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1. A Dual Threat: Redox‐Activity and Electronic Structures of Well‐Defined Donor–Acceptor Fulleretic Covalent‐Organic Materials

   https://doi.org/10.1002/anie.201914233  

   Leith, Gabrielle A.; Rice, Allison M.; Yarbrough, Brandon J.; Berseneva, Anna A.; Ly, Richard T.; Buck, III, Charles N.; Chusov, Denis; Brandt, Amy J.; Chen, Donna A.; Lamm, Benjamin W.; et al (February 2020, Angewandte Chemie International Edition)

   Abstract The effect of donor (D)–acceptor (A) alignment on the materials electronic structure was probed for the first time using novel purely organic porous crystalline materials with covalently bound two‐ and three‐dimensional acceptors. The first studies towards estimation of charge transfer rates as a function of acceptor stacking are in line with the experimentally observed drastic, eight‐fold conductivity enhancement. The first evaluation of redox behavior of buckyball‐ or tetracyanoquinodimethane‐integrated crystalline was conducted. In parallel with tailoring the D‐A alignment responsible for “static” changes in materials properties, an external stimulus was applied for “dynamic” control of the electronic profiles. Overall, the presented D–A strategic design, with stimuli‐controlled electronic behavior, redox activity, and modularity could be used as a blueprint for the development of electroactive and conductive multidimensional and multifunctional crystalline porous materials. 

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2. The role of photoinduced charge transfer for photocatalysis, photoelectrocatalysis and luminescence sensing in metal–organic frameworks

   https://doi.org/10.1039/d0dt02143a  

   Li, Xinlin; Surendran Rajasree, Sreehari; Yu, Jierui; Deria, Pravas (September 2020, Dalton Transactions)

   null (Ed.)

   Metal–organic frameworks (MOFs) have emerged as promising porous optoelectronic compositions for energy conversion and sensing applications. The enormous structural possibilities, the large variety of photo- and redox-active building blocks along with several post-synthetic functionalization strategies make MOFs an ideal platform for photochemical and photoelectrochemical developments. Because MOFs assemble all the active building units in a dense fashion, the non-aggregated yet proximally positioned species ensure efficient photon absorption to drive photoinduced charge transfer (PCT) reactions for energy conversion and sensing. Hence, understanding the PCT processes within MOFs as a function of the topological and electronic structures of the donor–acceptor (D–A) moieties can provide transformative strategies to design new low-density compositions. 

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3. Synthesis of 1,4‐dihydropyrrolo[3,2‐b]pyrrole‐containing donor–acceptor copolymers and their optoelectronic properties

   https://doi.org/10.1002/pol.20240093  

   Bell, Kenneth‐John J.; Sabury, Sina; Phan, Vanessa; Wagner, Ethan M.; Hawks, Allison M.; Bartlett, Kimberley A.; Collier, Graham S. (April 2024, Journal of Polymer Science)

   Abstract Donor–acceptor (D–A)‐conjugated polymers have achieved promising performance metrics in numerous optoelectronic applications that continue to motivate studying structure–property relationships and discovering new materials. Here, the materials toolbox is expanded by synthesizing D–A copolymers where 1,4‐dihydropyrrolo[3,2‐b]pyrrole (DHPP) is directly incorporated into the main chain of D–A copolymers for the first time via direct heteroarylation polymerization. Notably, the synthetic complexity of DHPP‐containing polymers coupled with thieno[3,2‐b]pyrrole‐4,6‐dione (TPD) or 3,6‐bis(2‐thienyl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (Th₂DPP) comonomers is calculated to be lower compared to many common conjugated polymers synthesized via direct arylation. The electron‐rich nature of DHPPs when coupled with TPD or DPP enables optoelectronic properties to be manipulated, evident by measuring distinctly different absorbance and redox properties. Additionally, these D–A copolymers demonstrate their potential in organic electronic applications, such as electrochromics and organic photovoltaics. The reported DHPP‐alt‐Th₂DPP copolymer is the first DHPP‐based colored‐to‐transmissive electrochrome and achieves power conversion efficiencies of ~2.5% when incorporated into bulk heterojunction solar cells. Overall, the synthetic accessibility of DHPP monomers and their propensity to participate in robust polymerizations highlights the value of establishing structure–property relationships of an underutilized scaffold. These fundamental attributes serve to inform and advance efforts in the development of DHPP‐containing copolymers for various applications. 

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4. Non-Aufbau orbital ordering and spin density modulation in high-spin donor–acceptor conjugated polymers

   https://doi.org/10.1039/d2cp02355e  

   Sabuj, Md Abdus; Muoh, Obinna; Huda, Md Masrul; Rai, Neeraj (October 2022, Physical Chemistry Chemical Physics)

   High-spin ground-state organic materials with unique spin topology can significantly impact molecular magnetism, spintronics, and quantum computing devices. However, strategies to control the spin topology and alignment of the unpaired spins in different molecular orbitals are not well understood. Here, we report modulating spin distribution along the molecular backbone in high-spin ground-state donor–acceptor (D–A) conjugated polymers. Density functional theory calculations indicate that substitution of different heteroatoms (such as C, Si, N, and Se) alters the aromatic character in the thiadiazole unit of the benzobisthiadiazole (BBT) acceptor and modulates the oligomer length to result in high-spin triplet ground-state, orbital and spin topology. The C, Si, and Se atom substituted polymers show a localized spin density at the two opposite ends of the polymers. However, a delocalized spin distribution is observed in the N substituted polymer. We find that the hybridization (sp 3 vs. sp 2 ) of the substituent atom plays an important role in controlling the electronic structure of these materials. This study shows that atomistic engineering is an efficient technique to tune the spin topologies and electronic configurations in the high-spin ground-state donor–acceptor conjugated polymers, compelling synthetic targets for room-temperature magnetic materials. 

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5. Molecular Origin of Strain‐Induced Chain Alignment in PDPP‐Based Semiconducting Polymeric Thin Films

   https://doi.org/10.1002/adfm.202100161  

   Zhang, Song; Alesadi, Amirhadi; Mason, Gage_T; Chen, Kai‐Lin; Freychet, Guillaume; Galuska, Luke; Cheng, Yu‐Hsuan; St_Onge, P_Blake_J; Ocheje, Michael_U; Ma, Guorong; et al (March 2021, Advanced Functional Materials)

   Abstract Donor–acceptor (D–A) type semiconducting polymers have shown great potential for the application of deformable and stretchable electronics in recent decades. However, due to their heterogeneous structure with rigid backbones and long solubilizing side chains, the fundamental understanding of their molecular picture upon mechanical deformation still lacks investigation. Here, the molecular orientation of diketopyrrolopyrrole (DPP)‐based D–A polymer thin films is probed under tensile deformation via both experimental measurements and molecular modeling. The detailed morphological analysis demonstrates highly aligned polymer crystallites upon deformation, while the degree of backbone alignment is limited within the crystalline domain. Besides, the aromatic ring on polymer backbones rotates parallel to the strain direction despite the relatively low overall chain anisotropy. The effect of side‐chain length on the DPP chain alignment is observed to be less noticeable. These observations are distinct from traditional linear‐chain semicrystalline polymers like polyethylene due to distinct characteristics of backbone/side‐chain combination and the crystallographic characteristics in DPP polymers. Furthermore, a stable and isotropic charge carrier mobility is obtained from fabricated organic field‐effect transistors. This study deconvolutes the alignment of different components within the thin‐film microstructure and highlights that crystallite rotation and chain slippage are the primary deformation mechanisms for semiconducting polymers. 

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