Versatile Control of Directed Supramolecular Assembly via Subtle Changes of the Rhodium(I) Pincer Building Blocks

Abstract

Various rhodium(I) pincer complexes with different structural features have been prepared and found to display interesting self-assembly properties due to the extensive Rh(I)···Rh(I) interactions. The incorporation of electron-withdrawing −CF3 substituent has been found to improve the stability of the complexes and also facilitate the directed assembly of complex molecules, providing an opportunity for the systematic investigation of the various noncovalent interactions in their versatile self-assembly behaviors and insights into the structure−property relationship in governing the intermolecular interactions. Density functional theory calculations have been performed to study the effect of –CF3 substituent on the assembly of the complex molecules, and the results reveal the presence of two conformations of comparable energies, with the eclipsed conformation being 1.42 kJmol1 higher in energy than the slightly staggered conformation. An isodesmic growth mechanism is identified for the solvent-induced aggregation process. The complex molecules exhibit intense low-energy absorption bands corresponding to the absorptions of the dimers, trimers, and higher order oligomers upon aggregation, with energies related to the electronic properties of the tridentate N-donor ligand. Chiral auxiliaries have also been introduced into the rhodium(I) complexes to build up helical supramolecular assemblies and soft materials. Reference: 1. Chan, A. K.-W.; Ng, M.; Low, K.-H.; Yam, V. W.-W. J. Am. Chem. Soc., 2018, 140, 8321–8329.