- Award ID(s):
- 1757220
- NSF-PAR ID:
- 10419493
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 24
- Issue:
- 38
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 23699 to 23711
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
null (Ed.)Stable organic semiconductors (OSCs) with a high-spin ground-state can profoundly impact emerging technologies such as organic magnetism, spintronics, and medical imaging. Over the last decade, there has been a significant effort to design π-conjugated materials with unpaired spin centers. Here, we report new donor–acceptor (D–A) conjugated polymers comprising cyclopentadithiophene and cyclopentadiselenophene donors with benzobisthiadiazole (BBT) and iso-BBT acceptors. Density functional theory calculations show that the BBT-based polymers display a decreasing singlet–triplet energy gap with increasing oligomer chain length, with degenerate singlet and triplet states for a N = 8 repeat unit. Furthermore, a considerable distance between the unpaired electrons with a pure diradical character disrupts the π-bond covalency and localizes the unpaired spins at the polymer ends. However, replacing the BBT acceptor with iso-BBT leads to a closed-shell configuration with a low-spin ground-state and a localized spin density on the polymer cores. This study shows the significance of the judicious choice of π-conjugated scaffolds in generating low- ( S = 0) and high-spin ( S = 1) ground-states in the neutral form, by modulation of spin topology in extended π-conjugated D–A polymers for emergent optoelectronic applications.more » « less
-
Abstract Conductive polymers largely derive their electronic functionality from chemical doping, processes by which redox and charge‐transfer reactions form mobile carriers. While decades of research have demonstrated fundamentally new technologies that merge the unique functionality of these materials with the chemical versatility of macromolecules, doping and the resultant material properties are not ideal for many applications. Here, it is demonstrated that open‐shell conjugated polymers comprised of alternating cyclopentadithiophene and thiadiazoloquinoxaline units can achieve high electrical conductivities in their native “undoped” form. Spectroscopic, electrochemical, electron paramagnetic resonance, and magnetic susceptibility measurements demonstrate that this donor–acceptor architecture promotes very narrow bandgaps, strong electronic correlations, high‐spin ground states, and long‐range π‐delocalization. A comparative study of structural variants and processing methodologies demonstrates that the conductivity can be tuned up to 8.18 S cm−1. This exceeds other neutral narrow bandgap conjugated polymers, many doped polymers, radical conductors, and is comparable to commercial grades of poly(styrene‐sulfonate)‐doped poly(3,4‐ethylenedioxythiophene). X‐ray and morphological studies trace the high conductivity to rigid backbone conformations emanating from strong π‐interactions and long‐range ordered structures formed through self‐organization that lead to a network of delocalized open‐shell sites in electronic communication. The results offer a new platform for the transport of charge in molecular systems.
-
Abstract Organic semiconductors with high-spin ground states are fascinating because they could enable fundamental understanding on the spin-related phenomenon in light element and provide opportunities for organic magnetic and quantum materials. Although high-spin ground states have been observed in some quinoidal type small molecules or doped organic semiconductors, semiconducting polymers with high-spin at their neutral ground state are rarely reported. Here we report three high-mobility semiconducting polymers with different spin ground states. We show that polymer building blocks with small singlet-triplet energy gap (Δ E S-T ) could enable small Δ E S-T gap and increase the diradical character in copolymers. We demonstrate that the electronic structure, spin density, and solid-state interchain interactions in the high-spin polymers are crucial for their ground states. Polymers with a triplet ground state ( S = 1) could exhibit doublet ( S = 1/2) behavior due to different spin distributions and solid-state interchain spin-spin interactions. Besides, these polymers showed outstanding charge transport properties with high hole/electron mobilities and can be both n- and p-doped with superior conductivities. Our results demonstrate a rational approach to obtain high-mobility semiconducting polymers with different spin ground states.more » « less
-
null (Ed.)DNA-encoded library (DEL) technology features a time- and cost-effective interrogation format for the discovery of therapeutic candidates in the pharmaceutical industry. To develop DEL platforms, the implementation of water-compatible transformations that facilitate the incorporation of multifunctional building blocks (BBs) with high C(sp 3 ) carbon counts is integral for success. In this report, a decarboxylative-based hydro alkylation of DNA-conjugated trifluoromethyl-substituted alkenes enabled by single-electron transfer (SET) and subsequent hydrogen atom termination through electron donor–acceptor (EDA) complex activation is detailed. In a further photoredox-catalyzed hydro arylation protocol, the coupling of functionalized, electronically unbiased olefins is achieved under air and within minutes of blue light irradiation through the intermediacy of reactive (hetero)aryl radical species with full retention of the DNA tag integrity. Notably, these processes operate under mild reaction conditions, furnishing complex structural scaffolds with a high density of pendant functional groups.more » « less
-
Abstract Organic semiconductors based on conjugated donor-acceptor (D–A) polymers are a unique platform for electronic, spintronic, and energy-harvesting devices. Understanding the electronic structure of D–A polymers with a small band gap is essential for developing next-generation technologies. Here, we investigate the electronic structure and optical spectra of cyclopentadithiophene-based closed/open-shell D–A polymers using density functional theory and the Bethe–Salpeter equation based on G
W$$_0$$ approximation. We explored the role of different acceptor units and chemical substitutions on the structural changes and, more importantly, electronic, optical, and dielectric behavior. We found that the computed first exciton peak of the polymers agreed well with the available experimentally measured optical gap. Furthermore, D–A polymers with open-shell character display higher dielectric constant than the closed-shell polymers. We show that the exceptional performance of polycyclopentadithiophene-thiophenylthiadiazoloquinoxaline (PCPDT-TTQ) as a scalable$$_0$$ n -type material for Faradaic supercapacitors can be partly ascribed to its elevated dielectric constant. Consequently, these D–A polymers, characterized by their high dielectric constants, exhibit significant potential for various applications, including energy storage, organic electronics, and the production of dielectric films.