Temperature dependence of spherical electron transfer in a nanosized [Fe14] complex

Wei Huang,Michael L Baker,Shinya Hayami,Dayu Wu,P Benčok ,Yao Li,Yoshihito Shiota,Naoya Kojima ,Mariko Noguchi,Xiangwei Gu,Tatsuya Kawae,Motohiro Nakano,Yuji Miyazaki,Takumi Nakanishi,Shinji Kanegawa,Shu‐Qi Wu ,Kazunari Yoshizawa,Atsushi Okazawa,Guilin Zhuang ,Yuji Inagaki,Osamu Sato

doi:10.1038/s41467-019-13279-y

Abstract

The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak. Herein, we report the synthesis of a nanosized complex, [Fe(Tp)(CN)3]8[Fe(H2O)(DMSO)]6 (abbreviated as [Fe14], Tp−, hydrotris(pyrazolyl)borate; DMSO, dimethyl sulfoxide), which has a fluctuating valence due to two mobile d-electrons in its atomic layer shell. The rate of electron transfer of [Fe14] complex demonstrates the Arrhenius-type temperature dependence in the nanosized spheric surface, wherein high-spin centers are ferromagnetically coupled, producing an S = 14 ground state. The electron-hopping rate at room temperature is faster than the time scale of Mössbauer measurements (<~10−8 s). Partial reduction of N-terminal high spin FeIII sites and electron mediation ability of CN ligands lead to the observation of both an extensive electron transfer and magnetic coupling properties in a precisely atomic layered shell structure of a nanosized [Fe14] complex.

Highlights

The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak
One of the challenges in realizing their functions is the introduction of fast electron transfer over a long distance that ubiquitously occurs in chemical and biological systems[4,5]
Intermetallic electron transfer-mediated through bridging ligands are normally weak; properties related to confined electron transfer processes in discrete nanosized complexes have remained hypothetical far[19,20]

Summary

Introduction

The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak. To confirm the valences and spin states of the Fe ions in the complex, 57Fe Mössbauer spectroscopic measurements were performed at various temperatures under zero magnetic field (Fig. 2a). The signals merge gradually into a unique doublet upon an increase in the temperature, indicating that valence fluctuation occurs due to electron hopping at the B sites.

Results

Conclusion