Induced Aggregation, Solvent Regulation, and Supracluster Assembly of Aluminum Oxo Clusters

Abstract

Metrics & MoreArticle RecommendationsCONSPECTUS: Recent years have witnessed the development of cluster materials as they are atomically precise molecules with uniform size and solution-processability, which are unattainable with traditional nanoparticles or framework materials. The motivation for studying Al(III) chemistry is not only to understand the aggregation process of aluminum in the environment but also to develop novel low-cost materials given its natural abundance. However, the Al-related clusters are underdeveloped compared to the coinage metals, lanthanides, and transition metals. The challenge in isolating crystalline compounds is the lack of an effective method to realize the controllable hydrolysis of Al(III) ions. Compared with the traditional hydrolysis of inorganic Al(III) salts in highly alkaline solutions and hydrolysis of aluminum trialkyl compounds conducted carefully in an inert operating environment, we herein developed an effective way to control the hydrolysis of aluminum isopropanol through an alcoxalation reaction. By solvothermal/low melting point solid melting synthesis and using "ligand aggregation, solvent regulation, and supracluster assembly" strategies, our laboratory has established an organic-inorganic hybrid system of aluminum oxo clusters (AlOCs). The employment of organic ligands promotes the aggregation and slows the hydrolysis of Al(III) ions, which in turn improves the crystallization process. The regulation of the structure types can be achieved through the selection of ligands and the supporting solvents. Compared with the traditional condensed polyoxoaluminates, we successfully isolated a broad range of porous AlOCs, including aluminum molecular rings and Archimedes aluminum oxo cages. By studying ring expansion, structural transformation, and intermolecular supramolecular assembly, we demonstrate unique and unprecedented structural controllability and assembly behavior in cluster science. The advancement of this universal synthetic method is to realize materials customization through modularly oriented supracluster assembly. In this Account, we will provide a clear-cut definition and terminology of "ligand aggregation, solvent regulation, and supracluster assembly". Then we will discuss the discovery in this area by using a strategy, such as aluminum molecular ring, ring size expansion, ring supracluster assembly, etc. Furthermore, given the internal and external pore structures, as well as the solubility and modifiability of the AlOCs, we will demonstrate their potential applications in both the solid and liquid phases, such as iodine capture, the optical limiting responses, and dopant in polymer dielectrics. The strategy herein can be applied to extensive cluster science and promote the research of main group element chemistry. The new synthetic method, fascinating clusters, and unprecedented assembly behaviors we have discovered will advance Al(III) chemistry and will also lay the foundation for functional applications.

Aluminum Molecular Ring Meets Deep Eutectic Solvents: Adaptive Assembly and Optical Behavior

“…For example, Saalfank et al controlled the radius of alkali metal cations to synthesize Fe 6 M and Fe 8 M (M = Li + , Na + , Cs + ); Munno and colleagues synthesized Cu 8 via the [Cu­(H 2 O) 6 ] 2+ template; Winpenny et al regulated organic amine templates (such as [Me 4 N] + , [H 2 NPr 2 ] + , and [Me 2 NH 2 ] + ) to synthesize heterogeneous molecular wheels (Cr 7 Ni, Cr 6 Co 2 , and Cr 10 Cu 2 ). − The third kind of template includes typical polyacid anion clusters and small-sized anion guests (e.g., ClO 4 – , SO 4 2– , halides, etc.). The ability of POMs as noncovalent templating agents has been demonstrated in the construction of some ionic macrocycles, such as [Mo 36 ] 8– ⊂ [Mo 150 ] 14– reported by Cronin and [SiMo 12 ] 4– ⊂ [Mo 24 Fe 12 ] 12– reported by Fang et al Small-sized anions are often used as acceptor molecules in the construction of cyclic compounds, such as [Fe 5 L 5 Cl] 9+ reported by Lehn and [Er 2 Yb 13 Cl] reported by Murugesu. − In previous studies, the synthesis of aluminum molecular rings usually uses self-templates such as primary alcohol, pyrazole, or alcohol amine. ,, The binding of the ionic template and aluminum molecular ring has not been systematically carried out. It is still challenging to find a suitable ionic template to participate in the construction of main-group metal molecular rings.…”