There is burgeoning interest among supramolecular chemists to develop novel molecular systems to detect biogenic amines and bio-thiols in aqueous and non-aqueous media due to their potential role in biological processes.
The extreme toxicity of mercury and its derivatives results from its high affinity for thiol groups in proteins and enzymes, leading to the dysfunction of cells and consequent health problems.
Five new imine-linked ligands (H 2 L1, H 4 L2, and L3− L5) were synthesize in two step reactions and final products were fully characterized with spectroscopic techniques. The binding behavior of these ligands was evaluated with the library of metal ions. However, substantial photophysical modulations were observed with the coordination of [Ni 2+ ] ion to the ligand pocket. The fact that Ni 2+ induced remarkable modulation in photophysical studies encouraged us to prepare the nickel complexes of respective ligands. The resultant coordination complexes offered interesting properties like tunable coordination geometry, variable stereochemistry, and possibility of electrostatic interactions which are important for biomolecular recognition. These properties of coordination complexes encouraged us to evaluate the antimicrobial activity of nickel complexes. All nickel complexes have shown appreciable antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). The SEM imaging studies were performed to know the mechanism of cell death, and results revealed that the cell wall inhibition is the main reason for bacterial cell death. The cytotoxicity of these complexes and their respective ligands for human cell lines was established with the HeLa cell, and observations affirm 85−90% cell viability after 24 h.
The hexadentate ligands H2L1-L3 with mixed S, N, O donor sites and possessing substituents having either "no" or electron-releasing/withdrawing nature at terminal ends are synthesized. The ligands H2L1-L3 were tested for binding with library of metal ions, wherein maximum efficiency was observed with Ni(2+), and it motivated us to prepare the Ni(2+) complexes. The ligand H2L1 underwent deprotonation and formed binuclear complex when interacted with Ni(2+) as evident from its crystal structure. The H2L2 and H2L3 having electron-withdrawing/electron releasing groups, respectively, were also deprotonated; however, they afforded mononuclear complexes with Ni(2+) ion. This signifies the importance of steric parameters instead of electronic factors in these particular cases. Impressed by differential behavior of complexes of H2L1 and H2L2/H2L3 with Ni(2+) and their photophysical and electrochemical properties, all the metal complexes were studied for their chemosensing ability. Nowadays with increased use of organophosphate, there is alarming increase of these agents in the environment, and thus we require efficient technique to estimate the level of these agents with high sensitivity and selectivity in aqueous medium. The Ni(2+) complexes with hydrophobic nature were suspended into aqueous medium for testing them as sensor for organophosphate. The (L1)2.(Ni(2+))2 could sense phosmet with detection limit of 44 nM, whereas L2.Ni(2+) and L3.Ni(2+) exhibited the detection limits of 62 and 71 nM, respectively, for chlorpyrifos.
The unregulated use of chemical weapons has aroused researchers to develop sensors for chemical warfare agents (CWA) and likewise to abolish their harmful effects, the degradation through catalysis has great advantage. Chemically, the CWAs are versatile; however, mostly they contain organophosphates that act on inhibition of acetyl cholinesterase. In this work, we have designed and synthesized some novel benzimidazolium based fluorescent cations and their fluorescent aggregates were fabricated using anionic surfactants (SDS and SDBS) in aqueous medium. The prepared fluorescent aggregates have shown aggregation induced emission enhancement, which was further used as detection of chemical warfare agent in aqueous medium. The aggregates (Benz-2/SDBS and Benz-3/SDBS) have shown significant changes in emission profile upon interaction with diethylchlorophosphate. Contrarily, the pure dipodal receptor Benz-4 has not shown any response in emission after interaction with organophosphate, and consequently, it was concluded that benzimidazolium cation plays a decisive role in sensing. The mechanism of sensing was fully validated using P NMR spectroscopy as well as GC-MS, which highlights the transformation of diethylchlorophosphate into diethylhydrogen phosphate. The aggregates selectively interact with diethylchlorophosphate over other biological important phosphates.
Two copper complexes C1 and C2 have been designed and developed for selective sensing of organophosphates. It is important to develop an efficient method for the detection of these agents for environmental analysis because the overuse of these agents in the environment causes harmful effects on living systems. Our attempts to utilize the copper complexes for the detection of organophosphates remained successful: the C1 complex has shown selective binding for the azamethiphos with a detection limit of 19 nM; while the C2 complex has not revealed any selectivity for any of the tested organophosphates. The results indicated that the coordination sphere of the C1 complex is proficiently engineered in such a way that it offers judicial binding sites for guest molecules.
Benzimidazole-based imine-linked
copper complexes L1. Cu
2+
–L3. Cu
2+
(assigned as C1–C3) have been synthesized and characterized with
various spectroscopic techniques. The structure of complex C1 was established with X-ray crystallography, which revealed it to
be a dinuclear complex that crystallized in a triclinic crystal system.
Currently, with the increasing demand of consumption of pharmaceutical
products by living beings their subsequent disposal to the environment
has increased progressively. These harmful pharmaceutical ingredients
enter into water bodies, which is not only affecting the ecological
environment but also affecting the living system as they accumulate
in the food chain causing adverse effects. Therefore, detection of
such harmful agents in the environment has turned out to be an important
parameter that needs much attention. Here, we utilized the copper
complex (C1) for the selective detection of cyproheptadine
and thiabendazole drug molecules. The modulations in the photophysical
properties of the complex were employed as a parameter which was studied
extensively for determination of targeted drugs. The investigation
confirmed that complex C1 was found to sense cyproheptadine
and thiabendazole in the nanomolar range. Real sample analysis was
also carried out and revealed that the complex under investigation
is a good sensor system for detection of the targeted drugs.
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