Mechanistic Inquisition on the Reduction of C17Si(NH2)2 to NH3: A DFT Study.

Activation of molecular nitrogen by silicon-substituted cyclo[18]carbon and its ability to produce the C17Si-(NH2)2 derivative, as the precursor of NH3, has been recently reported. This specific acquisition has piqued an interest to investigate the possibility of NH3 formation with further addition of H2 molecules in the gaseous reaction media. The current investigations reported in this article show that two moles of molecular H2 generate two molecules of NH3 and a C17Si-H2 byproduct from its precursor. The catalyst gets restored by an in situ reaction between some unreacted C17Si-N2 and the byproduct in the media. This reaction also produces the next C17Si-(NH)2 adduct, which restarts the catalytic cycle for NH3 production again.

Sleep quality evaluation, correlation with headache frequency, and propensity to conversion from episodic to chronic daily headache in migraine patients: A cross-sectional study.

Objective: The aim of the study was to determine the association between sleep quality with headache frequency in migraine patients and also to evaluate migraine trigger and non-headache symptoms in episodic and chronic migraine groups and evaluation of the same in poor and good sleepers (GSs) in migraine population. Materials and Methods: In a cross-sectional and observational study in a tertiary care hospital of East India between January 2018 and September 2020, migraine patients were evaluated. Migraine patients were divided into two groups: Episodic migraine (EM) and chronic migraine (CM) group according to ICHD 3 b classification and into poor sleepers (PSs, Global Pittsburgh Sleep Quality Index [PSQI] >5) and GSs (Global PSQI ≤5). Sleep was evaluated using PQSI - a self-rated questionnaire and disease pattern, associated non-headache symptoms, and triggers were evaluated in between groups. Demographic, headache character, and sleep parameters including seven "component" scores: Subjective sleep quality, sleep latency, sleeps duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction and global PQSI were compared between groups (EM and CM). Similar parameters were also compared between PSs and GSs group. Statistical analysis was performed using the χ2 test for categorical variables and the t-test and Wilcoxon rank-sum test for continuous variables. Correlation between two normally distributed numerical was tested by Pearson correlation coefficient assessment. Results: One hundred migraine patients were analyzed, among which 57 were PSs and 43 were GSs and 51 patients had EM and 49 patients had CM. Moderately significant "r" value noted in between headache frequency and global PQSI score (r = 0.45, P < 0.01). In non-headache symptoms, blurring of vision (EM 8 [16%] and CM 16 [33%] P = 0.05), nasal congestion (EM - 3 [6%] and CM - 12 [24%], P = 0.01), and cervical muscle tenderness (EM- 23 [45%] and CM - 34 [69%], P = 0.01) were more prevalent in chronic headache group along with allodynia (EM - 11 [22%] and CM - 25 [51%], P < 0.01). Conclusion: Chronic headache group had poor subjective sleep quality, increased sleep latency, decreased sleep duration, decreased sleep efficiency, and increased sleep disturbance in comparison to episodic group which has therapeutic implication. The non-headache symptoms which are more prevalent in CM patients increase the overall disability.

Discriminative 'Turn-on' Detection of Al3+ and Ga3+ Ions as Well as Aspartic Acid by Two Fluorescent Chemosensors.

In this work, two Schiff-base-based chemosensors L1 and L2 containing electron-rich quinoline and anthracene rings were designed. L1 is AIEE active in a MeOH-H2O solvent system while formed aggregates as confirmed by the DLS measurements and fluorescence lifetime studies. The chemosensor L1 was used for the sensitive, selective, and reversible 'turn-on' detection of Al3+ and Ga3+ ions as well as Aspartic Acid (Asp). Chemosensor L2, an isomer of L1, was able to selectively detect Ga3+ ion even in the presence of Al3+ ions and thus was able to discriminate between the two ions. The binding mode of chemosensors with analytes was substantiated through a combination of 1H NMR spectra, mass spectra, and DFT studies. The 'turn-on' nature of fluorescence sensing by the two chemosensors enabled the development of colorimetric detection, filter-paper-based test strips, and polystyrene film-based detection techniques.

