NBO analysis

MP2 method and different functionals such as M06-HF, M06-2X, CAM-B3LYP, PBE0, B3LYP and M06L incorporating different XC amounts were used to calculate the static first hyperpolarizabilies β(0) of eight molecules which are derivatives of benzene, stilbene and diphenylacetylene. The values were then compared to the experimental ones. The M06-2X functional was then selected for further calculations. NBO calculations were also performed to define the intramolecular charge transfer in each molecule. TD-DFT calculations were performed taking into account the solvent effect using the IEF-PCM formalism. Some parameters characterizing the vertical transitions such as the wavelength of the maximum absorption λ max were compared to the experimental ones. Finally, solvation Gibbs free enthalpy ΔG solv values have also been examined in order to determine which the specific solvent for a given molecule is.

This study aims to cast light on the physico-chemical nature and energetic of the non-conventional CH···O/N H-bonds in the biologically important natural nucleobase pairs using a comprehensive quantum-chemical approach. As a whole, the 36 biologically important pairs, involving canonical and rare tautomers of nucleobases, were studied by means of all available up-to-date state-of-the-art quantum-chemical techniques along with quantum theory "Atoms in molecules" (QTAIM), Natural Bond Orbital (NBO) analysis, Grunenberg's compliance constants theory, geometrical and vibrational analyses to identify the CH···O/N interactions, reveal their physico-chemical nature and estimate their strengths as well as contribution to the overall base-pairs stability. It was shown that all the 38 CH···O/N contacts (25 CH···O and 13 CH···N H-bonds) completely satisfy all classical geometrical, electron-topological, in particular Bader's and "two-molecule" Koch and Popelier's, and vibrational criteria of H-bonding. The positive values of Grunenberg's compliance constants prove that the CH···O/N contacts in nucleobase pairs are stabilizing interactions unlike electrostatic repulsion and anti-H-bonds. NBO analysis indicates the electron density transfer from the lone electron pair of the acceptor atom (O/N) to the antibonding orbital corresponding to the donor group σ(∗)(CH). Moreover, significant increase in the frequency of the out-of-plane deformation modes γ (CH) under the formation of the CH···O (by 17.2÷81.3/10.8÷84.7 cm(-1)) and CH···N (by 32.7÷85.9/9.0÷77.9 cm(-1)) H-bonds at the density functional theory (DFT)/second-order Møller-Plesset (MP2) levels of theory, respectively, and concomitant changes of their intensities can be considered as reliable indicators of H-bonding. The strengths of the CH···O/N interactions, evaluated by means of Espinosa-Molins-Lecomte formula, lie within the range 0.45÷3.89/0.62÷4.10 kcal/mol for the CH···O H-bonds and 1.45÷3.17/1.70÷3.43 kcal/mol for the CH···N H-bonds at the DFT/MP2 levels of theory, respectively. We revealed high linear mutual correlations between the H-bond energy and different physico-chemical parameters of the CH···O/N H-bonds. Based on these observations, the authors asserted that the most reliable descriptors of the H-bonding are the electron density ρ at the СН···О/N H-bond critical points and the NBO calculated stabilization energy E((2)). The linear dependence of the H-bond energy ECH···O/N (in kcal/mol) on the electron density ρ (in atomic units) was established (DFT/MP2): ECH···O = 248.501[Formula: see text]ρ-0.367/260.518[Formula: see text]ρ-0.373 and ECH···N = 218.125[Formula: see text]ρ-0.339/243.599[Formula: see text]ρ-0.441. Red-shifted and blue-shifted CH···O/N H-bonds behave in a similar way and can be described with the same fit parameters. It was found that the A-U HH2 and U-U3 nucleobase pairs are stabilized solely by the CH···O/N H-bonds. At the same time, in the A-U HH1, A-U HH2, A-Asyn 1, A-Asyn 2, A-Asyn 3, A-A4, A-G1, A-G2, G-U1, G-U2, G-U3, G-C HH1, U-U1, U-U2, U-U3 and A-C nucleobase pairs the CH···O/N H-bonds play a prominent role (>30%) in their stabilization. We suppose that unconventional CH···O/N H-bond plays the role of the third "fulcrum", ensuring structurally dynamic similarity of the isomorphic base pairs of different origin, which are incorporated equally well into the structure of the DNA double helix.

