Cobalt(II), Nickel(II), Copper(II), and Zinc(II) Complexes with ap-tert-Butylcalix[4]arene Fitted with Phosphinoyl Pendant Arms

Luminescent Fluorene-Based Bis-Pyrazolyl Aniline Ligand for Aluminum Detection

The design, synthesis, and photophysical properties of a new fluorene-based fluorescent chemosensor, 4-((E)-2-(2-(benzo[d]thiazol-2-yl)-9,9-diethyl-9H-fluoren-7-yl)vinyl)-N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzenamine (AXF-Al), is described for the detection of Al3+. AXF-Al exhibited absorption at 382 nm and strong fluorescence emission at 542 nm (fluorescence quantum yield, Φ F, of 0.80). The capture of Al3+ by the pyrazolyl aniline receptor resulted in nominal change in the linear absorption (372 nm) but a large hypsochromic shift of 161 nm in the fluorescence spectrum (542 to 433 nm, Φ F = 0.88), from which Al3+ was detected both ratiometrically and colorimetrically. The addition of other metal ions, namely Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg 2+ and Pb2+, produced only minimal changes in the optical properties of this probe. The emission band of this probe was also accessed by two-photon excitation in the near-IR, as two-photon absorption (2PA) is important for potential applications in two-photon fluorescence microscopy (2PFM) imaging. The 2PA cross section of the free fluorenyl ligand AXF-Al was 220 GM at 810 nm and 235 GM at 810 nm for the Al-ligand complex, practically useful properties for 2PFM.

Novel hydrophilic bis(1,2,3-triazolyl)fluorenyl probe for in vitro zinc ion sensing

A hydrophilic bis(1,2,3-triazolyl)fluorene derivative was synthesized as a multi-photon-absorbing, zinc-ion-sensing fluorescent probe. The fluorescence response was approximately five-fold greater in presence of Zn(2+), resulting in a large binding constant (1 × 10(9)) for a 1:2 ligand to zinc complex. A four-fold increase in the two-photon absorption cross section was achieved upon binding Zn(2+). In vitro two-photon fluorescence microscopy imaging revealed a significant fluorescence increase upon introduction of Zn(2+) into HeLa cells and reversible Zn(2+) binding, demonstrating the potential of this probe for zinc ion sensing.

Fluorescence Sensing of Zinc and Mercury Ions with Hydrophilic 1,2,3-Triazolyl Fluorene Probes

The ability to rapidly detect biologically and environmentally significant metal ions such as zinc and mercury is important to study a number of important cellular and environmental processes. Hydrophilic bis(1,2,3-triazolyl)fluorene-based derivatives, containing a 1,2,3-triazole-based recognition moiety, were synthesized through Click chemistry and characterized by UV-vis absorption, fluorescence emission, and two-photon absorption as new fluorescence sensing probes, selective for Zn(2+) and Hg(2+) ions. The UV-vis absorption and fluorescence emission spectra of the complexes exhibited blue-shifted absorption and emission spectra upon chelation to Zn(2+) and Hg(2+) ions, resulting in ca. two-fold enhancement in fluorescence. Fluorometric titration revealed that 1:2 and 1:3 ligand to metal complexes formed with binding constants of 10(8) and 10(16) for Zn(2+) and Hg(2+), respectively. The two-photon absorption cross sections for the probes and probe-metal ion complexes ranged from 200-350 GM at 800 nm. These novel fluorescent compounds may have potential as new metal ion sensors to probe cellular and biological environments.