inorganics Review Copper Dithiocarbamates: Coordination Chemistry and Applications in Materials Science, Biosciences and Beyond Graeme Hogarth 1, * and Damian C. Onwudiwe 2, *   Citation: Hogarth, G.; Onwudiwe, D.C. Copper Dithiocarbamates: Coordination Chemistry and Applications in Materials Science, Biosciences and Beyond. Inorganics 2021, 9, 70. https://doi.org/10.3390/ inorganics9090070 Academic Editor: Duncan H. Gregory Received: 4 August 2021 Accepted: 23 August 2021 Published: 10 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Chemistry, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK 2 Department of Chemistry, Faculty of Natural and Agricultural Science, North-West University, Mafikeng Campus, Private Bag X2046, Mmabatho 2735, South Africa * Correspondence: graeme.hogarth@kcl.ac.uk (G.H.); Damian.Onwudiwe@nwu.ac.za (D.C.O.) Abstract: Copper dithiocarbamate complexes have been known for ca. 120 years and find relevance in biology and medicine, especially as anticancer agents and applications in materials science as a single-source precursor (SSPs) to nanoscale copper sulfides. Dithiocarbamates support Cu(I), Cu(II) and Cu(III) and show a rich and diverse coordination chemistry. Homoleptic [Cu(S 2 CNR 2 ) 2 ] are most common, being known for hundreds of substituents. All contain a Cu(II) centre, being either monomeric (distorted square planar) or dimeric (distorted trigonal bipyramidal) in the solid state, the latter being held together by intermolecular C···S interactions. Their d 9 electronic configuration renders them paramagnetic and thus readily detected by electron paramagnetic resonance (EPR) spectroscopy. Reaction with a range of oxidants affords d 8 Cu(III) complexes, [Cu(S 2 CNR 2 ) 2 ][X], in which copper remains in a square-planar geometry, but Cu–S bonds shorten by ca. 0.1 Å. These show a wide range of different structural motifs in the solid-state, varying with changes in anion and dithiocarbamate substituents. Cu(I) complexes, [Cu(S 2 CNR 2 ) 2 ] − , are (briefly) accessible in an electrochemical cell, and the only stable example is recently reported [Cu(S 2 CNH 2 ) 2 ][NH 4 ]·H 2 O. Others readily lose a dithiocarbamate and the d 10 centres can either be trapped with other coordinat- ing ligands, especially phosphines, or form clusters with tetrahedral [Cu(μ 3 -S 2 CNR 2 )] 4 being most common. Over the past decade, a wide range of Cu(I) dithiocarbamate clusters have been prepared and structurally characterised with nuclearities of 3–28, especially exciting being those with intersti- tial hydride and/or acetylide co-ligands. A range of mixed-valence Cu(I)–Cu(II) and Cu(II)–Cu(III) complexes are known, many of which show novel physical properties, and one Cu(I)–Cu(II)–Cu(III) species has been reported. Copper dithiocarbamates have been widely used as SSPs to nanoscale copper sulfides, allowing control over the phase, particle size and morphology of nanomaterials, and thus giving access to materials with tuneable physical properties. The identification of copper in a range of neurological diseases and the use of disulfiram as a drug for over 50 years makes under- standing of the biological formation and action of [Cu(S 2 CNEt 2 ) 2 ] especially important. Furthermore, the finding that it and related Cu(II) dithiocarbamates are active anticancer agents has pushed them to the fore in studies of metal-based biomedicines. Keywords: copper; dithiocarbamate; clusters; nanomaterials; disulfiram; anticancer agents 1. Introduction Copper is an intriguing element with interesting and useful properties and has been widely used by mankind for ca. 6000 years. It is relatively abundant in the earth’s crust (50–60 ppm), being found in both its elemental form and in a range of minerals. Especially pertinent to this review, it is found in a range of copper sulfides including chalcopyrite, digenite, covellite and chalcocite [1]. Copper is an essential element for all living organisms, being a key constituent of the active site of respiratory enzymes cytochrome c oxidases, and a human contains 1.4–2.1 mg of copper per kg of body mass. Balancing copper levels in the body is extremely important, and recently major changes in copper concentrations and its Inorganics 2021, 9, 70. https://doi.org/10.3390/inorganics9090070 https://www.mdpi.com/journal/inorganics