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1. Symmetry Breaking and Photomechanical Behavior of Photochromic Organic Crystals

   https://doi.org/10.3390/sym12091478  

   Kitagawa, Daichi; Bardeen, Christopher J.; Kobatake, Seiya (September 2020, Symmetry)

   null (Ed.)

   Photomechanical materials exhibit mechanical motion in response to light as an external stimulus. They have attracted much attention because they can convert light energy directly to mechanical energy, and their motions can be controlled without any physical contact. This review paper introduces the photomechanical motions of photoresponsive molecular crystals, especially bending and twisting behaviors, from the viewpoint of symmetry breaking. The bending (right–left symmetry breaking) and twisting (chiral symmetry breaking) of photomechanical crystals are based on both intrinsic and extrinsic factors like molecular orientation in the crystal and illumination conditions. The ability to design and control this symmetry breaking will be vital for generating new science and new technological applications for organic crystalline materials. 

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2. 1,3,5–2,4,6‐Functionalized Benzene Molecular Cage: An Environmentally Responsive Scaffold that Supports Hierarchical Superstructures

   https://doi.org/10.1002/anie.202407805  

   Pang, Xin‐Yu; Zhou, Hang; Xie, Xiaojiang; Jiang, Wei; Yang, Yinhua; Sessler, Jonathan_L; Gong, Han‐Yuan (July 2024, Angewandte Chemie International Edition)

   Abstract New stimulus‐responsive scaffolds are of interest as constituents of hierarchical supramolecular ensembles. 1,3,5–2,4,6‐Functionalized, facially segregated benzene moieties have a time‐honored role as building blocks for host molecules. However, their user as switchable motifs in the construction of multi‐component supramolecular structures remains poorly explored. Here, we report a molecular cage 1, which consists of a bent anthracene dimer3paired with 1,3,5‐tris(aminomethyl)‐2,4,6‐triethylbenzene2. As the result of the pH‐inducedababab↔bababaisomerization of the constituent‐functionalized benzene units derived from2, this cage can reversibly convert between an open state and a closed form, both in solution and in the solid state. Cage 1was used to create stimuli‐responsive hierarchical superstructures, namely Russian doll‐like complexes with [K⊂18‐crown‐6⊂1]⁺and [K⊂cryptand‐222⊂1]⁺. The reversible assembly and disassembly of these superstructures could be induced by switching cage 1from its open to closed form. The present study thus provides an unusual example where pH‐triggered conformation motion within a cage‐like scaffold is used to control the formation and disassociation of hierarchical ensembles. 

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3. Organic crystal structure prediction and its application to materials design

   https://doi.org/10.1557/s43578-022-00698-9  

   Zhu, Qiang; Hattori, Shinnosuke (September 2022, Journal of Materials Research)

   Abstract In recent years, substantial progress has been made in the modeling of organic solids. Computer simulation has been increasingly shaping the area of new organic materials by design. It is possible to discover new organic crystals by computational structure prediction, based on the combination of powerful exploratory algorithms and accurate energy modeling. In this review, we begin with several key early concepts in describing crystal packing, and then introduce the recent state-of-the-art computational techniques for organic crystal structure prediction. Perspectives on the remaining technical challenges, functional materials screening and software development are also discussed in the end. It is reasonable to expect that, in the near future, accurate predictive computational modeling can be accomplished within a time frame that is appreciably shorter than that needed for the laboratory synthesis and characterization. Graphical abstract 

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4. Ionic Dopant‐Induced Ordering Enhances the Thermoelectric Properties of a Polythiophene‐Based Block Copolymer

   https://doi.org/10.1002/adfm.202106991  

   Dong, Ban Xuan; Liu, Ziwei; Onorato, Jonathan W.; Ma, Tengzhou; Strzalka, Joseph; Bennington, Peter; Luscombe, Christine K.; Ober, Christopher K.; Nealey, Paul F.; Patel, Shrayesh N. (September 2021, Advanced Functional Materials)

   Abstract Conjugated polymer‐based block copolymers (CP‐BCPs) are an unexplored class of materials for organic thermoelectrics. Herein, the authors report on the electronic conductivity (σ) and Seebeck coefficient (α) of a newly synthesized CP‐BCP, poly(3‐hexylthiophene)‐block‐poly (oligo‐oxyethylene methacrylate) (P3HT‐b‐POEM), upon solution co‐processing with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and subsequently vapor‐doping with a molecular dopant, 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ). It is found that the addition of the hydrophilic block POEM greatly enhances the processability of P3HT, enabling homogeneous solution‐mixing with LiTFSI. Notably, interactions between P3HT‐b‐POEM with ionic species significantly improve molecular order and unexpectedly cause electrical oxidizing doping of P3HT block both in solution and solid‐states, a phenomenon that has not been previously observed in Li‐salt containing P3HT. Vapor doping of P3HT‐b‐POEM‐LiTFSI thin films with F4TCNQ further enhances σ and yields a thermoelectric power factorPF=α²σ of 13.0 µW m⁻¹ K⁻², which is more than 20 times higher than salt‐free P3HT‐b‐POEM sample. Through modeling thermoelectric behaviors of P3HT‐b‐POEM with the Kang‐Snyder transport model, the improvement inPFis attributed to higher electronic charge mobility originating from the enhanced molecular ordering of P3HT. The results demonstrate that solution co‐processing CP‐BCPs with a salt is a powerful method to control structure and performance of organic thermoelectric materials. 

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5. A Janus carbaporphyrin pseudo-dimer

   https://doi.org/10.1038/s41467-024-47239-y  

   He, Haodan; Lee, Jiyeon; Zong, Zhaohui; Kim, Jiwon; Lynch, Vincent M; Oh, Juwon; Kim, Dongho; Sessler, Jonathan L; Ke, Xian-Sheng (April 2024, Nature Communications)

   LeBot, Nathalie; Larochelle, Stephane; Bergin, Enda; Saini, Prabhjot (Ed.)

   Abstract Carbaporphyrin dimers, investigated for their distinctive electronic structures and exceptional properties, have predominantly consisted of systems containing identical subunits. This study addresses the associated knowledge gap by focusing on asymmetric carbaporphyrin dimers with Janus-like characteristics. The synthesis of a Janus-type carbaporphyrin pseudo-dimer5is presented. It displays antiaromatic characteristics on the fused side and nonaromatic behavior on the unfused side. A newly synthesized tetraphenylene (TPE) linked bis-dibenzihomoporphyrin8and a previously reported dibenzo[g,p]chrysene (DBC) linked bis-dicarbacorrole9were prepared as controls. Comprehensive analyses, including¹H NMR spectral studies, single crystal X-ray diffraction analyses, and DFT calculations, validate the mixed character of5. A further feature of the Janus pseudo-dimer5is that it may be transformed into a heterometallic complex, with one side coordinating a Cu(III) center and the other stabilizing a BODIPY complex. This disparate regiochemical reactivity underscores the potential of carbaporphyrin dimers as versatile frameworks, with electronic features and site-specific coordination chemistry controlled through asymmetry. These findings position carbaporphyrin dimers as promising candidates for advances in electronic structure studies, coordination chemistry, materials science, and beyond. 

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