Nitroquinolone Fused Salicyl and Naphthyl Hydrazone Fluorescent Probes for the Detection of Fe3+and Pb2+ Ions.

The application of quinolones stretches over a large umbrella of medicinal field as well as chemosensor due to the presence of privileged heterocyclic aromatic rig system. Salicyl and Naphthyl Hydrazide motifs are also established fluorophore groups. Therefore in this work, we have designed and synthesized Salicyl hydrazide (3a-c) and naphthyl hydrazide fused nitroquinolones (5a-c) investigated for their fluorescent behaviour. Preliminary UV- absorption studies were carried out and the metal selectivity were examined with various metal ion. Among them, it was found that compound 3a was selective towards Fe3+ ions (λex = 330 nm, 1:1 DMF:H2O at pH = 7.4 in HEPES Buffer medium). 3a shows decrease emission intensity in presence of Fe3+ ions. Compound 5a shows enhancement in fluorescence intensity upon addition of Pb2+ ion (λex = 280 nm, 1:1 DMF:H2O at pH = 7.4 in HEPES Buffer medium). Further, the concentration dependence, competitive binding and EDTA reversibility were studied for selected compounds towards the respective cations selectivity. Jobs plot analysis indicate that 1:1 binding of 3a with Fe3+ ion (Ka = 3.17 x104M-1 and Limit Of Detection (LOD) = 5.1 × 10-7 M) whereas 5a showed 1:2 binding mode with Pb2+ ions (Ka = 2.14 × 106 M-1 and Limit Of Detection (LOD) = 2.613 × 10-9 M). Density Function Theoretical studies were performed as support for the experimental results.

Inquest for the interaction of canonical and non-canonical DNA/RNA bases with ternary based 2D Si2BN and doped Si2BN for biosensing applications.

Density functional theory (DFT) is invoked to investigate the interaction between the canonical (CN) and non-canonical (NC) bases with pristine Si2BN (Si2BN) and Phosphorous-doped Si2BN (P-dop-Si2BN) sheets. Inquest for the better sensing substrate is decided through the adsorption energy calculation which reveals that doping of phosphorous atom enhances the adsorption strength of AT (-83.74 kcal/mol) AU (-82.77 kcal/mol) and GC (-96.36 kcal/mol) base pairs. The CN and NC bases have higher adsorption energy than the previous reported values which concludes that the P-dop-Si2BN sheet will be optimal substrate to sense the bases. Meanwhile, the selected CN and NC (except hypoxanthine) bases interact with sheet in parallel manner which infers the π-π interaction with Si2BN and P-dop-Si2BN sheets. The energy gap variation (ΔEg%) of the P-dop-Si2BN complexes has a noticeable change, ranging from -24.75 to -197.28% which thrust the sensitivity of the P-dop-Si2BN sheet over the detection of CN and NC bases. The natural population analysis (NPA) and electron density difference map (EDDM) confirms that charges are transferred from CN and NC bases to Si2BN and P-dop-Si2BN sheet. The optical property of the P-dop-Si2BN complexes reveals that the noticeable red and blue shift in the visible and near-infrared regions (778 nm to 1143 nm) has been observed. Therefore, the above results conclude that the P-dop-Si2BN sheet plays a potential candidate to detect the CN and NC bases which contribute to the development of biosensors and DNA/RNA sequencing devices.Communicated by Ramaswamy H. Sarma.

Theoretical insights on the development of a 55-77 graphene sheet by embedding Agn=1-4 and Pdn=1-4 metal nanoclusters for efficient CO2 capture.

Recent advancements in two-dimensional (2D) allotropes of carbon materials and their usage as superior CO2 adsorbents can decrease the detrimental impact of CO2 on climate change. With the use of quantum chemical calculations, the effect of metal clusters (Agn = 1-4 and Pdn = 1-4) on the structural and electrical characteristics of 55-77 2D graphene sheet is examined in the current work with an aim towards enhancing CO2 capture capacity. The findings revealed that the binding energy (Eb) of the 55-77 sheet decoration with Pdn = 1-4 metal clusters are greater owing to chemisorption by 1.17 eV, 1.69 eV, 0.27 eV, and 1.58 eV than the decoration with Agn = 1-4 clusters. Moreover, CO2 molecules adsorb on the Pdn = 1-4 cluster decorated systems having -0.35 eV, 0.83 eV, 1.53 eV, and -0.98 eV greater adsorption energies than on the Agn = 1-4 decorated 55-77 sheet due to a stronger charge transfer. Further, the findings of an atoms in molecules (AIM) study show that the interaction between CO2 and Pdn = 1-4 decorated 55-77 sheet is partially covalent and non-covalent, confirming the greater charge transfer between the CO2 molecule and Pdn = 1-4 decorated 55-77 systems. Moreover, the CO2 adsorption on Pdn = 1-4 decorated 55-77 systems is clearly demonstrated by non-covalent interaction (NCI) analysis to be a strong electrostatic interaction at sign(λ2)ρ = -0.05 a.u, and this is further supported by an electron localization function (ELF) map. The highest CO2 adsorption capacity is obtained for 55-77/Pd1+CO2 with the value of 6.27 wt % which concludes 55-77 sheet with Pdn decoration is a more suitable structure for CO2 adsorption than the Agn decorated system.

