Room temperature phosphorescence characteristics of platinum(II) chelates with 8-quinolinol derivatives in aqueous micellar solutions

Phosphorescence from platinum(II) chelates of 8-quinolinol (8-Q), 5-sulfo-8 -quinolinol (SQ), and 5-sulfo-7-iodo-8-quinolinol (SIQ) at ca. 630 nm is st rongly enhanced in certain kinds of surfactant micellar solutions in the pr esence of sulfite ion as a chemical de-oxygenator. Among these ligand syste ms the [Pt(II)(SIQ)(2)](2-) chelate is most highly phosphorescent with a qu antum yield of 0.028 in n-dodecyl-beta-D-maltoside (DOM) micelles at 298 K because of the heavy-atom effect of iodine. The emission due to the dianion ic 1 : 2 chelates of SQ and SIQ are strongly facilitated either in cationic and non-ionic surfactant micelles such as hexadecyltrimethylammonium chlor ide (CTAC) or bromide (CTAB), Brij-35, Triton X-100, and DOM in sharp contr ast to the slight sensitization by sodium dodecylsulfate (SDS) micelles of similar charge. Anionic SDS micelles do not work well even for the uncharge d [Pt(II)(8-Q)(2)] chelate. The emission decay lifetimes of the chelates in de-oxygenated micellar solutions are in a similar range of 28 mu s with CT AB to 37 mu s with DOM, at 298 K. In a pre-micellar region of CTAC, below t he critical micelle concentration, the chelate is also luminescent as the i on-pair of (CTA)(2)[Pt(II)(SIQ)(2)]. The highly sensitive phosphorescence d etection of Pt(II) ion is achievable using the SIQ-DOM-sulfite system, givi ng a 3 sigma detection limit of 30 nM or 6 ng Pt ml(-1). (C)2000 Elsevier S cience B.V. All rights reserved.