Wangdong Zeng
Email Address
chmzewa@nus.edu.sg
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Publication Curved ?-conjugated corannulene dimer diradicaloids(Royal Society of Chemistry, 2018) Wang, Q.; Hu, P.; Tanaka, T.; Gopalakrishna, T.Y.; Herng, T.S.; Phan, H.; Zeng, W.; Ding, J.; Osuka, A.; Chi, C.; Siegel, J.; Wu, J.; CHEMISTRY; MATERIALS SCIENCE AND ENGINEERINGSo far, most reported open-shell singlet diradicaloids are based on planar ?-conjugated molecules. Herein, we report the bridged corannulene dimer diradicaloids, Cor-D1 and Cor-D2, both showing a three-dimensional curved ?-conjugated structure. Cor-D1 has a small diradical character (y0 = 5.4%) and behaves more like a closed-shell quinoidal compound at room temperature, while Cor-D2 is a typical open-shell diradicaloid with a larger diradical character (y0 = 16.9%). Both compounds exhibited paramagnetic activity at elevated temperatures, with a singlet-triplet energy gap (?ES-T) of -8.4 and -3.0 kcal mol-1, respectively. X-ray crystallographic analysis revealed that both molecules have a dumbbell-shaped geometry, with the two terminal corannulene bowls bent to opposite directions. The spin is largely delocalized onto the two bowls in Cor-D2 and there are multiple [CH??] interactions between the neighboring bowls. Chemical oxidation/reduction to their respective dications/dianions results in global aromaticity with [4n + 2] ?-electrons delocalized through the periphery of the whole framework. © 2018 The Royal Society of Chemistry.Publication N -annulated perylene-based push-pull-type sensitizers(American Chemical Society, 2015) Qi Q.; Wang X.; Fan L.; Zheng B.; Zeng W.; Luo J.; Huang K.-W.; Wang Q.; Wu J.; MATERIALS SCIENCE AND ENGINEERINGPublication [6]Cyclo-para-phenylmethine: An Analog of Benzene Showing Global Aromaticity and Open-shell Diradical Character(ACS, 2019-09-30) Z. Li; T. Y. Gopalakrishna; Y. Han; Y. Gu; L. Yuan; W. Zeng; D. Casanova; J. Wu; CHEMISTRY; CHEMICAL & BIOMOLECULAR ENGINEERINGPublication N-Annulated perylene-substituted and fused porphyrin dimers with intense near-infrared one-photon and two-photon absorption(Wiley-VCH Verlag, 2015) Luo, Jie; Lee, Sangsu; Son, Minjung; Zheng, Bin; Huang, Kuo-Wei; Qi, Qingbiao; Zeng, Wangdong; Li, Gongqiang; Kim, Dongho; Wu, Jishan; CHEMISTRYPublication Open-shell Graphene Fragments(Cell Press, 2021-02-11) W. Zeng; J. Wu; CHEMISTRYPublication Room-temperature Magnets Based on 1,3,5-Triazine Linked Porous Organic Radical Frameworks(Elsevier Inc, 2019-05-09) PHAN VAN HOA; HERNG TUN SENG; Wang, D.; LI XING; ZENG WANGDONG; DING JUN; LOH KIAN PING; WEE THYE SHEN,ANDREW; Wu Jishan; PHYSICS; CHEMISTRY; MATERIALS SCIENCE AND ENGINEERINGObtaining room-temperature (RT) molecule-based magnets is a long-sought-after goal in the materials community. However, so far, most of the reported magnets based on charge-transfer salts, pure organic radicals, and coordination polymers have shown low magnetic ordering temperatures. Herein, we propose an alternative approach for magnets by using covalently linked organic radical frameworks, in which neighboring radicals are ferromagnetically coupled. Stable hexacyanotrimethylenecyclopropanide radical anions ([CN6CP]M, M = K+ [1a], n-Bu4N+ [1b]) were found to undergo either thermal polymerization in the solid state at a relatively low temperature (300°C) without the need for ZnCl2 (for 1a) or trifluoromethanesulfonic-acid-mediated polymerization at 60°C (for 1b) to give 1,3,5-triazine-linked porous organic radical framework 2 or 3, respectively. The resulting material 2 exhibited spontaneous magnetization at RT with typical hysteresis of ferromagnets, and the ordering temperature was estimated to be 465 K, whereas the magnetic behavior of 3 is more like superparamagnetism. A long-sought-after dream in the materials community is to obtain room-temperature organic and molecule-based magnets, which would show considerable advantages over traditional metal and metal-oxide-based magnets. They can have potential applications in high-density data storage, quantum computing, spin sensors, spintronics, and so on. However, so far, most efforts of using pure organic radicals, charge-transfer salts, and coordination polymers have resulted in limited success, that is, the critical magnetic ordering temperature is usually lower than the boiling point of liquid nitrogen (77 K). Herein, we report a new approach by using covalently linked porous organic radical frameworks, in which the neighboring radicals are ferromagnetically coupled with each other. The newly synthesized 1,3,5-trizaine-linked porous organic radical frameworks exhibited spontaneous magnetization at room temperature with an estimated ordering temperature above 450 K. Wu and colleagues describe the synthesis of 1,3,5-triazine-linked porous organic radical frameworks by thermal or triflic acid assisted polymerization from the cyano-containing stable radical monomers. The radicals in the polymers are ferromagnetically coupled with each other through the newly formed 1,3,5-triazine connector. As a result, these materials exhibited spontaneous magnetization or superparamagnetism at room temperature.Publication Phenalenyl-fused porphyrins with different ground states(Royal Society of Chemistry, 2015) Zeng W.; Lee S.; Son M.; Ishida M.; Furukawa K.; Hu P.; Sun Z.; Kim D.; Wu J.; CHEMISTRYMaterials based on biradicals/biradicaloids have potential applications for organic electronics, photonics and spintronics. In this work, we demonstrated that hybridization of porphyrin and polycyclic aromatic hydrocarbon could lead to a new type of stable biradicals/biradicaloids with tunable ground state and physical property. Mono- and bis-phenalenyl fused porphyrins 1 and 2 were synthesized via an intramolecular Friedel-Crafts alkylation-followed-by oxidative dehydrogenation strategy. Our detailed experimental and theoretical studies revealed that 1 has a closed-shell structure with a small biradical character (y = 0.06 by DFT calculation) in the ground state, while 2 exists as a persistent triplet biradical at room temperature under inert atmosphere. Compound 1 underwent hydrogen abstraction from solvent during the crystal growing process while compound 2 was easily oxidized in air to give two dioxo-porphyrin isomers 11a/11b, which can be correlated to their unique biradical character and spin distribution. The physical properties of 1 and 2, their dihydro/tetrahydro-precursors 7/10, and the dioxo-compounds 11a/11b were investigated and compared. © 2015 The Royal Society of Chemistry.