New Sensitive and Selective Chemical Sensors for Ni²⁺ and Cu²⁺ Ions: Insights into the Sensing Mechanism through DFT Methods

Abstract

We report the synthesis and theoretical study of two new colorimetric chemosensors with special selectivity and sensitivity to Ni2+ and Cu2+ ions over other metal cations in the CH3CN/H2O solution. Compounds (E)-4-((2-nitrophenyl)­diazenyl)-N,N-bis­(pyridin-2-ylmethyl)­aniline (A) and (E)-4-((3-nitrophenyl)­diazenyl)-N,N-bis­(pyridin-2-ylmethyl)­aniline (B) exhibited a drastic color change from yellow to colorless, which allows the detection of the mentioned metal cations through different techniques. The interaction of sensors with these metal ions induced a new absorption band with a hypsochromic shift to the characteristic signal of the free sensors. A theoretical study via time-dependent density functional theory (TD-DFT) was performed. This method has enabled us to reproduce the hypsochromic shift in the maximum UV–vis absorption band and explain the selective sensing of the ions. For all of the systems studied, the absorption band is characterized by a π → π* transition centered in the ligand. Instead of Ni2+ and Cu2+ ions, the transition is set toward the σ* molecular orbital with a strong contribution of the 3d x 2- y 2 transition (π → 3d x 2- y 2). These absorptions imply a ligand-to-metal charge transfer (LMCT) mechanism that results in the hypsochromic shift in the absorption band of these systems.

Understanding the Deactivating/Activating Mechanisms in Three Optical Chemosensors Based on Crown Ether with Na+/K+ Selectivity Using Quantum Chemical Tools

“…The CAMÀ B3LYP was employed to analyze the charge transfer transition (CT) suggested in the experimental report for these systems due to its capacity for reducing deviations in the calculations of the CT excitation energies, which B3LYP can underestimates. [15,32,50,51] The solvation effects were considered via Conductor-like Screening Model (CPCM) using the parameters of water as solvent (ɛ = 58.5 and refraction = 1.33). [49,52] The local minima in the S 0 and S 1 states were studied with the vibrational frequency analysis.…”

“…[20,[22][23][24] The most common transduction mechanisms are photoinduced electron transfer (PET), [8,25,26] intramolecular charge transfer (ICT), [27,28] twisted intramolecular charge transfer (TICT), [12,29] ground, or excitedstate intramolecular proton transfer (GSIPT or ESIPT), [8,[30][31][32] and metal-ligand or ligand-metal charge transfer (MLCT or LMCT). [33][34][35] These transduction mechanisms and selectivity are determined by the electronic and molecular structure of the sensors. Because of the two processes that take place in the detection of analytes.…”

“…In this sense, the understanding of the transduction mechanisms in analytes sensing is an important factor towards achieving this goal. As these mechanisms depend on the careful tuning of the electronic and molecular structure of the sensors, theoretical calculations have been a powerful tool in understanding and predicting the electronic properties and the transduction mechanisms in the recognition of several analytes like metal ions, [25,33,37,38] anions, [39][40][41] pH, [15,42] contaminant and/or explosive organic compounds. [25,43] Additionally, computational studies have been based mainly on the analysis of the frontier molecular orbital (FMO) energy and the molecular structures employing the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) methods.…”

Insights into the selective sensing mechanism of a luminescent Cd(II)-based MOF chemosensor toward NACs: roles of the host–guest interactions and PET processes

“…The optical properties of the (absorption and emission) of the Cd-MOF and Cd-MOF/analyte systems were calculated using time-dependent density functional theory (TD-DFT), with the B3LYP functional and the same basis set employed in the geometry optimizations [50,51].…”

High Catalytic Activity of Fluorophore-Labeled Y-Shaped DNAzyme/3D MOF-MoS2NBs as a Versatile Biosensing Platform for the Simultaneous Detection of Hg2+, Ni2+, and Ag+ Ions

“…The excessive accumulation of Hg 2+ , Ni 2+ , and Ag + ions in humans has resulted in a wide range of diseases such as brain dysfunction, liver, kidneys, Minamata diseases, and neurodevelopment disorders in children. The anthropic sources, incineration of solid waste, metal smelting, and combustion of fossil fuels result in skin allergies, dermis, cancer, lung fibrosis, and disorders in the respiratory, central nervous, and cardiovascular systems. − As a result, many researchers have concentrated on the detection of single and dual heavy metal ions. However, the simultaneous detection of multiple ions is one of the hottest subjects in the field of water pollution monitoring.…”