Unimolecular isomerizations of CH radical cations: a computational study.

Concept: Eighteen concerted isomerization reactions of various CH radical cation (RC) species are studied and found to proceed via well-defined transition states, whose relative positions along the reaction pathway generally agree with Hammond's postulate. From the barrier heights, the rate coefficients of these reactions are estimated by using transition state theory, and the activation energies are computed. Through combination among themselves, these 18 isomerizations yielded 15 multi-step conversion routes of various CH species to the lowest energy benzene radical cation isomer 1, which routes are compared.

Bio-Nano Synergy in Therapeutic Applications: Drug-Graphene Oxide Nanocomposites for Modulated Acetylcholinesterase Inhibition and Radical Scavenging.

The current study explores the synergistic application of biophysical chemistry and nanotechnology in therapeutic treatments, focusing specifically on the development of advanced biomaterials to repurpose FDA-approved Alzheimer's disease (AD) drugs as potent antioxidants. By integration of AD drugs into graphene oxide (GO) nanocomposites, an attempt to enhance the acetylcholinesterase (AChE) inhibition and increase radical scavenging activity is proposed. This bionano synergy is designed to leverage the unique properties of both the nanomaterial surface and the bioactive compounds, improving treatment effectiveness.

New insights into the mechanism and kinetics of the addition reaction of unsaturated Criegee intermediates to CFCOOH and tropospheric implications.

In this work, we have investigated the mechanism, thermochemistry and kinetics of the reaction of --CHRCRCOO (where R, R = H, CH-) unsaturated Criegee intermediates (CIs) with CFCOOH using quantum chemical methods. The rate coefficients for the barrierless reactions were calculated using variable reaction coordinate variational transition state theory (VRC-VTST). For the --CHRCRCOO conformation in which conjugated CC and CO double bonds are aligned with each other, we propose a new pathway for the unidirectional addition of an OC-OH molecule (CFCOOH) to the CC double bond of --CHRCRCOO.

Strong Be-N Interaction Induced Complementary Chemical Tuning to Design a Dual-gated Single Molecule Junction.

The interaction between pyridines and the π-hole of BeH leads to the formation of strong beryllium-bonded complexes. Theoretical investigations demonstrate that the Be-N bonding interaction can effectively regulate the electronic current through a molecular junction. The electronic conductance exhibits distinct switching behavior depending on the substituent groups at the para position of pyridine, highlighting the role of Be-N interaction as a potent chemical gate in the proposed device.

Importance of water and intramolecular interaction governs substantial blue shift of C -H stretching frequency in complexes between chalcogenoaldehydes and water.

Geometrical structure, stability and cooperativity, and contribution of hydrogen bonds to the stability of complexes between chalcogenoaldehydes and water were thoroughly investigated using quantum chemical methods. The stability of the complexes increases significantly when one or more HO molecules are added to the binary system, whereas it decreases sharply going from O to S, Se, or Te substitution. The O-H⋯O H-bond is twice as stable as C -H⋯O and O-H⋯S/Se/Te H-bonds.

Strongly Bound π-Hole Tetrel Bonded Complexes between H SiO and Substituted Pyridines. Influence of Substituents.

Ab initio calculation at the MP2/aug-cc-pVTZ level has been performed on the π-hole based N Si tetrel bonded complexes between substituted pyridines and H SiO. The primary aim of the study is to find out the effect of substitution on the strength and nature of this tetrel bond, and its similarity/difference with the N C tetrel bond. Correlation between the strength of the N Si bond and several molecular properties of the Lewis acid (H SiO) and base (pyridines) are explored.

Auxiliary Therapeutic Role of Cholinergic Agents: Mechanistic Insights into the Antioxidant Behavior of Alzheimer's Disease Drugs.

Repurposing of existing drugs toward new therapeutic use(s) has become an emergent area of research in current times. In this context, the antioxidant behavior of eight cholinergic drugs used in the treatment of Alzheimer's disease (AD) was investigated theoretically. The low bond dissociation enthalpy values in all of the compounds advocated for the hydrogen atom transfer mechanism toward the observed antioxidant behavior.

Computational investigations on kinetics of reaction between t-butanol and OH radical and ozone formation potential.

The kinetics of the gas-phase atmospheric reaction of t-butanol with OH radicals is computationally studied using the CCSD(T)/aug-cc-pVTZ//M06-2X/6-311++G(d,p) level of calculation. The rate coefficients are evaluated for a wide temperature range of 250-1200 K and the calculated rate coefficient value of 0.83×10cmmolecules at 298K is in close agreement with experimental results.

