The morphology of cyanide-bridged palladium−cobalt (Pd−Co) gels, synthesized from aqueous solutions of Na2PdCl4 and K3[Co(CN)6], is elucidated using nitrogen and carbon dioxide adsorption, permeability measurements, electron microscopy, and small-angle X-ray scattering. The aerogels formed from the Pd−Co hydrogels possess both micro- and mesoporosity. Electron microscopy indicates that the aerogels are constituted of spherical microporous particles; the interstices between these particles constitute the mesopores. The aerogel surfaces are found to be fractal as analyzed by gas adsorption and small-angle X-ray scattering. Both these techniques yield, within experimental error, the same surface fractal dimension of 2.6 ± 0.2 for the aerogels. The Pd−Co xerogels, unlike the aerogels, are predominantly microporous with a narrow microporosity. Transmission electron microscopy reveals that the xerogels are constituted of particles of an average size of ∼10 nm. Unlike the aerogels, the xerogels do not possess surface fractality. The mechanism of adsorption of different gases on these gels is analyzed on the basis of the gel morphologies.

The cyanogel system involving PdCl(4)(2-) and the mixed-valence complex [(NC)(5)Fe(II)-CN-Pt(IV)(NH(3))(4)-NC-Fe(II)(CN)(5)](4-) is reported. The system has been characterized by UV-vis absorption, diffuse reflectance infrared, and resonance Raman spectroscopies. Gelation occurs through coordination of Pd(II) to the nitrogen atom of terminal cyanide ligands in the mixed-valence complex. Irradiation into the Fe(II) --> Pt(IV) intervalent electron transfer (IT) band of [(NC)(5)Fe(II)-CN-Pt(IV)(NH(3))(4)-NC-Fe(II)(CN)(5)](4-) results in the formation of a variety of Prussian-blue-like species within the rigid cyanogel matrix. Photochemical and dark mechanisms involving coupled cyanide loss and Fe(II) oxidation are proposed for the formation of Prussian-blue-like species. The optical contrast between irradiated and nonirradiated regions of the gel enables photochemical image generation with at least 12 microm resolution. This capability is demonstrated through the production of a series of diffraction gratings in cyanogel samples.