Coordination Amphiphile: Design of Planar-Coordinated Platinum Complexes for Monolayer Formation at an Air-Water Interface Based on Ligand Characteristics and Molecular Topology

Abstract

We aim to establish the importance of molecular design for the formation of monolayers at an air-water interface within the concept “coordination amphiphile”, which is based on ligand characteristics and molecular topology. For this purpose, five types of platinum complexes containing a coordination plane, including salicylaldiminato (SA) and β-(iminomethyl)azolato (IA) complexes, were prepared where the ligand characteristics were controlled. Polymethylene-vaulted and non-vaulted complexes were then examined to assess the effects of molecular topology on interfacial activity. SA complexes tend to undergo random aggregation at an air-water interface, while the weak hydrophilicity of SA can assist in the formation of a stable monolayer if hydrophobic and hydrophilic chains are introduced to the structure. In contrast, IA complexes exhibit topological specificity; imidazolato and pyrazolato complexes form monolayers only for non-vaulted and vaulted complex, respectively. Molecular modelling and association constants of the compounds suggest that an appropriate hydrophilicity of the coordination plane and intermolecular interactions involving hydrogen bonding are important factors for monolayer formation.

Chemistry of Materials Nanoarchitectonics for Two-Dimensional Films: Langmuir–Blodgett, Layer-by-Layer Assembly, and Newcomers

“…(B) Coordination amphiphilicity concept to spread complex molecules as monolayers on the water surface. Reproduced with permission from ref . Copyright 2022 Chemical Society of Japan.…”

“…As a new concept for metal-complexbased LB method, Naota, Mori, and co-workers proposed the concept of "coordination amphiphilicity" to spread complex molecules as monolayers on the water surface. 85 Platinum complexes with five different coordination planes were synthesized, including salicylaldiminato and β-(iminomethyl) azolato complexes, and hydrophobic alkyl chains were introduced to the ligands. The monolayer behavior of polymethylene-vaulted complexes, in which the ligands are connected by cyclic hydrophobic chains, was compared with that of nonvaulted complexes, in which the alkyl chains are introduced independently.…”

“…The resulting thin films were also shown to be usable as selective membranes for efficient CO 2 separation. As a new concept for metal-complex-based LB method, Naota, Mori, and co-workers proposed the concept of “coordination amphiphilicity” to spread complex molecules as monolayers on the water surface . Platinum complexes with five different coordination planes were synthesized, including salicylaldiminato and β-(iminomethyl) azolato complexes, and hydrophobic alkyl chains were introduced to the ligands.…”

Molecular Machines and Microrobots: Nanoarchitectonics Developments and On-Water Performances

“…The submarine-like control of optical properties by molecular manipulation in a nanometer-sized asymmetric interfacial environment has been named the submarine emission mechanism. Furthermore, the related molecular systems have been systematically analyzed the behavior of such complex molecules at the air-water interface and proposed the concept of coordination amphiphilicity [ 200 ]. Molecular modeling and analysis of the aggregation behavior of the compounds suggest that the appropriate hydrophilicity of the coordination surface and intermolecular interactions, including hydrogen bonding, are important factors for monolayer formation.…”

Layer-by-layer designer nanoarchitectonics for physical and chemical communications in functional materials

“…The Langmuir–Blodgett method is a technique for creating highly oriented monolayers at the liquid interface and building them up in layers on a solid substrate. 36 Generally speaking, this method is easy to obtain denser and more controlled thin-film structures, but it is not necessarily applicable to many types of materials. The layer-by-layer assembly method is a method to obtain multilayer thin films by sequentially adsorbing components into a film based on interactions between the materials.…”