Rajadurai Vijay Solomon

Elucidating the structures and binding of halide ions bound to cucurbit[6]uril, hemi-cucurbit[6]uril and bambus[6]uril using DFT calculations

Understanding the binding and nature of the interactions present in host–guest complexes are central to supramolecular chemistry. In this paper, we tried to understand the nature of bonding between halides and three related host molecules using density functional theory. We have addressed a number of issues such as the role of solvation, the role of cations and the use of appropriate density functional calculations that are crucial for modeling host–guest complexes. Calculations show that the binding of halides in cucurbit-[6]-uril is assisted by a cation, whereas in hemi-cucurbit-[6]-uril, it is assisted by solvents. AIM calculations reveal the nature of non-bonded interactions present in these host–guest complexes and in particular brings out the two types of hydrogen bonding present in hm-CB-[6] and BU-[6] complexes.

Surfactant–copper(II) Schiff base complexes: synthesis, structural investigation, DNA interaction, docking studies, and cytotoxic activity

A series of surfactant–copper(II) Schiff base complexes (1–6) of the general formula, [Cu(sal-R2)2] and [Cu(5-OMe-sal-R2)2], {where, sal = salicylaldehyde, 5-OMe-sal = 5-methoxy- salicylaldehyde, and R2 = dodecylamine (DA), tetradecylamine (TA), or cetylamine (CA)} have been synthesized and characterized by spectroscopic, ESI-MS, and elemental analysis methods. For a special reason, the structure of one of the complexes (2) was resolved by single crystal X-ray diffraction analysis and it indicates the presence of a distorted square-planar geometry in the complex. Analysis of the binding of these complexes with DNA has been carried out adapting UV-visible-, fluorescence-, as well as circular dichroism spectroscopic methods and viscosity experiments. The results indicate that the complexes bind via minor groove mode involving the hydrophobic surfactant chain. Increase in the length of the aliphatic chain of the ligands facilitates the binding. Further, molecular docking calculations have been performed to understand the nature as well as order of binding of these complexes with DNA. This docking analysis also suggested that the complexes interact with DNA through the alkyl chain present in the Schiff base ligands via the minor groove. In addition, the cytotoxic property of the surfactant–copper(II) Schiff base complexes have been studied against a breast cancer cell line. All six complexes reduced the visibility of the cells but complexes 2, 3, 5, and 6 brought about this effect at fairly low concentrations. Analyzed further, but a small percentage of cells succumbed to necrosis. Of these complexes (6) proved to be the most efficient aptotoxic agent.

Spectroscopic Studies on TiO 2 Enhanced Binding of Hypocrellin B with DNA

The binding of Hypocrellin B-TiO2 chelate with DNA has been studied by using absorption, steady state fluorescence, cyclic voltammetry, time resolved fluorescence and laser flash photolysis measurements. The experimental results show that the presence of TiO2 nanoparticles increases the binding of Hypocrellin B with DNA. The groove binding mode is confirmed by spectroscopic and docking studies. Laser flash photolysis studies confirm the presence of electrons in the conduction band of TiO2 which will produce active oxygen species and results in damage of DNA indicating the potential application of Hypocrellin B-TiO2 chelate in the field of photodynamic therapy (PDT).

A DFT/TDDFT mission to probe push–pull vinyl coupled thiophene oligomers for optoelectronic applications

Vinyl coupled thiophene oligomers (VCTOs) are one of the active components in organic solar cells. In the present study, VCTOs with various acceptor groups (–CN, –NO2 and –COOH) have been considered and their optoelectronic properties have been evaluated using DFT/TDDFT calculations. In total, 17 VCTOs, including 3 already reported, have been considered. The computed results reveal that the reference VCTOs (VCTO1, 2 and 3) can be used as possible electron transport materials, and the newly designed VCTOs are found to be promising hole transport materials. Among these, VCTO4b is found to show a lower band gap, whereas VCTO3c has a higher band gap. Furthermore, the study explores the roles of donor and acceptor groups in the band gap, ionization potential, electron affinity, exciton binding energy and light harvesting efficiency of these VCTOs. The spectral analysis shows that the modelled VCTOs have strong n → π* transitions, while the reference VCTOs were found to show predominant π → π* transitions. In summary, 9 out of 14 of the designed VCTOs were found to show better optoelectronic properties than their reference molecules.

