Synthesis and Structural and Electronic properties of the Mixed Complexes of Vinylene-Bridged Bis- and Tris(octaethylporphyrin)s with Ni(II), Pd(II), and Pt(II) Ions

摘要

Various mixed complexes of vinylene-bridged bis- and tris(octaethylporphyrin)s (bis(OEP)-(M1-M2) and tris(OEP)-(M1-M2-M3)) with d~8 transition-metal ions M(II) (M: M1, M2, and M3 = Ni or Pd or Pt) were synthesized by step-by-step and selective metallations of the respective free-bases (FB) with limited amounts of the metallation reagent. Metallation of tris(OEP)-(H_2-H_2-H_2) started in the central OEP ring, with the vinylene linkages of the product retaining the same (E,E)-configuration as those in FB. On the other hand, metallation of (E)- and (Z)-isomeric complexes under the similar conditions. Electronic absorption spectra of tris(OEP)-(M1-M2-M3) proved to be affected especially by the central OEP-M2 ring and by the heavier metals more intensively, resulting in the largest splitting of the Soret band for the Ni-Pd-Pt complex. Examination of the oxidation potential E_1 values indicated that the electron-releasing abilities of tris(OEP)-(M1-M2-M3) are intensively reduced for the complex carrying at least two consecutive heavier metal OEP rings. In the case of bis(OEP)-(M1-M2), the (E)-isomeric series exhibited the reduction of the electron-releasing abiilities regularly in order of the heavy metal complexes similarly to tris(OEP)-M, while the (Z0-isomeric series exhibited little dependence of the electron-releasing abilities upon the incorporated metals M.