Suicide, suicide attempts and self-harm in Moroccan prisons.

PURPOSE: High rates of suicide and self-harm are reported in prisons in Western countries, while fewer studies exist from a non-Western context. This study aims to identify rates of suicide, non-fatal suicide attempts and self-harm in Moroccan prisons and to better understand the context, methods, tools, predictors and profile of persons engaged in the acts. DESIGN/METHODOLOGY/APPROACH: The authors report findings from a mixed-methods study carried out before an intervention project. The study consists of a systematic literature review, an analysis of suicide case files, a quantitative survey on suicide attempts and self-harm, as well as interviews and focus group discussions. The authors calculate suicide, suicide attempt and self-harm rates and present descriptive data on the incidents. The authors use regression models to explore the association between the number of incidents per individual and selected predictors, adjusting for clustering by institution. FINDINGS: Over a four-year period, 29 detained persons in Morocco died by suicide (average annual suicide rate 8.7 per 100,000). Most were men under the age of 30. Hanging accounted for all but one case. In one year, 230 suicide attempts were reported. Over a three-months period, 110 self-harm cases were reported from 18 institutions, cutting being the most common method. Self-harm was significantly more prevalent among persons with a life sentence or repeated incarcerations. RESEARCH LIMITATIONS/IMPLICATIONS: To make the study manageable as part of an intervention project, the authors collected data on suicides and suicide attempts from all prisons, while data on self-harm were collected from fewer prisons and over a shorter time period. The authors did not collect comparable information from detained persons who did not die by suicide, attempt suicide or self-harm. This prevented comparative analyses. Further, it is possible that self-harm cases were not reported if they did not result in serious physical injury. Data were collected by prison staff; thus, the voice of incarcerated persons is absent. PRACTICAL IMPLICATIONS: This study provided a solid basis for designing an intervention project including the development of a national prison policy and guidelines on suicides, suicide attempts and self-harm and a country-wide training program for prison staff. It also led to a better surveillance system, allowing for trend analysis and better-informed policymaking. The qualitative results helped create an understanding of how staff may trivialize self-harm. This was integrated into the training package for staff, resulting in the creation of prison staff trainers who became the strongest advocates against the notion that self-harm was best ignored. ORIGINALITY/VALUE: To the best of the authors' knowledge, this is the first published data on suicide and self-harm in Moroccan prisons. It underscores the necessity for the intervention project and gives valuable insights into suicide and self-harm in a non-Western prison context. Further research is needed to assess whether the findings are typical of the region.

Adsorption studies of isoxazole derivatives as corrosion inhibitors for mild steel in 1M HCl solution: DFT studies and molecular dynamics simulation.

CONTEXT: The corrosion of mild steel is a significant issue in various industries, prompting the need for effective corrosion inhibitors. This study focuses on understanding the corrosion inhibition properties of organic compounds derived from isoxazole, namely series Iso(a), Iso(b), Iso(c), Iso(d), Iso(e), Iso(f), Iso(g), and Iso(h), which could have implications for materials science and industrial applications. By investigating the influence of different substitutions on these compounds, valuable insights can be gained into designing better corrosion inhibitors for practical use. METHODS: Theoretical studies were conducted using density functional theory (DFT) with the B3LYP functional and the 6-31G (d,p) basis set. These calculations enabled the evaluation of various parameters including frontier orbital energies (EHOMO, ELUMO), energy gap (∆E), electronegativity (χ), absolute hardness (η), softness (σ), fraction of transferred electrons (∆N), as well as local properties such as natural atomic populations and Fukui indices. Additionally, molecular dynamics simulations were performed to study the adsorption behavior of the inhibitors on the surface of Fe (110). The simulations were conducted using Materials Studio version 8.0 software package using COMPASS force field to understand the impact of different functional groups on the inhibitors before and after adsorption on the iron surface.

Rational Design of New Small Derivatives of 2,2'-Bithiophene as Hole Transport Material for Perovskite Solar Cells.

