Solid-state materials for anion sensing in aqueous solution: highly selective colorimetric and luminescence-based detection of perchlorate using a platinum(ii) salt

Abstract

The PF(6)(-) salt of a platinum(II) complex changes from yellow to red and becomes intensely luminescent upon exposure to aqueous ClO(4)(-). The response is remarkably selective. Spectroscopic changes are consistent with anion exchange resulting in shortening of the intramolecular PtPt distances between the square planar cations.

Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO4–

“…This transition originates from the occupied Pt 5d, O 2p, and Cl 3p orbitals to the unoccupied terpyridyl N 2p, C 2p, and Pt 5d orbitals. These calculations also predict a red-shift of the overall spectra of the [Pt(tpy)Cl]ClO 4 ·H 2 O trimer systems in comparison to that of the [Pt(tpy)Cl]PF 6 25 and the calculated transition at 520 nm is close to the MMLCT chargetransfer energy of 529 nm found by Taylor et al 25 We also note that discrepancies in the calculated results compared to the experimental measurements can be possibly attributed to the use of the PBE DFT functional for the geometry optimization, Inorg. Chem.…”

“…Such specificity also has been noted for detection of aqueous ClO 4 − using [Pt(tpy)Cl](PF 6 ). 25 Even for the analogous 1·AsF 6 salt, the response was less dramatic and definitive. Unlike 1·SbF 6 whose exposure to aqueous TcO 4 − "turns on" the emission upon 532 nm excitation, 1·AsF 6 is already luminescent under these conditions, and a similar exposure merely shifts the emission to longer wavelengths ( Figure S8, Supporting Information).…”

“…This reduction of the Pt···Pt distances and the spatial alignment facilitate metal−metal-to-ligand charge-transfer. 25 Indeed, analysis of the orbitals involved in the electronic transition manifesting as the visible absorption band at 520 nm shows evidence of MMLCT. This transition originates from the occupied Pt 5d, O 2p, and Cl 3p orbitals to the unoccupied terpyridyl N 2p, C 2p, and Pt 5d orbitals.…”

“…Initial calculations were conducted on the [Pt-(tpy)Cl](PF 6 )/ClO 4 − system, which had been experimentally characterized in our previous work. 25 Stacked dimer and trimer models were considered for the [Pt(tpy)Cl]PF 6 and [Pt(tpy)-Cl]ClO 4 ·H 2 O, and the aligned trimer structure was determined to give the best representation of these systems. With this in mind, we used a trimer model for the brominated complexes, which will be described shortly.…”

Chromogenic and fluorogenic chemosensors and reagents for anions. A comprehensive review of the years 2010–2011

“…165). 216 After immersing the red ClO 4 -exposed film into 0.5 M NH 4 PF 6 for 1 day, the original yellow colour was restored. Salt 343 was also fluorescent and emission changes upon addition of anions were studied.…”