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Among the metal-free dyes, boron dipyrromethene (BODIPY) has attracted much attention in the solar cell industry due to its thermal stability and tunable electronic and photophysical properties. However, the low power conversion efficiency of dye-sensitized solar cells based on BODIPY has limited their widespread application. Accordingly, different types of structural modifications have already been proposed to improve the photophysical properties of the BODIPY dyes. In this study, we used the strategy of constructing BODIPY-based covalent macrostructures by integrating two BODIPY subunits via a π-linker in linear and cyclic configurations. To this end, various types of the π-linkers including butadiyne, phenyl, and thiophene derivatives are considered. The structural, electronic, and optical properties as well as the photovoltaic performance of BODIPY dimers are theoretically calculated within DCM solvent. The results indicate that for a given linker, the BODIPY dimers with a linear configuration show better performance as compared to their macrocyclic counterparts. The reason is the enhancement of π-conjugation length, higher light harvesting ability, and proper charge carrier separation in linearly linked BODIPYs. In the cyclic series, the dyes incorporating phenyl linkers exhibit greater power conversion efficiency of up to 9%. For the dyes with a linear configuration, the involvement of a thienyl-thiophene bridge results in lower charge recombination and enhances the efficiency by up to 15%, which are expected to be potential candidates for organic dyes applied in DSSCs.

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In the present study, fluorogenic coumarin-based probes (1-3) through condensation of 4-hydroxy coumarin with malondialdehyde bis(diethyl acetal)/triethyl orthoformate were prepared. The absorption and fluorescence emission properties of 2b and 3 in different solvents were studied, and a considerable solvatochromic effect was observed. The sensitivity of chemosensors 2b and 3 toward various cations and anions was investigated. It was revealed that compound 3 had a distinct selectivity toward Sn2+, possibly via a chelation enhanced quenching mechanism. The fluorescence signal was quenched over the concentration range of 6.6-120 µM, with an LOD value of 3.89 µM. The cytotoxicity evaluation of 3 against breast cancer cell lines demonstrated that the chemosensor was nontoxic and could be used successfully in cellular imaging. The probe responded to tin ions not only via fluorescence quenching, but also through colorimetric signal change. The change in optical properties was observed in ambient conditions and inside living cells.

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Metal-organic frameworks incorporating mixed-metal sites (MM-MOFs) have emerged as promising candidates in the development of sensing platforms for the detection of paramagnetic species. In this context, the present study explores the photo-induced switching behavior of mixed-metal Fe-M (M = Co, Ni, Cu) formate (Fe-M(CO2H)4), as an experimentally feasible strategy for the reversible capture of nitric oxide (NO). Using Fe-M(CO2H)4 as a building block of synthesized MOFs based on BTC (benzene-1,3,5-tricarboxylic acid), molecular simulations of NO adsorption on Fe-M(CO2H)4 were conducted to provide a template for evaluating the behavior of BTC-based MOFs towards NO. Accordingly, the relationship between the magnetic properties and adsorption behaviors of Fe-M(CO2H)4 towards NO gas molecules was evaluated before and after photoexcitation. We show that the photo-induced effect on the magnetic properties of Fe-M(CO2H)4 changes the interaction strength between NO and the Fe-M(CO2H)4 systems. NO chemisorption over Fe-Ni(CO2H)4 indicates that nickel-doped Fe-BTC MOFs can be efficiently applied for capturing purposes. Moreover, our calculations show a switching behavior between physisorption and chemisorption of the NO molecules over Fe-Co(CO2H)4, occurring through magnetic modulation under UV-Vis irradiation. As far as we know, this is the first study that proposes light-controlled reversible NO capture using MOFs. The present study provides a promising platform for reversible NO capture using MM-MOF-incorporated BTC building blocks.