Using Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT) methods, this inquiry theoretically examines seven novel hole-transport materials (HTMs) namely DFBT1, DFBT2, DFBT3, DFBT4, DFBT5, DFBT6, and DFBT7 based on the 2,2'bithiophene core for future use as HTMs for perovskite solar cells (PSCs). The model molecule has been modified through substituting the end groups situated on the diphenylamine moieties with a tow acceptor bridged by thiophene, this modification was performed to test the impact of the π-bridge and acceptor on the electronic, photophysical, and photovoltaic properties of the newly created molecules. DFBT1 - DFBT7 displayed a lower band gap (1.49 eV to 2.69 eV) than the model molecule (3.63 eV). Additionally, the newly engineered molecules presented a greater λmax ranging from 393.07 nm to 541.02 nm in dimethylformamide solvent, as compared to the model molecule (380.61 nm). The PCEs of all newly designed molecules (22.42% to 29.21%) were high compared with the reference molecule (19.62%). Thus, this study showed that all seven newly small molecules were excellent candidates for a novel PSC.

Computational studies of the influence of auxiliary acceptors in the D-A'-π-A structure of organic dyes on the photovoltaic performance of dye solar cells.

CONTEXT: A series of five organic dyes (Mi, i = 1-5) of the D-A'-π-A structure were designed based on reference dye (Ref), and the influence of different auxiliary acceptors (A') on their efficiency in dye-sensitized solar cells (DSSC). METHODS: Was studied theoretically using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. In this context, the electronic structures, optical properties, and the parameters influencing the power conversion efficiency (PCE), such as light harvesting efficiency (LHE), electron injection driving force (∆Ginject.), and open circuit photo-voltage (VOC), have been evaluated and discussed. The modification of the auxiliary acceptor (A') in the D-A'-π-A structure of the designed organic dyes has the advantage of significantly decreasing the band gap, which leads to the broadening of the absorption band that is red-shifted and improves the photovoltaic characteristics compared to Ref. Theoretical results reveal that M1, and M5 can be used as excellent sensitizer candidates for DSSC applications.

A theoretical study on the role of the π-spacer in the thoughtful design of good light-absorbing dyes with phenothiazine for efficient dye-sensitized solar cells (DSSCs).

CONTEXT: In this work, we designed ten new organic phenothiazine dyes bridged by different πi-spacers (PTZ1-PTZ10) of D-π-A type based on the synthesized dye CC202-III for their efficacy in dye-sensitized solar cells (DSSC) applications. To learn how various π-spacers affect their performance in DSSCs, these isolated dyes and dye-cluster systems have had their geometries, electronic structures, absorption spectra, dipole moments, and molecular electrostatic potential examined and talked about. Additionally, a number of quantization parameters that affect power conversion efficiency (PCE), including light collection efficiency (LHE), reorganization energy (λtotal), vertical dipole moment (µnormal), strength electron injection driving force (ΔGinject), regeneration driving force (ΔGreg), excited state lifetime (τ), and open circuit voltage (VOC), were calculated in order to identify the organic dyes that would be best suited for DSSC applications. Calculated results revealed that the designed dyes PTZ3, PTZ4, PTZ5, and PTZ10 exhibit a lower energy gap among all dyes compared to the corresponding CC202-III. Additionally, PTZ3, PTZ4, PTZ5, PTZ7, PTZ8, PTZ9, and PTZ10 exhibit significant red-shifted absorption spectra compared to the other dyes with a larger oscillator strength, which improves the photocurrent density of the devices. The findings thus imply that bridge modification is a workable tactic to raise DSSC effectiveness. METHOD: We used density functional theory (DFT) and time-dependent DFT (TD-DFT) methods to study the electronic and photovoltaic properties of the dyes designed (PTZ1-PTZ10) to assess their effectiveness in DSSCs. DFT and TD-DFT simulations are theoretically used to deeply analyze key characteristics of all organic dyes that affect open-circuit voltage (VOC) and short-circuit current (JSC) to identify structure-property relationships.

