A Hidden Coordination-Bond Torsional Deformation as a Sign of Possible Spin Transition in Nickel(II)-Bis(nitroxide) Compounds
作者:Yukiya Kyoden、Takayuki Ishida
DOI:10.3390/molecules25173790
日期:——
After overviewing the results on the known X = Br, Cl, and NCS derivatives, the magnetic behavior is described in a common phase diagram. The Br and Cl compounds undergo the energy level crossing of the high-/low-spin states, but the NCS and NCO compounds do not in a conventional experimental temperature range. The spin transition mechanism in this series involves the exchange coupling switch between ferro-
在氰酸钠的存在下,四氟硼酸镍 (II) 和叔丁基 5-苯基-2-吡啶基氮氧化物 (phpyNO) 的复合形成得到了一个离散的分子 [Ni(phpyNO)2(X)2] (X = NCO)。Ni-ON-Csp2 扭转角在加热时减小;在 100 K 时为 33.5(5)° 和 36.2(4)°,而在 400 K 时为 25.7(10)° 和 32.3(11)°。磁性行为在大约低于约 100 K,并且 χmT 值在 400 K 时达到 1.04 cm3 K mol-1。使用 van't Hoff 方程的分析表明在 T1/2 >> 400 K 处可能发生自旋跃迁。密度泛函理论计算表明单线态-随着结构从 100 K 变为 400 K,五重态能隙减小。几何优化结果表明,抗磁态的 Ni-ON-Csp2 扭转角为 32.7°,而 Sttotal = 2 态的扭转角为 11.9°。后者即使在 400 K 下也无法通过实验观察到。在对已知的
High-Spin and Incomplete Spin-Crossover Polymorphs in Doubly Chelated [Ni(L)<sub>2</sub>Br<sub>2</sub>] (L = <i>tert</i>-Butyl 5-Phenyl-2-pyridyl Nitroxide)
作者:Yukiya Kyoden、Yuta Homma、Takayuki Ishida
DOI:10.1021/acs.inorgchem.9b00885
日期:2019.8.19
Complexation of nickel(II) bromide with tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) gave two morphs of doubly chelated [Ni(phpyNO)2Br2] as a 2p–3d–2p heterospin triad. The α phase crystallizes in the orthorhombic space group Pbcn. An asymmetric unit involves a half-molecule. The torsion angle around Ni–O–N–C2py is as small as 6.5(3)° at 100 K and 7.0(6)° at 400 K, guaranteeing an orthogonal arrangement
溴化镍(II)与叔丁基5-苯基-2-吡啶基硝基氮氧化物(phpyNO)的络合产生了两种形态的双螯合[Ni(phpyNO)2 Br 2 ],为2p-3d-2p杂旋三联体。α相在正交空间群Pbcn中结晶。不对称单元涉及半分子。Ni–O–N–C 2py周围的扭转角在100 K时小至6.5(3)°,在400 K时小至7.0(6)°,从而确保了磁性自由基π*和金属3d x 2 – y 2和3d z 2轨道。磁性研究表明,高旋转基态的交换耦合常数为2 J /k B = +288(5)K,基于对称自旋哈密顿量。β相在单斜空间群P 2 1 / n中结晶。整个分子是一个独立的单元。Ni–O–N–C 2py扭转角在100 K时为24.2(6)和37.2(5)°,在400 K时为10.4(7)和25.9(6)°。磁学研究显示非常缓慢且无磁滞的自旋过渡。尽管在400 K时磁化率未达到理论高旋转值,但基于van't
Spin-Transition-Like Behavior on One Side in a Nitroxide-Copper(II)-Nitroxide Triad System
作者:Atsushi Okazawa、Takayuki Ishida
DOI:10.1021/ic101536q
日期:2010.11.1
The ground spin-state of [Cu(phpyNO)(2)(H2O)(2)](BF4)(2) was switched between S-total = 1/2 and 3/2 across 175 K. On warming, the space group was changed from P2(1)2(1)2(1) to C222(1) in a single-crystal-to-single-crystal manner, and the transient structure could be monitored by means of the crystallographic analysis. The copper-radical exchange coupling changed from 2J/k(B) = -463(3) to +312(6) K with rather small Cu-O-N-C-2py twisting deformation on one side, while practically no distortion occurred on the other.
Magneto-Structure Relationship in Copper(II) and Nickel(II) Complexes Chelated with Stable <i>tert</i>-Butyl 5-Phenyl-2-pyridyl Nitroxide and Related Radicals
(varphi) around M-O-N-C 2py can be regarded as a reliable indicator for the plane geometry of chelates; namely, highly planar chelates defined by small varphi exhibit ferromagnetic coupling. An approximate linear relation was found in the J versus varphi plot using the data of the present complexes and related known compounds. The critical angle of varphi, at which the sign of the metal-radical exchange
我们已经分离并表征了一种新的顺磁性双齿配体,叔丁基5-苯基-2-吡啶基氮氧化物(phpyNO)。从电子自旋共振光谱可以清楚地知道在吡啶环上的自旋分布。phpyNO与镍(II)和铜(II)离子络合,得到ML 2型螯合化合物。[Ni(phpyNO)2(H 2O)2]。(ClO 4)2和[Cu(phpyNO)2(H 2O)]。(ClO 4)2.C 6H 4Cl 2的磁测量表明,金属-自由基交换偶合是铁磁性的,分别为2 J / k B = +409(10)和+434(12)K。可以将围绕MONC 2py的扭转角(varphi)视为螯合物平面几何形状的可靠指标;即,由小varphi定义的高度平面的螯合物表现出铁磁耦合。使用本发明配合物和相关已知化合物的数据,在J对varphi图中发现了近似的线性关系。金属自由基交换的符号从正变负的varphi的临界角为12.6(9)度。这个发现几乎可以通过密度泛函理