Dicopper(<scp>ii</scp>) complexes of a new di-para-xylyldioxatetraazamacrocycle and cascade species with dicarboxylate anions: thermodynamics and structural properties
作者:Sílvia Carvalho、Rita Delgado、Michael G. B. Drew、Vítor Félix
DOI:10.1039/b700115k
日期:——
The new dioxatetraazamacrocycle (L1) was synthesized by a 2 + 2 condensation and characterized. Stability constants of its copper(II) complexes were determined by spectrophotometry in DMSO at 298.2 K in 0.10 mol dm−3 KClO4. Mainly dinuclear complexes are formed and the presence of mononuclear species is dependent on the counterion (Cl− or ClO4−). The association constants of the dinuclear copper(II) complexes with dicarboxylate anions [oxalate (oxa2−), malonate (mal2−), succinate (suc2−), and glutarate (glu2−)] were also determined by spectrophotometry at 298.2 K in DMSO, and it was found that values decrease with an increase of the alkyl chain between the carboxylate groups. X-Band EPR spectra of the dicopper(II) complexes and of their cascade species in frozen DMSO exhibit dipole–dipole coupling, and their simulation, together with their UV-vis spectra, showed that the copper centres of the complexes in solution had square pyramidal geometries though with different distortions. From the experimental data, it was also possible to predict the Cu⋯Cu distances, the minimum being found at 6.4 Å for the Cu2L1Cl4 complex and then successively this distance slightly increases when the chloride anions are replaced by dicarboxylate anions, from 6.6 Å for oxa2− to 7.8 Å for glu2−. The crystal structures of the dinuclear copper cascade species with oxa2− and suc2− were determined and showed one anion bridging both copper centres and Cu⋯Cu distances of 5.485(7) Å and 6.442(8) Å, respectively.
新合成的二氧四氮大环化合物(L1)通过2 + 2冷凝反应合成并进行了表征。其铜(II)复合物的稳定常数在298.2 K、0.10 mol dm−3 KClO4的DMSO中通过光谱法确定。主要形成双核复合物,单核物种的存在取决于对离子(Cl−或ClO4−)。双核铜(II)复合物与二羧酸盐阴离子[草酸(oxa2−)、苹果酸(mal2−)、琥珀酸(suc2−)和戊二酸(glu2−)]的结合常数也在298.2 K的DMSO中通过光谱法确定,结果表明,值随着羧酸盐基团之间烷基链的增加而减小。冻存DMSO中双铜(II)复合物及其级联物种的X波段EPR光谱显示了偶极-偶极耦合,其模拟结果以及UV-vis光谱表明,复合物中的铜中心在溶液中具有方锥几何结构,但畸变不同。根据实验数据,还可以预测Cu⋯Cu距离,最小值为6.4 Å(Cu2L1Cl4复合物),然后随着氯离子被二羧酸盐阴离子取代,该距离略微增加,从oxa2−的6.6 Å到glu2−的7.8 Å。确定了含有oxa2−和suc2−的双核铜级联物种的晶体结构,显示一个阴离子桥接两个铜中心,Cu⋯Cu距离分别为5.485(7) Å和6.442(8) Å。