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The reaction mechanism, product branching ratios, and relevant rate constants for the reaction of imidogen (NH) with sulfur monoxide (SO) over singlet and triplet potential energy surfaces are theoretically investigated. Various quantum chemical methods at the single-reference methods (PBE, M06-2X, MP2, GBS-QB3, G3MP2B3, and CCSD(T)) and the multi-reference methods of CASPT2 are carried out to examine the characteristics of the title reaction's potential energy surface. Eighteen chemically activated intermediates and more than 35 different reaction channels are predicted over the singlet surface, while less species and channels are distinguished over the triplet surface. The entrance channels for both surfaces appeared to be barrier-less association reactions to form pre-reaction energized intermediates of singlet or triplet HNSO or HNOS. OH and NS radicals are indicated as the major products for the title reaction on both surfaces in agreement with the reported experimental observations. The RRKM-steady state approximation method is used to calculate the rate constants and branching ratios of the main products. The obtained overall rate constant is in agreement with the available reported experimental data over the wide range of temperature from 300 to 3000 K. By considering single-reference calculations, the singlet and triplet total rate constants were found to be k(T) = 5.04 × 1010 and 2.47 × 1012 T-0.83 exp(-1.56 kJ mol-1/T), respectively. Also, the total rate constant for the consumption of reactants by inclusion of multi-reference calculations was found to be in the range of 3.86 × 1010 to 4.18 × 1010, depending on the level of calculations. In addition, our results revealed that the total rate constant for the NH + SO reaction is pressure-independent in the range of 0.1-2000 Torr.

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A simple and informative quantitative structure-retention relationship (QSRR) model has been introduced for prediction of retention times in some anthraquinone derivatives using reversed-phase micellar liquid chromatography (MLC) technique. In the developed multiple linear regression model, the structural descriptors of analytes as well as the empirical parameters of organic modifiers in the applied MLC systems have been considered. Retention times of 77 chromatographic samples (16 anthraquinones were evaluated by using 6 different organic modifiers) were experimentally determined and utilized as the independent variables of the QSRR model. Five small-chain alcohols (methanol, ethanol, propanol, butanol, and pentanol) as well as acetonitrile were used as the eluent modifiers. A five-parametric model was attained for the logarithm of the retention time values which covered about 96 and 95% variance of the chromatographic data in training and cross-validation, respectively. The presence of an excellent correlation coefficient for external validation test (= 0.94) and a well-applicable domain proved the prediction ability of the constructed model. Both validity and reliability of the formulated model were examined through its application on diverse random-selected training and test sets. Moreover, quantum chemical calculations were performed in the framework of density functional theory to simulate the interactions between AQs and modifiers and gain mechanistic details about the retention behavior in the MLC system.

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Catalytic oxidation of carbon monoxide on perfect and defective structures of corrole complexes with aluminum, phosphorous and silicon have been investigated by performing density functional theory calculations. The main objective is to highlight the effect of structural defects on the catalytic activity of corrole complexes for the CO oxidation reaction. Moreover, we also study how phenyl substitution at the meso or axial position of the corrole will affect its catalytic efficiency. It is shown that a vacancy defect leads to the formation of an interior cavity inside the corrole structure which hinders proper orientation of reacting O2 and CO molecules. While corrole complexes with aluminum may serve as potential catalysts for CO oxidation with a moderate energy barrier, phosphorous corrole displays superior catalytic activity with a very low energy barrier. We also demonstrate that phenyl substitution at the axial position reduces the catalytic activity of corrole complexes, whereas phenyl substitution at the meso sites does not change the activity of corrole complexes toward O2 and CO molecules. The results of the present study are promising to develop highly efficient single atom phosphorous-nitrogen-carbon catalysts for low temperature CO oxidation.

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On the basis of the newly synthesized banana-shaped thieno[3,2- b] pyrrole building block [Bulumulla, C.; Gunawardhana, R.; Kularatne, R. N.; Hill, M. E.; McCandless, G. T.; Biewer, M. C.; Stefan, M. C. Thieno[3,2- b] pyrrole-Benzothiadiazole Banana-Shaped Small Molecules for Organic Field Effect Transistors. ACS Appl. Mater. Interfaces 2018, 10, 11818-11825], several small molecules that can be used as organic semiconducting materials were theoretically designed. We have shown that these novel molecules with the donor-π conjugated bridge-acceptor-π conjugated bridge-donor (D-π-A-π-D) building block exhibit superior charge transport properties in organic field-effect transistors (OFETs). A variety of donors, π-bridges, and acceptors are examined, and the structural, electronic, optical, and charge transport properties of designed semiconductors are systematically investigated. The results highlight the impact of the core acceptor in improving the transport properties of the designed molecules. In particular, this work points toward the benzo-bis(1,2,5-thiadiazole) as the most promising acceptor that can be combined with thiophene π-bridge and flanked benzo-thiadiazole terminal units to produce a reasonable candidate for synthesis and for incorporating into OFET materials. For the suggested semiconductor, the small electron reorganization energy and large intramolecular coupling originating from dense π-stacking gave rise to enhanced electron mobility. This strategy can be helpful for further improving the performance of curved small molecules in field-effect devices.