This work deals with the vibrational spectroscopy of 1-chloro-4-nitrobenzene (1C4NB) by means of quantum chemical calculations. The solid phase FT-IR and FT-Raman spectra of 1-chloro-4-nitrobenzene (1C4NB) have been recorded in the regions 4000–400 and 3500-50 cm −1 respectively. The fundamental vibrational frequencies and intensities of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6-311+G(d.p) method and frequencies were scaled using various scale factors. Simulation of infrared and Raman spectra utilizing the results of these calculations led to excellent overall agreement with the observed spectral patterns. The SQM approach applying selective scaling of the DFT force field was shown to be superior to the uniform scaling method in its ability to allow for making modifications in the band assignment, resulting in more accurate simulation of FT-IR and FT-Raman Spectra. The 1 H and 13 C nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method. The theoretical and experimental UV–VIS spectra of 1-chloro-4-nitrobenzene (1C4NB) were recorded and compared and the electronic properties, such as HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) energies were performed by time-dependent DFT (TD-DFT) approach. Information about the size, shape and charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density isosurface with Molecular Electro Static Potential (MESP).The dipole moment , polarizability, first order hyperpolarizability and mullikkan atomic charges of the title molecule were computed using DFT calculations. In addition Chemical reactivity and thermodynamic properties of 1C4NB at different temperatures were also computed.

Resumen.-Las entidades no lucrativas son organizaciones que se distinguen por el interés colectivo sin ánimo de lucro y por articularse desde la iniciativa social, por lo que pertenecen al denominado tercer sector de la sociedad. Dada su importancia, el objetivo de esta investigación fue mostrar la tipología de estas entidades, así como su evolución en el sistema jurídico mexicano, utilizando para su análisis el método documental sistémico-estructural-funcional, cuyos resultados muestran su taxonomía particular. El principal hallazgo es la pro-puesta de una clasificación propia del autor sobre las entidades no lucrativas, cuya originalidad estriba en su diferenciación segmentada en función a su finalidad; las limitaciones del estudio residen en la dificultad de un análisis más exhaustivo, dada la diversidad de los organismos no lucrativos. Abstract.-Non-profit organizations are distinguished by the collective interest with no interest in earning economic gains from acting from social initiative, which makes them belong to the third sector of society. Given the importance, the objective of this research was to show the typology of these entities, using a sistemic-structural-functional and documentary method, whose results demonstrate its taxonomic. The main finding is the proposal of an author's own classification of non-profit entities, whose originality lies in its segmented differentiation, which is made in function of its general purpose; the limitations of the study lie in the difficulty of a thorough analysis, given the diversity of non-profit organizations. Introducción En las sociedades modernas de economía de mercado se han articulado tres grandes sectores que configuran su estructura institucional (Butcher & Verduzco, 2016; Butcher, 2014; Estrada, 2016): el término primer sector ha sido designado para referirse a las instituciones de gobierno, las empresas públicas y los organismos públicos autónomos; el segundo sector corresponde a las empresas privadas, la industria y el comercio, que son de carácter predominantemente económico y lucrativo, también llamadas "el mercado"; por último está el tercer sector, el cual es identificado como un grupo complejo de entidades que no son públicas sino privadas, pero no persiguen los fines lucrativos de éstas aunque pudieran obtener beneficios económicos, en una especie de simbiosis organizacional. Las organizaciones más estudiadas por las ciencias económico-administrativas son las industrias y el comercio, dadas las implicaciones que tienen por ser entidades lucrativas; por lucrativo debemos entender lo que produce utilidad, ganancia o provecho (Canabellas, 2003); mientras el afán de los propietarios de aquellas es la obtención de ganancias, las entidades no lucrativas (ENL)-en cambio-están centradas en la consecución de ciertos fines sociales, para lo cual pueden o no realizar actividades de tipo económico (Simental-Franco, 2015; Martínez-Franco & Guzmán-Raja, 2014); es importante mencionar que algunas organizaciones consideradas no lucrativas sí procuran obtener provechos económicos para sus integrantes, como las organizaciones de tipo gremial o las cooperativas, aunque para lograrlo no realizan actividades con preponderancia económica ni se dedican a la especulación comercial (Gallardo-Neyra & Fernández-Paredes, 2004). Las ENL poseen características particulares, la principal es que trabajan por el interés colectivo sin ánimo de lucro y desde la iniciativa social (Barba, 2007); de ellas hay estudios sobre su gestión, sus finanzas, sus fines sociales y otros 1 Doctor en Materia Fiscal, Profesor investigador,