Generation, structures, relative energies, and isomerization reactions of CH cations.

The B3LYP, MP2, and CBS-QB3 quantum chemical methods are used to study the relative energy and isomerization reactions of CH cations. Ease of generation of 14 CH isomers by ionic dissociation of halide precursors does not correlate well with carbocation stability. The reaction profiles of concerted isomerization of various CH cations to six select cations are established along with the respective transition states.

Comparison between Chlorine-Shared and π-Halogen Bonds Involving Substituted Phosphabenzene and ClF Molecules.

Ab initio MP2/aug-cc-pVTZ calculations have been carried out in order to study the nature of P···Cl halogen bonding interaction between a phosphorus atom in an aromatic ring in para-substituted phosphabenzene (PPBZ) and ClF molecule. The interaction of PPBZ with ClF results in two different types of complexes: (i) complex formation through the chlorine-shared halogen bond (T1-X-PPBZ·ClF) and (ii) complex formation halogen-π interaction (T2-X-PPBZ·ClF). T1-X-PPBZ·ClF complexes are found to be more stable than the T2-X-PPBZ·ClF complexes.

Nature of the Interaction of Pyridines with OCS. A Theoretical Investigation.

Ab initio calculations were carried out to investigate the interaction between -substituted pyridines (X-CHN, X=NH, CH, H, CN, NO) and OCS. Three stable structures of pyridine.OCS complexes were detected at the MP2=full/aug-cc-pVDZ level.

Unusual Fluorine Substitution Effect on S···Cl Bonding between Sulfides and Atomic Chlorine.

A theoretical investigation on the interaction of various sulfides and their fluorinated counterparts (HS, HSF, FS, CHSH, CHSF, CHFSH, CHFSF, NHSH, NHSF) with atomic chlorine has been carried out using density functional theory (DFT) based LC-BLYP/aug-cc-pVTZ and sophisticated ab initio CCSD(T)/aug-cc-pVQZ methods. The present study is intended to discuss the influence of the substituents implanted at the sulfur atom on the bonding parameters. The optimized geometries reveal that intermolecular S···Cl distances are short and range between 2.

Theoretical investigation on gas-phase reaction of CF3CH2OCH3 with OH radicals and fate of alkoxy radicals (CF3CH(O•)OCH3/CF3CH2OCH2O•).

Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of CF3CH2OCH3 (HFE-263fb2) with OH radicals using ab-initio and DFT methods. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels, respectively. Our calculations reveal that hydrogen abstraction from the CH2 group is thermodynamically and kinetically more facile than that from the CH3 group.

A theoretical investigation on the conformation and the interaction of CHF₂OCF₂CHF₂ (desflurane II) with one water molecule.

The conformation and the interaction of CHF₂OCF₂CHF₂ (desflurane II) with one water molecule is investigated theoretically using the ab initio MP2/aug-cc-pvdz and DFT-based M062X/6-311++G(d,p) methods. The calculations include the optimized geometries, the harmonic frequencies of relevant vibrational modes along with a natural bond orbital (NBO) analysis including the NBO charges, the hybridization of the C atom and the intra- and intermolecular hyperconjugation energies. In the two most stable conformers, the CH bond of the F2HCO- group occupies the gauche position.

Photophysics of Soret-excited free base tetraphenylporphyrin and its zinc analog in solution.

Photophysical properties of free base tetraphenylporphyrin and its zinc analog are investigated in detail in solvents of varying polarity by using steady state and time-resolved techniques. Both the porphyrins are excited at the Soret band to have better signal-to-noise ratio. Also, the fluorescence emission measurements are carried out by using dilute solutions (~10(-7)mol/L) of the fluorophores in order to minimize the self-quenching effect.

Theoretical study of the O···Cl interaction in fluorinated dimethyl ethers complexed with a Cl atom: is it through a two-center-three-electron bond?

Theoretical investigations are carried out on the interaction between fluorinated dimethyl ethers (FDME, nF = 0-4) and the Cl atom. Short intermolecular O···Cl distances between 2.401 and 2.

Strong hyperconjugative interactions in isolated and water complexes of desflurane: a theoretical investigation.

Ab initio MP2/aug-cc-pvDZ and density functional B3LYP calculations with the 6-311++G(d,p) basis set are performed to investigate the conformation of desflurane (CHF2OCHFCF3), its acidity/basicity and its interaction with one water molecule. The calculations include the optimized geometries, the harmonic frequencies of relevant vibrational modes, the binding energies with water, and a detailed natural bond orbital (NBO) analysis Iincluding the NBO charges, the hybridization of the C atoms and the intra- and intermolecular hyperconjugations. The relative energies of the two most stable conformers are discussed as a function of the total hyperconjugative energies resulting from the interaction of lone pairs of the O and F atoms to the different antibonding orbitals of desflurane.