Solvent-regulated fluorescence off-on signaling of Ni(II) and Zn(II) with the formation of two mononuclear complexes with an ATP detection ability by Zn(II) assembly.

The current study shows that Schiff base HL, (Z)-2,4-dibromo-6-(((piperidin-2-ylmethyl)imino)methyl)phenol, can be used successfully as a selective chemosensor for Zn(II) and Ni(II) among several competing cations in purely aqueous and semi-aqueous media. Under UV light in methanol-water (9 : 1) HEPES buffer, the receptor gives its response by changing its color to cyan color in the presence of Zn(II) and to bluish cyan color in the presence of Ni(II). Surprisingly, the chemosensor can only reliably identify Zn(II) in a hundred percent aqueous medium by changing its color to light yellow. UV and fluorescence studies in both aqueous and semi-aqueous media are used to further investigate this Zn(II) and Ni(II) recognition phenomenon. The high values of the host-guest binding constants, obtained by electronic and fluorescence titration, ensure that a strong bond exists between HL and Ni(II)/Zn(II). As anticipated, two highly luminescent mononuclear, crystalline compounds, complexes 1 and 2, have been developed by a separate reaction of HL and Zn(II)/Ni(II), and the high luminous properties are due to the occurrence of Chelation Enhanced Fluorescence (CHEF). According to the single crystal structure, the asymmetric units of both complexes consist of two deprotonated chemosensor units and one Zn(II)/Ni(II), leading to the formation of an octahedral complex. For Ni(II) and Zn(II) sensing, the predicted LOD is in the nanomolar range. Both complexes 1 and 2 are fluorescence active and studies to check their ATP detection ability, but intriguingly, only complex 2 is capable of detecting ATP in a fully aqueous solution. Finally, the live cell imaging study validates the two sensors' biosensing functionality.

Activation and Conversion of Molecular Nitrogen to the Precursor of Ammonia on Silicon Substituted Cyclo[18]Carbon: a DFT Design.

Recent synthesis of sp-hybridized cyclo[18]carbon allotrope has attracted immense curiosity. Since then, a generous amount of theoretical studies concerning aromaticity, adsorption, and spectra of the molecule have been performed. However, very few stuides have been carried out concerning its reactivities and catalytic behaviour. In this article, a DFT-based inquisition has been reported regarding the reactivity of Si substituted cyclo[18]carbon molecule towards molecular N2 . Results show that the Si substituted derivative is effective in producing adducts with molecular nitrogen. Charge calculations and IRC trapping methods indicate that only the Si center of C17 Si and its (HOMO-1) level participate in N2 addition. The N-adduct so formed, is then found to spontaneously react with molecular H2 . The addition of two H2 molecules to the activated nitrogen molecule to give respective amine derivatives have also been studied. The successful generation of the precursor of NH3 by C17 Si lays a clear emphasis on its potentiality.

Influence of Linker Orientation and Regulative Factor(s) in Liposomal Gene Delivery: A Molecular Level Investigation.

Molecular level understanding of liposome-gene interaction is immensely important for the research progress and technological advancement of gene delivery, which is highly significant due to a wide range of applications of gene therapy. The liposomal gene delivery method is one of the most promising techniques due to its efficacy to easily fuse with the cell membrane and its lower toxicity. In vivo gene delivery using liposomes is reported to be extremely successful. However, the success of gene delivery depends on various factors including the chemical nature of the structural unit of the liposome. To explore the regulative factor(s) for liposomal gene delivery, we systematically analyze the linker orientation effect on the gene delivery efficiency of liposomes through a density functional theory (DFT) study. Interestingly, it is observed that the liposome-gene interaction is not the regulating factor for successful gene delivery. The success depends on the gel to liquid melting temperature of the liposome.

