Solid- and Solution Phase Synthesis of Diiminedichloroplatinum(II) Complexes

Tuning PtII -Based Donor-Acceptor Systems through Ligand Design: Effects on Frontier Orbitals, Redox Potentials, UV/Vis/NIR Absorptions, Electrochromism, and Photocatalysis

Asymmetric platinum donor-acceptor complexes [(pimp)Pt(Q2- )] are presented in this work, in which pimp=[(2,4,6-trimethylphenylimino)methyl]pyridine and Q2- =catecholate-type donor ligands. The properties of the complexes are evaluated as a function of the donor ligands, and correlations are drawn among electrochemical, optical, and theoretical data. Special focus has been put on the spectroelectrochemical investigation of the complexes featuring sulfonyl-substituted phenylendiamide ligands, which show redox-induced linkage isomerism upon oxidation. Time-dependent density functional theory (TD-DFT) as well as electron flux density analysis have been employed to rationalize the optical spectra of the complexes and their reactivity. Compound 1 ([(pimp)Pt(Q2- )] with Q2- =3,5-di-tert-butylcatecholate) was shown to be an efficient photosensitizer for molecular oxygen and was subsequently employed in photochemical cross-dehydrogenative coupling (CDC) reactions. The results thus display new avenues for donor-acceptor systems, including their role as photocatalysts for organic transformations, and the possibility to introduce redox-induced linkage isomerism in these compounds through the use of sulfonamide substituents on the donor ligands.

The synthesis and pH-dependent behaviour of Re(CO)3 conjugates with diimine phenolic ligands

In this report we present a study of a series of Re(CO)3 pyridine-imine complexes with pendant phenol groups. We investigated the effects of the position of the phenol hydroxyl group (para, meta or ortho to the imine) on the steric and electronic characteristics of a series of Re(CO)3X(pyca-C6H4OH) compounds, where X = Cl, Br and pyca = pyridine-2-carbaldehyde imine. These compounds can be generated either via ligand synthesis followed by metal chelation (compound 4) or via a one-pot method (compounds 2, 3, 5 and 6). All six compounds show striking differences in pH-dependent UV-visible absorption based on the position of the phenol hydroxyl group.

Rhenium(I) and platinum(II) complexes with diimine ligands bearing acidic phenol substituents: hydrogen-bonding, acid-base chemistry and optical properties

Tricarbonylchloro-rhenium(i) (1-4) and catecholato-platinum(ii) complexes (6, 7) of diimine ligands bearing phenol and O-protected phenol substituents have been prepared and fully characterised including single crystal structure analyses of 1, 4 and 7. The redox behaviour of the catecholato platinum(ii) complexes 6 and 7 has been probed by cyclic voltammetry, preparative oxidation and EPR spectroscopy (6˙(+), 7˙(+)). Reversible deprotonation of the hydroxy substituted complexes 1, 3 and 6 to 1(-), 3(-) and 6(-) resulted in significant changes in their electronic spectra. The luminescence properties of the diamagnetic complexes have been investigated using emission spectroscopy. DFT and TD-DFT calculations were invoked to shed some light onto the geometric and electronic structures as well as the experimental spectroscopic properties of the neutral complexes 1-7, the radical cations 6˙(+) and 7˙(+) and the conjugate bases 1(-), 3(-) and 6(-).