Inversion Symmetry Breaking in Order-Disorder Transitions of Globular Ligands Coordinating to Cobalt(II) and Nickel(II) Bisacetylacetonato Complexes During Heating
Inversion Symmetry Breaking in Order-Disorder Transitions of Globular Ligands Coordinating to Cobalt(II) and Nickel(II) Bisacetylacetonato Complexes During Heating
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DOI：
10.1002/chem.202004492
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发表时间：
2020-12-23
影响因子：
4.3
通讯作者：
Akutagawa, Tomoyuki
中科院分区：
文献类型：
--
作者：
Hoshino, Norihisa;Akutagawa, Tomoyuki
在加热过程中，[M(acac)(2)(abco)(2)] (1; M=Co2+, 2; Ni2+, acac(-)=2,4-戊二酮, abco=1-氮杂双环-[2.2.2]-辛烷=奎宁环)的有序-无序相变中观察到意外的反演对称性破缺。还研究了同构无过渡配合物 [M(acac)(2)(cabco)(2)] (3; M=Co2+, 4; Ni2+, cabco=3-氯-1-氮杂双环-[2.2.2]-辛烷=3-氯奎宁环)以进行比较。配合物1和2在100 K时在中心对称I2/m空间群中以有序相结晶，而在300 K时在非对称I2空间群中以无序相结晶。在1和2的电子密度图中观察到abco配体的60度步进旋转无序，这与差示扫描量热法（DSC）估计的转变焓一致。通过 DSC 和粉末 X 射线衍射 (PXRD) 在大约 225 K 下观察到 1 和 2 的逐渐相变。反演对称无序可能是由 abco 配体的局部伪对称性引起的，从三角形增加到六角形以及其中增加的空间排斥途径。
Unexpected inversion-symmetry breaking was observed in the order-disorder phase transitions of [M(acac)(2)(abco)(2)] (1; M=Co2+, 2; Ni2+, acac(-)=2,4-pentanedionato, abco=1-azabicyclo-[2.2.2]-octane=quinuclidine) during heating. The isostructural, transition-free complexes [M(acac)(2)(cabco)(2)] (3; M=Co2+, 4; Ni2+, cabco=3-chloro-1-azabicyclo-[2.2.2]-octane=3-chloroquinuclidine) were also studied for comparison. Complexes 1 and 2 crystallized in ordered phases in the centrosymmetric I2/m space group at 100 K, whereas they crystallized in disordered phases in the non-symmetric I2 space group at 300 K. The 60 degrees step rotation disordering of the abco ligands was observed in the electron density maps of 1 and 2, which was consistent with the transition enthalpies estimated by differential scanning calorimetry (DSC). Gradual phase transitions were observed for 1 and 2 by DSC and powder X-ray diffraction (PXRD) at approximately 225 K. The inversion-symmetry disordering was likely induced by the local pseudo-symmetry of the abco ligands, increasing from trigonal to hexagonal and the increased steric repulsion pathways among them.