Schematic Design of Metal-Free NHC-Mediated Sequestering and Complete Conversion of SO2 to Thiocarbonyl S-Oxide Derivatives at Room Temperature.

The sequestering and complete conversion of SO2 to valuable chemicals in a metal-free pathway is highly demanded. The recent success of SO2 fixation by N-heterocyclic carbenes instigated further studies in this regard. Previous reports were confined within the carbene-SO2 reaction mechanism and the stability of oxathiirane S-oxide derivatives. The complete conversion of captured SO2 to precious chemicals was not studied. The present inquisition has accomplished the scarcity of the earlier studies. It is observed that in the presence of an excess amount of carbene, the registered SO2 is converted to the ketone derivative and thiocarbonyl S-oxide derivative. An electronic level investigation of these reactions is carried out. From the change of the molecular orbitals along the reaction path, it is concluded that the reaction between the oxathiirane S-oxide derivative and carbene follows a frog's hunting mechanism.

Competitive Reactivity of SO2 and NO2 with N-Heterocyclic Carbene: A Mechanistic Study.

Recent DFT based molecular engineering to obtain stable oxathiirane S-oxide derivatives evokes the recommencement of the use of carbenes for the sequestering of SO2, which has been kept separate so far. Carbene is one of the key chemicals for the sequestering of various premier greenhouse gases like CO2, CO, N2O, etc. In this respect, a comparative study of the reactivity of carbenes with variant greenhouse gases is highly demanding. The present investigation is engrossed in the comparative reactivity of SO2 and NO2 with carbenes. All three selected carbenes are highly susceptible to SO2 and NO2. Through an immaculate mechanistic study, we are able to corroborate that the end product of the carbene-SO2 reaction is an adduct which has a preferable structure having a six-membered ring with hydrogen bonding instead of ketone and SO with higher thermodynamic stability than the corresponding oxathiirane S-oxide derivative. Carbene reacts with NO2 to form a stable carbene N, N-dioxide derivative which forms vibrationally excited oxaziridine N-oxide which rapidly dissociates to form a ketone derivative. The formation of carbene S, S-dioxide and carbene N, N-dioxide is a barrierless process. The dissociation of oxaziridene N-oxide is also a barrierless process.

DFT based Computational Methodology of IC50 Prediction.

BACKGROUND: IC50 is one of the most important parameters of a drug. But, it is very difficult to predict this value of a new compound without experiment. There are only a few QSAR based methods available for IC50 prediction, which is also highly dependable on a huge number of known data. Thus, there is an immense demand for a sophisticated computational method of IC50 prediction in the field of in silico drug designing. OBJECTIVE: Recently developed quantum computation based method of IC50 prediction by Bag and Ghorai requires an affordable known data. In present research work, further development of this method is carried out such that the requisite number of known data being minimal. METHODS: To retrench the cardinal data span and shrink the effects of variant biological parameters on the computed value of IC50, a relative approach of IC50 computation is pursued in the present method. To predict an approximate value of IC50 of a small molecule, only the IC50 of a similar kind of molecule is required for this method. RESULTS: The present method of IC50 computation is tested for both organic and organometallic compounds as HIV-1 capsid A inhibitor and cancer drugs. Computed results match very well with the experiment. CONCLUSION: This method is easily applicable to both organic and organometallic compounds with acceptable accuracy. Since this method requires only the dipole moments of an unknown compound and the reference compound, IC50 based drug search is possible with this method. An algorithm is proposed here for IC50 based drug search.

DFT based engineering of N-heterocyclic carbenes to exacerbate its activity for SO2 fixation and storage.

