Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai, 400076, India.
Chemphyschem. 2020 Jul 17;21(14):1564-1570. doi: 10.1002/cphc.202000332. Epub 2020 Jun 26.
A squaramide ring conjugated with Schiff-bases decorated with hydroxy and methoxy functional groups differentially senses zinc and cadmium ions, which turn on the fluorescence. The feebly emitting free ligands light up in the presence of zinc and cadmium acetates, with the acetate ion playing a pivotal role as a conjugate anion. The selective and differentiable emission responses for zinc and cadmium ions make these ligands efficient multi-analyte sensing agents. Furthermore, these ligands could be used to differentially sense zinc and cadmium ions even in aqueous environments. The NMR investigations reveal marginal differences in the binding of zinc and cadmium ions to the ligands, whereas density functional theory calculations suggest the different extent of ligand-to-metal charge transfer (LMCT) contributes to the differential behavior. Finally, comparison of the excited-state dynamics of free ligand and the metal complexes reveal the appearance of longer lifetime (about 500-700 ps) component with complexation, due to rigidified molecular skeleton, thereby impeding the non-radiative processes.
一个带有席夫碱的方酰胺环，其中的羟基和甲氧基官能团可以区分地感应锌和镉离子，从而使荧光开启。在锌和镉醋酸盐存在下，弱发射的游离配体被点亮，其中醋酸根离子作为共轭阴离子起着关键作用。锌和镉离子的选择性和可区分的发射响应使这些配体成为高效的多分析物传感试剂。此外，这些配体甚至可以在水相环境中区分地感应锌和镉离子。NMR 研究表明，锌和镉离子与配体的结合只有微小的差异，而密度泛函理论计算表明，配体到金属的电荷转移（LMCT）的不同程度导致了这种差异行为。最后，对游离配体和金属配合物的激发态动力学的比较表明，由于分子骨架的刚性化，配合物中出现了更长寿命（约 500-700 ps）的组分，从而阻碍了非辐射过程。