Probing of sequential atmospheric degradation of chlorine radical initiated 1,8-cineole in the presence of O2 and NO radical with the emission of secondary pollution.

1,8-cineole is an essential monoterpene cyclic ether which is released into the troposphere by many types of plants. It interacts with several atmospheric oxidants because of which is removed from the troposphere via oxidation. The oxidation of 1,8-cineole with Cl radical and the subsequent addition of atmospheric O2 and NO radical with the intermediates are studied using the quantum chemical method. Further, the thermodynamic parameters of 1,8-cineole, such as enthalpy and Gibbs free energy are calculated for all initial and subsequent reactions to facilitate perspicacity. The dissociation and formation of chemical bonds during H abstraction from 1,8-cineole at C2, C6, and C8 sites are described using Mayer bond order analysis. The reaction force analysis demonstrates that the structural rearrangement is dominant with the yield percentages of 85%, 50.80%, and 96.9% over electron reordering with the yield percentages of 15%, 49.19%, and 3.03% respectively in the H abstraction reaction of 1,8-cineole. In the temperature range of 278-350 K, the total CVT/SCT rate constant is calculated to be 2.94 × 10-12 cm3/molecule/sec, which is consistent with the experimentally available value of 2.2 × 10-10 cm3/molecule/sec. At 298 K, branching ratios of rate constant of alkyl radical intermediates I1A, I1B, and I1C are calculated with the percentage of 42.19%, 21.52%, and 36.29% respectively, which suggest that the Cl addition to the C2 site contributes more to the total rate constant rather than the other two sites (C6 and C8). The lifetime of 1,8-cineole is calculated to be 5.2 weeks, implies that the 1,8-cineole may be readily destroyed in the atmosphere after it is released. Secondary pollutants formed from this degradation mechanism may be harmful to the environment and the living things.

Reinforcing the tetracene-based two-dimensional C48H16 sheet by decorating the Li, Na, and K atoms for hydrogen storage and environmental application -A DFT study.

To meet the increasing need of energy resources, hydrogen (H2) is being considered as a promising candidate for energy carrier that has motivated research into appropriate storage materials among scientists. Thus, in this study for the first time, zig-zag and armchair edged tetracene based porous carbon sheet (C48H16) is investigated for H2 storage using the density functional theory. To explore the hydrogen storage capacity, the hydrogen molecule is initially positioned parallel to the C48H16 sheet at three different sites, resulting in lower adsorption energies of -0.020, -0.024, and -0.015 eV respectively. The Li, Na, and K atoms are decorated to improve H2 adsorption on the C48H16 sheet. The Li atom decorated C48H16 sheet has a higher binding energy value of -2.070 eV than the Na and K atom decorated C48H16 sheet. The presence of Li, Na, and K atoms on the C48H16 sheet enhance the H2 adsorption energy than the H2 on the pristine C48H16 sheet. The decrease of Mulliken charge in alkali metal atoms (Li, Na, and K atom) on the C48H16 sheet reveal that the electron is transferred from H-σ orbital to s orbital of alkali metal atoms on the C48H16 sheet, leads to the enhancement of H2 binding. Compared to H2 adsorption on Na and K atom decorated C48H16 sheet, the H2 adsorption on Li atom decorated C48H16 sheet has the maximum adsorption energy value of -0.389 eV. The obtained hydrogen storage capacity of Li, Na, and K atoms decorated C48H16 sheets are about 7.49 wt%, 7.31 wt%, and 7.14 wt% respectively for four H2 molecules, which is greater than the targeted hydrogen storage capacity of the United States Department of Energy (DOE). Thus the obtained results in this work reveal that the decorated C48H16 sheets with Li, Na, and K atom plays the potential role in the H2 storage.

Epigenetically modified nucleobases (5hmc, 5fc, and 5caC) interaction with boron and nitrogen doped porous graphene (B/N-pGr) as promising materials for biosensing application: A density functional theory calculations.

