Camouflaging Structural Diversity: Co-crystallization of Two Different Nanoparticles Having Different Cores but the Same Shell.

Two ligand protected new nanoscale pieces of silver - namely, [Ag46(SPhMe2)24(PPh3)8](NO3)2 and [Ag40(SPhMe2)24(PPh3)8](NO3)2 (abbreviated as Ag46 and Ag40, respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures were identical, the clusters were not able to distinguish each other separately and they got crystallized in the same crystal. The occupancy of each cluster was 50% in the co-crystal. The outer shell of both the clusters is composed of Ag32S24P8 which is reminiscent of fullerenes, and it encapsulates a well-studied core, Ag14 and a completely new core, Ag8 which correspond to a face-centered cube and a simple cube, respectively resulting in the Ag46 and Ag40 clusters. The presence of two entities (Ag40 and Ag46 clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time-dependent density functional theory (TD-DFT). Camouflaging diverse cores of this kind with unique shell may present a new paradigm in well-defined composite materials, leading to new properties.