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Carbon‐based organic radical spin filters
조대흠 대한화학회 2023 Bulletin of the Korean Chemical Society Vol.44 No.8
Single‐molecule magnetic junctions serve as an important component for the manipulation of spin‐polarized currents by chemical modifications and control of magnetic interactions in spintronic devices. We employed the nonequilibrium green function and spin‐polarized density functional theory simulations to investigate the performance of molecular junctions bearing an organic radical as spin filters. A spin‐polarized current could be generated using the junctions and, moreover, the spin‐filtering efficiency could be tuned by varying the number of magnetic units. Spin orbital and density of states analyses revealed the relationship effect of the shapes and energy levels of the dominant electron‐conducting channels in the spin‐filtering efficiency. Thus, the use of a tunable organic magnetic molecular junction system is an appealing approach for regulating spin‐polarized currents in spintronic devices.
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Signatures of Through-Space Charge Transfer in Two-Photon Absorption of Paracyclophane Derivatives
Abbas Salimi,조대흠,이진용,강선우,Shaul Mukamel 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.11
Third order polarizability, (?) taken from the collective electronic oscillator (CEO) method was used to calculate the two-photon absorption (TPA) of tetrastyryl-[2,2]paracyclophane derivatives with different through-space charge transfer configurations considering various donor and acceptor combinations at the terminal styryl groups. For the virtually same linear absorption, different TPA spectra were obtained. For controlling and fine-tuning frequency and cross-sections of TPA the through-space charge transfer interactions can be used. The results are explained by the electronic density matrices corresponding to governing oscillators in one- and two-photon absorption and the ground state. It is indicated that for the studied systems mainly the lowest four oscillators are responsible for the TPA cross-sections rather than a simple effective three-state model.
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이재영,Nayab Saira,Kumar Ameet,김동일,정혜원,이상호,조대흠,이효선 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.4
Cobalt(II) and copper(II) complexes supported by 4‐(quinolin‐2‐ylmethyl)morpholine (L) were characterized, and their reactivity toward the ring‐opening polymerization (ROP) of rac ‐lactide ( rac ‐LA) was studied. The use of [LMCl 2 ]/LiO i Pr and [LMCl 2 ]/LiMe (M = Co, Cu) resulted in over 95% conversion within 10 min at 25 °C. The effect of the initiating group and geometry of the metal complexes steered the heterotactic enchainment of the resultant polylactide(PLA). The Co(II)/LiMe system represents the first example of the ROP of rac ‐LA with high heterotactic enchainment ( P r = 0.92) with 98% conversion at 0 °C. Cobalt(II) and copper(II) complexes supported by 4-(quinolin-2-ylmethyl) morpholine (L) were characterized, and their reactivity toward the ringopening polymerization (ROP) of rac-lactide (rac-LA) was studied. The use of [LMCl2]/LiOiPr and [LMCl2]/LiMe (M = Co, Cu) resulted in over 95% conversion within 10 min at 25 C. The effect of the initiating group and geometry of the metal complexes steered the heterotactic enchainment of the resultant polylactide(PLA). The Co(II)/LiMe system represents the first example of the ROP of rac-LA with high heterotactic enchainment (Pr = 0.92) with 98% conversion at 0 C.
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