This paper is a logical continuation of the theoretical survey of the CH⋯O/N specific contacts in the nucleobase pairs using a wide arsenal of the modern methods, which was initiated in our previous study [J. Biomol. Struct. & Dynam., 2014, 32, 993–1022]. It was established that 34 CH⋯O and 7 CH⋯N interactions, that were detected by quantum-chemical calculations in the 39 biologically important pairs involving modified nucleobases, completely satisfy all geometrical, vibrational, electron-topological, in particular Bader’s and “two-molecule” Koch and Popelier’s, Grunenberg’s compliance constants theory and natural bond orbital criteria indicating that they can be identified as true H-bonds. The geometrical criteria of the H-bond formation are fulfilled for all considered CH⋯O/N H-bonds without any exception. It was shown that the classical rule of the stretching vibration shifts does not work in the ~95% cases of the CH⋯O/N H-bonds. Furthermore, significant increase in the frequency of the out-of-plane deformation modes γ(CH) under the formation of CH⋯O/N H-bonds and corresponding changes of their intensities can be also considered as reliable indicators of the H-bonding. We revealed high linear mutual correlations between the electron density, Laplacian of the electron density, H-bond energy at the (3, −1) bond critical points of the CH⋯O/N H-bonds, and different physico-chemical parameters of the CH⋯O/N H-bonds. We suggested that the electron density ρ and the interaction energy E(2) of the lone orbital pairs are the most reliable descriptors of the H-bonding. The linear dependence of the H-bond energy ECH⋯O/N on the electron density ρ was established: ECH⋯O = 250.263∙ρ – .380/258.255∙ρ – .396 and ECH⋯N = 196.800∙ρ – .172/268.559∙ρ – .703 obtained at the density functional theory (DFT)/Møller−Plesset (MP2) levels of theory, respectively. The studies of the interaction energies show that the contribution of the CH⋯O and CH⋯N H-bonds into the base pairs stability varies from 3.0/4.2 to 35.1/31.2% and from 3.0/4.3 to 44.4/46.5% at the DFT/MP2 levels of theory, accordingly. Energy decomposition analysis performed for all base pairs involving canonical and modified nucleobases defines the electrostatic attraction and Pauli repulsion as dominant stabilizing forces in all complexes. This observation was additionally confirmed by the results of the QTAIM delocalization indexes analysis. The studies reported here advance our understanding of the biological role of the weak CH⋯O/N H-bonds, that dictates the requirements for the structural and dynamical similarity of the canonical and mismatched pairs with Watson–Crick (WC) geometry, which facilitates their enzymatic incorporation into the DNA double helix during DNA replication. Thus, these H-bonds in the base pairs with WC geometry may be also considered as “the last drop” at the transmission of the electronic signal that launches the chemical incorporation of the incoming nucleoside triphosphate into DNA.

