We report the synthesis and characterization of the first non-fullerene acceptor containing a boron difluoride formazanate core end-capped with N-annulated perylene diimides.
The first example of a π-conjugated polymer incorporating boron difluoride (BF2) formazanates is introduced. The film-forming properties, controllable reduction chemistry, and low optical band gap (ca. 1.4 eV) of the polymer make it an excellent candidate for use as a light-harvesting n-type semiconductor in organic electronics. Comparison of the polymer to model compounds confirmed that its unique optoelectronic properties can be directly attributed to the presence of the BF2 formazanate repeat unit and that the [Pt(PBu3)2]2+ unit must also be present to achieve the narrow band gaps observed.
π-Conjugated molecules with acceptor-donor-acceptor (A-D-A) electronic structures make up an important class of materials due to their tunable optoelectronic properties and applications in, for example, organic light-emitting diodes, nonlinear optical devices, and organic solar cells. The frontier molecular orbital energies, and thus band gaps, of these materials can be tuned by varying the donor and acceptor traits and πelectron counts of the structural components. Herein, we report the synthesis and characterization of a series of A-D-A compounds consisting of BF 2 formazanates as electron acceptors bridged by a variety of π-conjugated donors. The results, which are supported by density functional theory calculations, demonstrate rational control of optoelectronic properties and the ability to tune the corresponding band gaps. The narrowest band gaps (E g Opt = 1.38 eV and E g CV = 1.21 eV) were observed when BF 2 formazanates and benzodithiophene units were combined. This study provides significant insight into the band gap engineering of materials derived from BF 2 formazanates and will inform their future development as semiconductors for use in organic electronics.
Boron difluoride (BF2) formazanate dyes are contenders for molecular species that exhibit a large Stokes shift and bright red emission. Excitation of 3‐cyanoformazanate complexes with 10 μs wide pulses of specific wavelengths resulted in strong luminescence at 663 nm at both room temperature in solution and at 77 K in a frozen solution. Analysis of the short‐lived excitation spectrum from this luminescence shows that it arises from a vibronic manifold of a higher‐lying excited state. This dark state relaxes to the emitting state over 10 μs. TD‐DFT calculations of the two lowest‐energy excited states show that the relaxed geometries are planar for S1 but highly distorted in S2. The specific time‐ and wavelength‐dependence of the excitation profile provides a unique optical encryption capability through the comparison of emission intensities between adjacent vibronic bands only accessible in the 0–12 μs time domain.
Oligoynes and polyynes are 1D chains of conjugated sp-hybridized carbon atoms consisting of alternating single and triple bonds. Their stability rapidly decreases with increasing chain length beyond only a few repeating units. Design strategies, such as the use of bulky end-capping groups, allow for their characterization and isolation while not contributing significantly to their physical properties. In this study, we incorporate redox-active BF 2 formazanate dyes (BF 2 ) as end-caps to prepare symmetric (BF 2 À [C�C] n À BF 2 ) and asymmetric (BF 2 À [C�C] n À Si(iPr) 3 ) families of oligoynes containing up to 10 alkyne units. In doing so, we introduce stable oligoynes that possess a blend of optical and redox properties that cannot be achieved by either oligoynes or BF 2 formazanates individually (e.g., panchromatic absorption, multiple and tunable reversible redox waves). This approach is transferable to other functional end-caps to facilitate the preparation of π-conjugated materials with utility in the organic electronics arena.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.