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Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)4Cl2 (detu = N,N′-Diethylthiourea)
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2016-02-02 00:00:00 , DOI: 10.1021/acs.inorgchem.5b02203
Ibrahim A. Alfurayj 1 , Victor G. Young 2 , Michael P. Jensen 1
Affiliation  

Consecutive thermochromic lattice distortional and spin crossover equilibria in solid-state Ni(detu)4Cl2 (detu = N,N′-diethylthiourea) are investigated by variable-temperature X-ray crystallography (173–333 K), DFT calculations, and differential scanning calorimetry. Thermochromism and anomalous magnetism were reported previously (S. L. Holt, Jr., et al. J. Am. Chem. Soc.1964, 86, 519–520); the latter was attributed to equilibration of a singlet ground state and a thermally accessible triplet state, but structural data were not obtained. A crystal structure at 173(2) K revealed [Ni(detu)4]2+ centers with distorted planar ligation of nickel(II) to the four sulfur atoms, with an average Ni–S bond length of 2.226(3) Å. The nickel ion was displaced out-of-plane by 0.334 Å toward a proximal apical chloride at a nonbonding distance of 3.134(1) Å. Asymmetry in the trans S–Ni–S angles was coupled to a monoclinic ↔ tetragonal lattice distortion (T1/2 = 254 ± 11 K), resulting in thermochromism. Spin crossover occurs by tetragonal modulation of nickel(II) with approach of the proximal chloride at higher temperatures (T1/2 = 383 ± 18 K), which is consistent with a contraction of −0.096(4) Å in the Ni···Cl separation observed at 293 K. A high-spin (S = 1) square-pyramidal [Ni(dmtu)4Cl]+ model (dmtu = N,N′-dimethylthiourea) was optimized by DFT calculations, which estimated limiting equatorial Ni–S bond lengths of 2.45 Å and an apical Ni–Cl bond of 2.43 Å. Electronic spectra of the spin isomers were calculated by TD-DFT methods. Assignment of the FTIR spectrum was assisted by frequency calculations and isotope substitution.

中文翻译:

热致变色的结构表征和自旋平衡在固态的Ni(DETU)42(DETU = ÑÑ '-Diethylthiourea)

固态Ni(detu)4 Cl 2(detu = NN'-二乙基硫脲)在固态Ni(detu)4 Cl中的连续热致变色晶格畸变和自旋交叉平衡通过可变温度X射线晶体学(173–333 K),DFT计算和差示扫描量热法。热致变色和反常磁先前报道(SL霍尔特,Jr。等人。J.化学会志。196486,519-520); 后者归因于单线态基态和热可及三线态的平衡,但未获得结构数据。173(2)K处的晶体结构显示[Ni(detu)4 ] 2+中心的镍(II)与四个硫原子的平面连接变形,平均Ni-S键长为2.226(3)Å。镍离子以3.134(1)Å的非键合距离朝近端顶端氯化物平面外移位0.334Å。S-Ni-S角的不对称性与单斜晶↔四方晶格畸变(T 1/2 = 254±11 K)有关,从而导致热致变色。自旋交叉是通过在较高温度(T 1/2 = 383±18 K)下接近氯化物的四方调制镍(II)而发生的,这与Ni··中的-0.096(4)Å收缩一致·在293 K处观察到Cl的分离。高自旋(S = 1)方形金字塔形[Ni(dmtu)4Cl] +模型(dmtu = NN'-二甲基硫脲)通过DFT计算进行了优化,计算得出的赤道极限Ni-S键长为2.45Å,顶端Ni-Cl键长为2.43Å。通过TD-DFT方法计算自旋异构体的电子光谱。FTIR光谱的分配通过频率计算和同位素替代来辅助。
更新日期:2016-02-02
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