A series of divinyl-pyrene derivatives of the form D-vinyl-pyrene-vinyl-A, in which D corresponds to an electron donor group and A to an electron acceptor group, were studied in this work. The first purpose was to determine the optimal HF % exchange as incorporated in a range of hybrid functionals (M06HF, M062X, M06L, CAM-B3LYP, PBE0, BMK, and B3LYP) capable to produce, reliably and as close as possible to those obtained from MP2 calculations, NLO parameters and, in particular, first-order static hyperpolarizabilities. The CAM-B3LYP functional was revealed to be the most suitable one. The pair N(CH 3) 2 /NO 2 was then determined as the most efficient pair of groups in producing appreciable NLO responses. The effect of the substitution position on the pyrene moiety was also investigated, whereby aligning the two substituents involving the D and A groups in the direction of the dipole moment as in the (1,6 DVP) derivatives was shown to be most favorable for increasing the NLO parameters. ■ INTRODUCTION Because of their numerous applications in the areas of photonics and optoelectronics, 1−3 various types of NLO active materials have been developed over the recent years. These materials are used in technical applications like lasers, 4 optical data storage devices, biological imaging, 5 signal processing, and in electro-optical modulation as well. 6,7 These materials range from being inorganic to organic to organometallic. 8−11 In order to identify additional and more efficient materials for further NLO applications, many studies were conducted on organic materials, including, for instance, the polycyclic aromatic hydrocarbons (PAH) or, polynuclear aromatic hydrocarbons. 12−15 These latter are a series of hydrocarbons in which carbon atoms are arranged in multiple aromatic rings sharing one or more C−C bond. The resulting structures are molecules wherein all carbon and hydrogen atoms are lying in the same plane. Accordingly, their physical and chemical characteristics make them eligible as π-conjugated bridges 16 or chromophores in push−pull systems, 17 which contain a donor (D) and an acceptor (A) group end-capping the π-conjugated backbone. 18−20 Thereby, an enhancement of the intramolecular charge transfer (ICT) is obtained, 21−23 which results in a strong NLO response. The latter is closely connected to several factors such as the energy gap (ΔE H-L = ε LUMO − ε HOMO), the occupation quotient π*/π, the central bond length, the bond-length alternation (BLA), the delocalization energy E(2), the electronic transitions parameters, the polarizability α, and, finally, the most important factors: the static first order hyper-polarizability β 0 and the dipole moment μ 0 , 24−26 which have been at the center of much interest from theoretical chemists 27−34 for the past couple of decades. In this field, pure and hybrid DFT methods have been demonstrated to fail in calculating reliable hyperpolarizabilities, 35−38 while post-HF methods reproduce hyperpolarizabilities with a good accuracy 39 and are considered in the present work as a reference. The wrong asymptotic behavior of DFT methods 40 has been shown to be at the origin of the resulting inaccurate values. 41,42 Therefore, enhancing the incorporated HF exchange (X) fraction in hybrid DFT fuctionals as well as long-range corrections become very important in order to improve results, and many papers have appeared dealing with this goal. 43,44,37,38 Despite the popularity of the Minnesota M06 functionals, 45,46 their performance in calculating NLO responses of push−pull molecules has not been extensively tested. In this work, we focus on calculating NLO responses of various divinylpyrene derivatives that we consider as sufficiently large systems to test to what extent DFT methods can produce satisfactory results. Actually, as a special case of a PAH, we have pyrene, which consists of four fused benzene rings 47,48 (Figure 1). Since some years, pyrene and its derivatives have attracted considerable attention in the field of NLO because of their remarkable ICT. Actually, they have been frequently used as materials in organic light emitting diodes (OLED), in organic field effect transistors (OFET), and in organic photovoltaic cells. 49,50 So far, some 1-monosubstituted pyrene derivatives have been studied using the DFT-B3LYP/6-31g (d,p) level of theory. 51 It was demonstrated that the pyrene structure is strongly affected by the nature of the substituent. These variations are then obviously reflected in appreciable changes in the dipole moments values. Another work also using the B3LYP/6-31g (d,p) and dealing with some 1,3,6,8 tetra-hologeno-substituted

