Search

A new 1,10-phenanthroline (Phen) derivative, 3,8-bis(5-methylthiophen-2-yl)-1,10-phenanthroline (PHT1), has been synthesized and fully characterized including by single-crystal X-ray structure analysis. The electron-donating effects of the two 5-methylthiophene groups lead to distinctive fluorescence emission enhancement on complexation with Zn2+ compared with non-emissive Phen. However, PHT1 shows stronger Zn2+-sensing ability than 3,8-bis(thiophen-2-yl)-1,10-phenanthroline (PHT0) or 3,8-bis(3-methylthiophen-2-yl)-1,10-phenanthroline (PHT2) and longer-wavelength fluorescence emission ( λem = 461 nm), which is vital for studies of living systems, mainly because of the lower steric hindrance and the electron-donating effects of the 5-methyl groups on the thiophene rings. More interestingly, PHT1 displays high selectivity towards Zn2+ over a broad range of pH and has an extremely low detection limit (5 ppb). An approximately 51-fold Zn2+-selective CHEF response has been attributed to the formation of a 1:2 metal-ligand complex, and the association equilibrium constant ( Kass0) of [Zn(PHT1)2](ClO4)2 was determined to be 3.4 × 1012. Anionic effects and variations in the 1H NMR spectra before and after zinc(II) ion complextion were observed. Moreover, the ability of probe PHT1 to sense Zn2+ within living HL-60, yeast, and HepG-2 cells has been explored, and the Zn2+-probing process in living cells was found to be reversible with a zinc chelator solution of N, N, N′, N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN). [ABSTRACT FROM AUTHOR]