Synthesis, Fluorescence, and Two‐Photon Absorption of Bidentate Phosphane Oxide Derivatives: Complexation with Pb²⁺ and Cd²⁺ Cations

Abstract

A series of fluorescent phosphane oxide derivatives based on diphenylphosphanoethane (DPPE) and diphenylphosphanomethane (DPPM) skeletons has been prepared by means of Grignard reactions and Sonogashira cross-couplings. The photophysical properties and the linear and nonlinear spectra of these compounds have been investigated. An edge-to-face conformation resulting in the formation of an excimer was confirmed by fluorescence lifetime measurements of these multichromophoric derivatives. Upon complexation with heavy metal ions such as Pb2+ and Cd2+, a red shift of the one- and two-photon excitation spectra was observed in the absorption and emission spectra. Furthermore, enhancement of the electron-withdrawing character of the phosphane oxide resulted in a significant enhancement of the two-photon absorption cross-section, leading to the first biphotonic Cd2+ sensors combining high affinity for Cd2+, large two-photon absorption cross-sections, and significant enhancement of the two-photon excited fluorescence in the presence of the cation. Such derivatives are highly promising for incorporation into devices for the detection of heavy metal ions in water and effluents.

Zweiphotonenabsorption und das Design von Zweiphotonenfarbstoffen

“…[86,87] In 74 [85] wird die chelatisierende Endgruppe des Chromophors durch Bindung von Zn 2+ an die Pyridinringe zu einem stärkeren Elektronenakzeptor, sodass d steigt. Dieser Ansatz wurde auf Chelatliganden für Schwermetallkationen einschließlich Quecksilber [88] und Cadmium [89] sowie auf das Anion Fluorid ausgedehnt, [90] und auch pH-Sonden nutzen dieses Prinzip.…”

Fluorene-Based Metal-Ion Sensing Probe with High Sensitivity to Zn2+ and Efficient Two-Photon Absorption

“…Well-known advantages of 2PA processes, such as a higher excitation selectivity, deeper penetration, and photochemical stability of chemosensors under IR irradiation,5–7 facilitate measurements of metal ion concentrations and their volumetric distribution in the medium 8–10. To date, these investigations are of great interest for biophysical and biomedical applications,4, 11–14 along with the development of new environmental sensing 2PA materials 7, 9, 15.…”

“…High Ca 2+ affinity together with efficient two-photon action cross sections δ 2 PA ·Φ ~100 GM ( δ 2 PA and Φ are the 2PA cross section and fluorescence quantum yield, respectively) make such probes suitable in quantitative determination of Ca 2+ in biological samples. New 2PA sensors for Pb 2+ and Cd 2+ based on phenylethynyl phosphine oxide derivatives with several fluorescent arms were recently reported 5. These compounds are of interest as the first efficient 2PA sensors for Cd 2+ and possess potential for the detection of toxic heavy metals in the environment.…”

New Two-Photon-Absorbing Probe with Efficient Superfluorescent Properties

“…Directional synthesis of new fluorescent labels and comprehensive investigations of their linear photophysical, nonlinear-optical and photochemical properties can appreciably extend the abilities of bioimaging applications. High fluorescence quantum yield, Φ , large values of 2PA cross sections, δ 2 PA , as well as their product, $\Phi \cdot {\delta }_{2PA}={\delta }_{2PA}^{\mathit{\text{act}}}$ (so-called two-photon action cross section8), and photochemical stability under high intensity laser irradiation are the primary properties required for 2PFM-based applications of organic chromophores 9-11. A number of potential fluorescence labels with suitable 2PA properties have been synthesized for two-photon bioimaging use (see, e.g., nonlinear optical properties of water soluble [2.2]paracyclophane-based fluorophores with high values of ${\delta }_{2PA}^{\mathit{\text{act}}}$,8 2,6-bis( p -dialkylaminostyryl)anthracene derivatives,12 and dipyrrylmetheneboron difluoride compounds13).…”