Recognition of anions using urea and thiourea substituted calixarenes: A density functional theory study of non-covalent interactions

Synthesis of new chromogenic sensors containing thiourea and selective detection for F–, H2PO4–, and Ac– anions

Two new chromogenic sensors 1-(2-hydroxyphenyl)-3-(4-nitrophenyl)thiourea 1 and 1-(3-hydroxypyridin-2-yl)-3-(4-nitrophenyl)thiourea 2 bearing nitrophenyl and thiourea groups were designed and synthesized by one-step procedure and characterized through 1H NMR, 13C NMR, FTIR, and MS. The anion recognition property of the receptors was studied via naked-eye detection, UV–vis, and 1H NMR. Based on the existence of amino gen and hydroxyl moieties in receptors, receptors 1 and 2 exhibit obvious selectivity by the redshift of UV–vis signals, colour changes through naked-eye detection, and binding effects for F–, H2PO4–, and Ac–. Surprisingly, the detection limits of receptor 1 for F– and Ac– were calculated to be 5.45 × 10−7 and 2.11 × 10−7 (mol/L)−1, respectively, which indicated that F– and Ac– can be identified with high sensitivity by receptor 1. Besides, simple “test strips” were developed and were used as sensors for recognition of F–, H2PO4–, or Ac– in DMSO solution. Lastly, the mechanisms of the recognition process were studied through DFT calculation and 1H NMR titration.

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.

Host-guest complexation studies of NO3, NO2, CO2, and N2 gas with the calix[4]arene molecule

Calix[n]arenes (abbreviated as CX[n]) are the macro-molecules based on phenol groups with a hydrophobic cavity to encapsulate a gas or small molecules. They are used as molecular vehicles. For instance, these molecules are used in the activation of the solubility of monomers in the specific media and in pharmaceutical drug delivery. The limit of the development of gaseous pollutants will be a vital subject in the future. The polluting gases NO₃, NO₂, CO₂, N₂, etc., need cage molecules, such as CX[4], to be encapsulated. In this report, the red shift of the H-bonding interactions of the CX[4]-gas (by adding the gas inside or outside the cavity) is clearly explained by the vibrational analysis. The electronic spectra of the complexes of CX[4] with NO₃, NO₂, CO₂, and N₂) exhibit a blue-shift pick in comparison with the ones observed for the CX[4] molecule. The electrophilic and nucleophilic sites of the stable host-guest have been investigated. Additionally, the non-covalent interactions have been calculated based on the reduced density gradient RDG and QTAIM theory.

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.

A DFT study of inclusion complexes of substituted calix[n]arenes with dasatinib and lapatinib

Herein, we have presented the results of Density Functional Theory (DFT) based calculations of inclusion complexes of lapatinib and dasatinib with calix[n]arene macrocycles. A total of 48 calix [n]arene complexes were modeled via considering varied ring sizes (n = 4,5,6,8) and upper-rim functionalization viz. SO₃H, tert-Butyl, iso-Propyl, COOH, C₂H₅OH, and C₂H₅NH₂. From the results of multilevel molecular docking, DFT energetics, and reactivity descriptors; it has been demonstrated that dasatinib form optimal complexes with calix 4f, 3f (-35 to -40 kcal/mol). Moreover, for lapatinib, hosts 3f, 4a, 1f, 3d have the capability to generate promising complexes (>35 kcal/mol). Based on counterpoise corrected binding energies (E_bind) and global reactivity descriptors, we anticipate that the proposed complexes can vitally be used as analogous to carrier-mediated-drug-delivery.

Sensors Based on Bio and Biomimetic Receptors in Medical Diagnostic, Environment, and Food Analysis

Analytical chemistry is now developing mainly in two areas: automation and the creation of complexes that allow, on the one hand, for simultaneously analyzing a large number of samples without the participation of an operator, and on the other, the development of portable miniature devices for personalized medicine and the monitoring of a human habitat. The sensor devices, the great majority of which are biosensors and chemical sensors, perform the role of the latter. That last line is considered in the proposed review. Attention is paid to transducers, receptors, techniques of immobilization of the receptor layer on the transducer surface, processes of signal generation and detection, and methods for increasing sensitivity and accuracy. The features of sensors based on synthetic receptors and additional components (aptamers, molecular imprinted polymers, biomimetics) are discussed. Examples of bio- and chemical sensors' application are given. Miniaturization paths, new power supply means, and wearable and printed sensors are described. Progress in this area opens a revolutionary era in the development of methods of on-site and in-situ monitoring, that is, paving the way from the "test-tube to the smartphone".