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

Abstract

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 Zn2+ in THF and a water/ACN 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:Zn2+ 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 Zn2+, 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.

Metal-Ion-Responsive Fluorescent Probes for Two-Photon Excitation Microscopy

“…In the former solvent, the 2PA cross section decreased from 130 to 65 GM (λ = 780 nm) upon Zn(II)-binding (Table 4), whereas in the latter the cross section remained essentially constant around 50 GM (λ = 780 nm) 61. As observed for 29 , the peak emission was blue-shifted by more than 30 nm upon saturation with Zn(II), rendering 30 potentially suitable for ratiometric imaging of Zn(II) in biological systems.…”

Two‐Photon Absorption and Time‐Resolved Stimulated Emission Depletion Spectroscopy of a New Fluorenyl Derivative

“…An unsymmetrical compound 1 exhibited two well-defined 2PA bands at λ ex ≈ 640–680 nm and 880–900 nm, with maximal cross-sections δ 2 PA ≈ 200–350 GM and 400–600 GM, respectively, and revealed a weak dependence of 2PA efficiency on solvent polarity. The shape of these spectra is typical for unsymmetrical fluorene derivatives, [39, 40] where a relatively strong2PA band overlaps with the main one-photon–allowed long-wavelength absorption contour. The nature of this band can be attributed to the possible changes in the stationary dipole moment of 1 , Δ μ 01 , under electronic excitation, S 0 → S 1 , in accordance with the expression, based on simplified three-level model of 2PA processes: [41] …”

Quantum chemical and master equation study of OH + CH2O → H2O + CHO reaction rates in supercritical CO2 environment

“…Gaussian 2009 was used for quantum chemical calculations, 23 and MOLDEN was used to visualize the results. 24 Density functional theory (DFT) was shown to be useful in several areas of chemistry, [25][26][27][28][29] providing the best accuracy to computational cost ratio. [30][31][32][33] In this work, all geometry optimizations and ZPE calculations were performed using M11 density functional, 34 Grimme's 3-body dispersion correction (GD3), 35 and 6-311G(d,p) basis set.…”