Study on the construction of photoresponsive single-molecule magnets in frozen solutions

对于单自旋单分子磁体的构造，我们提出了利用由2 p有机自旋和3d金属离子组成的异自旋体系。在我们的异自旋体系中，吡啶配体上的单、二和三卡宾（S分别为2/2，4/2和6/2）和高自旋Co（II）离子CoCl_2和Co（p-tolsal）_2分别被用作2 p有机自旋和3d金属离子。两种组分，重氮-吡啶配体和Co（II）离子，在溶液中的各种组合以适当的比例混合。为了避免分子间的磁相互作用，冷冻溶液条件被用作SQUID测量的样品。对六个配合物样品进行了辐照前后的交流和直流磁化率测量。在6个样品的交流磁化率测量中，观察到与外加频率相关的同相和异相分量（分别为χ'和χ"），表明钴配合物具有缓慢的磁弛豫。六<eff>种配合物的自旋翻转激活能垒U_（？）为40- 93 K。在1.9K下的磁化强度与直流磁场的关系中，六个配合物都观察到了较大的磁滞回线，矫顽力H_c=7-10 kOe。对<eff>六种配合物的U_、τ_0和H_c的测定值进行了总结，并与相关配合物的测定值进行了比较。在本工作中，我们成功地在冷冻溶液中制备了单分子磁体。此外，通过系统地改变配合物的S值，发现随着配合物<eff>S值的增加，自旋翻转的激活能垒U增加，共振量子隧穿效应引起的弛豫时间减小.

For the construction of monometallic single-molecule magnets (SMMs), We proposed to use the heterospin systems consisting of the 2p organic spins and the 3d metal ions. In our heterospin systems, pyridine ligands carrying mono-, di-, and tricarbene (S=2/2,4/2, and 6/2, respectively) and high-spin Co(II) ions, CoCl_2 and Co(p-tolsal)_2, were employed as the 2p organic spins and the 3d metal ions, respectively. Various combinations of two components, diazo-pyridine ligands and Co(II) ions, in solutions were mixed in appropriate ratios. To avoid the intermolecular magnetic interaction, the frozen solution conditions were used as the samples for SQUID measurements. The ac and dc magnetic susceptibility measurements for six samples of the complexes were carried out before and after irradiation. In ac magnetic susceptibility measurements after irradiation of six samples, the in-phase and out-of phase components (χ' and χ", respectively) with the applying frequency dependence were observed, indicating that the cobalt complexes have slow magnetic relaxations. The values of the activation barriers, U_<eff>, for flipping the spin were estimated to be 40- 93 K for the six complexes. In the dc field dependence of magnetization at 1.9 K, relatively large hysteresis loops with coercive force, H_c=7-10 kOe for the six complexes were observed. Obtained values of U_<eff>, τ_0, and H_c, for all six complexes were summarized together with those for the related complexes. In this work, we successfully prepared the monometallic single-molecule magnets in frozen solution. Furthermore, by changing the S values of the complexes systematically, it was concluded that the activation barrier, U_<eff>, for flipping the spin and the relaxation time due to the resonant quantum tunneling effect increased and decreased, respectively, with increasing S value of the complex.