Crystalline Superlattices of Nanoscopic CdS Molecular Clusters: An X-ray Crystallography and 111Cd SSNMR Spectroscopy Study.

Systematic 111Cd solid-state (SS) NMR experiments were performed to correlate X-ray crystallographic data with SSNMR parameters for a set of CdS-based materials, varying from molecular crystals of small complexes [Cd(SPh)4]2- and [Cd4(SPh)10]2- to superlattices of large monodisperse clusters [Cd54S32(SPh)48(dmf)4]4- and 1.9 nm CdS. Methodical data analysis allowed for assigning individual resonances or resonance groups to particular types of cadmium sites residing in different chemical and/or crystallographic environments. For large CdS frameworks, 111Cd resonances were found to form three groups. This result is noteworthy, since for related systems with size polydispersity and variations in composition, such as CdS or CdSe nanoparticles protected with an organic ligand shell, typically only two groups of resonances were observed. The generalized information obtained in this work can be used for the interpretation of 111/113Cd SSNMR data for large CdS clusters and nanoparticles, for which crystal structure analysis remains inaccessible. Comparison of the powder X-ray diffraction patterns for freshly prepared and dried superlattices of large CdS clusters revealed an interesting superstructure rearrangement that was not observed for the smaller frameworks.