Molecular Design of Bisphosphonates To Adjust Their Reactivity toward Metal Sources for the Surfactant-Assisted Synthesis of Mesoporous Films

Partial Hydrolysis of Diphosphonate Ester During the Formation of Hybrid TiO2 Nanoparticles: Role of Acid Concentration

The hydrolysis of the phosphonate ester linker during the synthesis of hybrid (organic-inorganic) TiO2 nanoparticles is important when forming porous hybrid organic-inorganic metal phosphonates. In the present work, a method was utilized to control the in-situ partial hydrolysis of diphosphonate ester in the presence of a titania precursor as a function of acid content, and its impact on the hybrid nanoparticles was assessed. Organodiphosphonate esters, and more specific, their hydrolysis degree during the formation of hybrid organic-inorganic metal oxide nanoparticles, are relatively under explored as linkers. Here, a detailed analysis on the hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) as diphosphonate linker to produce hybrid TiO2 nanoparticles is discussed as a function of acid content. Quantitative solution NMR spectroscopy revealed that during the synthesis of TiO2 nanoparticles, an increase in acid concentration introduces a higher degree of partial hydrolysis of the TEPD linker into diverse acid/ester derivatives of TEPD. Increasing the HCl/Ti ratio from 1 to 3, resulted in an increase in degree of partial hydrolysis of the TEPD linker in solution from 4 % to 18.8 % under the applied conditions. As a result of the difference in partial hydrolysis, the linker-TiO2 bonding was altered. Upon subsequent drying of the colloidal TiO2 solution, different textures, at nanoscale and macroscopic scale, were obtained dependent on the HCl/Ti ratio and thus the degree of hydrolysis of TEPD. Understanding such linker-TiO2 nanoparticle surface dynamics is crucial for making hybrid organic-inorganic materials (i. e. (porous) metal phosphonates) employed in applications such as electronic/photonic devices, separation technology and heterogeneous catalysis.

A metal-free radical cascade reaction of phosphine oxides with 2-aryloxy phenylacetylenes to synthesize diphosphonyl xanthene derivatives

A radical cascade reaction of 2-aryloxy phenylacetylenes with phosphine oxides promoted by K2S2O8 was developed, which provided diphosphonyl xanthenes as products. This reaction proceeds under transition metal-free and mild conditions with simple operation and good yields. The mechanistic study indicated that phosphine oxide was induced into a phosphonyl radical, and then the following double radical addition/cyclization with 2-aryloxy phenylacetylenes generated bisphosphonyl xanthenes.

Advances and Challenges in the Creation of Porous Metal Phosphonates

In the expansive world of porous hybrid materials, a category of materials that has been rather less explored than others and is gaining attention in development is the porous metal phosphonates. They offer promising features towards applications which demand control over the inorganic–organic network and interface, which is critical for adsorption, catalysis and functional devices and technology. The need to establish a rationale for new synthesis approaches to make these materials in a controlled manner is by itself an important motivation for material chemists. In this review, we highlight the various synthetic strategies exploited, discussing various metal phosphonate systems and how they influence the properties of porous metal phosphonates. We discuss porous metal phosphonate systems based on transition metals with an emphasis on addressing challenges with tetravalent metals. Finally, this review provides a brief description of some key areas of application that are ideally suited for porous metal phosphonates.

Further Understanding of the Reactivity Control of Bisphosphonates to a Metal Source for Fabricating Highly Ordered Mesoporous Films

Mesoporous metal organophosphonates having embedded organic functions are a promising platform to hybridize organics and non-siliceous inorganic frameworks in their molecular scale. However, the reactivity between a bisphosphonate and a metal source is dramatically different for their combination and then hampers to construct ordered mesoporous structures even when using amphiphilic organic molecules. By proposing an advanced method to adjust such reactivity, we recently succeeded in fabricating ordered mesoporous aluminum organophosphonate (AOP) films with chemically designable benzene units inside their hybrid frameworks. The reactivity of the organically bridged bisphosphonates has been controlled by utilizing dissimilar reactivities of acid-base pairs like P-OH and P-OEt groups to AlCl₃ . Here, we further prove our reactivity-control concept through the introduction of organic groups, such as those having symmetric thiophene, asymmetric amide, and hydrophilic ether units. Liquid-state ³¹ P NMR measurements further clarified the usefulness of the control of the -OH/ -OEt ratio in the same bisphosphonate molecules for obtaining highly ordered mesostructured AOP films.

The rational synthesis of aerosol-assisted alumina powders having uniform mesopores and highly accessible surfaces

Several important factors to fabricate high-quality aerosol-assisted mesoporous alumina powders are summarized by considering rational and reliable synthetic routes.