Design, Synthesis, and Structure of Copper Dithione Complexes: Redox‐Dependent Charge Transfer

• Published in: European journal of inorganic chemistry Vol. 2019; no. 46; pp. 4939 - 4948
• Main Authors: Colston, Kyle J., Dille, Sara A., Mogesa, Benjamin, Astashkin, Andrei V., Brant, Jacilynn A., Zeller, Matthias, Basu, Partha
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 15.12.2019
• Subjects: Charge transfer; Coordination compounds; Copper; Crystal structure; Crystallization; Dithione; Dye-sensitized solar cells; Inorganic chemistry; Ligands; Molecular structure; Oxidation dependent charge transfer; Photovoltaic cells; Redox chemistry; Transition metal compounds
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201901222

Redox‐active ligands impart versatility in transition metal complexes, which are attractive for photosensitizers, dye sensitized solar cells, photothermal therapy, etc. Dithiolene (Dt) ligands can transition between fully reduced and fully oxidized states. Herein, we report the syntheses, characterization, crystal structures and electronic properties of four [Cu(R2Dt0)2]+/2+ (R = Me, iPr) complexes, [Cu(iPr2Dt0)2][PF6] (1a), [Cu(iPr2Dt0)2][PF6]2 (1b), and [Cu(Me2Dt0)2][PF6] (2a), [Cu(Me2Dt0)2][PF6]2 (2b), where iPr2Dt0 = N,N′‐diisopropyl‐1,2‐piperazine dithione and Me2Dt0 = N,N′‐dimethyl‐1,2‐piperazine dithione. In addition, the molecular structure of [Cu(iPr2Dt0)2][BF4]2(1c) is also reported. Complexes 1a and 2a crystallized in the triclinic, P1 space group, and 1c crystallized in the monoclinic crystal system, space group C2/c. The single‐crystal X‐ray diffraction measurements show that the Cu(I) complexes have a distorted tetrahedral geometry, whereas the Cu(II) complex exhibits a true square‐planar geometry. Cu(I) complexes exhibit a low energy charge‐transfer band (450–650 nm), which are not observed in Cu(II) complexes. Electrochemical studies of these complexes show both ligand‐ and metal‐based redox couples. Copper complexes of oxidized dithione ligands have been synthesized and characterized. The complexes exhibit intense charge transfer transitions depending on the oxidation state of copper.