A multispectroscopic and molecular docking investigation of the binding interaction between serum albumins and acid orange dye

The interaction of Acid Orange 10 (AO10) with bovine serum albumin (BSA) was investigated comparatively with that of human serum albumin (HSA) using multispectroscopic techniques for understanding their toxic mechanism. Further, density functional theory calculations and docking studies have been carried out to gain more insights into the nature of interactions existing between AO10 and serum albumins. The fluorescence results suggest that AO10 quenched the fluorescence of BSA through the combination of static and dynamic quenching mechanism. The same trend was followed in the interaction of AO10 with HSA. In addition to the type of quenching mechanism, the fluorescence spectroscopic results suggest that the binding occurs near the tryptophan moiety of serum albumins and the binding. AO10 has more binding affinity towards BSA than HSA. An AO10-Trp model has been created to explicitly understand the CHπ interactions from Baders quantum theory of atoms in molecules analysis which confirmed that AO10 bind more strongly with BSA than that of HSA due to the formation of three hydrogen bonds with BSA whereas it forms two hydrogen bonds in the case of HSA. These obtained results provide an in-depth understanding of the interaction of the acid azo dye AO10 with serum albumins. This interaction study provides insights into the underlying reasons for toxicity of AO10 relevant to understand its effect on bovids and humans during the blood transportation process.

Evidence for the powerful catalytic ability of imidozirconocene complex from its epoxide ring cleavage reactions – A DFT mechanistic view#

AbstractImidozirconocene complex is known for its bifunctional reactivity and catalytic ability and this complex mediates ring cleavage of epoxides. Cyclooctene oxide (1) Norbornene oxide (2) and 2,5-dimethyl cyclohexene oxide (3) undergo ring cleavage in the presence of imidozirconocene complex. Epoxide 1 has accessible β-hydrogens (type I) while epoxide 2 and 3 do not have them (type II). Normally type I epoxides undergo elimination while type II epoxides prefer insertion. All the insertion reactions lead to five-membered metallacycle formation and elimination results in thermodynamically stable allyl-alkoxy product. The insertion is a two-step process following either diradical or zwitterionic pathway, while elimination is a one-step concerted reaction. DFT (density functional theory) modelling of these reactions at B3LYP/LANL2DZ level show that epoxide 1 undergoes elimination in agreement with experiment. However, calculations indicate that epoxide (2) proceeds through diradical intermediate in contrast to experimental observations. Surprisingly, epoxide (3) that has both the β positions blocked by methyl groups undergoes elimination rather than insertion. AIM and EDA analyses offer further insights on the reaction mechanism and bifunctional reactivity of imidozirconozene complex. Graphical AbstractDFT calculations provide clear evidence for the bifunctional reactivity of imidozirconocene through bonding changes in the ring cleavage of epoxides Cyclooctene epoxide undergoes elimination and norbornene oxide follows insertion. Surprisingly, cyclohexene oxide which has both β positions blocked by methyl groups undergoes elimination instead of insertion due to carbocation stability.

A Spectroscopic Approach with Theoretical Studies to Study the Interaction of 9-aminoacridine with Certain Phenols

Abstract The influence of phenols upon the fluorescence quenching of 9-aminoacridine (9-AA) was examined in acetonitrile solution by employing steady state and time-resolved fluorescence measurements. On increasing the concentration of quencher molecules the absorption spectra of 9-AA change with significant bathochromic shift. The fluorescence intensity of 9-AA change in presence of quencher molecules were measured at various temperatures as a function of the quencher concentrations. The observed bimolecular quenching rate constant (kq) depends on the nature and electronic effect of substituent present in the quencher molecules. The bimolecular quenching rate constant (kq) decreases on increasing the oxidation potential of quencher molecules. To examine the quenching behavior, kq values were correlated with the free energy change (ΔG). To get forthcoming in the quenching process, fluorescence quenching experiments were carried out in different solvents of varying polarities. The observed result suggest the involvement of charge-transfer quenching mechanism. Lifetime measurements support static quenching. Further, the radical scavenging potential is calculated from density functional theory (DFT) calculations to address the quenching behavior of the quencher molecules. DFT result reveals that electronic features are important in tuning the quenching ability of the quencher molecules and found to agree with the obtained experiment result.