Rhodamine-based probes for metal ion-induced chromo-/fluorogenic dual signaling and their selectivity towards Hg(ii) ion
作者:Bamaprasad Bag、Ajoy Pal
DOI:10.1039/c0ob01179g
日期:——
The new signaling probes 2–6, rhodamine-B derivatives of various receptors which contain different donor atoms for effective metal ion coordination, were synthesized and their absorption as well as fluorescence spectral responses were evaluated in the presence of various metal ions. All these probes along with the reference probe 1 have exhibited optimal metal ion-induced absorption and fluorescence enhancement with Hg(II) ion in the longer wavelength region (>500 nm) in MeCN, exploiting the spectral characteristics of metal ion-induced structural transformation of rhodamine. The selectivity and sensitivity towards Hg(II) ion were better pronounced in MeCN–H2O (1 : 1 v/v) medium, implying the role of the solvent molecules, water in particular, in the preferential Hg(II) coordination environment. Complexation of Hg(II) to 1–6 not only enhanced the absorption at ∼560 nm, which turned the colourless solution into pink to facilitate a naked eye detection, but also amplified the fluorescence intensity simultaneously to offer high sensitivity of detection at lower concentration. The Hg(II)-induced photo-physical spectral responses of 1–6 in presence of other competitive metal ions rendered their high selectivity towards Hg(II). Further, their reversible dual channel signaling pattern under the action of counter anions, exploiting coordination tendency of anions towards Hg(II), which compete with probe-metal interaction, implied the reversibility in their Hg(II) coordination. The selectivity, sensitivity and reversibility, in principle, establishes the potential of these probes as chemosensors for Hg(II) ion detection.
新合成的信号探针2-6是罗丹明B衍生物,具有不同的供体原子以有效配位金属离子,并评估了它们在存在各种金属离子时的吸收和荧光光谱响应。所有这些探针与参考探针1一起,在MeCN中对Hg(II)离子的吸收和荧光增强表现出最佳效果,尤其是在较长波长区域(>500 nm),利用了金属离子诱导的罗丹明结构转变的光谱特征。在MeCN–水(1:1 v/v)介质中,对Hg(II)离子的选择性和灵敏度更为明显,这表明溶剂分子,尤其是水,在Hg(II)优先配位环境中的作用。Hg(II)与探针1-6的配合不仅增强了约560 nm的吸收,使无色溶液变为粉红色以便肉眼检测,同时也放大了荧光强度,从而在较低浓度下提供高灵敏度的检测。在其他竞争金属离子存在时,探针1-6对Hg(II)的光物理光谱响应表现出高选择性。此外,它们在对阴离子的作用下呈现可逆的双通道信号模式,利用了阴离子对Hg(II)的配位倾向,这与探针-金属相互作用竞争,进一步暗示了其Hg(II)配位的可逆性。选择性、灵敏度和可逆性的特性,原则上建立了这些探针作为Hg(II)离子检测化学传感器的潜力。