Abstract : Single crystal X-ray diffraction analysis and X-ray photoelectron spectroscopy have been employed to investigate a bis(phthalocyaninato)-neodymium(III) compound which exhibits electrochromism. A neodymium ion occupies a central position between two parallel but staggered phthalocyanine ligands. An acidic hydrogen may play an important role in electrochromism of the compound, but apparently does not bind strongly to any of the pyrrole nitrogen atoms, in opposition to the structure proposed by Nicholson and Galiaridi. However, a weak interaction between the hydrogen and nitrogen atom(s) cannot be excluded. (Author)