Synthesis and structural characterization of xanthate ligated hydrido Cu(I) clusters and Cu(I) coordination polymer

Superstructures of copper nanoclusters as NIR TADF emitters: solvent-dependent optical and morphological modulation

Herein, we report 2-mercaptopyridine-templated copper nanoclusters (CuNCs) which display near infra-red (NIR) emission, both in the solid and colloidal states. Interestingly, the NIR emission can be modulated to orange emission by preparing the CuNCs in a mixed solvent system of chloroform and methanol instead of water. The drastic change in the photo-physical properties of the CuNCs when prepared in two different solvent systems is accompanied by a unique morphological tuning. Further studies reveal that the strong NIR emission is the result of thermally activated delayed fluorescence (TADF) which is confirmed by the long excited state lifetime (∼4 μs at room temperature), time resolved emission spectroscopy (TRES) measurements, temperature-dependent photoluminescence studies, temperature-dependent lifetime studies, and excitation-transmittance dependent TRES intensity measurements. The CuNCs exhibit an exceptionally small singlet-triplet energy gap of 58.2 meV, indicating a highly efficient TADF in the system. Moreover, the solvent-dependent morphological tuning of the nanocluster superstructures rendering a drastic change in the photo-physical signatures is the consequence of different ΔE(S1-T1) values for the CuNCs in different solvent environments. Further findings corroborate that the electronic structure of the surface ligands can also help us to tune the ΔE(S1-T1) energy gap for these nanoclusters.

A chemically induced, room temperature, single source precursor to CuS (covellite) nanomaterials: synthesis and reactivity of [Cu(S2CNHBz)]n

Addition of two equivalents of NaS2CNHBz to CuSO4 affords the yellow diamagnetic coordination polymer [Cu(S2CNHBz)]n (1), resulting from intramolecular electron-transfer and concomitant formation of the thiourea, (BzNH)2CS. 1 reacts with PPh3 and 1,1'-bis(diphenylphosphino)ferrocene (dppf) in CH2Cl2 to give monomeric [Cu(κ2-S2CNHBz)(PPh3)2] (2) and [Cu(κ2-S2CNHBz)(κ2-dppf)] (3), respectively, both of which have been crystallographically characterised. While 1 is thermally stable in dimethylsulfoxide (DMSO) up to ca. 70 °C, addition of nBuNH2 to 1 leads to its rapid decomposition to afford CuS (covellite) nanomaterials; indeed in neat nBuNH2, covellite formation is rapid at room temperature. Thus, 1 serves as an effective low-temperature base-induced single source precursor to covellite nanomaterials.

1H NMR global diatropicity in copper hydride complexes

Understanding the magnetic response of electrons in nanoclusters is essential to interpret their NMR spectra thereby providing guidelines for their synthesis towards various target applications. Here, we consider two copper hydride clusters that have applications in hydrogen storage and release under standard temperature and pressure. Through Born-Oppenheimer molecular dynamics simulations, we study dynamics effects and their contributions to the NMR peaks. Finally, we examine the electrons' magnetic response to an applied external magnetic field using the gauge-including magnetically induced currents theory. Local diatropic currents are generated in both clusters but an interesting global diatropic current also appears. This diatropic current has contributions from three μ₃-H hydrides and six Cu atoms that form a chain together with three S atoms from the closest ligands resulting in a higher shielding of these hydrides' ¹H NMR response. This explains the unusual upfield chemical shift compared to the common downfield shift in similarly coordinated hydrides both observed in previous experimental reports.

Copper nanoclusters: designed synthesis, structural diversity, and multiplatform applications

Atomically precise metal nanoclusters (MNCs) have gained tremendous research interest in recent years due to their extraordinary properties. The molecular-like properties that originate from the quantized electronic states provide novel opportunities for the construction of unique nanomaterials possessing rich molecular-like absorption, luminescence, and magnetic properties. The field of monolayer-protected metal nanoclusters, especially copper, with well-defined molecular structures and compositions, is relatively new, about two to three decades old. Nevertheless, the massive progress in the field illustrates the importance of such nanoobjects as promising materials for various applications. In this respect, nanocluster-based catalysts have become very popular, showing high efficiencies and activities for the catalytic conversion of chemical compounds. Biomedical applications of clusters are an active research field aimed at finding better fluorescent contrast agents, therapeutic pharmaceuticals for the treatment and prevention of diseases, the early diagnosis of cancers and other potent diseases, especially at early stages. A huge library of structures and the compositions of copper nanoclusters (CuNCs) with atomic precisions have already been discovered during last few decades; however, there are many concerns to be addressed and questions to be answered. Hopefully, in future, with the combined efforts of material scientists, inorganic chemists, and computational scientists, a thorough understanding of the unique molecular-like properties of metal nanoclusters will be achieved. This, on the other hand, will allow the interdisciplinary researchers to design novel catalysts, biosensors, or therapeutic agents using highly structured, atomically precise, and stable CuNCs. Thus, we hope this review will guide the reader through the field of CuNCs, while discussing the main achievements and improvements, along with challenges and drawbacks that one needs to face and overcome.