作者:Kuljit Kaur、Subodh Kumar
DOI:10.1039/c0dt01016b
日期:——
Dansyl-anthracene dyads 1 and 2 in CH3CN–H2O (7 : 3) selectively recognize Cu2+ ions amongst alkali, alkaline earth and other heavy metal ions using both absorbance and fluorescence spectroscopy. In absorbance, the addition of Cu2+ to the solution of dyads 1 or 2 results in appearance of broad absorption band from 200 nm to 725 nm for dyad 1 and from 200 nm to 520 nm for dyad 2. This is associated with color change from colorless to blue (for 1) and fluorescent green (for 2). This bathochromic shift of the spectrum could be assigned to internal charge transfer from sulfonamide nitrogen to anthracene moiety. In fluorescence, under similar conditions dyads 1 and 2 on addition of Cu2+ selectively quench fluorescence due to dansyl moiety between 520–570 nm (for 1)/555–650 nm (for 2) with simultaneous fluorescence enhancement at 470 nm and 505 nm for dyads 1 and 2, respectively. Hence these dyads provide opportunity for ratiometric analysis of 1–50 μM Cu2+. The other metal ions viz. Fe3+, Co2+, Ni2+, Cd2+, Zn2+, Hg2+, Ag+, Pb2+, Li+, Na+, K+, Mg2+, Ca2+, Ba2+ do not interfere in the estimation of Cu2+ except Cr3+ in case of dyad 1. The coordination of dimethylamino group of dansyl unit with Cu2+ causes quenching of fluorescence due to dansyl moiety between 520–600 nm and also restricts the photoinduced electron transfer from dimethylamino to anthracene moiety to release fluorescence between 450–510 nm. This simultaneous quenching and release of fluorescence respectively due to dansyl and anthracene moieties emulates into Cu2+ induced ratiometric change.
在CH3CN–H2O (7 : 3)中,Dansyl-蒽(dyads 1 和 2)选择性识别Cu2+离子,与碱金属、碱土金属及其他重金属离子相比,使用吸收和荧光光谱进行检测。在吸收光谱中,向dyads 1或2的溶液中添加Cu2+时,dyad 1的吸收带扩展至200 nm至725 nm,而dyad 2的吸收带扩展至200 nm至520 nm。这伴随着颜色变化,从无色变为蓝色(对于1)和荧光绿色(对于2)。此光谱的红移可以归因于从磺酰胺氮向蒽基团的内部电荷转移。在荧光方面,在相似条件下,dyads 1和2在添加Cu2+后,选择性淬灭了dansyl基团在520–570 nm(对于1)/555–650 nm(对于2)区间的荧光,同时在470 nm和505 nm处分别增强荧光。因此,这些类化合物为1–50 μM Cu2+的比率分析提供了机会。其他金属离子如Fe3+、Co2+、Ni2+、Cd2+、Zn2+、Hg2+、Ag+、Pb2+、Li+、Na+、K+、Mg2+、Ca2+、Ba2+在估算Cu2+时不会干扰,只有在dyad 1的情况下Cr3+会造成干扰。Dansyl单元的二甲氨基团与Cu2+的配位导致520–600 nm区间的荧光淬灭,并限制了从二甲氨基团到蒽基团的光诱导电子转移,从而释放450–510 nm区间的荧光。这种由于dansyl和蒽基团分别引起的荧光淬灭和释放,导致了Cu2+诱导的比率变化。