Optical Spectroscopy and Theoretical Studies in Calixarene Chemistry

Photophysical, Antioxidant, Antibacterial and NBO, LOL, ELF Analysis of Alkyl Groups Substituted Calix[4]resorcinarenes

In our work to investigate the photophysical, antioxidant, antibacterial, DFT and topological analysis of four C-alkyl calix[4]resorcinarenes (3a-3d - C4RAs). The photophysical properties of C4RAs in selected solvents were recorded using both UV-Visible and fluorescence spectral studies. The absorption and emission maximum of four C4RAs were observed around 280 nm and 318 nm in selected solvents. The solvatochromism with selected solvents were analysed from the plot between Stoke's shift and ETN. The antioxidant activity and antibacterial activity of four C4RAs were evaluated by phosphomolybdate assay and Kirby-Bauer method. The structure of four C4RAs was optimized using DFT B3LYP 6-311G method to calculating the various theoretical parameters in the gas phase. The stability, reactivity, formation of hydrogen bond, donor-acceptor interactions were reported from the interpretation of theoretical values. The non-covalent interactions of four C4RAs were characterized by LOL and ELF topological analysis.

Photophysical, antioxidant, antibacterial and NBO, LOL, ELF analysis of alkyl groups substituted calix[4]resorcinarenes.. [DOI: 10.21203/rs.3.rs-2707368/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

In our work to investigate the photophysical, antibacterial, theoretical and topological analysis of four C-alkyl calix[4]resorcinarenes (C4RAs). The solvatochromism and photophysical properties of C4RAs in different solvents were recorded in both UV-Visible and fluorescence spectral studies. The total antioxidant capacity and antibacterial activity of four C4RAs were evaluated by phosphomolybdate assay and kirby-bauer method. Theoretical parameters such as HOMO, LUMO, energy gap and Mulliken atomic charges and NBO were optimized by DFT B3LYP 6-311G method. From the results of HOMO and LUMO energies were used to determine the theoretical parameters of four C4RAs. The nucleophilic and electrophilic substitution reactivity of four C4RAs were analyzed by molecular electrostatic potential map analysis. Natural bonding orbital analysis was used to determine the intramolecular charge transfer within the energy difference between acceptor and donor orbitals. The non-covalent interactions of four C4RAs were characterized by LOL and ELF topological analysis.

DFT study of the conformation, hydrogen bonds, IR, Raman, and NMR spectra of 1,3-disubstituted p-tert-butylthiacalix[4]arenes

CONTEXT

The molecular design of spatially preorganized molecules is one of the critical issues in organic chemistry. Molecular recognition and multipoint binding define them. They organize nanoscale assemblies and devices and stably form host-guest inclusion complexes. Not only is this kind of research important in theory but it also has applications. They are used to create the basic elements of sensory devices: elements of cellular electronics, functional nanofilms and coatings, molecular switches, etc. Thiacalix[4]arenes are a useful molecular platform for constructing a wide range of preorganized receptor structures. This research aims to examine the structure and spectra of distally substituted para-tert-butylthiacalix[4]arene aliphatic (C1) and aromatic (C2) esters. The comparison of the spectra of C1, C2, and C3 makes it possible to reveal the structures and H-bonds of these compounds. The structures and H-bonds of these compounds can be seen by analyzing the spectra of C1, C2, and C3. Calculations were made for the spectra of various C1 and C2 molecule conformations. The most stable conformation for C1 and C2 molecules is a distorted cone 2 (DC2) with the same ester group orientation. The pinched cone (PC) conformation is the most unstable. Thiacalixarene molecules' cavities shrink from 3.61 to 3.57 Å when aromatic ester groups take the place of aliphatic ester groups. Two OH groups are linked to an oxygen atom in the DC1 and DC2 conformations of the C1 and C2 molecules. H-bonds in C1 and C2 molecules affect the supramolecular characteristics of these molecules. A drop in ionization energy and increases in electron affinity, chemical potential, softness, electrophilicity index, and dipole moment occur when aliphatic esters are replaced with aromatic ones.

METHODS

Disubstituted aliphatic and aromatic esters' IR, Raman, and NMR spectra have been investigated. The DFT/B3LYP/6-311G(d,p) method and the GAUSSIAN 09W software were used to determine the vibrational spectra of molecules and optimize their geometry. A gauge-independent (GIAO) approach was used to determine chemical shifts in the NMR spectra with respect to tetramethylsilane.

