Optical properties of [M(L–L)2M(L–L)2X2](ClO4)4, (M = Pt, Pd; L–L = 1,2-diaminoethane or 1,2-diaminopropane; X = Cl, Br, I): bulk and small particles

Abstract

The optical absorption and scattering spectra of small particles of [M(L–L)₂M(L–L)₂X₂](ClO₄)₄, deposited on quartz plates or suspended in CCl₄, have been studied. We found that the position of the maxima in the spectra depends on the size and shape of the particles. The peak positions of small spheres and small needles occur, respectively, at shorter and longer wavelengths than the peak position of the single-crystal reflectance spectrum. In the case of [Pt(dapn)₂Pt(dapn)₂I₂](ClO₄)₄, for example, we found peaks at 730 (spheres), 975 (needles) and 825 nm (single crystals). The corresponding calculated spectra were obtained by employing Gan's equations. The optical parameters required for the calculation have been obtained by least-squares fitting of the reflectance spectra to the Lorentz model. The calculated spectra were found to be in qualitative agreement with the experiment.