Exploring gold(I) as a luminophore for emissive coordination polymers

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Coordination Polymers

This thesis focuses on the incorporation of gold(I) as a luminophore in photoluminescent materials via coordination polymer (CP) methodology. This is explored via two avenues: (i) the use of dicyanoaurate, [Au(CN)2]– as a building block with lanthanide metals and (ii) the design of electron-rich gold(I) building blocks containing the ‘aurothiolate’ motif. A series of dicyanoaurate/lanthanide CPs [nBu4N]2[Ln(NO3)4Au(CN)2] (LnAu) Ln = Ce, Nd, Sm, Eu, Gd, Tb, and Dy were synthesized. LnAu CPs are strongly luminescent at room temperature and this behaviour is primarily lanthanide-based. These results contrast those reported for Ln[Au(CN)2]3·3H2O (LnAu3), which is only faintly emissive at room temperature. Solid-solutions of Eu(III)/Tb(III) were prepared to explore these differences. The emission colour in LnAu could be varied between red and green corresponding to Eu/Tb ratio, whereas in LnAu3 only red Eu(III) emission is observed. Short Ln–Ln contacts in LnAu3 enable energy transfer, whereas in LnAu the long Ln–Ln distances preclude this, allowing for colour tunable emission. Colour tuning was explored to find the maximum available gamut, and it was found that white emission, and multiple emission colours is possible at room temperature. Design considerations for an electron-rich gold(I) building block were evaluated and the dithiocarbmate building block [Au2(dopdtc)2] was synthesized. The would-be building block is hindered in its ability to form CPs but its luminescence proved to be interesting; the pressure dependent emission energy is significantly lower than for similar materials, despite similar Au–Au distances. The role of geometry becomes clear when probed using DFT; deviations from linearity in aurophilic chains result in the transition becoming MLCT in nature, which is less sensitive to applied pressure. To improve the utility of an electron rich Au(I) building block, [Au2(i-mnt)2]2– (i-mnt = S2C=C(C#N)22–) was explored for its ability to form intermolecular aurophilic interactions. Aurophilic materials were prepared via substituting [nBu4N]+ cations with those containing the N-H+ functional group, illustrating that [Au2(i-mnt)2]2– is a good candidate for aurophilic CPs. To that end, some preliminary results in the preparation of [Au2(i-mnt)2]2– CPs are reported.

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This thesis may be printed or downloaded for non-commercial research and scholarly purposes. Copyright remains with the author.
Senior supervisor: 
Daniel Leznoff
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.