Identification of single photoswitchable molecules in nanopores of silica xerogels using powder diffraction

Single photoswitchable molecules of (CN₃H₆)₂[Fe(CN)₅NO] (GuNP) are embedded into nanopores of an SiO₂ xerogel. It is shown that it is possible to identify the structural motif (`fingerprint') of the embedded complex by analyzing neutron powder diffraction data in a limited Q range (Q < 37 nm⁻¹) using the Debye approach. The structural study reveals that the pores are occupied by GuNP monomers with a fill factor of 60–80%. The mutual arrangement of the anion and cations in the GuNP monomer is slightly changed (∼1% elongation), while the bond lengths within the anion and cation are changed by less than 0.2% with respect to the single-crystalline form of GuNP.