Theoretical investigation of the effect of changing the auxiliary acceptor on the performance of organic D-A'-A dyes used as sensitizers in DSSCs.

CONTEXT: Dye-sensitized solar cells (DSSCs) have displayed huge potential in inexpensive, efficient, and clean solar energy technology. In this work, seven new dyes with the structure D-A'-A were designed in which the thiophene in the reference dye was replaced by auxiliary acceptors (A'). These dyes consist mainly of a pyranylidene-based electron donor D and the cyanoacrylic acid moiety as acceptor A. A computational investigation was carried out on the effect of various auxiliary acceptors A' on the efficiency of D-A'-A dyes in isolation and after binding to the semiconductor TiO2. Optimized structures, geometrical, optoelectronic, and photovoltaic parameters were calculated to predict promising dyes for potential use as solar cell sensitizers, including band gap (Egap), natural bond orbital (NBO) analysis, nonlinear optical properties (NLO), UV-Vis absorption spectra, maximum absorption wavelength (λmax), reorganization energy (λtotal), light-harvesting efficiency (LHE), electron injection driving force (ΔGinject) and open-circuit photovoltage (VOC). The results of this study revealed that all designed dyes, compared to the reference dye, are characterized by small Egap and λtotal values as well as large λmax, in addition to significant NLO properties and large adsorption energy (Eads). Therefore, all studied dyes can be used as sensitizers in DSSC. METHODS: Using Density Functional Theory (DFT) approaches with the B3LYP functional and the 6-31G(d,p) basis set, all ground state geometries of the isolated dyes were fully optimized. Time-Dependent Density Functional Theory (TD-DFT) method using the CAM-B3LYP/6-31G(d,p)/IEF-PCM level was applied to simulate the UV-visible absorption properties. All isolated dye calculations were performed using the Gaussian 09 software package. DFT calculations have been carried out with the DMol3 package included in Materials Studio for simulating the adsorption of the investigated dyestuff on the TiO2 surface of anatase (101), using the generalized gradient corrected approximation (GGA) approach of the Perdew-Burke-Ernzerhof (PBE) functional with the basic set of digital double polarisation (DNP). To study the optical performance of dye@TiO2 the PBE/DNP method present in DMol3 was applied.

Identification of terpenoids as potential inhibitors of SARS-CoV-2 (main protease) and spike (RBD) via computer-aided drug design.

The scientific community has been faced with a major challenge in the fight against the SARS-CoV-2 virus responsible for the COVID-19 pandemic, due to the lack of targeted antiviral drugs. To address this issue, we used an in silico approach to screen 23 natural compounds from the terpenoid class for their ability to target key SARS-CoV-2 therapeutic proteins. The results revealed that several compounds showed promising interactions with SARS-CoV-2 proteins, specifically the main protease and the spike receptor binding domain. The molecular docking analysis revealed the importance of certain residues, such as GLY143, SER144, CYS145 and GLU166, in the main protease of the SARS-CoV-2 protein, which play a crucial role in interactions with the ligand. In addition, our study highlighted the importance of interactions with residues GLY496, ARG403, SER494 and ARG393 of the spike receptor-binding domain within the SARS-CoV-2 protein. ADMET and drug similarity analyses were also performed, followed by molecular dynamics and MM-GBSA calculations, to identify potential drugs could be repurposed to combat COVID-19. Indeed, the results suggest that certain terpenoid compounds of plant origin have promising potential as therapeutic targets for SARS-CoV-2. However, additional experimental studies are required to confirm their efficacy as drugs against COVID-19.Communicated by Ramaswamy H. Sarma.

Computational Investigation of Conformational Properties of Short Azapeptides: Insights from DFT Study and NBO Analysis.

