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首页> 外文期刊>Journal of the American Chemical Society >Goldilocks Effect in Magnetic Bistability: Remote Substituent Modulation and Lattice Control of Photoinduced Valence Tautomerism and Light-Induced Thermal Hysteresis
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Goldilocks Effect in Magnetic Bistability: Remote Substituent Modulation and Lattice Control of Photoinduced Valence Tautomerism and Light-Induced Thermal Hysteresis

机译：戈尔德洛克在双稳态中的作用：远程取代基调制和光诱导价互变异构和光致热滞现象的晶格控制。

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摘要

The thermal-induced and photoinduced valence tautomerism of a series of Co(dioxolene)_2(4-X-py)2 complexes (dioxolene = 3,5-di-tert-butylcatecholate or 3,5-di-tert-butylsemiquinonate; 4-X-py = 4-(X)pyridine, X = H (1), OMe (2), Me (3), CN (4), Br (5), NO_2 (6)) is described. The thermal valence tautomerism (Is-Co~(III)(SQ)(Cat)(4-X-py)_2 ←→ hs-Co~(II)(SQ)(SQ)(4-X-py)_2) is only observed for complexes 4, 5, and 6 where each is accompanied by a hysteresis loop of ca. 5 K. When a crystalline sample of 4-6 is held at 10 K in a SQUID magnetometer and irradiated with white light (λ = 400-850 nm), the hs-Co~(II) tautomer is formed. When the light source is removed, and the sample is slowly heated, the hs-Co~(II) tautomer persists until ca. 90 K, approximately 40 K higher than the thermal stability of previously reported complexes. Heating and cooling the sample while maintaining irradiation results in the appearance of a new light-induced thermal hysteresis loop below 90 K (ΔT= ca. 25 K). Below 50 K, the hs-Co~(II) tautomer displays temperature-independent relaxation to the Is-Co~(III) form, and above 50 K, the relaxation is thermally activated with an activation energy E_a > ca. 1500 cm~(-1). The coordination geometry (trans-pyridines), pyridine substitution, and crystal packing forces conspire to create the comparatively thermally stable photogenerated hs-Co~(II) tautomer, thus providing an excellent handle for molecular and crystal engineering studies.
机译：一系列Co（dioxolene）_2（4-X-py）2配合物（dioxolene = 3,5-二叔丁基邻苯二酚或3,5-二叔丁基半醌）的热诱导和光诱导价互变异构现象; 4描述了-X-py = 4-（X）吡啶，X = H（1），OMe（2），Me（3），CN（4），Br（5），NO_2（6））。热价互变异构（Is-Co〜（III）（SQ）（Cat）（4-X-py）_2←→hs-Co〜（II）（SQ）（SQ）（4-X-py）_2）仅对于复合物4、5和6观察到“α”，其中每个复合物都带有一个ca的磁滞回线。 5K。当4-6的晶体样品在SQUID磁力计中保持在10 K并用白光（λ= 400-850 nm）照射时，形成hs-Co-（II）互变异构体。移开光源并缓慢加热样品后，hs-Co〜（II）互变异构体将持续存在，直到大约200℃。 90 K，比以前报道的配合物的热稳定性高约40K。在保持辐照的同时加热和冷却样品会导致在90 K以下出现新的光诱导热滞回线（ΔT=约25 K）。低于50 K时，hs-Co-（II）互变异构体表现出与Is-Co-（III）形式无关的温度弛豫，而高于50 K时，该弛豫被活化能E_a> ca热活化。 1500厘米〜（-1）配位几何结构（反式吡啶），吡啶取代和晶体堆积力共同产生了相对热稳定的光生hs-Co〜（II）互变异构体，从而为分子和晶体工程研究提供了极好的方法。

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  • 来源
    《Journal of the American Chemical Society》 |2010年第17期|P.6261-6273|共13页
  • 作者

    R. D. Schmidt; D. A. Shultz; J. D. Martin; P. D. Boyle;

  • 作者单位

    Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204;

    rnDepartment of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204;

    rnDepartment of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204;

    rnDepartment of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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