Cyclopalladated ethylenediamine complexes on the basis of 4-phenylpyrimidine and 4,6-diphenylpyrimidine

Mono-and binuclear cyclopalladated complexes Pd(ppm)En]ClO₄, Pd(Hdphpm)En]ClO₄, and (PdEn)₂(μ-dphpm)]ClO₄ (ppm^? is the deprotonated form of 4-phenylpyridine, Hdphpm^? and dphpm^2? are the mono-and bisdeprotonated forms of 4,6-diphenylpyrimidine, En is 1,2-diaminoethane) were prepared and characterized by means of ¹H NMR and electronic absorption and emission spectroscopy, and cyclic voltammetry. It was shown that cyclopalladation leads to a bathochromic shift of intraligand absorption and phosphorescence bands, appearance of new absorption band associated with metal-to-ligand charge transfer, and an anodic potential shift of the ligand-centered electroreduction Hppm ≈ H₂dphpm < Pd(ppm)En]⁺ ≈ Pd(Hdphpm)En]⁺ < (PdEn)₂(μ-dphpm)]²⁺.