Structures and Spectroscopic Properties of Chain Polymeric Complexes of Copper(II) Halides with 2,3,5,6-Tetrafluoro-1,4-bis(2-pyridylsulfenyl)benzene and Its 4-Pyridylsulfenyl Analogue

The syntheses are reported of the “extended reach” ligand 2,3,5,6-tetrafluoro-1,4-bis(2-pyridylsulfenyl)benzene
(L1), its 4-pyridylsulfenyl analogue (L2), and their copper(II) complexes CuLX2 (X = Cl or Br). X-ray studies
have been carried out on L1, L2, and the complexes Cu(L1)Cl2·2CHCl3 (1) and [Cu(L2)(DMF)Br2]·DMF (2).
Complex 1 has a chain polymeric structure with a trans-planar CuCl2N2 coordination geometry. Complex 2 is
also a chain polymer structure, but in this case a DMF molecule is bonded in the apical position above a trans-CuBr2N2 unit, producing a slightly distorted square pyramidal geometry at the copper centers. The transition
energies obtained from the single-crystal electronic spectrum of Cu(L1)Cl2·2CHCl3 and the g-values from its
EPR spectrum are used to derive bonding parameters, and these are compared with those of other planar CuL2Cl2
complexes with amine ligands. The electronic reflectance spectrum of [Cu(L2)(DMF)Br2]·DMF implies broadly
similar amine bonding parameters. This compound exhibits an unusual g-tensor with g|| < g⊥, which is interpreted
in terms of exchange-averaging of the molecular g-tensors of the two molecules in the unit cell.

本研究报道了“加长型”配体2,3,5,6-四氟-1,4-二(2-吡啶硫基)苯（L1）、其4-吡啶硫基类似物（L2），以及它们的铜(II)配合物CuLX₂（X=Cl或Br）的合成。对L1、L2，以及配合物Cu(L1)Cl₂·2CHCl₃（1）和[Cu(L2)(DMF)Br₂]·DMF（2）开展了X射线晶体学研究。配合物1具有链状聚合物结构，配位几何为反式平面型CuCl₂N₂。配合物2同样为链状聚合物结构，但在此体系中，一个N,N-二甲基甲酰胺（N,N-Dimethylformamide，简称DMF）分子结合在反式CuBr₂N₂单元的轴向位置，使得铜中心呈现轻微畸变的四方锥配位几何。通过Cu(L1)Cl₂·2CHCl₃的单晶电子光谱得到的跃迁能，以及其电子顺磁共振谱（Electron Paramagnetic Resonance，简称EPR）得到的g因子，被用于推导成键参数，并将其与其他带有胺类配体的平面型CuL₂Cl₂配合物的成键参数进行对比。[Cu(L2)(DMF)Br₂]·DMF的电子反射光谱表明其胺类配体成键参数整体相似。该配合物呈现出非常规的g张量，满足g∥ < g⊥，这一现象可通过晶胞内两个分子的分子g张量的交换平均效应来解释。