Iridium(III) complexes were synthesized with the general form [Ir(L^1–6)₂(bpy)]PF₆ (bpy = 2,2′-bipyridine), where ligands (LH^1–6) are based on the N-functionalization of 2-phenyl-N-aryl/alkyl-quinoline-4-carboxamides. Single crystal X-ray diffraction studies were undertaken on two complexes, which show that each adopts a distorted octahedral coordination geometry with retention of the expected trans-N, cis-C arrangement of the cyclometalated ligands. Electrochemical studies confirmed the subtle perturbing of theIr^III/IV redox couple as a function of ligand structure. Scalar relativistic DFT studies provided qualitative descriptions of the HOMO and LUMO energy levels of the six complexes. The calculated HOMO is generally located over the Ir(5d) centre (about 45 %) and the amide-substituted 2-phenylquinoline ligand, whilst the LUMO is localized over the ancillary 2,2′-bipyridine ligand. Similar calculations for [Ir(L⁶)₂(bpy)]PF₆ revealed a different HOMO depiction with locale on the pendant chromophores. A companion calculation, using an alternative relativistic approach (i.e. incorporating spin–orbit coupling effects) conducted on a simplified model compound, provided HOMO/LUMO depictions that are essentially identical to the non-relativistic calculation, which predicts long-lived phosphorescent emission from the HOMO–LUMO transition. Luminescence studies showed the predictable and tunable phosphorescent emission wavelengths between 585–627 nm. The experimental and theoretical studies suggest that the electronic nature of the pendant amide substituent influences the energy of the emitting state – the strongly electron-withdrawing groups bathochromically shift the luminescence wavelength.

The syntheses of six new mixed P/S-donor two-coordinate Au^I complexes are described. The complexes incorporate a pteridinyl ligand coordinated through a thiolate donor, and an ancillary tertiary phosphane (PPh₃ or PCy₃). The mercapto-pteridine ligands (L¹–L³) differ in the nature of the substituents on the pteridine core. An X-ray crystal structure was obtained for one of the examples, [(L¹)Au(PPh₃)], revealing weak intermolecular interactions between two molecules of the complex: π–π contacts between aromatic rings appear to support an intermolecular Au–Au contact of approximately 3.05 Å. All of the complexes are luminescent in solution, with emission arising from tuneable ligand-based excited states, and characterised as a perturbed fluorescence in nature. In this context, complexes of L³ displayed useful visible absorption and emission. Preliminary cytotoxicity assessments were conducted using the MTT assay, and the complexes each displayed impressive anti-proliferative activities (IC₅₀ < 5 μM) with respect to four different adenocarcinoma cell lines (MCF7, A549, PC3 and LOVO). For a given pteridine moiety, triphenylphosphane appeared to be the co-ligand of choice for enhancing biological activity.

The syntheses of the two tetraazamacrocyclic ligands L1 and L2 bearing a [(methoxy-2-nitrophenyl)amino]carbonyl chromophore, i.e., an N-(methoxy-2-nitrophenyl)acetamide moiety, together with their corresponding lanthanide-ion complexes are described. A combined spectroscopic (UV/VIS, ¹H-NMR), structural (X-ray), and theoretical (DFT) investigation revealed that the absorption properties of the chromophores were dictated by the extent of electronic delocalisation, which in turn was determined by the position of the MeO substituent at the aromatic ring. X-Ray crystallographic studies showed that when attached to the macrocycle, both isomeric forms of the N-(methoxy-2-nitrophenyl)acetamide unit can participate in coordination, via the CO, to an encapsulated potassium cation. Luminescence measurements confirmed that such a binding mode also exists in solution for the corresponding lanthanide complexes (q ca. ≤1), with the para-MeO derivative allowing longer wavelength sensitization (λ_ex 330 nm).