Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
SHUQI WU Last modified date:2021.07.14

Assistant Professor / Institute for Materials Chemistry and Engineering / Department of Fundamental Organic Chemistry / Institute for Materials Chemistry and Engineering


Presentations
1. Shu-Qi Wua, Pritam Sadhukhana, Shinji Kanegawaa, Osamu Sato, Molecular Pyroelectricity via Directional Electron Transfer in Valence Tautomeric Complexes, 17th International Conference on Molecule Based Magnets, 2021.06, [URL], Pyroelectricity is one of the most efficient ways to harvest energy from heat. Herein, we propose a molecular approach towards constructing novel pyroelectric materials based on valence tautomeric (VT) complexes. A thorough investigation of a mononuclear cobalt complex, [Co(phendiox)(rac-cth)](ClO4)·0.5EtOH (H2phendiox = 9, 10-dihydroxyphenanthrene, rac-cth = racemic 5, 5, 7, 12, 12, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane), is illustrated as a proof-of-concept. The complex crystallizes in the polar P21 space group and exhibits a two-step VT transition. The electron transfer during the VT process is directional, thus can be amplified to a single-crystal level, enabling the repeated observation of two pyroelectric peak currents in the same temperature domain of the VT transition without the application of an electric field. The photo-induced magnetometry and infrared spectroscopy show that the polarization-switching metastable state could be trapped at low temperature, meaning that the Co compound exhibits photo-tunable polarization bistability.1 Discussion will be extended to a pseudo symmetric dinuclear complex, [(Fe(RR-cth))(Co(SS-cth))(μ-dhbq)](PF6)3 (H2dhbq = 2,5-dihydroxy-1,4-benzoquinone). Spectroscopic studies reveal that the compound exhibits a more complicated electronic transition than conventional VT transition. However, pyroelectricity clearly evidences its electron-redistribution nature.
Reference:
1. S. –Q. Wu, M. Liu, K. Gao, S. Kanegawa, Y. Horie, G. Aoyama, H. Okajima, A. Sakamoto, T. Abe, Y. Shiota, K. Yoshizawa, W. Xu, H. –Z. Kou, O. Sato, Macroscopic Polarization Change via Electron Transfer in a Valene Tautomeric Cobalt Complex, Nat. Commun., 2020, 11, 1992.
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2. Shu-Qi Wu, Shinji Kanegawa, Osamu Sato, Macroscopic Polarization Change via Electron Transfer in a Valence Tautomeric Cobalt Complex , 1st Asian Conference on Molecular Magnetism, 2021.03, [URL], Polarization is one of the most fundamental properties of materials, and switching polarization by different external stimuli provides an efficient way for energy harvesting. Herein, we investigate electronic pyroelectricity in the single crystal of a mononuclear cobalt complex, [Co(phendiox)(rac-cth)](ClO4)·0.5EtOH (H2phendiox = 9, 10-dihydroxyphenanthrene, rac-cth = racemic 5, 5, 7, 12, 12, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane), which crystallizes in the polar P21 space group and exhibits a two-step valence tautomerism (VT). The change of the molecular dipole moment during the VT process is amplified to a single-crystal level, enabling the repeated observation of two pyroelectric peak currents in the same temperature domain of the VT transition without application of an electric field. Furthermore, pump-probe measurements show that the polarization can be switched via electron transfer with electronic excitation by light. The photo-induced polarization-switching metastable state could be trapped at low temperature, meaning that the Co compound exhibits photo-tunable polarization bistability..
3. Shu-Qi Wu, Shinji Kanegawa, Osamu Sato, Macroscopic Polarization Change via Electron Transfer in a Valence Tautomeric Cobalt Complex , 4th IRCCS International Symposium, 2021.03, Polarization of materials characterizes the degree of co-alignment of permanent molecular dipole moments. Switching polarization by different external stimuli provides an efficient way for energy conversion. Herein, we report electronic pyroelectricity in the single
crystal of a mononuclear cobalt complex, [Co(phendiox)(rac-cth)](ClO4)·0.5EtOH (H2phendiox = 9, 10-dihydroxyphenanthrene, rac-cth = racemic 5, 5, 7, 12, 12, 14-hexamethyl1, 4, 8, 11-tetraazacyclotetradecane) crystallized in the polar P21 space group
. The complex exhibits a two-step valence tautomerism (VT), and the co-alignment of the complex motifs amplifies the change of the molecular dipole moment during the VT process to a macroscopic level, giving two pyroelectric peak currents in the same temperature domain of the VT transition. Different from common ferroelectric materials, no pre-polarization process is needed to obtain the optimized pyroelectric coefficient. The photo-induced metastable state could be trapped at low temperature, meaning that the Co compound exhibits photo-tunable polarization bistability.
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