Cyclometallated ruthenium(II) carbonyl complexes with 1-pyrenaldehyde 4-R-3-thiosemicarbazones: Regioselective ruthenation of the 1-pyrenyl group

Abstract

A facile method for the synthesis of a series of cyclometallated ruthenium(II) carbonyl complexes with 1-pyrenaldehyde 4-R-3-thiosemicarbazones (H\(_{2}\textit {L}^{\mathrm {n}}\) where the two H’s represent the dissociable thioamide and pyrenyl protons; R = H, Me and Ph) has been described. The characterization of the complexes having the general molecular formula trans-[Ru(Ln)(CO)(EPh3)2] (where E = P or As) were accomplished by elemental (CHN) analysis, magnetic susceptibility and spectroscopic (ESI-MS, IR, UV-Vis, emission and 1H-NMR) measurements. Electronic spectra of the complexes display multiple strong absorptions in the range 440–224 nm due to intraligand transitions. All the complexes exhibit emission bands that are characteristic of ligand centred emissive states. X-ray diffraction studies with representative complexes reveal a pincer-like 5,5-membered fused chelate rings forming CNS coordination mode of the thiosemicarbazonate ligand (Ln)2- via regioselective activation of 1-pyrenyl ortho C–H and formation of a distorted octahedral C2NSE2 coordination sphere around the ruthenium(II) centre. Cyclometallated ruthenium(II) carbonyl complexes with 1-pyrenaldehyde 4-R-3-thiosemicarbazones (H2Ln) are reported. In these complexes of formula trans-[Ru(Ln)(CO)(EPh3)2] (E = P or As), the 1-pyrenyl group of (Ln)2- is regioselectively ortho metallated and it acts as pincer-like CNS-donor. All the complexes are diamagnetic and they display ligand centred absorption and emission bands.