Synthesis, crystal structures and photoelectric properties of copper(I) alkynyl nanoclusters

Abstract

<p indent="0mm">Metal nanoclusters (NCs) are composed of several to thousands of metal atoms with a diameter of &lt; <sc>3 nm.</sc> Such metal NCs exhibit dramatically unique electronic/geometric structures and physical/chemical properties which differ from those of bulk metal materials. Among metal NCs, coinage metal (Au, Ag, and Cu) NCs have received extensive attention because of their chirality, optical and catalytic properties. Cu is more abundant than Au and Ag, yet copper(0)/copper(I) is more reactive and easier to oxidize than silver or gold, which makes it more difficult to prepare Cu NCs and investigate their properties. By taking guidelines from Au and Ag NC research, thiolate, phosphine, and alkynyl ligand-protected Cu NCs have recently received increasing attention. Alkynyl ligands have more abundant coordination modes compared to thiolate and phosphine ligands. Some copper(I) alkynyl NCs with unique crystal structures, good stability and rich properties have been recently reported. Herein, firstly, this paper introduces recent advances in developing efficient synthetic methods for copper(I) alkynyl NCs, highlighting the underlying physical and chemical properties that make the delicate control of their sizes and surfaces possible. The synthesis of copper(I) alkynyl NCs can be roughly classified into four categories: Solvothermal, reduction, template, and ligand exchange. Generally, the steric effect of the introduced protective ligand breaks their polymeric structures and improves solubility. Some copper(I) alkynyl NCs can also be produced by adjusting the auxiliary ligands and anionic templating agents. In addition, the concentration of ligands and precursors, pH and temperature of the reaction system can be used to adjust the reaction kinetics, and this leads to the formation of the monodisperse copper(I) alkynyl NCs. Secondly, we discuss recent advances in the structural determination of copper(I) alkynyl NCs, of which the size and shape can be controlled to a certain extent by the judicious choice of templating anions and auxiliary ligands. The atomically precise nature of their structures enables the investigation of the structure-property relationship, which may further optimize their performance. One of the most important properties of copper(I) alkynyl NCs is the luminescence, which offers potential applications as photoelectric detectors and in sensing and bio-imaging. We highlight some examples of copper(I) alkynyl NCs to demonstrate their photoelectric properties. Finally, the brief conclusion and outlook on the research and challenges of copper(I) alkynyl NCs are presented. We expect this review will serve as an introduction and reference for researchers who are interested in exploring metal NCs.