Carbene compounds are very reactive to SO2 which assert their candidature to seize this greenhouse gas. Unfortunately, most of the carbenes which produce S,S-dioxide with SO2, undergo dissociation to yield ketone derivative and SO through an intermediate formation of oxathiirane S-oxide derivative. Thus, carbenes are excluded from the list of catalyst for SO2 fixation and storage technology. To eradicate this retardation, the stability of different oxathiirane S-oxide derivatives obtained from SO2 and 56 carbenes of various structures are studied using Density Functional Theory (DFT). Through our study, we are able to find out three oxathiirane S-oxide derivatives which have positive ΔG values for their decomposition to the respective ketone derivatives. This study corroborates that proper engineering of carbene leads to produce a stable oxathiirane S-oxide derivative as a stable product. We observed that carbenes are highly efficient to nab SO2 at room temperature. This finding should necessitate the recommencement of the use of carbene for SO2 fixation technology. We also found three carbenes which are able to produce sulfene derivative (C - S bond length is less than 1.7 Å) on reaction with SO2.

"Dial-In" Emission from a Unique Flexible Material with Polarization Tuneable Spectral Intensity.

The development of organic photoluminescent materials, which show promising roles as catalysts, sensors, organic light-emitting diodes, logic gates, etc., is a major demand and challenge for the global scientific community. In this context, a photoclick polymerization method is adopted for the growth of a unique photoluminescent three-dimensional (3D) polymer film, E, as a model system that shows emission tunability over the range 350-650 nm against the excitation range 295-425 nm. The DFT analysis of energy calculations and π-stacking supports the spectroscopic observations for the material exhibiting a broad range of emission owing to newly formed chromophoric units within the film. Full polarization spectroscopic Mueller matrix studies were employed to extract and quantify the molecular orientational order of both the ground (excitation) and excited (emission) state anisotropies through a set of newly defined parameters, namely the fluorescence diattenuation and fluorescence polarizance. The information contained in the recorded fluorescence Mueller matrix of the organic polymer material provided a useful way to control the spectral intensity of emission by using pre- and post-selection of polarization states. The observation was based on the assumption that the longer lifetime of the excited dipolar orientation is attributed to the compactness of the film.

A phototunable anion receptor for C-HX interactions with benzoate anions.

A supramolecular receptor consisting of two anthracene moieties with binding motifs for binding of benzoate anions is reported here. NMR studies indicate that the binding involves π-π interactions and CHX interactions. Upon exposure to >350 nm light, the receptor undergoes a [4 + 4] photoelectrocyclization restricting the access to the binding site for benzoate. The reverse reaction works in the presence of the dual stimuli of 254 nm light and the benzoate anions. The work thus demonstrates a light mediated dynamic control of the binding pocket of a supramolecular anion receptor.

Facile synthesis of highly disperse Ni-Co nanoparticles over mesoporous silica for enhanced methane dry reforming.

A synergistic approach was made to develop a highly stable and carbon resistant catalyst system based on cobalt and nickel supported over modified mesoporous silica for the dry reforming of methane (DRM). Modified mesoporous silica is prepared by a hydrothermal method, and the total Co & Ni composition is taken at around 5% by using the deposition-precipitation technique. CO2 reforming with methane was performed at 400-800 °C under atmospheric pressure as well as at a pressure of 1 MPa, keeping the CH4/CO2 ratio equal to unity. The catalyst assembly before and after the reaction was thoroughly characterized by a wide range of analytical techniques including N2 physisorption, XRD, TPR, TPO, TPH, XPS, SEM, TEM, elemental mapping, TG-DTG. The physicochemical characterization results confirmed the homogeneous distribution of nanosized metal particles into the hexagonal framework of modified silica, which plays a vital role towards a stronger metal support interaction that renders carbon deposition upon the active metal surface as well as avoids metal sintering at higher temperatures. At the same time, the coexistence of nanosized Co and Ni into the mesopores produced a synergy which provides better stability without any deactivation at high pressure reaction conditions. In situ DRIFT analysis evidenced that the reaction proceeds over these catalysts through an initial pathway in which both methane and carbon dioxide initially dissociate over the metal along with a bifunctional pathway in which methane dissociates over the active metal and carbon dioxide activated over the basic support surface via a formate intermediate. Density Functional Theory (DFT) calculations were also performed and further support the proposed mechanism from DRIFT studies.

