PARASHIFT Probes: Solution NMR and X-ray Structural Studies of Macrocyclic Ytterbium and Yttrium Complexes
PARASHIFT Probes: Solution NMR and X-ray Structural Studies of Macrocyclic Ytterbium and Yttrium Complexes
复制标题
DOI：
10.1021/acs.inorgchem.6b02291
复制
发表时间：
2017-04-03
影响因子：
4.6
通讯作者：
Parker, David
中科院分区：
文献类型：
--
作者：
Mason, Kevin;Rogers, Nicola J.;Parker, David
镱和钇配合物的八齿配体的基础上的1，4，7，10-四氮杂环十二烷与配位的吡啶基和三羧酸酯（L-1）或三次膦酸酯（L-2）供体形成扭曲的正方形反棱柱结构。前者在中心对称群P2（1）/c中结晶，两个分子通过反转中心相关，而后者在手性空间群P2（1）中被发现为不寻常的氪杂环。纯位移NMR和EXSY光谱允许检测[Y.L-2]复合物的（RRR）-Delta-（delta delta delta）和（RRR）-Lambda-（lambda lambda lambda）TSAP非对映异构体之间的动态交换。Delta和Lambda异构体之间交换的限速步骤涉及协同配体臂旋转，[Ln.L-1]比[Ln.L-2]快得多。NOESY、COSY、HSQC和HMBC光谱的详细分析证实，溶液中的主要构象异构体是（RRR）-λ-（λ），与晶体结构分析和DFT计算一致。从全赝接触化学位移分析中得到的[Yb.L-1]和[Yb.L-2]的磁化率张量非常不同，与CASSCF计算一致。显着不同的pseudocontact位移行为的解释的pseudocontact位移场的方向的变化，定义的欧拉角的磁化率张量。
Ytterbium and yttrium complexes of octadentate ligands based on 1,4,7,10-tetraazacyclododecane with a coordinated pyridyl group and either tricarboxylate (L-1) or triphosphinate (L-2) donors form twisted-square-antiprismatic structures. The former crystallizes in the centrosymmetric group P2(1)/c, with the two molecules related by an inversion center, whereas the latter was found as an unusual kryptoracemate in the chiral space group P2(1). Pure shift NMR and EXSY spectroscopy allowed the dynamic exchange between the (RRR)-Delta-(delta delta delta delta) and (RRR)-Lambda-(lambda lambda lambda lambda) TSAP diastereomers of the [Y.L-2] complex to be detected. The rate-limiting step in the exchange between Delta and Lambda isomers involves cooperative ligand arm rotation, which is much faster for [Ln.L-1 than for [Ln.L-2]. Detailed analysis of NOESY, COSY, HSQC, and HMBC spectra confirms that the major conformer in solution is (RRR)-Lambda-(lambda lambda lambda lambda), consistent with crystal structure analysis and DFT Calculations. The magnetic susceptibility tensors for [Yb.L-1] and [Yb.L-2], obtained from a full pseudocontact chemical shift analysis, are very different, in agreement with a CASSCF calculation. The remarkably different pseudocontact shift behavior is explained by the change in the orientation of the pseudocontact shift field, as defined by the Euler angles of the susceptibility tensor.