Self‐Assembly through Noncovalent Preorganization of Reactants: Explaining the Formation of a Polyfluoroxometalate

Abstract

High-order elementary reactions in homogeneous solutions involving more than two molecules are statistically improbable and very slow to proceed. They are not generally considered in classical transition-state or collision theories. Yet, rather selective, high-yield product formation is common in self-assembly processes that require many reaction steps. On the basis of recent observations of crystallization as well as reactions in dense phases, it is shown that self-assembly can occur by preorganization of reactants in a noncovalent supramolecular assembly, whereby directing forces can lead to an apparent one-step transformation of multiple reactants. A simple and general kinetic model for multiple reactant transformation in a dense phase that can account for many-bodied transformations was developed. Furthermore, the self-assembly of polyfluoroxometalate anion [H F NaW O ] from simple tungstate Na WO F was demonstrated by using 2D F- F NOESY, 2D F- F COSY NMR spectroscopy, a new 2D F{ W} NMR technique, as well as ESI-MS and diffusion NMR spectroscopy, and the crucial involvement of a supramolecular assembly was found. The deterministic kinetic reaction model explains the reaction in a dense phase and supports the suggested self-assembly mechanism. Reactions in dense phases may be of general importance in understanding other self-assembly reactions.

Precursor Self‐Assembly Identified as a General Pathway for Colloidal Semiconductor Magic‐Size Clusters

“…Our suggested self‐assembly pathway is in agreement with the recent report on the high concentration synthesis of CdS MSCs . Reactions leading to clusters or aggregates can share a general pathway driven by reactant self‐assembly to occur in dense phases …”

“…The self‐assembly pathway hypothesized in the present study provides insight into the high‐concentration‐based synthesis of CdS MSCs reported recently . In addition to the other systems, self‐assembly processes have been reported recently for the formation of polymeric vesicles (via the control of two monomer feed amounts) and polyoxometalate (POM) . We believe that the self‐assembly process reported embraces the advances of cluster science and the science of crystallization, while providing impetus for the development of desirable nucleation theories (with the concept of degree of supersaturation modified) after classical nucleation theory (CNT) and those nonclassical alternatives (Scheme S2, Supporting Information) …”

“…Figure (bottom) and Figure S5‐2 (Supporting Information) present our solution NMR studies at room temperature of two toluene solutions as indicated. It has been acknowledged that the mobility of a species in solution is related to its size, with a larger species exhibiting a smaller diffusion coefficient . The specific relationship between the mobility ( D , diffusion coefficient) and size ( d H , hydrodynamic diameter) follows the Stokes–Einstein equationwith k B the Boltzmann constant and η the dynamic viscosity of the liquid.…”

“…We anticipate that the present understanding of the formation of ZnSe IP‐299 via the self‐assembly of the various Zn and Se precursors will help comprehend molecular association, the concept of which has been explored to advance the science of crystallization (such as for crystalline organic materials due to increasing complexity from industries) . While the interpretation of the pathway to the IP formation from the starting precursors via self‐assembly is in its infancy, molecular simulation could be able to connect the thermodynamic nature of the molecular self‐association taking place during the initial stage of crystallization, and to provide the composition information regarding the resulting IP.…”

“…Cluster science is dedicated to bridge the gap of the evolution of fundamental properties with size from individual molecules toward extended bulk materials, while self‐assembly of small building blocks has been demonstrated to generate larger structures . Crystallization is a unique case of self‐assembly, occurring frequently in nature and being vital for many applications including pharmaceutical and chemical manufacturing.…”