Recent developments on optical and electrochemical sensing of copper(II) ion based on transition metal complexes

Copper(II), Cu2+, ion plays not only a fundamental role to sustain important physiological processes in living organisms, but also an important environmental pollutant. A large number of chemosensors that employ the chromogenic, fluorogenic or electrochemical properties of molecules have been reported for selective sensing of copper ions with absorbance and emission in the visible region. Nevertheless, most of these chemosensors for Cu2+ ions have some limitations including low water-solubility, tedious sample treatment, multistep synthetic routes, or unstable detection signal. Therefore, the challenge in the development of light-up chemosensors which are cost-effective, rapid, facile, biocompatible and applicable to the environmental and biological milieus is still a topical issue. In the context of optical sensing of Cu2+ ion, the unique features offered by transition metal complexes over organic fluorophores have made them a suitable candidate to monitor Cu2+ ions in biological systems. Encouraged by the importance of Cu2+ ions, we herein summarize the recent development of transition metal complexes, particularly those of d(6) or d(10) complexes based on rhenium(I), ruthenium(II), iridium(III), zinc(II) and gold(I) complexes, for optical and electrochemical sensing or biosensing applications of Cu2+ ion. (C) 2017 Elsevier B.V. All rights reserved

Synthesis and characterization of monometallic rhenium(I) complexes and their application as selective sensors for copper(II) ions

Novel imine functionalized monometallic rhenium(I) polypyridine complexes (1-4) comprising two phenol moieties attached to 2,20-bipyridine ligands L1-L4 have been synthesized and characterized. These complexes exhibit selective and sensitive detection towards copper(II) ions and this is observed through changes in UV-visible absorption, luminescence and time-resolved spectroscopic techniques. An enormous enhancement is observed in emission intensity, quantum yield and luminescence lifetime with the addition of copper(II) ions, and this can be attributed to the restriction of C=N isomerization in the Re(I) complexes. The strong binding between copper(II) ions and these complexes reveals that the binding constant values are in the range of 1.1 x 10(3)-6.0 x 103 M-1. The absorption spectral behavior of the complexes is supported by DFT calculations

Sensing of insulin fibrillation using alkoxy-bridged binuclear rhenium(I) complexes

For the first time we report the simple, cost-effective, sensitive detection of human insulin fibrils using an alkoxy-bridged binuclear rhenium(I) complexes by the enhancement in luminescence intensity, emission lifetime and the formation of fibrils. The Re(I) complexes are weakly emissive, when it is dissolved with native insulin in an incubation buffer, but it becomes highly luminescent after the formation of insulin fibrils. This binding of human insulin fibrils is attributed to the hydrophobic as well as pi - pi stacking interaction of naphthalene moiety present in rhenium(I) complexes. (C) 2016 Elsevier B.V. All rights reserved

Aggregation-Induced Emission Enhancement in Alkoxy-Bridged Binuclear Rhenium(I) Complexes: Application as Sensor for Explosives and Interaction with Microheterogeneous Media

The aggregation-induced emission enhancement (AIEE) characteristics of the two alkoxy-bridged binuclear Re­(I) complexes [{Re­(CO)₃(1,4-NVP)}₂(μ₂-OR)₂] (<b>1</b>, R = C₄H₉; <b>2</b>, C₁₀H₂₁) bearing a long alkyl chain with 4-(1-naphthylvinyl)­pyridine (1,4-NVP) ligand are illustrated. These complexes in CH₂Cl₂ (good solvent) are weakly luminescent, but their intensity increased enormously by almost 500 times by the addition of poor solvent (CH₃CN) due to aggregation. By tracking this process via UV–vis absorption and emission spectral and TEM techniques, the enhanced emission is attributed to the formation of nanoaggregates. The nanoaggregate of complex <b>2</b> is used as a sensor for nitroaromatic compounds. Furthermore, the study of the photophysical properties of these binuclear Re­(I) complexes in cationic, cetyltrimethylammonium bromide (CTAB), anionic, sodium dodecyl sulfate (SDS), and nonionic, <i>p-tert</i>-octylphenoxypolyoxyethanol (TritonX-100, TX-100), micelles as well as in CTAB–hexane–water and AOT–isooctane–water reverse micelles using steady-state and time-resolved spectroscopy and TEM analysis reveals that the nanoaggregates became small and compact size