Effect of Noble Metals on Luminescence and Single-Molecule Magnet Behavior in the Cyanido-Bridged Ln-Ag and Ln-Au (Ln = Dy, Yb, Er) Complexes

Kunal Kumar; Olaf Stefańczyk; Szymon Chorazy; Koji Nakabayashi; Barbara Sieklucka; Shin-Ichi Ohkoshi

doi:10.1021/acs.inorgchem.8b03634

Effect of Noble Metals on Luminescence and Single-Molecule Magnet Behavior in the Cyanido-Bridged Ln-Ag and Ln-Au (Ln = Dy, Yb, Er) Complexes

Inorg Chem. 2019 May 6;58(9):5677-5687. doi: 10.1021/acs.inorgchem.8b03634. Epub 2019 Apr 18.

Authors

Kunal Kumar¹, Olaf Stefańczyk¹, Szymon Chorazy^{1

2}, Koji Nakabayashi¹, Barbara Sieklucka², Shin-Ichi Ohkoshi¹

Affiliations

¹ Department of Chemistry, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan.
² Faculty of Chemistry , Jagiellonian University , Gronostajowa 2 , 30-387 Kraków , Poland.

PMID: 30998322
DOI: 10.1021/acs.inorgchem.8b03634

Abstract

Self-assembly of lanthanide(III) complexes of 2,2':6',2″-terpyridine (terpy) with dicyanidoargentate(I) and dicyanidoaurate(I) anions in water results in the formation of six isostructural dinuclear systems [Ln^III(terpy)(H₂O)(NO₃)₂][M^I(CN)₂] (Ln^III/M^I = Dy/Ag, 1; Dy/Au, 2; Yb/Ag, 3; Yb/Au, 4; Er/Ag, 5; Er/Au, 6). They form three-dimensional supramolecular networks based on dinuclear molecules linked by hydrogen bonds, π-π interactions, and argentophilic (Ag···Ag) or aurophilic (Au···Au) interactions. All of the assemblies show complex solid-state strong UV and weak vis-NIR absorption due to overlapping contributions from 2,2':6',2″-terpyridine, dicyanidoargentate(I), dicyanidoaurate(I), and lanthanide(III) ions. Moreover, they exhibit excitation-wavelength-dependent multicolor photoluminescence ranging from bright white to blue via yellow, green, and cyan colors due to variable contributions from the dicyanidometalate and ligand. Assemblies 3-6 show NIR emission originating from Yb^III and Er^III metal centers. Furthermore, compounds 1-6 and their magnetically diluted samples are magnetic-field-induced single-molecule magnets with energy barriers of up to 35 K. The effect of noble metal substitution on the magnetic properties of particular lanthanide ions is described. The influence on the thermal anisotropic energy barrier, which relates to the strength of the magnetic anisotropy, depends on the type of lanthanide used. The Ag-to-Au substitution enhances the anisotropy of the prolate Yb^III ion and decreases it for the oblate Dy^III ion. It also modifies the strength of dipolar interactions affecting the slow magnetic relaxation processes.