Phosphorescence at Low Temperature by External Heavy-Atom Effect in Zinc(II) Clusters

Fumiya Kobayashi; Ryo Ohtani; Saki Teraoka; Masaki Yoshida; Masako Kato; Yingjie Zhang; Leonard F Lindoy; Shinya Hayami; Masaaki Nakamura

doi:10.1002/chem.201900343

Phosphorescence at Low Temperature by External Heavy-Atom Effect in Zinc(II) Clusters

Chemistry. 2019 Apr 23;25(23):5875-5879. doi: 10.1002/chem.201900343. Epub 2019 Mar 12.

Authors

Fumiya Kobayashi¹, Ryo Ohtani¹, Saki Teraoka¹, Masaki Yoshida², Masako Kato², Yingjie Zhang³, Leonard F Lindoy⁴, Shinya Hayami^{1

5}, Masaaki Nakamura¹

Affiliations

¹ Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
² Department of Chemistry, Faculty of Science, Hokkaido University, North-10 West-8, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan.
³ Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW, 2232, Australia.
⁴ School of Chemistry, The University of Sydney, NSW, 2006, Australia.
⁵ Institute of Pulsed Power Science (IPPS), Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.

PMID: 30860310
DOI: 10.1002/chem.201900343

Abstract

Luminescent Zn^II clusters [Zn₄ L₄ (μ₃ -OMe)₂ X₂ ] (X=SCN (1), Cl (2), Br (3)) and [Zn₇ L₆ (μ₃ -OMe)₂ (μ₃ -OH)₄ ]Y₂ (Y=I^- (4), ClO₄ ^- (5)), HL=methyl-3-methoxysalicylate, exhibiting blue fluorescence at room temperature (λ_max =416≈429 nm, Φ_em =0.09-0.36) have been synthesised and investigated in detail. In one case the external heavy-atom effect (EHE) arising the presence of iodide counter anions yielded phosphorescence with a long emission lifetime (λ_max =520 nm, τ=95.3 ms) at 77 K. Single-crystal X-ray structural analysis and time-dependent density-functional theory (TD-DFT) calculations revealed that their emission origin was attributed to the fluorescence from the singlet ligand-centred (¹ LC) excited state, and the phosphorescence observed in 4 was caused by the EHE of counter anions having strong CH-I interactions.

Keywords: external heavy-atom effect; long emission lifetime; luminescence; phosphorescence; zinc.

Abstract

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