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Issue 7, 2020
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Peculiarities of crystal structures and photophysical properties of GaIII/LnIII metallacrowns with a non-planar [12-MC-4] core

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Abstract

A new series of gallium(III)/lanthanide(III) metallacrown (MC) complexes (Ln-1) was synthesized by the direct reaction of salicylhydroxamic acid (H3shi) with GaIII and LnIII nitrates in a CH3OH/pyridine mixture. X-ray single crystal analysis revealed two types of structures depending on whether the nitrate counterion coordinate or not to the LnIII: [LnGa4(shi)4(H2shi)2(py)4(NO3)](py)2 (Ln = GdIII, TbIII, DyIII, HoIII) and [LnGa4(shi)4(H2shi)2(py)5](NO3)(py) (Ln = ErIII, TmIII, YbIII). The representative Tb-1 and Yb-1 MCs consist of a Tb/YbGa4 core with four [GaIII–N–O] repeating units forming a non-planar ring that coordinates the central LnIII through the oxygen atoms of the four shi3− groups. Two H2shi groups bridge the LnIII to the GaIII ring ions. The YbIII in Yb-1 is eight-coordinated while the ligation of the nine-coordinated TbIII in Tb-1 is completed by one chelating nitrate ion. Ln-1 complexes in the solid state showed characteristic sharp f–f transitions in the visible (Tb, Dy) and near-infrared (Dy, Ho, Er, Yb) spectral ranges upon excitation into the ligand-centered electronic levels at 350 nm. Observed luminescence lifetimes and absolute quantum yields were collected and discussed. For Yb-1, luminescence data were also acquired in CH3OH and CD3OD solutions and a more extensive analysis of photophysical properties was performed. This work demonstrates that while obtaining highly luminescent lanthanide(III) MCs via a direct synthesis is feasible, many factors such as molar absorptivities, triplet state energies, non-radiative deactivations through vibronic coupling with overtones of O–H, N–H, and C–H oscillators and crystal packing will strongly contribute to the luminescent properties and should be carefully considered.

Graphical abstract: Peculiarities of crystal structures and photophysical properties of GaIII/LnIII metallacrowns with a non-planar [12-MC-4] core

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Supplementary files

Article information


Submitted
17 Dec 2019
Accepted
21 Feb 2020
First published
02 Mar 2020

Inorg. Chem. Front., 2020,7, 1553-1563
Article type
Research Article

Peculiarities of crystal structures and photophysical properties of GaIII/LnIII metallacrowns with a non-planar [12-MC-4] core

T. N. Nguyen, S. V. Eliseeva, C. Y. Chow, J. W. Kampf, S. Petoud and V. L. Pecoraro, Inorg. Chem. Front., 2020, 7, 1553
DOI: 10.1039/C9QI01647C

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