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The new planar tetracoordinate carbon (ptC) compounds have received significant research attention in recent years. The present study is devoted to investigating the structural, electronic, and magnetic features of one-dimensional chains and two-dimensional sheets composed of C2Al4(CH3)8 building blocks. All possible condensations were studied, and the stabilities of different ptC assemblies were compared. Several properties such as energy gap, dipole polarizability, electronic excitation energies, and nucleus chemical shift were computed for chains up to 7 and sheets up to 16 units. A systematic analysis was performed to assess the impact of condensation pattern and number of units on the calculated properties. Topological analysis of density and electron localization functions reveals that Al-C bonds in the considered ptCs have mixed covalent/ionic character with larger ionic contribution. It is found that the electronic spectra of the condensed ptCs exhibit red shift toward larger wavelengths when compared to the C2Al4(CH3)8 building block. The amount of red shift enhances with increasing number of units. We show that the stability trend, predicted by electronic and magnetic descriptors, are in qualitative agreement with the thermodynamic stability obtained through Gibbs free energy change of condensation reaction.

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Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Polymer solar cells (PSCs) hold promise for their potential to be used as low-cost and efficient solar energy converters. PSCs have been commonly made from bicontinuous polymer:fullerene composites or so-called bulk heterojunctions. The conjugated polymer donors and the fullerene derivative acceptors are the key materials for high performance PSCs. In the present study, we have performed density functional theory calculations to investigate the electronic structures and magnetic properties of several representative C60 fullerene derivatives, seeking ways to improve their efficiency as acceptors of photovoltaic devices. In our survey, we have successfully correlated the LUMO energy level as well as chemical hardness, hyper-hardness, nucleus-independent chemical shift, and static dipole polarizability of PC60BM-like fullerene derivative acceptors with the experimental open circuit voltage of the photovoltaic device based on the P3HT:fullerene blend. The obtained structure-property correlations allow finding the best fullerene acceptor match for the P3HT donor. For this purpose, four new fullerene derivatives are proposed and the output parameters for the corresponding P3HT-based devices are predicted. It is found that the proposed fullerene derivatives exhibit better photovoltaic properties than the traditional PC60BM acceptor. The present study opens the way for manipulating fullerene derivatives and developing promising acceptors for solar cell applications.

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A new double-hybrid density functional, termed B2-PPW91, is presented which includes the Becke88 (B88) exchange in conjunction with Perdew-Wang91 (PW91) gradient-corrected correlation functional. The fitting parameters are obtained by minimization of mean absolute error of the static dipole polarizability of 4d transition metal monohalides against the CCSD(T)∕aug-cc-pVTZ∕SDD results. The performance of proposed functional has been assessed for estimation of other response properties, such as dipole moment and excitation energy, for the same species. We then proceed to explore the validity of B2-PPW91 method for calculation of the dipole polarizability of some 5d transition metal monofluorides. In all cases, the improvement compared to common density functional methods and even previously reported double-hybrid functionals such as B2-PLYP and mPW2-PLYP has been observed. This indicates that the utility of double-hybrid density functional methods can be further extended to study linear and non-linear optical properties of transition metal containing molecules.

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The structural and thermodynamic characteristics of lowest-energy structures of group 13-15 mixed heptamers in two distinct series [(HM)(k)(HM')(l)(NH)(7)] (M, M' = B, Al, Ga and k + l = 7) and [(HGa)(7)(YH)(m)(Y'H)(n)] (Y,Y' = N, P, As and m + n = 7) have been systematically investigated using the density functional approach. Our main goal is to get knowledge of the preferential bonding patterns of the first three rows of group 13-15 elements for the construction of mixed heptameric clusters. Structural parameters, thermodynamic properties of oligomerization reaction, band gaps, and dipole moments of the 18 lowest-energy structures of the studied heptamers in each series are compared to their corresponding binary parents, that is, [(HM)(7)(NH)(7)] and [(HGa)(7)(YH)(7)]. The stability of different isomer structures is discussed to reveal the competitiveness of group 13 and 15 bonding. Mixed heptamers are predicted to be thermodynamically more stable compared to a mixture of monomers. However, the favorability for the generation of mixed heptamers strongly depends on the nature of inserted metal and nonmetal pairs of group 13-15. Moreover, it is found that among all studied heptamers the smaller band gaps correspond to arsenic containing species which are close to the semiconducting regime, around 4.62-4.98 eV.

