Enhanced phosphorescence of Pd(II) and Pt(II) complexes adsorbed onto Laponite for optical sensing of triplet molecular dioxygen in water

Abstract

Two isoleptic complexes involving Pd(II) and Pt(II) centres with a tetradentate luminophoric ligand were adsorbed onto Laponite (LAP), yielding H2O-dispersible nanohybrids with remarkable photoexcited state properties. The adsorption promoted rigidification of the coordination compounds and suppression of roto-vibrational deactivation pathways, thus enhancing the performance of the molecular species. Interestingly, room temperature phosphorescence was achieved in the case of the Pd(II)-containing nanohybrid along with a marked 3O2 sensitivity, whereas the photoluminescence of the Pt(II)-based material showed only a mild dependence on the presence of 3O2 while reaching up to 37% quantum yield.

Luminescence and Palladium: The Odd Couple

“…The complex 80 from Figure 22 was used in a subsequent study [ 89 ] aiming an enhanced phosphorescence by adsorption onto Laponite. However, in this case, the photophysical properties were not improved by aggregation in the same way as in the previous article.…”

Room-temperature luminescence from Pd(ii) and Pt(ii) complexes: from mechanochromic crystals to flexible polymer matrices

“…For analogous Pd(II) complexes in fluid solution, an emission originated from weakly coupled aggregates with LCexcimer character has been previously reported, where the luminescence spectra present a red-shifted and less resolved vibrational progression. 17,36,37,41,44 The results reported herein suggest that the emission in fluid solution is originated from a mixture of monomeric and aggregated species; since the emission of the monomers is weak, even traces of the intrinsically shielded aggregates are detected. Our attempt to suppress aggregation by further dilution only led to bad signal-to-noise ratios, as the Pd(II) have an inherently low photoluminescence intensity, particularly at r.t.…”

“…Herein, we introduced n-hexyloxy moiety, which enabled us to increase the solubility of the resulting complexes, particularly in the case of the Pd(II) complexes showing a lower solubility than their Pt(II) analogues. 44 Interestingly, no metal-metal interactions are observed in the crystals.…”

Comparison of Phosphorescent Pt(II) Complexes with C^N^N vs N^N^N Chelators and Caffeine‐Based NHC‐co‐ligands†

“…Owing to the d 8 ‐electron configuration of the metal center, Pt(II) complexes tend to have a square‐planar coordination environment. As a consequence of the planar geometry, the Pt‐Pt distances can reach values below 3.5 Å, and thereupon the d z 2 orbitals of the Pt(II) centers can interact with each other, leading to a red‐shifted emission from aggregates, if compared with the monomeric species (37–40). The emerging red‐shifted luminescence from aggregated species stems from excited states with metal–metal to ligand–ligand charge‐transfer character (MMLLCT, d z 2 ‐ d z 2 ‐ π *‐ π *), whereas the emission of the monomers occurs mostly from triplet metal‐perturbed ligand‐centered states ( 3 MP‐LC) as admixtures of ligand‐centered (LC, π‐π *) and metal‐to‐ligand charge‐transfer (MLCT, d ‐ π *) configurations (10,11,41–43).…”

“…Owing to the d 8 -electron configuration of the metal center, Pt(II) complexes tend to have a square-planar coordination environment. As a consequence of the planar geometry, the Pt-Pt distances can reach values below 3.5 Å, and thereupon the d z 2 orbitals of the Pt(II) centers can interact with each other, leading to a red-shifted emission from aggregates, if compared with the monomeric species (37)(38)(39)(40). The emerging red-shifted luminescence from aggregated species stems from excited states with metal-metal to ligand-ligand charge-transfer character (MMLLCT, d z 2 -d z…”