Stability, spectroscopic, electrochemistry and QTAIM analysis of Cu-Znn-1On clusters for glucose sensing application: A study on theoretical and experimental insights

Clusters of (ZnO)_n (n = 2-4) have been shown to play a central role in the detection of glucose entity based on the existence of photo-induced electrons (PE), which facilitates the interaction between (ZnO)_n clusters and glucose entity guests. The electrochemistry experiment has confirmed the detection of glucose by the title clusters. The optimization, energetic parameters, and vibrational frequency calculations have indicated that the Cu-Zn_n-1O_n-glucose are more stable than the (ZnO)_n-glucose complexes. It has been demonstrated that the Cu doping enhanced the chemical behavior of the clusters and formed a high intramolecular charge transfer (ICT) in the system. The glucose sensing by all the forms of Cu-Zn_n-1O_n clusters showed that the Cu-Zn₃O₄, Cu-Wurtzite, and Cu-Rocksalt clusters are the most suitable for adsorbing the glucose guest. The HOMO/LUMO iso-surfaces of the complexes showed that the electron concentrations are localized in the d orbitals and mainly in the form of the d¹⁰ orbitals around Zn atoms. The molecular electrostatic potential (MEP) has clearly indicated that a high charge transfer occurs between the copper and the oxygen atoms, which facilitate the adsorption of glucose. The reactivity parameters also indicated that the Wurtzite-glucose complex has a high electrophilicity index (ω), which means a good acceptor behavior to interact with glucose. Additionally, the bond between the (ZnO)_n clusters and the glucose polar element has been studied in detail by using QTAIM theory. Finally, the theoretical and experimental studies prove that the Cu-Zn_n-1O_n clusters are very suitable and competent compounds for detecting glucose.

Azo-methoxy-calix[4]arene complexes with metal cations for chemical sensor applications: Characterization, QTAIM analyses and dispersion-corrected DFT- computations

In this work, the structures, quantum chemical descriptors, morphologic characterization of the azo-methoxy-calix[4]arene were investigated. The analyses and interpretation of the theoretical and the experimental IR spectroscopy results for the corresponding compounds was performed. The complexation of the azo-methoxy-calix[4]arene with Zn²⁺,Hg²⁺ , Cu²⁺ , Co²⁺, Ni²⁺ , Pb²⁺ and Cd²⁺metal cations has been calculated by the dispersion corrected density functional theory (DFT-D3). The values of the interaction energies show that the specific molecule is more selective to the Cu²⁺ cation. The study of the reactivity parameters confirms that the azo-methoxy-calix[4]arene molecule is more reactive and sensitive to the Cu²⁺ cation than that Co²⁺ and Cd²⁺. In addition, the investigation of the electrophilic and nucleophilic sites has been studied by the molecular electrostatic potential (MEP) analysis. The Hirshfeld surface (HS) analysis of the azo-methoxy-calix[4]arene-Cu²⁺ interaction have been used to understand the Cu⋯hydrogen-bond donors formed between the cation and the specific compound. The Quantum Theory of Atoms in Molecules (QTAIM) via Non covalent Interaction (NCI) analysis was carried out to demonstrate the nature, the type and the strength of the interaction formed between the Cu²⁺ cation and the two symmetrical ligands and the cavity. Finally, the chemical sensor properties based on the Si/SiO₂/Si₃N₄/Azo-methoxy-calix[4]arene for detection of Cu²⁺ cation were studied. Sensing performances are determined with a linear range from 10^-5.2 to 10^-2.2 M. The Si/SiO₂/Si₃N₄/azo-methoxy-calix[4]arene structure is a promoter to have a good performance sensor.

Theoretical assessment of calix[4]arene-N-β-ketoimine (n=1-4) derivatives: Conformational studies, optoelectronic, and sensing of Cu2+cation

Herein, we have investigated the key functions of the calix[4]arene, abbreviated as CX [1], and designed its several derivatives by substitution of the functional groups. Molecular geometry provides an intuitive understanding of the effect of functional groups on various physical properties. The addition of the N-β-ketoimine (n = 1-4) ligands has a direct effect on the stretching vibration of the H-bonding interaction. The results showed that all molecules possess absorption bands at 190 nm and in the range between 200 and 300 nm assigned to π-π* and n-π* transitions. HOMO-LUMO energy gap of the CX[4]-N-β-ketoimine, one with chemical hardness of 1.62 eV, has been found to be 3.24 eV calculated at B3LYP/6-31 + G(d) level of theory. This finding explains the good kinetic stability of this compound. The large values of electrophilicity make the current molecules as a good electrophilic species. The atom in molecule (AIM) and the reduced density gradient (RDG) analyses showed the type and the strength of the interactions taking place between Cu²⁺ and the β-ketoimine ligands.

A theoretical study of the global and local electrophilicity, nucleophilicity, polarizability and QTAIM theory for calix[4]arene-gas interaction

The calix[4]arene molecule, abbreviated as CX[4], is known by the four phenolic groups and a hydrophobic cavity able to enclose small molecules. The interactions between CX[4] and NO3, NO2, CO2, and N2 gas molecules have been studied. These guest species are placed inside and outside the cavity of the host molecule CX[4]. The formation of H-bonding has been deeply discussed based on the infrared spectrum and the polarizability analysis. Global and local indices have been calculated for a series of gas (NO3, NO2, CO2 and N2) in interaction with the CX[4] molecule to explain the electrophilic or nucleophilic activations in endo-vs. exo-cavity interaction zone. As expected, there is a correlation between the proposed global electrophilicity and global nucleophilicity together for an explanation of the chemo-selectivity region. Finally, the topological parameter analyses of the host-guests interactions have been estimated by using DFT calculations.

DFT and TD-DFT investigation of calix[4]arene interactions with TFSI- ion

Understanding the interactions of the calix[n]arene molecules with a variety of invited chemicals entities is getting very important. In this context, we have studied a new host-guest such as the interaction of the calix[4]arenes with the bis (trifluoromethylsulfonyl) imide TFSI- ion. The energy gap has decreased from 3.53 eV to 2.11 eV indicating the reliability of the electrochemical evaluation of HOMO and LUMO energy levels. In a predominant number of cases, we obtain the spatial accumulation of HOMO and LUMO at the interface of phenol groups. Then, according to the QNBO charge distribution of these host-guests interactions, we have demonstrated the direction of charge transfer between the CX[4] molecule and the TFSI- ion. More importantly, the non covalent interactions (NCI) have been investigated that the endo-cavity position of the TFSI-4 is the most stable position between all these host-guests. By using DFT quantum methods, we have identified as a suitable host for TFSI- which can be used in the electronic technology.