Dual-radical-based molecular anisotropy and synergy effect of semi-conductivity and valence tautomerization in a photoswitchable coordination polymer

Jing-Wei Dai; Yu-Qin Li; Zhao-Yang Li; Hai-Tao Zhang; Carmen Herrmann; Shohei Kumagai; Marko Damjanović; Markus Enders; Hiroyuki Nojiri; Masakazu Morimoto; Norihisa Hoshino; Tomoyuki Akutagawa; Masahiro Yamashita

doi:10.1093/nsr/nwad047

Dual-radical-based molecular anisotropy and synergy effect of semi-conductivity and valence tautomerization in a photoswitchable coordination polymer

Natl Sci Rev. 2023 Feb 23;10(6):nwad047. doi: 10.1093/nsr/nwad047. eCollection 2023 Jun.

Authors

Affiliations

¹ State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin300071, China.
² School of Materials Science and Engineering, Nankai University, Tianjin300350, China.
³ Institute of Inorganic and Applied Chemistry, University of Hamburg, Hamburg22761, Germany.
⁴ Department of Chemistry, Graduate School of Science, Tohoku University, Sendai980-8578, Japan.
⁵ Institute of Inorganic Chemistry, University of Heidelberg, HeidelbergD-69120, Germany.
⁶ Institute for Materials Research, Tohoku University, Sendai980-8577, Japan.
⁷ Department of Chemistry, Rikkyo University, Tokyo171-8501, Japan.
⁸ Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai980-8577, Japan.

Abstract

Organic radicals are widely used as linkers or ligands to synthesize molecular magnetic materials. However, studies regarding the molecular anisotropies of radical-based magnetic materials and their multifunctionalities are rare. Herein, a photoisomerizable diarylethene ligand was used to form {[Co^III(3,5-DTSQ^·-)(3,5-DTCat^2-)]₂(6F-DAE-py₂)}·3CH₃CN·H₂O (o-1·3CH₃CN·H₂O, 6F-DAE-py₂ = 1,2-bis(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene), a valence-tautomeric (VT) coordination polymer. We directly observed dual radicals for a single crystal using high-field/-frequency (∼13.3 T and ∼360 GHz) electron paramagnetic resonance (EPR) spectroscopy along the c-axis, which was further confirmed by angle-dependent Q-band EPR spectroscopy. Moreover, a conductive anomaly close to the VT transition temperature was observed only when probes were attached at the ab plane of the single crystal, indicative of synergy between valence tautomerism and conductivity. Structural anisotropy studies and density functional theory (DFT) calculations revealed that this synergy is due to electron transfer associated with valence tautomerism. This study presents the first example of dual-radical-based molecular anisotropy and charge-transfer-induced conductive anisotropy in a photoswitchable coordination polymer.

Keywords: charge transfer; coordination polymer; diradical; photo switching; valence tautomerization.