Fluorene-Based Metal-Ion Sensing Probe With High Sensitivity To Zn \u3csup\u3e2+\u3c/sup\u3e And Efficient Two-Photon Absorption

The photophysical, photochemical, two-photon absorption (2PA) and metal ion sensing properties of a new fluorene derivative (E)-1-(7-(4-(benzo[d]thiazol-2- yl)styryl)-9,9-bis(2-(2-ethoxyethoxy)ethyl)-9H-fluoren-2-yl)-3-(2-(9,10,16,17, 18,19,21,22,23,24-decahydro-6H dibenzo[h,s][1,4,7,11,14,17] trioxatriazacycloicosin-20(7H)-yl)ethyl)thiourea (1) were investigated in organic and aqueous media. High sensitivity and selectivity of 1 to Zn 2+ in tetrahydrofuran and a water/acetonitrile mixture were shown by both absorption and fluorescence titration. The observed complexation processes corresponded to 1:1 stoichiometry with the range of binding constants ∼(2-3) - 105 M-1. The degenerate 2PA spectra of 1 and 1/Zn 2+ complex were obtained in the 640-900 nm spectral range with the maximum values of two-photon action cross section for ligand/metal complex ∼(90-130) GM, using a standard two-photon induced fluorescence methodology under femtosecond excitation. The nature of the 2PA bands was analyzed by quantum chemical methods and a specific dependence on metal ion binding processes was shown. Ratiometric fluorescence detection (420/650 nm) provided a good dynamic range (10-4 to 10-6 M) for detecting Zn 2+, which along with the good photostability and 2PA properties of probe 1 makes it a good candidate in two-photon fluorescence microscopy imaging and sensing of Zn ions. © 2010 American Chemical Society

Solvent Effect On The Steady-State Fluorescence Anisotropy Of Two-Photon Absorbing Fluorene Derivatives

The effect of solvent polarity on the fluorescence properties of several two-photon absorbing fluorene derivatives was investigated. A strong solvatochromic effect was observed for symmetrical fluorene compound, which can be explained by large changes in the quadrupolar moment under excitation. Limiting values of excitation anisotropy of the investigated fluorenes exhibited a dependence on solvent polarity, and the angles between the absorption and emission transition dipole moments decrease in polar solvents by more than a factor of two. © 2006 Elsevier B.V. All rights reserved