PNNL

Abstract

Four new Zeise’s family ions with mixed halide ligands, i.e., PtClnX3-n(C2H4)? (X = Br, I; n = 1, 2), were synthesized via ligand-exchange reactions of KX salts with KPtCl3(C2H4) in aqueous solutions, and were detected in vacuum via electrospray ionization mass spectrometry. Their photoelectron spectra reveal a series of well-resolved spectral peaks with their electron binding energies (EBEs) decreasing with increasing halide size, with I having a much stronger effect than Br, i.e., 4.57 (–Cl3) > 4.56 (–Cl2Br) > 4.53 (–ClBr2) > 4.34 (–Cl2I) > 4.30 eV (–ClI2). Ab initio electronic structure calculations including spin-orbit coupling (SOC) predict that the cis- and trans- conformers are nearly isoenergetic with the cis- for –Cl2X, and the trans- for –ClX2 slightly favored, respectively. Excited-state spectra calculated with time-dependent density functional theory (TDDFT), and their comparison with the observed ones suggest that for each species, both the cis- and trans- configurations coexist in the experiments and contribute to the observed spectra, a fact that clearly violates the prediction from the widely accepted trans-effect, which suggests that only one isomer would have formed.