CNRS, CRPP , UPR 8641, F-33600 Pessac, France.
J Am Chem Soc. 2013 Oct 2;135(39):14840-53. doi: 10.1021/ja407570n. Epub 2013 Sep 19.
The spin-crossover complex [Fe(LN5)(CN)2]·H2O (1, LN5 = 2,13-dimethyl-3,6,9-12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene), reported previously by Nelson et al. in 1986, was reinvestigated, and its structure determined by single crystal X-ray diffraction for the first time. The reaction between Mn(III)(saltmen)(H2O) and this photomagnetic linker yielded the trinuclear molecular complex {Mn(saltmen)}2FeHS(LN5)(CN)22·0.5CH3OH (2) and the one-dimensional compound {Mn(saltmen)}2FeLS(LN5)(CN)22·0.5C4H10O·0.5H2O (3) depending on the addition order of the reagents (HS: High-Spin; LS: Low-Spin). Compound 3 exhibits a wave-shaped chain structure built from the assembly of the trinuclear [Mn(III)-NC-Fe(II)] motif found in 2. Static magnetic measurements revealed the existence of antiferromagnetic Mn(III)···Fe(II) (Fe(II) HS, S = 2) interactions in the trinuclear entity of 2 via the cyanido bridge leading to an ST = 2 ground state. In the case of 3, concomitant ferromagnetic and antiferromagnetic exchange interactions are found along the chain due to the presence of two crystallographically independent {Mn2(saltmen)2} units, which behave differently as shown by the magnetic susceptibility analysis, while the Fe(II) (LS, S = 0) cyanido-bridging moiety is isolating these dinuclear Mn(III) units. ac susceptibility experiments indicated slow relaxation of the magnetization arising from the ferromagnetically coupled [Mn2] units (τ0 = 1.1 × 10(-7) s and Δ(eff)/k(B) = 13.9 K). Optical reflectivity and photomagnetic properties of 1 and 3 have been investigated in detail. These studies reveal that the photomagnetic properties of 1 are kept after its coordination to the acceptor Mn(III)/saltmen complexes, allowing in 3 to switch "on" and "off" the magnetic interaction between the photoinduced Fe(II) HS unit (S = 2) and the Mn(III) ions. To the best of our knowledge, the compound 3 represents the first example of a coordination network of single-molecule magnets linked by spin-crossover units inducing thermally and photoreversible magnetic and optical properties.
Nelson 等人于 1986 年报道的自旋交叉配合物[Fe(LN5)(CN)2]·H2O（1，LN5=2,13-二甲基-3,6,9-12,18-五氮杂环十八烷-1(18)，2,12,14,16-五烯）被重新研究，并首次通过单晶 X 射线衍射确定了其结构。[Mn(III)(saltmen)(H2O)]+与这种光磁配体之间的反应生成了三核分子配合物{Mn(saltmen)}2FeHS(LN5)(CN)22·0.5CH3OH（2）和一维化合物{Mn(saltmen)}2FeLS(LN5)(CN)22·0.5C4H10O·0.5H2O（3），这取决于试剂的添加顺序（HS：高自旋；LS：低自旋）。化合物 3 呈现出由三核[Mn(III)-NC-Fe(II)]基序组装而成的波浪形链状结构，该基序存在于 2 中。静态磁性测量表明，通过氰基桥，2 中的三核实体中存在反铁磁 Mn(III)···Fe(II)（Fe(II) HS，S=2）相互作用，导致 ST=2 基态。在 3 的情况下，由于存在两个结晶学上独立的{Mn2(saltmen)2}单元，因此在链上发现了同时存在铁磁性和反铁磁性交换相互作用，这些单元的行为不同，如磁感性分析所示，而 Fe(II)（LS，S=0）氰基桥接部分隔离了这些双核 Mn(III)单元。交流磁化率实验表明，由于铁磁耦合[Mn2]单元的存在，磁化强度的弛豫缓慢（τ0=1.1×10(-7) s 和Δ(eff)/k(B)=13.9 K）。详细研究了 1 和 3 的光反射率和光磁性质。这些研究表明，1 的光磁性质在与受体 Mn(III)/saltmen 配合物配位后得以保留，这使得 3 能够在光诱导的 Fe(II) HS 单元（S=2）和 Mn(III)离子之间“打开”和“关闭”磁相互作用。据我们所知，化合物 3 代表了由自旋交叉单元连接的单分子磁体的配位网络的第一个例子，该网络诱导热和光可逆的磁性和光学性质。
