‐band capturing dyes with the absorption ranging from 250–1000 nm. Parallel electrochemical studies revealed that TPA moiety in 1 and 2 is easier to oxidize when compared to azaBODIPY moiety, which are in congruent with the computational studies indicating that TPA moiety would behave as an electron donor and azaBODIPY as an acceptor in PET processes. Steady‐state fluorescence studies indicated that the photo‐excitation of the TPA moiety in 2 resulted in the occurrence of PET from 1TPA* to azaBODIPY generating (TPA)2+⋅‐(azaBODIPY)−⋅ while that of naphthalene in 3 resulted in PEnT from 1(naphthalene)* to azaBODIPY forming (Naph)2‐1(azaBODIPY)*. Interestingly, in 1, excitation of naphthalene moiety resulted in sequential PEnT from 1(naphthalene)* to azaBODIPY followed by the PET from TPA to 1(azaBODIPY)* generating a charge‐separated state, (TPA)2+⋅‐(azaBODIPY)−⋅‐(Naph)2 Fluorescence lifetime studies have indicated that the electron and energy transfer processes occurred in nanosecond time scales.

Excitation wavelength-reliant light-induced energy and electron processes in pyrene and naphthalene functionalized dual-dye integrated polyaromatic azaborondipyrromethenes

“…This kind of NMR behaviour was also observed in naphthalene functionalized azaBODIPYs reported by our research group earlier. 92…”

“…Compounds, 3 and Tolyl-azaBODIPY ( TABPY ) were synthesized according to the literature procedures. 92,95…”

“…89,90 Recently, our group has reported azaBODIPYs flanked with triphenylamine and naphthalene moieties at both the 1,7- and 3,5-positions and the role of the azaBODIPY core as an energy and electron receiver has been explored. 92…”

“…89,90 Recently, our group has reported azaBODIPYs flanked with triphenylamine and naphthalene moieties at both the 1,7-and 3,5-positions and the role of the azaBODIPY core as an energy and electron receiver has been explored. 92 Even though azaBODIPYs substituted with naphthalene or pyrene moieties at 1,7-positions of the core have been reported in the literature and PEnT from the singlet excited aromatic fluorophores to azaBODIPY macrocycle was observed, 8,17,62 to the best of our knowledge, no scientific report containing dualdye architecture i.e., both the pyrene and naphthalene moieties directly integrated onto the azaBODIPY platform and exploiting the photophysical properties of both the PAHs has been published to date. In this context, we have designed and synthesized multifluorophoric azaBODIPY, 1, functionalized with both pyrene and naphthalene moieties at the 1,7-and 3,5positions respectively, and 2 and 3 with pyrene at the 1,7positions and naphthalene at the 3,5-positions, respectively, and investigated the behavior of the individual constituents in the light induced energy and electron transfer processes (Chart 1).…”

Far‐Red Excitation Induced Electron Transfer in Bis Donor‐AzaBODIPY Push‐Pull Systems; Role of Nitrogenous Donors in Promoting Charge Separation

“…[43] These are in addition to studies reported by other groups. [44][45][46][47][48][49][50][51][52][53][54][55] In the present study, we report a new series of bisdonoracceptor push-pull systems featuring nitrogenous electron donors, viz., N,N-dimethylaniline (NND), triphenylamine (TPA), and phenothiazine (PTZ) with the help of acetylene linkers (see Figure 1 for structures along with those of the control compounds). Here, the azaBODIPY core is different from the traditionally used azaBODIPY in which two β-pyrrole-phenyl rings have been replaced with thiophene units and the αphenyl groups have acetenyl-phenyl entities.…”