The important and perspective molecular building blocks composed of hexaphenylbenzenes (HPBs) or their oxidized derivatives, hexa-peri-hexabenzocoronenes (HBCs), and metalloporphyrins have recently received significant attention of the researchers. In this study, motivated by recent findings, we have addressed the modifications of structures and properties of HBC-porphyrin compounds by using instead of aromatic porphyrins antiaromatic 20π isophlorin derivatives of thiophene or selenophene. We have reported the first comparative computational investigation of the following systems: (i) HBC with one non-metallated aromatic porphyrin, P(N4H2), unit, HBC-P(N4H2), (ii) HBC with one S-core-modified antiaromatic porphyrin (S-isophlorin), PS4, unit, HBC-PS4, and (iii) HBC with one Se-core-modified antiaromatic porphyrin (Se-isophlorin), PSe4, unit, HBC-PSe4. The study has been done employing the B3LYP/6-31G* approach (in the gas phase and in the implicit solvents, benzene and dichloromethane), and comparison with the B3LYP/6-31G** and B3LYP/6-311G* approaches was performed, where relevant. The effects of the core-modified antiaromatic isophlorins on the structures, electronic, and other properties, potentially including reactivity, of the whole building block HBC-isophlorin have been shown to be quite pronounced and to be noticeably stronger than the effects of the original aromatic non-metallated porphyrin. Thus, we have demonstrated theoretically that the complete porphyrin core-modification with other elements, this time with S and Se leading to the formation of the antiaromatic isophlorins, should be considered as a promising way for modifying and tuning structures, electronic properties and reactivity of the hexabenzocoronene-porphyrin(s) building blocks.

This work focuses on the study of the degradation to four acid dyes by advanced oxidation; the dyes used are called blue acid 113, 114, 118 and 120. The goal of this study is the determination of the most reactive sites at the levels of the dyes studied, in order to understand the mechanisms of degradation of these dyes in the field of water depollution. The study was carried out theoretically by ab initio methods. The corresponding results were calculated by CAM-B3LYP functional combined with the 6-31++G(d, p) basis set. The calculated parameters are the local Fukui indices for radical attacks, hardnesses, dipole moments, sol-vation Gibbs free enthalpy DG solv , wavelengths of the maximum absorption and oscillator Strengths. The results showed a good agreement between the mechanisms proposed experimentally and the mechanisms calculated theoretically. Hence, the confirmations of these mechanisms were obtained by local Fukui indices. The latter's revealed larger values for the nitrogen atoms constituting the four dyes, which confirm that these sites are the most reactive by radical attacks. This study is dedicated for advanced oxidation applications.

Numerous metalloporphyrin stacks have been synthesized and studied. Electronic interactions between constituent metalloporphyrins are able to determine the structures and properties of porphyrin arrays. In 2016, Co(II)–, Cu(II)–, Pt(II)–, and Zn(II)–porphyrins were shown to pack to form dimers as well as trimers. Porphyrin rings were found to strongly overlap with lateral shifts between ring centers. However, no binding energies and electronic structures of these stacks have been reported. We have performed first computational study of the dimers of Co(II)–, Cu(II)–, and Zn(II)–porphyrins, both in vacuum and in two implicit solvents. For all three stacks the configurations with strong overlap of the metalloporphyrin rings with lateral shifts between ring centers were found to be the global minimum structures, 1A for [ZnP]2 and 3A for [CuP]2 and [CoP]2. Also, open-shell singlets with the same energy or close-lying in energy were found for [CuP]2 and [CoP]2. The binding energies were calculated to be significant, from ca. −13 to −39 kcal/mol (gas phase, depending on the computational approach). The computational results showed quite good agreement with the experimental data. The dimers were found to be bound by strong bonding combinations of the monomer MOs which explained significant binding energies computed for the dimers. The shifted dimer configurations could be explained by the way how the monomer MOs preferably overlap.

