Abstract
In this work, we investigate the self-assembly between Ag(I) and Au(I) centers and pyridyl donors to form hexagonal metallacycles and related linear complexes. The precipitation of hexagonal metallacycles upon assembly in chloroform/methanol mixtures results in high solid-state photo-stability. Whereas, the Ag(I) species have fast kinetics and high formation constants in acetone, this solvent interferes in the formation of the analogous Au(I) complexes. The photophysical properties of this suite of metallacycles was investigated including steady-state absorption, emission, and time-resolved lifetime measurements. All ligands and hexagons exhibited ligand-centered singlet emissions with ground-state absorption and emission perturbed upon coordination. The ligand-based fluorescent photoluminescence was affected by the heavy-atom effect when halide or metals are present, attenuating quantum yields as evidenced by increases in the experimentally measured non-radiative rate constants. The formation of group 11 metallacycles is motivated by their potential applications in mixed-matrix materials wherein metal ions can interact with substrate to facilitate separations chemistry with reduced energy requirements, in particular the isolation of ethylene and light olefins. Existing processes involve cryogenic distillation, an energy intensive and inefficient method.
Highlights
Coordination-driven self-assembly (Leininger et al, 2000) is a valuable strategy for the design and synthesis of discrete molecular complexes such as metallacycles and metallacages for biomedical (Cook et al, 2013; Casini et al, 2017) catalytic (Ito et al, 2000; Brown et al, 2009; Smulders and Nitschke, 2012; Vardhan and Verpoort, 2015; Kuijpers et al, 2016), molecular sensing (Tashiro et al, 2005; Kim and Ahn, 2008; Wang et al, 2011; Zwijnenburg et al, 2016; Cao et al, 2017), and small molecule adsorption and separation applications (Sudik et al, 2005; Zhao et al, 2010; Riddell et al, 2011; Amayuelas et al, 2016). This strategy exploits pre-programmed directionality information on metal acceptor and ligand donor building blocks to form complex architectures driven by metal-ligand coordination (Cook and Stang, 2015)
A careful design of building blocks coupled with thermodynamic driving forces favors the convergent formation of discrete molecular
Inspired by previous reports on hexagonal self-assemblies from trans-capped Pt(II) precursors (Yang et al, 2007) and 120◦ bidentate pyridine-type ligands, which are known for their luminescent properties, and other luminescent Pt(II)based metallacycles (Huang et al, 2017; Tang et al, 2018), we report the self-assembly of hexagonal metallacycles from the same class of ligand donors and Ag(I) and Au(I) metal acceptors
Summary
Coordination-driven self-assembly (Leininger et al, 2000) is a valuable strategy for the design and synthesis of discrete molecular complexes such as metallacycles and metallacages for biomedical (Cook et al, 2013; Casini et al, 2017) catalytic (Ito et al, 2000; Brown et al, 2009; Smulders and Nitschke, 2012; Vardhan and Verpoort, 2015; Kuijpers et al, 2016), molecular sensing (Tashiro et al, 2005; Kim and Ahn, 2008; Wang et al, 2011; Zwijnenburg et al, 2016; Cao et al, 2017), and small molecule adsorption and separation applications (Sudik et al, 2005; Zhao et al, 2010; Riddell et al, 2011; Amayuelas et al, 2016) This strategy exploits pre-programmed directionality information on metal acceptor and ligand donor building blocks to form complex architectures driven by metal-ligand coordination (Cook and Stang, 2015). Efforts are ongoing to improve the solubilities of these metallacycles including but not limited to pre- and post-assembly ligand modification
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