The [M(N_∧N)(Hdphpm)]ClO4 and [(M(N_∧N))2(μ-dphpm)](ClO4)2 complexes (M = Pd(II), Pt(II); (N_∧N) is ethylenediamine (En) and orthophenanthroline (Phen); Hdphpm− and dphpm2− are the mono- and bisdeprotonated forms of 4,6-diphenylpyrimidine) are obtained and characterized by 1H NMR spectroscopy and electronic absorption and emission spectroscopy. The magnetic nonequivalence of protons of (N_∧N) ligands is explained by a difference in the trans-effect of the carbanion and pyrimidine parts of the cyclometalated ligand. The long-wavelength absorption bands and the vibrationally structured luminescence bands of ethylenediamine complexes are attributed to optical transitions in the {M(Hdphpm)} and {M2(μ-dphpm)} metal-complex fragments. The complexes with orthophenanthroline exhibit two low-energy optical transitions involving π* orbitals localized on the cyclometalated and chelating ligands; the difference in their energies depends on the metal and is much larger for Pt(II) than for Pd(II). It is found that the replacement of Pd(II) by Pt(II) in the [(M(phen))2(μ-dphpm)]2+ complexes changes the direction of the photoexcitation energy degradation due to the energy transfer between the {M2(μ-dphpm)} bridging fragment and peripheral phenanthroline ligands.