A series of chiral binaphthyl titanium alkoxide complexes were synthesized. Among them, chiral titanium complex [(R)-3,3'-dibromo-2,2'-binaphthoxy](di-tert-butoxy)titanium(IV) (R-3) exists as a crystallographic C2 dimer in the solid state but a monomer in solution at room temperature. Application of R-3 in the helix-sense-selective polymerization of achiral carbodiimide, N-(1-anthryl)-N'-octadecylcarbodiimide (1), yielded a well-defined regioregular, stereoregular poly[N-(1-anthryl)-N'-octadecylguanidine] (poly-1b) with a relatively narrow polymer dispersity index of 2.7. Full racemization of poly-1b at +80 degrees C in toluene requires more than 100 h. Interestingly, poly-1b was found to undergo fast reversible chiroptical switching at +38.5 degrees C in toluene. Furthermore, at room temperature, poly-1b shows a positively signed Cotton effect in toluene, but negative ones in THF and chloroform, respectively. The chiroptical switching takes place around the toluene content of 90% (vol) in the mixed toluene/THF solvents. This is the first example of chiroptical switching phenomenon occurring in a helical polymer possessing no chiral moieties in the polymer chains. We believe this reversible chiroptical switching phenomenon occurs by reorientation of anthracene rings relative to the chain director.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1021/ja0453533 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Asymmetric Synthesis of Azahelicenes via CPA-Catalyzed Kinetic Resolution.
Org Lett
January 2025
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, P. R. China.
The azahelicenes are structurally fascinating and practically useful chiral scaffolds, but their synthesis, especially in a catalytically asymmetric manner, is rather challenging. Herein, we report a CPA-catalyzed transfer hydrogenation process, which enables a rapid kinetic resolution of aza[6]helicenes. The established strategy provides facile access to enantioenriched aza[6]helicenes and tetrahydro[6]helicenes from easily available starting materials.
View Article and Find Full Text PDFPhoto-Controllable Förster Resonance Energy Transfer Based on Dynamic Chiral Self-Assembly of Sequence-Defined Amphiphilic Alternating Azopeptoids.
Small
January 2025
Shanghai Key Laboratory of Advanced Polymeric Materials, Frontiers Science Center for Materiobiology and Dynamic Chemistry, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai, 200237, China.
Endowing biomimetic sequence-controlled polymers with chiral functionality to construct stimuli-responsive chiral materials offers a promising approach for innovative chiroptical switch, but it remains challenging. Herein, it is reported that the self-assembly of sequence-defined chiral amphiphilic alternating azopeptoids to generate photo-responsive and ultrathin bilayer peptoidosomes with a vesicular thickness of ≈1.50 nm and a diameter of around ≈290 nm.
View Article and Find Full Text PDFB,N-Embedded Helical Nanographenes Showing an Ion-Triggered Chiroptical Switching Function.
Angew Chem Int Ed Engl
January 2025
Okayama Daigaku Daigakuin Shizen Kagaku Kenkyuka, Division of Applied Chemistry, JAPAN.
Intramolecular aromatic oxidative coupling of 3,6-bis(m-terphenyl-2'-yl)carbazole provided a bis(m-terphenyl)-fused carbazole, while that of 3,6-bis(m-terphenyl-2'-yl)-1,8-diphenylcarbazole afforded a bis(quaterphenyl)-fused carbazole. Borylation of the latter furnished a B,N-embedded helical nanographene binding a fluoride anion via a structural change from the three-coordinate boron to the four-coordinate boron. The anionic charge derived from the fluoride anion is stabilized over the expanded p-framework, which leads to the high binding constant (Ka) of 1 × 105 M-1.
View Article and Find Full Text PDFDynamically Tunable Chiroptical Activities of Flexible Chiral Plasmonic Film via Surface Buckling.
Small
December 2024
School of Physical Science and Technology, ShanghaiTech University, 393 Huaxia Middle Rd. Pudong, Shanghai, 201210, P. R. China.
Article Synopsis
- Plasmonic nanoparticle-based chiral materials utilize strong light-matter interaction and tunable resonance frequencies but face challenges in dynamic modulation of their chiroptical properties.
- Researchers created chiral assemblies using gold nanospheres (AuNSs) through mechanical-induced surface buckling, resulting in a unique "S-shaped" 3D structure that enhances circular dichroism (CD) responses.
- This method allows for reversible adjustments in CD signal magnitude and handedness, presenting opportunities for advanced applications in information encryption and paving the way for new design strategies in chiral optical materials.
Sensitive Detection of Hg and l-Cysteine through Optical Asymmetry-Tuned Fluorescence Switch Off-On Behavior in N-Doped Chiral Carbon Dot.
ACS Appl Bio Mater
January 2025
Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India.
Blue-emissive nitrogen-doped chiral carbon dots (d-NCD230 and l-NCD230) exhibiting antipodal chiroptical activity, synthesized from the thermal pyrolysis of citric acid and d/l-aspartic acid in 1:2 molar ratios, have been explored as chirality-based fluorescent turn-off/on probes for the detection of Hg and l-cysteine (l-Cys). Circular dichroism (CD) spectroscopy revealed that the chiroptical activity originates from a synergy among intrinsic chirality, chiral precursors on the NCD surface, and hybridization of lower energy levels within the embedded chiral chromophore. Quantitative analysis of optical asymmetry using the Kuhn asymmetry factor () at the CD signal of 312 nm showed a higher value for d-NCD230 (1.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!