Azapeptides have gained much attention due to their ability to enhance the stability and bioavailability of peptide drugs. Their structural preferences, essential to understanding their function and potential application in the peptide drug design, remain largely unknown. In this work, we systematically investigated the conformational preferences of three azaamino acid residues in tripeptide models, Ac-azaXaa-Pro-NHMe [Xaa = Asn (4), Asp (5), Ala (6)], using the popular DFT functionals, B3LYP and B3LYP-D3. A solvation model density (SMD) was used to mimic the solvation effect on the conformational behaviors of azapeptides in water. During the calculation, we considered the impact of the amide bond in the azapeptide models on the conformational preferences of models 4-6. We analyzed the effect of the HB between the side-chain main chain and main-chain main-chain on the conformational behaviors of azapeptides 4-6. We found that the predicted lowest energy conformation for the three models differs depending on the calculation methods. In the gas phase, B3LYP functional indicates that the conformers tttANP-1 and tttADP-1 of azapeptides 4 and 5 correspond to the type I of ß-turn, the lowest energy conformation with all-trans amide bonds. Considering the dispersion correction, B3LYP-D3 functional predicts the conformers tctANP-2 and tctADP-3 of azapeptide 4 and 5, which contain the cis amide bond preceding the Pro residue, as the lowest energy conformation in the gas phase. The results imply that azaAsx and Pro residues may involve cis-trans isomerization in the gas phase. In water, the predicted lowest energy conformer of azapeptides 4 and 5 differs from the gas phase results and depends on the calculational method. For azapeptide 6, regardless of calculation methods and phases, tttAAP-1 (ß-I turn) is predicted as the lowest energy conformer. The results imply that the effect of the side chain that can form HBs on the conformational preferences of azapeptides 4 and 5 may not be negligible. We compared the theoretical results of azaXaa-Pro models with those of Pro-azaXaa models, showing that incorporating azaamino acid residue in peptides at different positions can significantly impact the folding patterns and stability of azapeptides.

Designing and theoretical study of benzocarbazole-based D-π-D type small molecules donor for organic solar cells.

Seven new molecules (S1-S7) of D-π-D type have been designed for organic photovoltaic applications. The DFT and TD-DFT methods were used to investigate the effect of different central bridge groups on the geometric, optoelectronic, and charge transport properties of the constructed molecules. Among them, S4 and S6 have the lowest energy band gap and a red shift in the absorption spectra, revealing the perfect relationship between the central bridge and the strong electron withdrawal character through extended conjugation. Similarly, S6 explored the lowest reorganization energy (RE) value for electron and hole revealing its enhanced charge transition, also shows better ICT characteristics with its highest NLO properties. Compound S4 showed the smallest value of ΔEL-L and Eb, and the highest Voc due to its low HOMO, which improves the photocurrent density of the devices. Thus, the results suggest that bridge modification is a practical strategy to improve the efficiency of OSCs.

Designing and Theoretical Study of Dibenzocarbazole Derivatives Based Hole Transport Materials: Application for Perovskite Solar Cells.

Hole-transporting materials (HTMs) are essentials in producing the efficient and stable perovskite solar cells (PSCs). In this article, we provided the investigation results of electronic structures and photophysical characteristics of eight designed derivatives (HTM1a-HTM4a and HTM1b-HTM4b) of a dibenzocarbazole-based compound HTMR. HTMR was modified by substituting the terminal groups located on the diphenylamine moieties with two and four electron donor groups (ED1-ED4) of different character. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been used to optimize the geometry of the ground state and for excited state calculations, respectively. The nature and number of electron donor substitutions on the frontier molecular orbitals (FMOs), ionization potential (IP), electronic affinity (AE), maximum absorption wavelengths ([Formula: see text], solubility ([Formula: see text], stability (η), exciton binding energy ([Formula: see text], reorganization energies ([Formula: see text] and charge mobility (k) are examined and discussed in detail. On this basis, the features such as proper HOMO levels (-5.464 and -4.745 eV), comparable hole mobilities ([Formula: see text] (4.632 × 1013 and 1.177 × 1014 s-1), a significant [Formula: see text] (367.13 and 398.27 nm), and high η (1.440 and 1.667 eV) have made these structures suitable hole transport materials (HTMs) to provide perovskite solar cells with a high efficiency.