Calix[4]arene-Based Porous Organic Nanosheets

Calixarenes are a common motif in supramolecular chemistry but have rarely been incorporated in structurally well-defined covalent 2D materials. Such a task is challenging, especially without a template, because of the nonplanar configuration and conformational flexibility of the calixarene ring. Here, we report the first-of-a-kind solvothermal synthesis of a calix[4]arene-based 2D polymer (CX4-NS) that is porous, covalent, and isolated as few-layer thick (3.52 nm) nanosheets. Experimental and theoretical characterization of the nanosheets is presented. Atomic force microscopy and transmission electron microscopy results are consistent with the calculated lowest energy state of the polymer. In the lowest energy state, parallel layers are tightly packed, and the calixarenes adopt the 1,2-alternate conformation, which gives rise to a two-dimensional pattern and a rhombic unit cell. We tested the material's ability to adsorb I₂ vapor and observed a maximum capacity of 114 wt %. Molecular simulations extended to model I₂ capture showed excellent agreement with experiments. Furthermore, the material was easily regenerated by mild ethanol washings and could be reused with minimal loss of efficiency.

Complexation of solvents and conformational equilibria in solutions of the simplest calix[4]arenes

Structure optimization and calculation of electronic adsorption spectra of 25,26,27,28-tetrahydroxycalix[4]arene and 25,27-dimethoxy-26,28-dihydroxycalix[4]arene conformers have been performed by density-functional theory using hybrid B3LYP functional in cc-p VTZ and cc-p VDZ basis sets in Gaussian 09 package. Analysis of experimental UV-Vis spectra of solutions of 25,26,27,28-tetrahydroxycalix[4]arene, 4-tert-butylcalix[4]arene and 25,27-dimethoxy-26,28-dihydroxycalix[4]arene in various solvents has been carried out. It was shown that the ratio of absorption maxima at characteristic wavelengths at ca. 274 and 283 nm may be used to assess the extent of calix[4]arene/solvent interactions. The conclusion is drawn that spectral characteristics of calix[4]arenes are strongly affected by acid-base interactions.

Computational investigation of a new ion-pair receptor for calix[4]pyrrole

Theoretical studies of a new ion-pair receptor, meso-octamethylcalix[4]pyrrole (OMCP), and its interactions with the halide anions F(-), Cl(-), and Br(-) and the cesium halides CsF, CsCl, and CsBr have been performed. Geometries, binding energies, and binding enthalpies were evaluated with the restricted hybrid Becke three-parameter exchange functional (B3LYP) method using the 6-31+G(d) basis set and relativistic effective core potentials. The optimized geometric structures were used to perform natural bond orbital (NBO) analysis. The two typical types of hydrogen bonds, N-H…X(-) and C-H…X(-), were investigated. The results indicate that hydrogen bonding interactions are dominant, and that the halide anions (F(-), Cl(-), and Br(-)) offer lone pair electrons to the σ*(N-H) or σ*(C-H) antibonding orbitals of OMCP. In addition, electrostatic interactions between the lone pair electrons of the halide anion and the LP* orbitals of Cs(+) as well as cation-π interactions between the metal ion and π-orbitals of the pyrrole rings have important roles to play in the Cs(+)•OMCP•X(-) complexes. The current study further demonstrates that this easy-to-make OMCP host compound functions as not only an anion receptor but also an ion-pair receptor.

Molecular recognition of 1,5 diamino anthraquinone by p-tert-butyl-calix(8)arene

The molecular recognition properties of p-tert-butyl-calix(8)arene with 1,5 -diamino anthraquinone (1,5 DAAQ) were studied by using UV-Visible and Fluorescence spectroscopic techniques. The binding constant was determined by using the Benesi-Hilde brand expression. It was found that the host-guest complex was formed between 1,5 DAAQ and p-tert-butyl- calix(8)arene in the 1:2 Stoichiometry ratio.

Modeling K+ and Ag+ complexation by thiacalix[4]arene amides using DFT: the role of intramolecular hydrogen bonding

Complexation of methyl-glycine-amide functionalized thiacalix[4]arene with K(+) and Ag(+) has been studied using density functional theory (DFT) in the gas phase. To account for the conformational possibilities of the ligand, the free ligand and its potassium complexes were subjected to global minima searches on the molecular mechanics (MM) level of theory with the OPLS (optimized potentials for liquid simulations) force field. For the free ligand, the order of the energies and geometries of the ligand conformers is in agreement between MM and DFT; however, the position of K(+) in the ligand's cavity was predicted differently by these methods. Hydrogen bonding of amide hydrogens in the ligands' podand arms was found to take place predominantly with the ether oxygens of the same arm rather than the other arms' carbonyls. According to DFT calculations, the silver cation preferred to coordinate with one sulfur bridge and three carbonyl groups, whereas potassium cation favored interaction with the four carbonyl oxygens of the podand amide arms. Neither cation preferred the N-mode of coordination. For all obtained conformers, intramolecular hydrogen bonds disfavor complexation, increasing the preorganizational energy to be paid.