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The interactions between eight amino acid based anions and four imidazolium-based cations have been investigated by density functional theory. The electronic and structural properties of the resulting amino acid ionic liquids (AAILs) have been unveiled by means of the atoms in molecules framework. The calculated interaction energy was found to increase in magnitude with decreasing alkyl chain length at imidazolium ring. Moreover, AAILs composed of an amino acid with some functional group such as aromatic ring had decreased interaction energy. Finally, several correlative relationships between glass transition temperature and interaction energy as well as density at bond critical point have been checked for 1-ethyl-3-methylimidazolium based ILs. Although the obtained correlations do not show excellent fits, a preliminary estimation of the glass transition temperature of different AAILs can be achieved by use of their electronic properties.

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Halogen-hydride interactions between Z-X (Z = CN, NC and X = F, Cl, Br) as halogen donor and H-Mg-Y (Y = H, F, Cl, Br, CH(3)) as electron donor have been investigated through the use of Becke three-parameter hybrid exchange with Lee-Yang-Parr correlation (B3LYP), second-order Møller-Plesset perturbation theory (MP2), and coupled-cluster single and double excitation (with triple excitations) [CCSD(T)] approaches. Geometry changes during the halogen-hydride interaction are accompanied by a mutual polarization of both partners with some charge transfer occurring from the electron donor subunit. Interaction energies computed at MP2 level vary from -1.23 to -2.99 kJ/mol for Z-F···H-Mg-Y complexes, indicating that the fluorine interactions are relatively very weak but not negligible. Instead, for chlorine- and bromine-containing complexes the interaction energies span from -5.78 to a maximum of -26.42 kJ/mol, which intimate that the interactions are comparable to conventional hydrogen bonding. Moreover, the calculated interaction energy was found to increase in magnitude with increasing positive electrostatic potential on the extension of Z-X bond. Analysis of geometric, vibrational frequency shift and the interaction energies indicates that, depending on the halogen, CN-X···H interactions are about 1.3-2.0 times stronger than NC-X···H interactions in which the halogen bonds to carbon. We also identified a clear dependence of the halogen-hydride bond strength on the electron-donating or -withdrawing effect of the substituent in the H-Mg-Y subunits. Furthermore, the electronic and structural properties of the resulting complexes have been unveiled by means of the atoms in molecules (AIM) and natural bond orbital (NBO) analyses. Finally, several correlative relationships between interaction energies and various properties such as binding distance, frequency shift, molecular electrostatic potential, and intermolecular density at bond critical point have been checked for all studied systems.

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The static and dynamic polarizabilities for the lowest-energy structures of pure aluminum clusters up to 31 atoms have been investigated systematically within the framework of density functional theory. The size evolution of several electronic properties such as ionization potential, electron affinity, the energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital, and chemical hardness have also been discussed for aluminum clusters. Our primary focus in this article, however, has been upon the study of polarizability of aluminum clusters, although we also looked at the role of other electronic properties. From the energetics point of view, the relative stability of aluminum clusters at different sizes is studied in terms of the calculated second-order difference in the total energy of cluster and fragmentation energy, exhibiting that the magic numbers of stabilities are n = 7, 13, and 20. Moreover, the minimum polarizability principle is used to characterize the stability of aluminum clusters. The results show that polarizabilities and electronic properties can reflect obviously the stability of clusters. Electronically, the size dependence of ionization potential and electron affinity of clusters is determined. On the basis of the Wood and Perdew model these quantities converge asymptotically to the value of the bulk aluminum work function.

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In this work the molecular electrostatic potential (MEP) is proposed as an effective approach in describing the influence of substituent on the rate constant of etherification reaction. A relationship on the basis of density functional theory has been established to show that the etherification rate constant should be proportional to the electrostatic potential on the atomic sites. Indeed, we employed the MEP at the atomic sites as a local quantum descriptor to estimate the reaction rate constant variation caused by substituent effect. Taking the experimental rate constants of 30 substituted phenols, the validity of the proposed method has been verified. Moreover, the atoms-in-molecules (AIM) charge scheme as another local descriptor was tested for its ability to represent variations in the kinetic data for etherification reaction of phenols. It was shown that the changes in these two descriptors were strongly correlated with the variation of experimental rate constant data. The outcome of good correlations in this study offers a relatively simple and effective method to compute the rate constant for etherification reaction of substituted phenols based on MEP and AIM charge.

