Variation of the Emission Efficiency and Wavelength from Fluorescent Zinc Salen Complexes upon Systematic Structural Modifications

Abstract

Understanding the photophysical properties of metal salen complexes is not straightforward because the emission efficiency is altered irregularly upon structural modifications. The present study prepared zinc salen complexes with systematic structural variations to pinpoint critical factors to determine the emission efficiency. One of the important experimental observations is the regiochemistry of a phenolate substituent affecting emission efficiency from a salicylidene fluorophore, which is nicely assigned as arising from the photoexcited electronic structure of metal salen complexes. Another significant finding is the thermal fluctuation of a salen ligand arising from the mismatched ligand–metal interaction, which has a significant impact on fluorescence lifetime. The present study sheds light on hidden factors that alter photophysical properties of a metal salen complex, which provide valuable insights into designing new photoactive salen ligands.

A Zinc(II) Schiff Base Complex as Fluorescent Chemosensor for the Selective and Sensitive Detection of Copper(II) in Aqueous Solution

“…As the formation of the paramagnetic Cu(salmal) complex upon transmetalation of 1 involves a quenching of the fluorescence, complex 1 has also been involved for the fluorometric detection of Cu 2+ . However, although the 5,5 -t-butyl substitution in Zn(salmal) enhances its solubility, on the other hand it leads to a very poor fluorescence, presumably for the specific substitution pattern in the 5,5 -positions of the salicylidene rings [38]. In fact, the resulting fluorometric sensitivity of 1 towards Cu 2+ is slightly lower than that obtained from the colorimetric detection [37].…”