Conclusions

Nanotechnology demands maneuvering materials atom by atom, which renders the conventional macroscopic material processing methods (mixing, milling, and heating) crude and imprecise. The need for methods enabling controlled growth of nanomaterial has led to the use of SSPs, which inherently possess the requirements of the nanomaterial (element combination and bonding features of the solid phase) in the molecular state. This review underlines the potential of molecular templating of nanomaterials of different compositions and shows that original solutions can be achieved through the chemical design of the precursor. The directed manipulation of molecular aggregates as elementary fragments of solid-state structure seems to be an efficient strategy for the preconceived synthesis of nanomaterials at the atomic level.

The incorporation of different elements into a molecular source to obtain the target material from a single source simplifies the material synthesis by drastically reducing the process parameters. The SSPs with a predefined metal stoichiometry and reaction (decomposition) chemistry can enforce a molecular-level homogeneity in the obtained materials. The hydrolytic or pyrolytic transformations of molecular derivatives have been used for the phase-selective synthesis of a large variety of ceramics and composites, which illustrates the potential of molecular clusters to "preform" the material on a molecular level (Tables 1-4). Although the field is still far from maturity, the continuing efforts of a large number of research groups in controlling various aspects of the molecule source strategy, such as enhanced volatility, low decomposition temperature, clean and efficient ligand elimination mechanisms, and control of stoichiometry, have boosted the use of single-molecule sources in the synthesis of functional nanomaterials, both films and particles, as is evident from the rapid increase in the publications dealing with this concept and the diversity of the composition of the materials synthesized (Tables 1-4). However, it should be noted that a significant number of reports have emerged from the material curiosity of a synthetic chemist, and the targeted development of experimental chemical methods, necessary to achieve nanoscopic structures by controlled and/or self-organized growth, needs greater attention.

A better understanding of underlying principles of chemical synthesis and the process of molecule-to-material conversion can make possible the rational synthesis of new inorganic materials. The current status of nanomaterials chemistry can be analyzed from two viewpoints: one corresponds to the synthesis of a material from an available precursor followed by the analysis of the nature of the precursor (chemical reactivity, stability, fragmentation, etc.) in light of the results obtained and can be termed as a synthetic approach; the other is from a retrosynthetic direction, which involves going backward from a target material to molecular starting materials by performing conceivable retro-reactions (subject to the knowledge base) to design the material at the molecular scale. The second case, which in principle forms the basis for illustrating the potential of molecular design, is less practiced for obvious reasons. Although the basic principles of the building-block approach to (nano)materials can obviously be extended to inorganic materials/phases hitherto "unknown," the lack of systematic investigations regarding the molecular templating or the conditions under which a molecular compound can be transformed into an extended solid poses an application barrier. Consequently, a large number of metal-organic compounds are potential "assemblers" for the controlled assembly of meso- and nanoscopic

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