Theoretical investigation by DFT and TDDFT the extension of π-conjugation of novel carbazole-based donor materials for bulk heterojunction organic solar cell applications.

In this study, we have proposed seven designed symmetrical compounds (C2-C8) having a D-π-A-π-D structure based on derivative carbazole as a donor by introducing various π-spacer groups into the reference compound C1-Ref having a D-A-D structure in order to understand the influence of different π-spacers on their efficiency in BHJ solar cells. Various parameters such as geometrical structures, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), nonlinear optical properties (NLO), optical properties, light-harvesting efficiency (LHE), reorganization energy, chemical reactivity indices, exciton binding energy (Eb), open-circuit voltage (VOC), and fill-factor (FF) have been investigated using the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The results show that the extended π-conjugation of the designed compounds (C2-C8) produces a lower energy gap (Eg), a stronger and broader absorption spectrum, lower reorganization energies and exciton binding, and higher nonlinear optical properties compared to C1-Ref, indicating that these designed compounds are promising as electron donors in BHJ-OSCs. Additionally, the calculated Voc, FF, and LHE of all compounds showed that the C2, C3, C4, C5, and C7 compounds have the best performance in BHJ solar cells compared to the others. In particular, C4 and C5 are excellent candidates for the effective donor materials of BHJ solar cells due to their large Voc, FF, and LHE than the other compounds. This theoretical investigation is expected to provide new strategies to synthesize efficient donor materials for BHJ-OSCs.

Conformational preferences of Ac-Pro-azaXaa-NHMe (Xaa = Asn, Asp, Ala) and the effect of intramolecular hydrogen bonds on their stability in gas phase and solution.

The conformational preferences of three azadipeptides Ac-Pro-azaXaa-NHMe [Xaa = Asn (1), Asp (2), Ala (3)] have been carried out in gas phase and solution (water) using the density functional method B3LYP/6-311 + + G(d,p) to explore the effect of the change of side chain of azaamino acids at the i + 2 position on the stability of these components. The most stable conformations of compounds (1), (2), and (3) have an amid bond oriented trans, trans, and cis, respectively, in gas phase, whereas the orientation of amid bond in water solvent of compounds (2) and (3) has changed to cis and trans, respectively. We have also noticed the importance of backbone-side chain hydrogen bonds in the stabilization of the ß turn motif in gas phase since this motif is more stable in the case of compounds (1) and (2) and less stable in the case of compound (3) in which these hydrogen bonds are absent. Furthermore, the ßII(ßII') turn structure is more stable than ßI turn for all conformations of the three compounds in gas phase, while it is not true in the case of some conformations in solution. Moreover, the stability of ß turn increases from azaAsn to azaAsp which could be due to the side chain's basic nature of azaAsn. In general, hydrogen bonds were found to play a key role in the stabilization of these compounds since most of conformers are lower in energy when they have more than two hydrogen bond interactions while conformations with one or no hydrogen bonds are higher in energy and thus less stable.

QSAR, molecular docking and ADMET properties in silico studies of novel 4,5,6,7-tetrahydrobenzo[D]-thiazol-2-Yl derivatives derived from dimedone as potent anti-tumor agents through inhibition of C-Met receptor tyrosine kinase.

A quantitative structure-activity relationship (QSAR) study is performed on 48 novel 4,5,6,7-tetrahydrobenzo[D]-thiazol-2 derivatives as anticancer agents capable of inhibiting c-Met receptor tyrosine kinase. The present study is conducted using multiple linear regression, multiple nonlinear regression and artificial neural networks. Three QSAR models are developed after partitioning the database into two sets (training and test) via the k-means method. The obtained values of the correlation coefficients by the three developed QSAR models are 0.90, 0.91 and 0.92, respectively. The resulting models are validated by using the external validation, leave-one-out cross-validation, Y-randomization test, and applicability domain methods. Moreover, we evaluated the drug-likeness properties of seven selected molecules based on their observed high activity to inhibit the c-Met receptor. The results of the evaluation showed that three of the seven compounds present drug-like characteristics. In order to identify the important active sites for the inhibition of the c-Met receptor responsible for the development of cancer cell lines, the crystallized form of the Crizotinib-c-Met complex (PDB code: 2WGJ) is used. These sites are used as references in the molecular docking test of the three selected molecules to identify the most suitable molecule for use as a new c-Met inhibitor. A comparative study is conducted based on the evaluation of the predicted properties of ADMET in silico between the candidate molecule and the Crizotinib inhibitor. The comparison results show that the selected molecule can be used as new anticancer drug candidates.