Theoretical studies on the kinetics and mechanism of the gas-phase reactions of CHF(2)OCHF (2) with OH radicals.

The mechanism, kinetics and thermochemistry of the gas-phase reactions between CHF(2)OCHF(2) (HFE-134) and OH radical are investigated using the high level ab initio G2(MP2) and hybrid density functional model MPWB1K quantum chemical methods. Two relatively close in energy conformers are found for CHF(2)OCHF(2) molecule; both of them are likely to be important in the temperature range (250-1000 K) of our study. The hydrogen abstraction pathway for both the conformers with OH radical is studied and the rate constants are determined for the first time in a wide temperature range of 250 - 1000 K.

Exploring hydrogen bond in the excited state leading toward intramolecular proton transfer: detailed analysis of the structure and charge density topology along the reaction path using QTAIM.

Excited state intramolecular proton transfer (ESIPT) reaction along the O-H[Symbol: see text][Symbol: see text][Symbol: see text][Symbol: see text]O hydrogen bond of o-hydroxy benzaldehyde (OHBA), methyl salicylate (MS) and salicylic acid (SA) was investigated by ab-initio quantum chemical calculation and theory of atoms and molecules (QTAIM) for the first time. Variation in several geometric as well as QTAIM parameters along the reaction coordinate was monitored in the fully relaxed excited state potential energy curve (PEC) obtained from intrinsic reaction coordinate (IRC) analysis. Although, the excited state barrier height for the forward reaction (∆E (0) (#) ) reduces substantially in all the systems, MS and SA do not show any obvious asymmetry for proton transfer.

A theoretical investigation of the interaction between substituted carbonyl derivatives and water: open or cyclic complexes?

The structures and binding energies of complexes between substituted carbonyl bases and water are the B3LYP/6-311++G(d,p) computational level. The calculations also include the proton affinity (PA) of the O of the C=O group, the deprotonation enthalpies (DPE) of the CH bonds along a natural bond orbital analysis. The calculations reveal that stable open C=O···H(w) O(w) as well as cyclic CH···O(w)H(w) ···O=C complexes are formed.

Effect of solvent hydrogen bonding on excited-state properties of luminol: a combined fluorescence and DFT study.

The effect of solvent on the photoluminescence behavior of luminol was studied by steady-state fluorescence spectroscopy. The fluorescence spectral behavior of luminol is markedly different in polar protic solvents compared to that in aprotic solvents. A quantitative estimation of the contribution from different solvatochromic parameters, like solvent polarizibility (pi*), hydrogen-bond donor (alpha), and hydrogen-bond acceptor (beta), was made using the linear free energy relationship based on the Kamlet-Taft equation.

Theoretical investigation of the interaction between fluorinated dimethyl ethers (nF = 1-5) and water: role of the acidity and basicity on the competition between OH...O and CH...O hydrogen bonds.

Theoretical calculations have been carried out using ab initio MP2 and B3LYP density functional methods to investigate the interaction between fluorinated dimethyl ethers (nF = 1-5) and water. Depending on the number of F atoms implanted on the dimethyl ethers, linear structures stabilized by intermolecular O(w)H(w)..

Theoretical studies on kinetics and reactivity of the gas-phase addition and H-abstraction reactions of pyridine with atomic chlorine.

Theoretical investigations are carried out on the mechanism, kinetics, and thermochemistry for the reaction between pyridine and atomic chlorine with use of the hybrid density functional model BB1K, BHandHLYP, and the ab initio MP2 method. Both addition to and hydrogen abstraction reaction from all the potential sites are considered. Barrier heights and thermochemistry for all the possible addition and abstraction processes are calculated for the first time.

Synthesis, crystal structures, cytotoxicity and qualitative structure-activity relationship (QSAR) of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes, (n)Bu2Sn(L)2.

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes has been synthesized and characterized by (1)H-, (13)C-, (119)Sn NMR, ESI-MS (electrospray ionization mass spectrometry), IR and (119m)Sn Mössbauer spectroscopic techniques in combination with elemental analyses. The structures of four di-n-butyltin(IV) complexes, viz., (n)Bu(2)Sn(L(3))(2) (3), (n)Bu(2)Sn(L(4))(2) (4), (n)Bu(2)Sn(L(5))(2) (5) and (n)Bu(2)Sn(L(7))(2).