Representative works conducted under the Grant-in-Aid for Scientific Research Innovative Area (Coordination Asymmetry: Design of Asymmetric Coordination Sphere and Anisotropic Assembly for the Creation Molecules) (Planned research) “Structure, Physical Property and Reaction of Supermolecules with asymmetric metal crystal field) Masahiro Ehara (FY2016－FY2021)
Mechanism of olefin migration reaction in Metal-Macrocycle Framework (MMF)
Shionoya group (The University of Tokyo) has developed Pd-loaded Metal-Macrocycle Framework (MMF) which is formed by self-assembly. Various unique functions have been achieved with this MMF such as diastereo-selective absorption of chiral molecules and immobilization of acid catalysts. Recently, switching function of photo-reaction has been observed owing to controlling the space of this MMF.
We have clarified the mechanism of the generation of reactive site and the switching function of photo-reaction by collaborating with experimental group (J. Am. Chem. Soc. 2018). We demonstrate that the olefin migration reaction proceeds in “alkyl” mechanism and the rate-determining step is the proton-migration to Pd center. We succeeded to explain the isotope effect (1,2 D-shift) which was observed in the experiment (Chem. Asian. J. 2021).
Heat-resistant phosphorescence of π-extended Pt(II) complexes and its correlation with aromaticity
Naota group (Osaka University) has developed series of light-emitting Pt(II) complexes with various π-conjugation and structure restriction. They are focusing on the control of the emission energy variation and heat-resistant property of phosphorescence.
We studied the excited states of these π-conjugated Pt complexes. We found that there are characteristic local minima such as MLCT, MC and MECP, and clarified that the heat-resistant property of phosphorescence is anti-correlated with the aromaticity of the rings adjacent to Pt center (Chem. Eur. J.).
Electronic asymmetry of the condensed-phase Ag nanocluster
Nakashima group (Nara Institute of Science and Technology) has observed the circular dichroism (CD) and circularly polarized light (CPL) for condensed-phase Ag nanocluster (Ag29(DHLA)12) (Chem. Commun. 2017). Recently, they found that this Ag nanocluster has a chiral structure and observed a mirror-image CD spectra of the enantiomers which were separated by chiral column.
We clarified that Ag13(3-), a core of this nanocluster, has a superatomic electronic structure and the CD spectrum originates in the helical structures and interface electronic states of the adsorbates. The excited states are characterized as the transitions from HOMO (P-orbitals of Ag13 core and S p-orbitals) to LUMO (D-orbitals of Ag13 core) (Chem. Sci. 2020).