Theoretical study of organic sensitizers based on 2, 6-diphenyl-4H-pyranylidene/1, 3, 4-oxadiazole for dye-sensitized solar cells.

In this work, we theoretically studied ten organic dyes using the DFT and TD-DFT methods, where triphenylamine was used as the donor for the D1-D5 dyes, while the 2, 6-diphenyl-4H-pyranylidene donor was used for the D6-D10 dyes. Substituents (alkyl and methoxy) were also introduced into these donor groups. These dyes also include 1, 3, 4-oxadiazole and phenyl as a bridge π and cyanoacrylic acid as acceptor. The electronic and optical properties of all dyes have been calculated as EHOMO, ELUMO, EGAP, Voc (the open-circuit photovoltage), λmax, Eex, LHE (the light-harvesting efficiency) and ΔGinj (the free injection energy) in order to compare their performance as DSSC sensitizers. The donor effect of all dyes was discussed on the one hand and on the other hand the effects of the introduction of substituents (alkyl and methoxy) to the donor before and after binding to TiO2 cluster. The results show that the performance of the dyes using 2, 6-diphenyl-4H-pyranylidene as donor has improved compared with the rest of the dyes, which may improve the power conversion efficiency. Therefore, these dyes D6-D10 are good candidates for use as DSSC sensitizers.

DFT and TD-DFT calculation of new thienopyrazine-based small molecules for organic solar cells.

BACKGROUND: Novel six organic donor-π-acceptor molecules (D-π-A) used for Bulk Heterojunction organic solar cells (BHJ), based on thienopyrazine were studied by density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches, to shed light on how the π-conjugation order influence the performance of the solar cells. The electron acceptor group was 2-cyanoacrylic for all compounds, whereas the electron donor unit was varied and the influence was investigated. METHODS: The TD-DFT method, combined with a hybrid exchange-correlation functional using the Coulomb-attenuating method (CAM-B3LYP) in conjunction with a polarizable continuum model of salvation (PCM) together with a 6-31G(d,p) basis set, was used to predict the excitation energies, the absorption and the emission spectra of all molecules. RESULTS: The trend of the calculated HOMO-LUMO gaps nicely compares with the spectral data. In addition, the estimated values of the open-circuit photovoltage (Voc) for these compounds were presented in two cases/PC60BM and/PC71BM. CONCLUSION: The study of structural, electronics and optical properties for these compounds could help to design more efficient functional photovoltaic organic materials.

Theoretical design of thiazolothiazole-based organic dyes with different electron donors for dye-sensitized solar cells.

In this study, we have designed four novel organic donor-π-acceptor dyes (D1, D2, D3, D4), used for dye sensitized solar cells (DSSCs). The electron acceptor (anchoring) group was 2-cyanoacrylic for all dyes whereas the electron donor unit varied (coumarin, indoline, carbazole, triphenylamine) and the influence was investigated. These dyes, based on thiazolothiazole as π-spacer, were studied by density functional theory (DFT) and its extensible time dependant DFT (TDDFT) approaches to shed light on how the π-conjugation order influence the performance of the dyes in the DSSCs. The theoretical results have shown that the LUMO and HOMO energy levels of these dyes can be ensuring positive effect on the process of electron injection and dye regeneration. The trend of the calculated HOMO-LUMO gaps nicely compares with the spectral data. Key parameters in close connection with the short-circuit current density (Jsc), including light harvesting efficiency (LHE), injection driving force (ΔGinject.) and total reorganization energy (λtotal), were discussed. The calculated results of these dyes reveal that dye D2, with indoline as electron donor group, can be used as a potential sensitizer for TiO2 nanocrystalline solar cells due to its best electronic and optical properties and good photovoltaic parameters.

