Photophysical Properties and Kinetic Studies of 2-Vinylpyridine-Based Cycloplatinated(II) Complexes Containing Various Phosphine Ligands

A series of cycloplatinated(II) complexes with general formula of [PtMe(Vpy)(PR3)], Vpy = 2-vinylpyridine and PR3 = PPh3 (1a); PPh2Me (1b); PPhMe2 (1c), were synthesized and characterized by means of spectroscopic methods. These cycloplatinated(II) complexes were luminescent at room temperature in the yellow–orange region’s structured bands. The PPhMe2 derivative was the strongest emissive among the complexes, and the complex with PPh3 was the weakest one. Similar to many luminescent cycloplatinated(II) complexes, the emission was mainly localized on the Vpy cyclometalated ligand as the main chromophoric moiety. The present cycloplatinated(II) complexes were oxidatively reacted with MeI to yield the corresponding cycloplatinated(IV) complexes. The kinetic studies of the reaction point out to an SN2 mechanism. The complex with PPhMe2 ligand exhibited the fastest oxidative addition reaction due to the most electron-rich Pt(II) center in its structure, whereas the PPh3 derivative showed the slowest one. Interestingly, for the PPhMe2 analog, the trans isomer was stable and could be isolated as both kinetic and thermodynamic product, while the other two underwent trans to cis isomerization.

The Exchange of Cyclometalated Ligands

Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a cyclometalated compound and an incoming ligand that replaces a previously cyclometalated ligand to form a new metalacycle: + H-C*~Z ⇄ + H-C~Y. Originally discovered for PdII complexes with Y/Z = N, P, S, the exchange appeared to be a mechanistically challenging, simple, and convenient routine for the synthesis of cyclopalladated complexes. Over four decades it was expanded to cyclometalated derivatives of platinum, ruthenium, manganese, rhodium, and iridium. The exchange, which is also questionably referred to as transcyclometalation, offers attractive synthetic possibilities and assists in disclosing key mechanistic pathways associated with the C–H bond activation by transition metal complexes and C–M bond cleavage. Both synthetic and mechanistic aspects of the exchange are reviewed and discussed.

The Impact of Cyclometalated and Phosphine ligands on the Luminescence Properties of Cycloplatinated(II) Complexes: Photophysical and Theoretical Investigations

The present work investigates the synthesis and characterization of a series of cycloplatinated(II) complexes, bearing the dfppy (2-(2,4-difluorophenyl)pyridine) cyclometalated ligand with the general formula of [Pt(dfppy)(Cl)(L)], L = dmso, dimethyl...

Dinuclear platinum(ii) complex dominated by a zig-zag-type cyclometalated ligand: a new approach to realize high-efficiency near infrared emission

Two new zig-zag type di- and mono-nuclear platinum(ii) complexes of (BuPh-BDIQ)Pt2(dpm)2 and (BuPh-BDIQ)Ptdpm were synthesized and characterized by using a zig-zag type cyclometalating ligand BuPh-BDIQ.

How do ligands influence the quantum yields of cyclometalated platinum(ii) complexes, a theoretical research study

Quantum yield differences were explained by the cyclometalated ligand, molecular rigidity and ligand-field strength.