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    Home > JACS: a new type of organic low dimensional magnetic chain was discovered by Wang Xinping's research group of Nanjing University

    JACS: a new type of organic low dimensional magnetic chain was discovered by Wang Xinping's research group of Nanjing University

    • Last Update: 2018-06-06
    • Source: Internet
    • Author: User
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    The law of motion of micro particles satisfies the equation of motion of quantum mechanics - Schrodinger equation, but the Schrodinger equation can not complete the description of the whole behavior of multiparticle system composed of a large number of atoms Quantum spin system is an important field in the study of quantum correlated multibody system Low dimensional magnetic chain is a typical quantum spin system, with novel quantum states (such as quantum fluctuations), which has been a hot research direction in condensed matter physics In 1983, Haldane (winner of 2016 Nobel Prize in Physics) put forward the famous Haldane conjecture: for the quantum antiferromagnetic Heisenberg model with s spin, the volume system has energy gap in the case of integer spin, while the system has no gap in the case of semi integer spin The topological connotation of "Haldane phase" can be used to describe a large class of quantum states Haldane's conjecture in the one-dimensional chain of S = 1 antiferromagnetic Heisenberg was soon confirmed by a large number of transition metal compounds, but the known one-dimensional magnetic chain of S = 1 metal compounds is not an ideal one-dimensional chain research model due to its large anisotropy Generally, the anisotropy of organic radicals is small, and the magnetic one-dimensional chain formed by them has aroused great interest However, only one case of S = 1 antiferromagnetic organic one-dimensional chain has been reported so far In recent years, Wang Xinping's research group of School of chemistry and chemical engineering of Nanjing University has synthesized a series of air stable nitrogen heterodouble free radicals, and discovered the magnetic bistability phenomenon based on organic double free radicals in 2016 Recently, the group has successfully synthesized an organic magnetic one-dimensional chain based on two free radicals The results were published online in J am Chem SOC (DOI: 10.1021 / JACS 8b02415) The first author of the thesis is Wang Wenqing, the second author is Chen Chao, the doctoral student, Professor Wang Xinping and Professor Andrzej rajca of Nebraska university are the corresponding authors After twice oxidation of tetraazacyclo compounds, a very stable double cation (> 180oC) was obtained EPR spectra and theoretical calculations show that the compound has a three line ground state (s = 1) The χ m t value in the temperature range of 80k-350k from the squid test results was simulated, and the energy difference of single three line state was 2 J = Δ EST = 240 K; the χ m value in the temperature range of 1.85 k-60 K was simulated, and it was found that two free radicals formed one-dimensional magnetic chain, and there was antiferromagnetic coupling between molecules (J '= – 5.4 K) The crystal structure shows that the double radicals accumulate in a one-dimensional chain along the diagonal direction of the cell and form through the π - π interaction between the peripheral aryl groups The Haldane energy gap of one-dimensional chain is 0.41 × 2| J '/ K | 4.4k, which is highly isotropic (| D / 2 J | 7 | 10-4), while the coupling between chains is very small (Q | 0.3k) Therefore, this study provides an ideal s = 1 Magnetic one-dimensional chain model At present, the research group is studying the related quantum state of the one-dimensional chain through cooperation This research is supported by the Ministry of education, the Ministry of science and technology, the National Natural Science Foundation and the natural science foundation of Jiangsu Province.
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