Synthesis of AgWCNx Nanocomposites for the One-Step Conversion of Cyclohexene to Adipic Acid and Its Mechanistic Studies.

A novel catalyst composed of silver nanoparticles grafted on WCNx has been prepared by using a facile pH-adjusted method. The material reported in this study presents a non-mineral acid route for the synthesis of the industrially significant monomer adipic acid through the selective oxidation of cyclohexene. Ag has been stabilized in the hydrophobic matrix during the formation of the mesoporous silica material by using aniline as stabilizing agent. A cyclohexene conversion of 92.2 % with 96.2 % selectivity for adipic acid was observed with the AgWCNx -2 catalyst, therefore, the AgWCNx catalyst was found to be efficient for the direct conversion to adipic acid with respect to their monometallic counterparts. The energy profile diagrams for each reaction path by using the AgWCNx catalyst were studied along with their monometallic counterparts by using the Gaussian 09 package. The reported material can avoid the use of harmful phase-transfer catalysts (PTC) and/or chlorinated additives, which are two among other benefits of the reported work.

Enhancement of biocompatibility and photoacoustic contrast activity of metal clusters.

Organometallic carbonyl clusters (OMCC) of group VIII elements are water soluble, bio-compatible and stable high-contrast photoacoustic agents for live cell imaging. But, they have limited application due to weak absorption within 700-1000nm wavelength which is known as the biological window of absorption. In this article, we report that hexa-nuclear iron (Fe6) carbonyl cluster derivatized with sodium thio-propanoate has very good absorption within 700-1600nm wave length. This modeled compound is water soluble and bio-compatible. The bio-compatibility of this compound is tested through cytotoxicity, LogP and metabolic probability at CYP450-2D6 enzyme.

Development of Quantum Chemical Method to Calculate Half Maximal Inhibitory Concentration (IC50 ).

Till date theoretical calculation of the half maximal inhibitory concentration (IC50 ) of a compound is based on different Quantitative Structure Activity Relationship (QSAR) models which are empirical methods. By using the Cheng-Prusoff equation it may be possible to compute IC50 , but this will be computationally very expensive as it requires explicit calculation of binding free energy of an inhibitor with respective protein or enzyme. In this article, for the first time we report an ab initio method to compute IC50 of a compound based only on the inhibitor itself where the effect of the protein is reflected through a proportionality constant. By using basic enzyme inhibition kinetics and thermodynamic relations, we derive an expression of IC50 in terms of hydrophobicity, electric dipole moment (µ) and reactivity descriptor (ω) of an inhibitor. We implement this theory to compute IC50 of 15 HIV-1 capsid inhibitors and compared them with experimental results and available other QASR based empirical results. Calculated values using our method are in very good agreement with the experimental values compared to the values calculated using other methods.

First- and second-order electrical properties computed at the FSMRCCSD level for excited states of closed-shell molecules using the constrained-variational approach.

Fock space multireference coupled-cluster (FSMRCC) method emerged as an efficient tool to describe the electronic structure of nearly degenerate cases. Development of linear response has been one of the challenging problems in FSMRCC due to the multiple-root nature of the effective Hamiltonian. A response from any of the roots would span the space for getting the properties. Hence, all roots perturbed by the external field would proliferate the excited states. We recently developed the FSMRCC method for the efficient evaluation of analytic response properties using a constrained variation approach. In this paper, we present analytic dipole moments and polarizabilities of H(2)O, O(3), and CH(+) molecules in low-lying excited states along with brief discussion of singlet triplet decoupling of (1,1) sector of FSMRCC resulting from spin adaptation.