Development of a photo luminescent multinuclear sandwich complex: The first observation of circularly polarized luminescence originated from the sandwich framework

Multinuclear sandwich complexes have recently been developing, but the studies focus on their remarkable structural features and reactivities. The collaborative research by Prof. Keisuke Umakoshi and Assist. Prof. Shinnosuke Horiuchi from Nagasaki Uni­ver­sity, Prof. Guido H. Clever from TU Dortmund, Germany, and their colleagues have found a new type of multinuclear sandwich complexes, that can show circularly polarized luminescence (CPL) property. This research will represent a new horizon in cluster and material chemistry. Their results have been published on 23th Mar 2021 in the online edition of Angewandte Chemie International Edition. This paper was selected as a hot paper and highlighted by a cover picture in the journal.

Sandwich complexes, which possess one metal ion between two small organic molecules, are one of the classical organometallic compounds. This type of molecules now play an important role in catalysis and materials chemistry. Multinuclear sandwich complexes, which contain multiple metal ions between two supporting ligands, have been established recently to show remarkable fluxional behaviors and reactivities, such as dynamic rotation of the supporting ligands, reversible metalation–demetalation sequences, and translocation of metal clusters. However, unique photophysical properties derived from the sandwich structure have been unexplored so far.

The research group of Prof. Keisuke Umakoshi and Assist. Prof. Shinnosuke Horiuchi created new types of multinuclear sandwich complexes consisting of an Ag₃ cluster unit sandwiched by two square-planar Pt complex units. The Ag₃ sandwich complex showed remarkable fluxional behaviors, dynamic rotation of the supporting units and metalation–demetalation reactivity, as seen in the chemistry of multinuclear sandwich complexes. Furthermore, this complex displayed intense photoluminescent properties.

The Ag₃ sandwich complex contained chiral center at the Pt₂Ag₃ cluster based on the sandwich framework, allowing optical resolution to separate S-, and R-enantiomer of the sandwich complexes. Prof. Guido. H. Clever and colleagues from TU Dortmund succeeded in observing right- and left-handed circularly polarized luminescence (CPL) from the each enantiomer of the sandwich complex. This is the first example for observing the CPL property from multinuclear sandwich-shaped metal complexes. These materials displaying CPL properties are potential candidates for 3D organic light emitting diode (OLED) devices. Therefore, these results extend structural concepts of multinuclear sandwich complexes and give impulses for development of novel chiral luminescent materials based on sandwich-shaped multinuclear complexes.

Original Paper:
“Multinuclear Ag Clusters Sandwiched by Pt Complex Units: Fluxional Behavior and Chiral-at-Cluster Photoluminescence”

S. Horiuchi, S. Moon, A. Ito, J. Tessarolo, E. Sakuda, Y. Arikawa, G. H. Clever, K. Umakoshi

Angew. Chem. Int. Ed., 2021, in press. DOI:10.1002/anie.202101460

ＵＲＬ: https://onlinelibrary.wiley.com/doi/10.1002/anie.202101460

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