Theoretical investigation of new thiazolothiazole-based D-π-A organic dyes for efficient dye-sensitized solar cell.

Novel ten organic donor-π-acceptor dyes (D-π-A), used for dye-sensitized solar cells (DSSCs), based on thiazolothiazole were studied by density functional theory (DFT) and time dependant DFT (TDDFT) approaches to shed light on how the π-conjugation order influence the performance of the dyes. The electron acceptor (anchoring) group was 2-cyanoacrylic for all dyes whereas the electron-donor unit varied and the influence was investigated. The theoretical results have shown that TDDFT calculations using the Coulomb attenuating method CAM-B3LYP with the polarized split-valence 6-31G (d,p) basis sets and the polarizable continuum model (PCM) were reasonably capable of predicting the excitation energies, the absorption and the emission spectra of the molecules. The LUMO and HOMO energy levels of these dyes can ensure a positive effect on the process of electron injection and dye regeneration. The trend of the calculated HOMO-LUMO gaps nicely compares with the spectral data. Key parameters in close connection with the short-circuit current density (Jsc), including light-harvesting efficiency (LHE), injection driving force (ΔG(inject)) and total reorganization energy (λtotal), were discussed. In addition, the estimated values of open-circuit photovoltage (Voc) for these dyes were presented. The calculated results of these dyes reveal that the D6 dye can be used as a potential sensitizer for TiO2 nanocrystalline solar cells due to its best electronic and optical properties and good photovoltaic parameters.

Interaction of lead atom with atmospheric dioxygen and ozone: quantic study of the structure and the stability of resulting Pb(On) (n=1,2,3) compounds.

Lead reaction with oxygen and ozone molecules is of a great importance for the study of the impact of this metal in the atmosphere medium. Stable species, intermediates, and transition states of possible resulting complexes have been studied with the three parameter hybrid B3LYP exchange-correlation DFT method, and coupled cluster with single, double, and triple excitation methods. Geometry, and spectroscopic and thermodynamic properties obtained for the different species are presented, discussed, and compared to available experimental data. On the basis of the knowledge of the thermal dissociation enthalpies and the absorbed wave length edges calculated for each species, we have drawn the most probable oxygenated complexes present in the atmosphere.

Interaction of lead atom with atmospheric hydroxyl radical. An ab initio and density functional theory study of the resulting complexes PbOH and HPbO.

The two potential hypersurfaces 2A' (ground state) and 2A" (excited state) have been studied through ab initio and density functional theory (DFT) methods for the Pb(OH) complex. Two processes have been identified. The first one concerns the hydrogen inversion process in the coordination of PbOH and the second one the isomerization of PbOH into HPbO. Eight stationary points have been found; four of them correspond to the stable structures with symmetries PbOH(2A'), PbOH(2A"), HPbO(2A'), and HPbO(2Pi), and four correspond to transition states [TS] with the symmetries 2Pi, 2A', 2Sigma+, and 2A". The hydrogen inversion process in PbOH exhibits the so-called Renner-Teller effect with a rather low barrier, whereas the isomerization process PbOH-->HPbO exhibits a rather high barrier. The energetic, structural, spectroscopy, and thermodynamics results obtained at various levels through, e.g., DFT with BLYP, B3LYP exchange-correlation functionals, coupled clusters methods, namely CCSD (single and double excitations) and CCSD(T) (with triple excitations, by perturbation) are presented for the whole sets of the stationary points and their dissociation products. The relativistic effects, as well as spin-orbit interaction, taken into account in the case of the BLYP exchange-correlation functional, have been estimated and discussed in order to measure their importance in the case of system including heavy metals such as Pb. Reactions of lead (Pb) with oxidizing atmospheric molecules (OH, HO2, O2, and O3) have been studied at various levels of approximation in order to study the possible existence of PbOH in the atmosphere.