In this present work, porous graphene (pGr), boron (B-pGr), and nitrogen (N-pGr) doped porous sheets are explored as a bio-sensor device for sensing modified nucleobases (MBs) in cancer therapy using density functional theory (DFT). The obtained geometrical, energetic and electronic properties revealed that the B-pGr is highly reactive and it adsorbs MBs better than the pGr and N-pGr, because B atom holds empty p-orbitals which easily interact with partially filled p-orbital of N and O atom. Thus, the adsorption energies of 5hmc, 5caC, and 5fc on B-pGr are high rather than the pGr and N-pGr. The corresponding adsorption energies are -96.074, -77.0, and -60.721 kcal/mol for 5hmc, 5caC, and 5fc respectively. The positive signature of ΔN values (0.005 eV, 0.076 eV, and 0.047 in MBs on pGr and 0.171 eV, 0.252 eV and 0.205 eV in MBs on N-pGr) are obtained at MBs on pGr and N-pGr complex. The negative ΔN values (-0.141 eV, -0.032 eV, and -0.061 eV in MBs on B-pGr) are obtained at MBs of B-pGr. The calculated absorption values shows that the B-pGr is strongly adsorbed MBs at 342 nm. The obtained results exhibit that the B-pGr sheet retains significant therapeutic potential as a bio-sensing application for cancer therapy.

Kinetics and degradation of camphene with OH radicals and its subsequent fate under the atmospheric O2 and NO radicals - A theoretical study.

Camphene (C10H16) is an abundant bicyclic monoterpene in the atmosphere which can be easily oxidized by the atmospheric OH radicals. In this study, the oxidation of camphene with OH radicals and its subsequent reactions are studied using quantum chemical method. Thermochemical parameters show that the addition of OH radicals to the terminal C10 atom of camphene is thermodynamically more stable than the addition of OH radicals to the internal C7 atom of camphene. The reaction force profile demonstrates that the formation of two hydroxyalkoxy radical intermediates (I1a and I2a) are mainly dominated by the structural rearrangement with 94.28% and 99.43% of the total energy, respectively. The overall reaction rate coefficient for camphene + OH radical is 2.1⨯10-12 cm3 molecule-1 sec-1 at 298 K and 1 atm which agree well with the experimental reaction rate coefficient (5.58⨯10-11 cm3 molecule-1 sec-1) for the reaction of camphene with OH radical. The branching ratio for the addition of OH radical to the C10 position of camphene is 68.32%, and the C7 position of camphene is 31.68% at 298 K. The calculated lifetime reveals that camphene degrades quickly in the atmosphere owing to its short lifetime of 5.3 h. The obtained mechanistic and kinetic results reveal that the addition of OH radical to the C10 position is more dominant than the C7 position, and it is more stable and spontaneous in the atmosphere.

Exploring two-dimensional graphene and boron-nitride as potential nanocarriers for cytarabine and clofarabine anti-cancer drugs.

Development in two-dimensional (2D) drug-delivery materials have quickly translated into biological and pharmacological fields. In this present work, pristine graphene (PG) and hexagonal boron nitride (h-BN) sheets are explored as a drug carrier for cytarabine (CYT) and clofarabine (CLF) anti-cancer drugs using density functional theory (DFT). The obtained geometrical, energetic and electronic properties revealed that the PG sheet is more reactive and it adsorbs CYT and CLF anti-cancer drugs better than the h-BN sheet. The adsorption energies of CYT and CLF on PG sheet is -24.293 and -23.308 kcal/mol respectively, this is due to the delocalized electrons present in the PG sheet. The flow of electron direction between anti-cancer drugs and 2D sheet are calculated by ΔN, ΔEA(B), and ΔEB(A) parameters and Natural bond orbital analysis (NBO). The electronic and optical properties are calculated to understand the chemical reactivity and stability of the complex systems. The obtained results exhibit that the PG sheet retains significant therapeutic potential as a drug delivery vehicle for a drug molecule to treat cancer therapy.

Exploring the nature of interaction and stability between DNA/RNA base pairs and defective & defect-dopant graphene sheets. A possible insights on DNA/RNA sequencing.

A quantum chemical investigation is performed to understand the adsorption behaviour of DNA/RNA base pairs onto the defective (Di-Vacancy (DV) and Stone-Wales (SW)), boron (B) and silicon (Si) defect-dopant graphene (B-DV, Si-DV, B-SW, and Si-SW) sheets using density functional theory (DFT). The stability of DNA/RNA base pairs on the Si-SW sheet is found to be -80.59 kcal/mol (G-C), -70.21 kcal/mol (A-T), and -69.78 kcal/mol (A-U). The quantum theory of atoms in molecule (QTAIM) analysis concluded that the interaction of DNA/RNA base pair on Si-SW sheet has partially electrostatic and partially covalent (Si⋯N) characters. The natural bond orbital analysis (NBO), electron density difference map (EDDM), and natural population analysis (NPA) are revealed that the charge has been transferred from DNA/RNA base pair to defective and defective-dopant graphene sheet. From the time-dependent density functional theory (TD-DFT), a strong redshift is observed at 482 nm for GC-Si-SW, 494 nm for AT-Si-SW, and 497 nm for AU-Si-SW. Hence, the substantial variations in the HOMO-LUMO gap (∆EHL) and UV spectra of Si-SW sheet after the adsorption of DNA/RNA base pair can be beneficially exploited to design a new bio-sensor or DNA/RNA sequencing devices.