Diketopyrrolopyrrole Derivatives Functionalized with N‐Annulated PDI and Se‐Annulated PDI by Direct (Hetero)Arylation Methods

Abstract

We report on the synthesis of diketopyrrolopyrrole (DPP) derivatives functionalized with Nannulated and Se-annulated perylene diimide (NPDI and SePDI, respectively) via direct (hetero)arylation methods. DPP is symmetrically bifunctionalized with SePDI (SePDI-DPP-SePDI) and unsymmetrically functionalized with SePDI and NPDI (SePDI-DPP-NPDI). The effects of Se substitution compared to N substitution on physical, electrochemical, and optical properties are investigated along with performance as non-fullerene acceptors in photovoltaic devices. It is found that Se substitution increases the electron affinity of the -conjugated molecule and blue shifts the optical absorption spectra, observations that were supported by computational analysis. Steric strain between the PDI endcap and DPP core prevent complete electronic communication along the -conjugated backbone and results in the unsymmetrical compound, SePDI-DPP-NPDI, having electronic and optical properties that are a linear combination of both 2 the symmetrical SePDI and NPDI based compounds. Different is that the SePDI-DPP-NPDI compound has a distinct melt observed at 343 °C and organic photovoltaic devices based on this compound had lower than expected open-circuit voltages, suggesting a unique solid-state packing arrangement. SePDI-based compounds performed worse than the NPDI-based compound in organic photovoltaic devices using the donor polymer PTB7-Th.

Sustainable protocols for direct C–H bond arylation of (hetero)arenes

“…The authors successfully used the same catalytic system for the preparation of diketopyrrolo[3,4-c]pyrrole 69 (DPP)-based small molecules 64-66 for organic electronics, by direct C-H arylation of the thiophene rings of bis-thienylDPP derivatives 60 with brominated phthalimides 61, 70 benzothioxanthenes 62 71 and perylene diimides 63 (Scheme 26). 72 More recently, SiliaCat® DPP-Pd was also used by Welch et al in the direct C-H arylation polymerization of a bis-thienylDPP derivative with 2,7-dibromo-9,9′-spirobifluorene, affording the corresponding co-polymer in good yield (88%) and molecular weight (M n = 10 900), 73 as well as in the synthesis of a borane-containing non-fullerene acceptor by direct arylation of the thiophene rings of a bisthienylborane with a brominated perylene diimide derivative. 74 It is worth emphasizing that also in this case the works focused on the synthesis of π-conjugated materials, rather than on the development of a general direct arylation protocol: therefore, a complete evaluation of the recyclability and heterogeneity of SiliaCat® DPP-Pd in these reaction is missing, although the authors have repeatedly highlighted all the advantages of its use compared to other homogeneous Pd catalysts.…”

Direct (Hetero)arylation: A Tool for Low-Cost and Eco-Friendly Organic Photovoltaics

“…Later on, several examples of DPP based small molecules were investigated, where DHA was used as coupling reaction. − Furthermore, the most efficient NFAs for OPV, specifically Y6 (or BTP), ITIC and IDTBR like molecules, require between five and ten synthetic steps, which contributes greatly to the material cost. , Therefore, several research groups are focusing on simple molecular design involving direct (hetero)­arylation (DHA) coupling to reduce the material synthetic complexity . For example, Welch’s group worked intensively in the past few years in the design of perylene diimide (PDI) based NFA prepared by DHA. − …”

Effects of solvent vapor annealing on the optical properties and surface adhesion of conjugated D : A thin films

“…Post-deposition treatments have also been used to increase power conversion efficiency, such as thermal annealing 12 or solvent vapor annealing (SVA). 12,17,18 Generally, these procedures result in devices with better photovoltaic responses, by increasing the crystallinity of the active layer, improving the active layer/electrodes interface and the acceptor distribution along the active layer. The effect of the type of solvent and the time of SVA have also been extensively studied.…”

“…14 It is important to point out that this system presented a broad absorption spectrum and adequate stability to air and high temperatures (up to 428 1C). 15 This compound has been used as an electron acceptor in OSCs with adequate power conversion efficiency values and devices with relatively robust work stability in air.…”