Synthesis and characterisation of copper-based monometallic and bimetallic (ir-cu, ru-cu) complexes

Otaru, Habiba 2024. Synthesis and characterisation of copper-based monometallic and bimetallic (ir-cu, ru-cu) complexes. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis describes the synthesis of monometallic Cu(II) complexes derived from chiral diamine and triamine ligands, and Ir(III)-Cu(II) and Ru(II)-Cu(II) heterobimetallic complexes derived from ditopic ligands. The monometallic copper(II) complexes derived from chiral diamine and triamine ligands have been designed as model complexes from which the heterobimetallic complexes were derived. The ditopic ligands used for the heterobimetallic complexes have been carefully designed and synthesised such that one of the two binding sites is made up of polypyridyl unit that can support and modulate the photophysical properties metal ions such as Ir(III) and Ru(II), while the other site is comprised of chiral amine ligand system that can act as auxiliary ligand for copper catalysis. The ability of the heterobimetallic complexes to act as catalysts in the photoredox-assisted Chan-Evans-Lam coupling reaction was investigated using EPR and Mass Spectrometric techniques. The syntheses and characterisation of chiral diamine and triamine ligands and their corresponding Cu(II) complexes were discussed in Chapter 3. Chiral diamine ligands L1 and L2 with R configurations featuring primary and tertiary amine functionalities were obtained from commercial sources. Condensation reaction between 2-pyridine carboxaldehyde and L1 and L2 respectively in ethanol under refluxing condition and subsequent reduction of the condensation products with NaBH4 furnished Chiral triamine ligands L3 and L4 in good yields. These ligands have been fully characterised using 1H, 13C{1H} and 2D NMR techniques, UV/Visible spectroscopy, and Mass Spectrometry. These ligands have been used for the synthesis of six Cu(II) complexes, CuL1, CuL2, CuL3a, CuL3b, CuL4a and CuL4b, which are blue, purple, turquoise blue, green, blue, and green colours respectively. These paramagnetic Cu(II) complexes have been characterized by UV/Visible spectroscopy, EPR spectroscopy, single-crystal X-ray diffraction and High-Resolution Mass Spectrometry. In Chapter 4, the synthesis of ditopic ligands and Ir(III)-Cu(II) heterobimetallic complexes were discussed. The ditopic ligands were synthesised by the functionalisation of bipyridine and 1,10-phenanthroline moieties. Regioselective addition of chiral diamines to 5-bromo-2,2’- bipyridine was achieved by Buchwald-Hartwig amination catalysed by the combination of tris(dibenzylideneacetone)palladium(0) and 2, 2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap) in toluene. The resulting functionalised bipyridine ligands, L5 and L6 have been characterised by 1H, 13C{1H} and 2D NMR spectroscopy and HRMS. These ligands were used to assemble mononuclear cyclometalated [Δ-(R)/Ʌ-(R)]-Ir(III) complexes. These chiral-at- v iridium complexes were obtained by combining iridium(III) starting materials bearing two labile ligands such as bis(2-phenylpyridine-C,N’)-bis(acetonitrile)iridium(III) tetrafluoroborate and dichlorotetrakis(2-(2-pyridyl)phenyl)diiridium(III) with the appropriate C1-functionalised ligands (L5 and L6) with chiral amine appendages which will serve as the coordination site for copper(II) ion. The ditopic ligand, L7, derived from 1,10-phenanthroline, was synthesised in a different way as the second metal binding domain containing N and P donor atoms. This could lead to poor selectivity during the initial Ir(III) coordination due to the soft P donor atom, which could make the N, P site compete with the phenanthroline binding site. We circumvented this by first synthesising monometallic cyclometalated Ir(III) complex with 1,10-phenanthroline-5-amine. This monometallic precursor, bearing amine functionality on the 1,10-phenanthroline, was functionalised post-complexation by condensation reaction with 2-(diphenylphosphaneyl)benzaldehyde to obtain L7. Lastly, the potential of these heterobimetallic complexes to undergo single electron transfer (SET) from Cu(II) to Ir(III) and Cu(II) to Ru(II) in order to generate Cu(III) ion, which is a required intermediate that facilitates the reductive elimination of C-N coupled product in Chan-Evans-Lam amination reaction was explored in situ using EPR techniques and Mass spectrometry.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Chemistry
Date of First Compliant Deposit:	9 April 2025
Last Modified:	10 Apr 2025 08:14
URI:	https://orca.cardiff.ac.uk/id/eprint/177499

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