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The usefulness of a novel type of electronic descriptors called quantum topological molecular similarity (QTMS) indices for describing the quantitative effects of molecular electronic environments on the O-methylation kinetic of substituted phenols has been investigated. QTMS theory produces for each molecule a matrix of descriptors, containing bond (or structure) information in one dimension and electronic effects in another dimension, instead of other methods producing a vector of descriptors for each molecule. A collection of chemometrics tools including principal component analysis (PCA), partial least squares (PLS), and genetic algorithms (GA) were used to model the structure-kinetic data. PCA separated the bond and descriptor effects, and PLS modeled the effects of these parameters on the rate constant data, and GA selected the most relevant subset of variables. The model performances were validated by both cross-validation and external validation. The results indicated that the proposed models could explain about 95% of variances in the rate constant data. The significant effects of variables on the reaction kinetic were identified by calculating variable important in projection (VIP). It was found that the rate constant of esterification of phenols is highly influenced by the electronic properties of the C2--C1--O--H fragment of the parent molecule. Indeed, the C2--X and C4--X bonds (corresponding to ortho and para substituents) were found as highly influential parameters. All of the eight calculated QTMS indices were found significant however, lambda1, lambda2, lambda3, epsilon, and K(r) were detected as highly influential parameters.

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The strengths of N-H---N and N-H---O hydrogen bonds in 15 nucleic acid base pairs have been investigated using different descriptors. Geometrical and energetic criteria, atoms in molecules topological parameters, natural bond orbital analysis, and spectroscopic measurements have been used to detect the H-bonds and evaluate their strengths in the intermolecular interactions between five nucleic acid bases. Different correlations have been obtained between many of these descriptors to provide a global view of H-bond interaction. We found good linear correlations for the dependence of some descriptors such as atomic interpenetration and hyperconjugation energy on density at bond critical point, while others like destabilization of H-atom energy, variation in N-H frequency, and NMR parameters correlate in a much worse fashion. The calculations suggest that almost all H-bonds in different base pairs belong to medium strength H-bonds. We found in thymine the H-bond interaction is more likely through the amide-type oxygen while the situation is reverse for uracil in which the urea-type oxygen is more accessible to form an H-bond. Cytosine and guanine can also form H-bonds via their amine-type or amide-type nitrogens. In cytosine, the amine-type nitrogen is involved in an N-H---O bond interaction, while, in guanine, the amide-type nitrogen has a greater contribution to H-bond interaction.

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The usefulness of a novel type of electronic descriptors called quantum topological molecular similarity (QTMS) indices for describing the quantitative effects of molecular electronic environments on the antagonistic activity of some dihydropyridine (DHP) derivatives has been evaluated. QTMS theory produces a matrix of descriptors, including bond (or structure) information in one dimension and electronic effects in another dimension, for each molecule. Some different modeling tools such as multiple linear regression (MLR), principal component analysis (PCA), partial least squares (PLS) and genetic algorithms (GA) were employed to find some appropriate models for noted biological activity. GA was used in order to select the proper variables and also PCA was used for data compression. Then modeling was performed by MLR and PLS. The model performances were accessed by both cross-validation and external prediction set. The results showed that the proposed models could explain above 90% of variances in the biological activity. The significant effects of chemical bonds on the antagonistic activity were identified by calculating variable important in projection (VIP). It was obtained that those belonging to the substituted 4-phenyl ring represent high influence on the biological activity which, confirms their importance in mechanism of action of DHP derivatives.

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Three-way analyses of quantum topological molecular similarity descriptors were used for quantitative structure property relationship modeling of the acidity constant of some phenol derivatives. A three-way data was built for different molecules by constructing a data matrix for each molecule. The matrix was produced by considering different bonds in each molecule and different descriptors in each bond. The three-way models parallel factor analysis and N-way partial least squares, and two-way models including partial least squares were used for modeling structure-acidity relationships. Comparison of the results showed that the three-way arrays produced more predictive models with lower over-fitting. The bilinear partial least square model resulted in a biased estimation of acidity constant of prediction set with average relative error of prediction of 1.87%, whereas that obtained by parallel factor analysis and N-way partial least squares was near to zero (i.e. -0.41 and -0.33, respectively). Additionally, the three-way methods allowed investigating the significant impact of different bonds and different descriptors using leverages of the parallel factor analysis loadings.

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