Cu（D，L-alanine）2的反铁磁自旋链行为和向3D磁序的转变：氢键的作用
Antiferromagnetic spin chain behavior and a transition to 3D magnetic order in Cu(D,L-alanine)2: Roles of H-bonds
摘要：
我们研究的自旋链行为，过渡到3D磁序和交换相互作用的金属-氨基酸配合物Cu（D，L-丙氨酸）2. H2O，模型化合物，以调查交换耦合支持的化学路径特征的生物分子的幅度。获得了作为温度（T）和磁场（B 0）的函数的热数据和磁数据。在0.48和30 K之间测量的比热的磁贡献显示高于1.8 K的一维自旋链行为，其可以与链内反铁磁（AFM）交换耦合常数2 J 0 =（-2.12 $\pm$ 0.08）cm $^{-1}$拟合，在4.49 Ω处沿着通过非共价键和H键连接的链的相邻铜之间。我们还观察到一个狭窄的比热峰在0.89 K表示一个相变的3D磁有序相。在固定T = 2、4和7 K下，B 0在0和9 T之间，以及在T在2和300 K之间，B 0具有几个固定值的磁化曲线通过链内AFM交换耦合常数2 J 0 =（-2.27 $\pm$ 0.02）cm $^{-1}$和g = 2.091 $\pm$ 0.005进行全局拟合。通过总长度为9.51 μ m的长化学路径连接的相邻链中的铜之间的链间相互作用J 1估计在0.1 < |2J1| < 0.4 cm $^{-1}$的范围内，覆盖各种近似的预测。我们分析了2 J 0和2 J1的幅度在相应的化学路径的结构。在支持链内相互作用的主要贡献是分配给H-键，而链间相互作用的支持路径包含H-键和羧酸桥，与H-键的作用是占主导地位的。我们比较所获得的链内耦合的化合物的研究表现出类似的行为，并讨论了允许计算链间相互作用的近似的有效性。
英文摘要：
We study the spin chain behavior, a transition to 3D magnetic order and the magnitudes of the exchange interactions for the metal-amino acid complex Cu(D,L-alanine)2.H2O, a model compound to investigate exchange couplings supported by chemical paths characteristic of biomolecules. Thermal and magnetic data were obtained as a function of temperature (T) and magnetic field (B0). The magnetic contribution to the specific heat, measured between 0.48 and 30 K, displays above 1.8 K a 1D spin-chain behavior that can be fitted with an intrachain antiferromagnetic (AFM) exchange coupling constant 2J0 = (-2.12 $\pm$ 0.08) cm$^{-1}$, between neighbor coppers at 4.49 Å along chains connected by non-covalent and H-bonds. We also observe a narrow specific heat peak at 0.89 K indicating a phase transition to a 3D magnetically ordered phase. Magnetization curves at fixed T = 2, 4 and 7 K with B0 between 0 and 9 T, and at T between 2 and 300 K with several fixed values of B0 were globally fitted by an intrachain AFM exchange coupling constant 2J0 = (-2.27 $\pm$ 0.02) cm$^{-1}$ and g = 2.091 $\pm$ 0.005. Interchain interactions J1 between coppers in neighbor chains connected through long chemical paths with total length of 9.51 Å are estimated within the range 0.1 < |2J1| < 0.4 cm$^{-1}$, covering the predictions of various approximations. We analyze the magnitudes of 2J0 and 2J1 in terms of the structure of the corresponding chemical paths. The main contribution in supporting the intrachain interaction is assigned to H-bonds while the interchain interactions are supported by paths containing H-bonds and carboxylate bridges, with the role of the H-bonds being predominant. We compare the obtained intrachain coupling with studies of compounds showing similar behavior and discuss the validity of the approximations allowing to calculate the interchain interactions.
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