School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK.
Inorg Chem. 2012 Feb 6;51(3):1450-61. doi: 10.1021/ic2017006. Epub 2012 Jan 25.
The Pd(II) complexes Pd([9]aneS(3))(2)(2)·2MeCN (1) ([9]aneS(3) = 1,4,7-trithiacyclononane) and Pd([18]aneS(6))(2) (2) ([18]aneS(6) = 1,4,7,10,13,16-hexathiacyclooctadecane) can be oxidized electrochemically or chemically oxidized with 70% HClO(4) to Pd([9]aneS(3))(2) and Pd([18]aneS(6)), respectively. These centers have been characterized by single crystal X-ray diffraction, and by UV/vis and multifrequency electron paramagnetic resonance (EPR) spectroscopies. The single crystal X-ray structures of Pd(III)([9]aneS(3))(2)(6)·(H(3)O)(3)·(H(2)O)(4) (3) at 150 K and Pd([18]aneS(6))(6)·(H(5)O(2))(3) (4) at 90 K reveal distorted octahedral geometries with Pd-S distances of 2.3695(8), 2.3692(8), 2.5356(9) and 2.3490(6), 2.3454(5), 2.5474(6) Å, respectively, consistent with Jahn-Teller distortion at a low-spin d(7) Pd(III) center. The Pd(II) compound Pd([9]aneS(3))(2)(2) shows a one-electron oxidation process in MeCN (0.2 M NBu(4)PF(6), 293 K) at E(1/2) = +0.57 V vs. Fc(+)/Fc assigned to a formal Pd(III)/Pd(II) couple. Multifrequency (Q-, X-, S-, and L-band) EPR spectroscopic analysis of Pd([9]aneS(3))(2) and Pd([18]aneS(6)) gives g(iso) = 2.024, |A(iso(Pd))| = 18.9 × 10(-4) cm(-1); g(xx) = 2.046, g(yy) = 2.041, g(zz) = 2.004; |A(xx(Pd))| = 24 × 10(-4) cm(-1), |A(yy(Pd))| = 22 × 10(-4) cm(-1), |A(zz(Pd))| = 14 × 10(-4) cm(-1), |a(xx(H))| = 4 × 10(-4) cm(-1), |a(yy(H))| = 5 × 10(-4) cm(-1), |a(zz(H))| = 5.5 × 10(-4) cm(-1) for Pd([9]aneS(3))(2), and g(iso) = 2.015, |A(iso(Pd))| = 18.8× 10(-4) cm(-1); g(xx) = 2.048 g(yy) = 2.036, g(zz) = 1.998; |a(xx(H))| = 5, |a(yy(H))| = 5, |a(zz(H))| = 6 × 10(-4) cm(-1); |A(xx(Pd))| = 23× 10(-4) cm(-1), |A(yy(Pd))| = 22 × 10(-4) cm(-1), |A(zz(Pd))| = 4 × 10(-4) cm(-1) for Pd([18]aneS(6)). Both Pd([9]aneS(3))(2) and Pd([18]aneS(6)) exhibit five-line superhyperfine splitting in the g(zz) region in their frozen solution EPR spectra. Double resonance spectroscopic measurements, supported by density functional theory (DFT) calculations, permit assignment of this superhyperfine to through-bond coupling involving four (1)H centers of the macrocyclic ring. Analysis of the spin Hamiltonian parameters for the singly occupied molecular orbital (SOMO) in these complexes gives about 20.4% and 25% Pd character in Pd([9]aneS(3))(2) and Pd([18]aneS(6)), respectively, consistent with the compositions calculated from scalar relativistic DFT calculations.
Pd(II) 配合物 Pd([9]aneS(3))(2)(2)·2MeCN (1) ([9]aneS(3) = 1,4,7-三硫杂环壬烷) 和 Pd([18]aneS(6))(2) (2) ([18]aneS(6) = 1,4,7,10,13,16-六硫杂环十八烷) 可以通过电化学或用 70% HClO(4) 化学氧化为 Pd([9]aneS(3))(2) 和 Pd([18]aneS(6))。这些中心通过单晶 X 射线衍射、紫外/可见和多频电子顺磁共振 (EPR) 光谱进行了表征。Pd(III)([9]aneS(3))(2)(6)·(H(3)O)(3)·(H(2)O)(4) (3)（在 150 K 下）和 Pd([18]aneS(6))(6)·(H(5)O(2))(3) (4)（在 90 K 下）的单晶 X 射线结构揭示了具有 Pd-S 距离为 2.3695(8)、2.3692(8)、2.5356(9) 和 2.3490(6)、2.3454(5)、2.5474(6) Å 的扭曲八面体几何形状，与低自旋 d(7)Pd(III) 中心的 Jahn-Teller 扭曲一致。Pd(II) 化合物 Pd([9]aneS(3))(2)(2) 在 MeCN（293 K 时 0.2 M NBu(4)PF(6)) 中显示出单电子氧化过程，E(1/2) = +0.57 V 与 Fc(+)/Fc 相比，指定为形式 Pd(III)/Pd(II) 对。Pd([9]aneS(3))(2) 和 Pd([18]aneS(6)) 的多频 (Q-、X-、S-和 L- 波段) EPR 光谱分析给出 g(iso) = 2.024，|A(iso(Pd))| = 18.9×10(-4) cm(-1)；g(xx) = 2.046，g(yy) = 2.041，g(zz) = 2.004；|A(xx(Pd))| = 24×10(-4) cm(-1)，|A(yy(Pd))| = 22×10(-4) cm(-1)，|A(zz(Pd))| = 14×10(-4) cm(-1)，|a(xx(H))| = 4×10(-4) cm(-1)，|a(yy(H))| = 5×10(-4) cm(-1)，|a(zz(H))| = 5.5×10(-4) cm(-1) 用于 Pd([9]aneS(3))(2)，并且 g(iso) = 2.015，|A(iso(Pd))| = 18.8×10(-4) cm(-1)；g(xx) = 2.048 g(yy) = 2.036，g(zz) = 1.998；|a(xx(H))| = 5，|a(yy(H))| = 5，|a(zz(H))| = 6×10(-4) cm(-1)；|A(xx(Pd))| = 23×10(-4) cm(-1)，|A(yy(Pd))| = 22×10(-4) cm(-1)，|A(zz(Pd))| = 4×10(-4) cm(-1) 用于 Pd([18]aneS(6))。Pd([9]aneS(3))(2) 和 Pd([18]aneS(6)) 在其冷冻溶液 EPR 光谱的 g(zz) 区域均显示出五条超精细分裂线。通过密度泛函理论 (DFT) 计算支持的双共振光谱测量，允许将这种超精细分配给涉及大环环四个 (1)H 中心的键合耦合。对这些配合物中占据分子轨道 (SOMO) 的自旋哈密顿参数的分析给出了大约 20.4% 和 25%的 Pd 特征，分别用于 Pd([9]aneS(3))(2) 和 Pd([18]aneS(6))，与从相对论性 DFT 计算得出的组成一致。
