1,1-dithiolate ligands in coordination chemistry: a study of their electronic and molecular structures

Keramidas, Odysseas Dimitrios (2025) 1,1-dithiolate ligands in coordination chemistry: a study of their electronic and molecular structures. PhD thesis, University of Glasgow.

Abstract

Dithio-ligands are known for their versatility in coordinating to various metal centres. Among them, 1,1- and 1,2-dithiolates stand out for their extended conjugated backbone and unusual redox properties upon coordination. While early studies have shown clear differences in bonding and redox behaviour between the two systems, 1,1-dithiolates remain far less explored.
A series of new NiII and CuII bis-1,1-dithiolate complexes were prepared and compared alongside other homoleptic dithio-complexes. The 1,1-dithiolate ligand scope was expanded to the unprecedented para-R- phenylacetonitrile dithiolate R-padt2− derivatives (R = OMe, H, Cl, meta-CF3, para-CF3, CN, NO2), enabling a systematic variation of the electron-donating and electron-withdrawing substituents on the backbone. All complexes were characterised by ligand-specific bands in their IR spectra and chemical shifts in their 1H/13C NMR spectra. In their EPR spectra, the characteristic profile of a CuS4 centre was observed and their electronic absorption spectroscopy was characterised by ligand-to-ligand charge transfer (LLCT) as well as ligand-field (LF) transitions. Additionally, a reversible oxidation process was observed during cyclic voltammetry experiments and was proved to be formally metal-centred. The square-planar structure was confirmed by X-ray crystallography, and DFT calculations provided further insight into their MO energy levels and bonding. By using the Hammett and pKa values, predictable substituent effects were confirmed across the series, creating a correlation between the molecular and electronic structure of these complexes. Oxidation of the CuII 1,1-dithiolate complexes stabilised the formal CuIII state and the potentials were directly affected by the substituent effects of the backbone groups of each 1,1-dithiolate.
The final part of the thesis extended to studying the chemistry of 1,1-dithiolate ligands in heteroleptic NiII and CuII complexes containing α-diimines and the non-conjugated N-donor ligand tetramethyl ethylenediamine (TMEDA). The NiII 1,1-dithiolate–diimine complexes exhibited distinct LLCT transitions containing the HOMO and LUMO, as well as diimine-based reductions. The energy of the LLCT and the potentials of the reductions showed correlations with the Hammett and pKa values corresponding to the α-diimine and 1,1-dithiolate coordinated ligands. Electron-withdrawing substituents on the α-diimine ligands stabilised the π* orbitals, leading to red-shifted LLCT transitions and more positive reduction potentials, whereas electron-donating groups had the opposite effect.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from School of Chemistry, University of Glasgow.
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Sproules, Dr. Stephen and Moiras, Professor Haralampos
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85659
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 06 Jan 2026 16:11
• Last Modified: 06 Jan 2026 16:23
• Thesis DOI: 10.5525/gla.thesis.85659
• URI: https://theses.gla.ac.uk/id/eprint/85659