Cyclometallated platinum(ii) complexes containing pyridyl-acetylide ligands: the selective influence of lead binding on luminescence

Abstract

The design, synthesis, photophysical properties, and the ion-binding properties of cyclometallated platinum(II) complexes containing pyridyl-appended alkynyl ligands are described. When the pyridyl group is incorporated into an azamacrocycle, a specific response towards lead(II) cations involves a change in the nature of the excited charge transfer state, resulting in the appearance of a low-energy absorption band and a partial quenching of luminescence.

Switching of excited states in cyclometalated platinum complexes incorporating pyridyl-acetylide ligands (Pt–CC–py): a combined experimental and theoretical study

“…The corresponding blue-shift in 3 is a little larger (l em = 566 nm, CH 3 CN solution), qualitatively mirroring the trend in absorption. 31 Computational studies of complexes 1-3…”

“…In a previous preliminary contribution, 31 we described how the complexation of Pb 2+ ions into the macrocyclic cavity of complex 3 (Chart 1) resulted in the appearance of a new low-energy band, concomitant with the extinction of the luminescence. These surprising changes were tentatively attributed to an example, unprecedented for cyclometalated Pt(II) acetylide derivatives, of a switch of CT to the opposite direction upon metal binding, from mixed MLCT/L 0 LCT to ML 0 CT; in other words, the acceptor ligand in the CT process was thought to change in response to binding of the cation.…”

Metal Cation Induced Modulation of the Photophysical Properties of a Platinum(II) Complex Featuring a Dipicolylanilino–Acetylide Ligand

“…The organic layer was dried with MgSO 4 and evaporated under reduced pressure. 6,150.3,148.8,137.3,133.9,122.6,121.1,112.6,110.5,75.6,57.6 ppm. HRMS: calcd.…”

“…For example, a switch from phosphorescence to fluorescence occurs upon addition of lead(II) cations to such a complex incorporating a flavone receptor R. [5] In contrast, binding of lead(II) cations to a pyridyl-based macrocyclic receptor R induces a change in the direction of the charge transfer for the lowest-energy excited state. [6] We decided to extend this design strategy to a nitrogen-based host receptor, the bis(2-picolyl)anilino (DPA) group. This receptor has been widely used for detection of divalent metal cations (e.g., Zn 2+ , Cd 2+ , Cu 2+ ) [7] and was recently incorporated into luminescent Re [8] and cationic Ir [9] complexes in which a 2,2Ј-bipyridine ligand is connected to the receptor by either a vinyl or an ethynyl π linker.…”

Strong red emissions induced by Pt–Pt interactions in binuclear cycloplatinated(II) complexes containing bridging diphosphines

“…The luminescence properties of the cyclometalated platinum(II) complexes make them appropriate candidates for investigation by many research groups . Regarding these properties, cycloplatinated(II) complexes have various applications such as in light‐emitting devices, dye‐sensitized solar cells, photoswitches, photocatalysts and chemical or biochemical sensors . Normally, the emission character in these kinds of complexes originates from triplet intra‐ligand‐centred ( 3 IL), metal‐to‐ligand charge transfer ( 3 MLCT) and metal–ligand‐to‐ligand charge transfer ( 3 MLL′CT) excited states.…”