Evidence for Molecular Packing of Monovalent Iridium (III) Complexes within Interlayer Spaces of Sodium Montmorillonite

1. Enantiopure monovalent iridium(III) complexes formed mono- or bi-molecular layers in the interlayer spaces of montmorillonite at 50 and 100 % CEC loading, respectively.
2. Solid state vibrational circular dichroism (VCD) spectra were applied to investigate the intermolecular interactions within adsorption layers.
3. VCD signals were revealed to be sensitive enough to reflect the detailed features in the molecular packing of adsorbed molecules.

Chiral recognition by an asymmetrically modified clay surface was reported by one of the present authors forty years ago. However, how chiral metal complexes organize in the interlayer space of a clay mineral on a molecular scale had not been clarified. In this report, the intermolecular interactions were investigated on the clay minerals intercalating a chiral complex, - (or -)[Ir(bzq)2(phen)]+ (bzqH = benzo[h]quinoline; phen = 1,10-phenanthroline). The compound had a three-bladed propeller type structure with a monovalent charge (+1). Notably, the complex formed a mono- or bi-molecular layer at the loading level of 50% and 100% CEC, respectively. The solid state vibrational circular dichroism　(VCD) method was applied to detect the subtle changes of vibrational properties caused by intermolecular interactions. The work demonstrated how useful the VCD method was in revealing the details of intermolecular interactions in solid samples. The obtained results give promise to the possibility of VCD application in the fields of heterogeneous asymmetric reactions.

Reference URL: https://doi.org/10.1016/j.clay.2022.106621

Bibliographic Information

Vibrational Circular Dichroism Spectroscopy toward Intercalation Compounds of Sodium Montmorillonite: Evidences for Molecular Packing of Enantiopure Monovalent Ir(III) Complexes within Interlayer Spaces
Hisako Sato,* Kazuyoshi Takimoto, Akihiko Yamagishi, Jun Yoshida and Mitsuo Hara
Applied Clay Science, 2022, 228, 106621　https://doi.org/10.1016/j.clay.2022.106621

Fundings

• Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number JP17H03044, JP19K05508, JP20K21090
• JSPS Fellows (JP21J15602)

Media

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  VCD for molecular interaction

  Molecular packing in intercalation states was reflected on the relative intensity of a VCD signal.

  credit : Hisako Sato,Ehime Univercity
  Usage Restriction : Please get copyright permission