Shen Fu-Xing, Pi Qian, Shi Le, Shao Dong, Li Hong-Qing, Sun Yu-Chen, Wang Xin-Yi
State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
Dalton Trans. 2019 Jun 28;48(24):8815-8825. doi: 10.1039/c9dt01326a. Epub 2019 May 28.
We present here the syntheses, crystal structures, and thermal and magnetic properties of a series of mononuclear Fe spin crossover (SCO) complexes of the formula [Fe(bamp)]·Anion·Solv (Anion = NDS, Solv = 2HO, 1; Anion = BPDS, Solv = 4.4HO, 2; Anion = ABDS, Solv = EtO and HO, 3; Anion = DNDS, Solv = MeCN, 4; bamp = 2,6-pyridinedimethanamine, HNDS = 1,5-naphthalenedisulphonic acid, HBPDS = 4,4'-biphenyldisulphonic acid, HABDS = 4,4'-azobenzenedisulfonic acid, HDNDS = 4,4'-dinitrostilbene-2,2'-disulfonic acid). The structures and SCO properties of these complexes can be finely modified by organodisulfonate couteranions. Single-crystal X-ray analyses revealed that all these compounds are hydrogen-bonded three-dimensional frameworks constructed from the charge-assisted hydrogen bonds between bamp donors, organodisulfonate acceptors, and/or crystallized solvent molecules. SCO behavior was observed in all four complexes and has been evidenced by detailed structural and magnetic investigations. While 1 exhibits a sharp cooperative SCO transition with a transition temperature T of 247 K, 2, 3, and 4 undergo more gradual SCO transitions with T values of 176, 171 and 158 K, respectively. Magneto-structural relationship studies revealed that the tunable SCO properties, including the trend of the transition temperatures and the cooperativity of the SCO transition, are mainly attributable to the size of the organodisulfonate anions. This study shows that in order to exhibit cooperative SCO properties, "efficient" hydrogen bonds directly connecting the SCO centers, rather than those between the SCO centers and the innocent neighboring groups, are preferred.
我们在此展示了一系列通式为[Fe(bamp)]·阴离子·溶剂（阴离子 = NDS，溶剂 = 2HO，1；阴离子 = BPDS，溶剂 = 4.4HO，2；阴离子 = ABDS，溶剂 = EtO 和 HO，3；阴离子 = DNDS，溶剂 = MeCN，4；bamp = 2,6 - 吡啶二甲胺，HNDS = 1,5 - 萘二磺酸，HBPDS = 4,4'-联苯二磺酸，HABDS = 4,4'-偶氮苯二磺酸，HDNDS = 4,4'-二硝基芪 - 2,2'-二磺酸）的单核铁自旋交叉（SCO）配合物的合成、晶体结构以及热学和磁学性质。这些配合物的结构和 SCO 性质可通过有机二磺酸根抗衡阴离子进行精细调控。单晶 X 射线分析表明，所有这些化合物都是由 bamp 供体、有机二磺酸根受体和/或结晶溶剂分子之间的电荷辅助氢键构成的三维氢键框架。在所有四种配合物中均观察到了 SCO 行为，详细的结构和磁性研究证实了这一点。1 表现出尖锐的协同 SCO 转变，转变温度 T 为 247 K，而 2、3 和 4 经历的 SCO 转变更为平缓，T 值分别为 176 K、171 K 和 158 K。磁结构关系研究表明，可调控的 SCO 性质，包括转变温度的变化趋势和 SCO 转变的协同性，主要归因于有机二磺酸根阴离子的大小。这项研究表明，为了展现协同 SCO 性质，直接连接 SCO 中心的“有效”氢键，而非 SCO 中心与无害相邻基团之间的氢键，更为可取。
