Bromine-adsorption behavior of a one-dimensional bromine-bridged mixed-valence palladium (II), (IV) complex, [Pd(chxn)2][PdBr2(chxn)2]Br4

The bromine-adsorption behavior of [Pd(chxn)2][PdBr2(chxn)2]Br4 (chxn: 1R,2R-cyclohexanediamine) has been investigated by elemental analysis, X-ray powder diffraction (XRD), 1H NMR and ESR. From XRD, the reaction of the palladium complex with bromine was revealed to be reversible depending on the partial pressure of bromine around the complex. Elemental analysis suggested the adsorption of two Br2 molecules per the formula unit. Temperature dependence of the ESR intensity showed the existence of Curie and thermally activated spins in both compounds with and without bromine-adsorption. The spin density, as well as the fraction of Curie spins, decreased after bromine-adsorption suggesting the oxidation of paramagnetic Pd(III) into Pd(IV). 1H NMR spin-lattice relaxation of these compounds is determined by the coupling with the thermally activated spins as well as with the Curie spins.