To investigate the magnetic properties and the spin entanglement of dinuclear arrays, we prepared compounds [{Cu(pAB)(phen)H2O}2·NO3·pABH·2H2O], 1, and [Cu2(pAB)2(phen)2pz]n, 2 (pABH = p-aminobenzoic acid, phen = 1,10-phenanthroline and pz = pyrazine). The structure of 1 is known and we report here that of 2. They contain similar dinuclear units of CuII ions with 1/2-spins S1 and S2 bridged by pairs of pAB molecules, with similar intradinuclear exchange and fine interactions , but different 3D crystal arrays with weak interdinuclear exchange J', stronger in 2 than in 1. To investigate the magnetic properties and the spin entanglement produced by J', we collected the powder spectra of 1 and 2 at 9.4 GHz and T between 5 and 298 K, and at 34.4 GHz and T = 298 K and single-crystal spectra at room T and 34.4 GHz as a function of magnetic field (B0) orientation in three crystal planes, calculating intradinuclear magnetic parameters J(1)0 = (-75 ± 1) cm-1, J(2)0 = (-78 ± 2) cm-1, |D(1)| = (0.142 ± 0.006) cm-1, |D(2)| = (0.141 ± 0.006) cm-1 and E(1) ∼ E(2) ∼ 0. Single crystal data indicate a quantum entangled phase in 2 around the crossing between two fine structure EPR absorption peaks within the spin triplet. This phase also shows up in powder samples of 2 as a U-peak collecting the signals of the entangled microcrystals, a feature that allows estimating |J'|. Transitions between the two quantum phases are observed in single crystals of 2 changing the orientation of B0. We estimate interdinuclear exchange couplings |J'(1)| < 0.003 cm-1 and |J'(2)| = (0.013 ± 0.005) cm-1, in 1 and 2, respectively. Our analysis indicates that the standard approximation of a spin Hamiltonian with S = 1 for the dinuclear spectra is valid only when the interdinuclear coupling is large enough, as for compound 2 (|J'(2)/J(2)0| ∼ 1.7 × 10-4). When J' is negligible as in 1, the real spin Hamiltonian with two spins 1/2 has to be used. Broken-symmetry DFT predicts correctly the nature and magnitude of the antiferromagnetic exchange coupling in 1 and 2 and ferromagnetic interdinuclear coupling for compound 2.

中文翻译：

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相似的铜双核单元的两个不同阵列中的交换耦合和量子相。

为了研究双核阵列的磁性和自旋纠缠，我们制备了化合物[{Cu（pAB）（phen）H2O} 2·NO3·pABH·2H2O]，1和[Cu2（pAB）2（phen）2pz] n，2（pABH =对氨基苯甲酸，phen = 1,10-菲咯啉，pz =吡嗪）。1的结构是已知的，我们在此处报告2的结构。它们包含类似的CuII离子双核单元，其中的1/2旋S1和S2由成对的pAB分子桥接，具有相似的核内交换和精细的相互作用，但具有不同的3D晶体弱核间交换J'的阵列，在2中比在1中更强。为了研究J'产生的磁性能和自旋纠缠，我们收集了9.4 GHz和T在5和298 K之间的粉末光谱1和2，以及在34.4 GHz和T = 298 K时，以及在T和34室时的单晶光谱。4 GHz作为三个晶面中磁场（B0）取向的函数，计算核内磁参数J（1）0 =（-75±1）cm-1，J（2）0 =（-78±2）cm -1，| D（1）| =（0.142±0.006）cm-1，| D（2）| ＝（0.141±0.006）cm-1且E（1）〜E（2）〜0。单晶数据表明自旋三重态中两个精细结构EPR吸收峰之间的交叉处的量子纠缠相为2。此阶段还在2个粉末样品中显示为U峰，收集了纠缠的微晶的信号，该特性可以估算| J'|。在改变B0方向的2的单晶中观察到两个量子相之间的跃迁。我们估计核间交换耦合| J'（1）| <0.003 cm-1和| J'（2）| =（0.013±0.005）cm-1，分别在1和2中。我们的分析表明，对于双核光谱，自旋哈密顿量（S = 1）的标准近似仅在核间耦合足够大时才有效，如化合物2（| J'（2）/ J（2）0 |〜1.7 ×10-4）。当J'如1中可忽略不计时，必须使用具有两个自旋1/2的实自旋哈密顿量。对称的DFT可以正确预测化合物1和2中反铁磁交换耦合的性质和强度以及化合物2的铁磁核间耦合。