Abstract Interaction mechanisms of fullerene derivatives and various types of molecules have been paid increasing attention. In this research, interaction mechanism, structural and electronic properties, natural bond orbital (NBO) analyses of 4-Phenylpyridine (4-phpy) interacted undoped or doped (B or Si) C60 fullerenes were examined based on quantum mechanical calculations. Bond order and binding energy results suggest a possible chemisorption between nitrogen atom of 4-phpy and boron or silicon atoms of doped fullerene cages and the examined B- or Si-doped complexes yielded with higher binding energies in water media calculations. Results also show that unlike C60…4-phpy indicating a very weak binding energy, B or Si doped C60 fullerenes can be used to carry 4-phpy molecule for various purposes including drug delivery systems.

Phthalocyanines (Pcs) and their derivatives have attracted a lot of attention because of their both biological importance and technological applications. The properties of Pcs can be tuned by replacing the central atom, by modifying the periphery of phthalocyanine ring, and by changing the meso-atoms. One more promising pathway for modifying Pcs and their derivatives can be the core-modification, or substitution of the core isoindole nitrogen(s) by other elements. Motivated by the results obtained for some core-modified porphyrins, we investigated computationally complete core-modification of regular Zn phthalocyanine (ZnPc) with P and S. We performed density functional theory studies of the structures, charges, and frontier molecular orbitals of P-core-modified and S-core-modified ZnPcs, ZnPc(P)4 and ZnPc(S)4, using both B3LYP and two dispersion-corrected functionals. Also, we studied computationally formation of complexes between the fullerene C60 and ZnPc(P)4 and ZnPc(S)4. Both ZnPc(P)4 and ZnPc(S)4 show strong bowl-like distortions similar to the results obtained earlier for ZnP(P)4 and ZnP(S)4. The size of the “bowl” cavity of the both core-modified Pcs is essentially the same, showing no dependence on the core-modifying element. For ZnPc(S)4, the HOMO is quite different from those of ZnPc and ZnPc(P)4. When the fullerene C60 forms complexes with the ZnPc(P)4 and ZnPc(S)4 species in the gas phase, it is located relatively far (4.30–5.72 Å) from the one of the P-centers and from the Zn-center of ZnPc(P)4, whereas with ZnPc(S)4 C60 forms relatively short bonds with the Zn-center, varying from ca. 2.0 to ca. 3.0 Å. The very strong deformations of both the ZnPc(P)4 and ZnPc(S)4 structures are observed. The calculated binding energy at the B3LYP/6-31G* level for the C60-ZnPc(P)4 complex is quite low, 1.2 kcal/mol, which agrees with the quite long distances fullerene - ZnPc(P)4, whereas it is noticeably larger, 13.6 kcal/mol, for the C60-ZnPc(S)4 complex which again agrees with the structural features of this complex. The binding energies of the complexes optimized using the dispersion-corrected functionals, CAM-B3LYP and wB97XD, are significantly larger, varying from ca. 14 till 52 kcal/mol which corresponds with the shorter distances between the fullerene and ZnPc(X)4 species.

Interaction mechanisms of fullerene derivatives and various types of molecules have been paid increasing attention. In this research, interaction mechanism, structural and electronic properties, natural bond orbital (NBO) analyses of 4-Phenylpyridine (4-phpy) interacted undoped or doped (B or Si) C60 fullerenes were examined based on quantum mechanical calculations. Bond order and binding energy results suggest a possible chemisorption between nitrogen atom of 4-phpy and boron or silicon atoms of doped fullerene cages and the examined B- or Si-doped complexes yielded with higher binding energies in water media calculations. Results also show that unlike C60…4-phpy indicating a very weak binding energy, B or Si doped C60 fullerenes can be used to carry 4-phpy molecule for various purposes including drug delivery systems.

2-Ethylhexyl 4-methoxycinnamate (EHMC) is one of the most commonly used sunscreen ingredient. In this study we investigated photodegradation of EHMC in the presence of such common oxidizing and chlorinating systems as H2O2, H2O2/HCl, H2O2/UV, and H2O2/HCl/UV. Reaction products were detected by gas chromatography with a mass spectrometric detector (GC-MS). As a result of experimental studies chloro-substituted 4-methoxycinnamic acid (4-MCA), 4-methoxybenzaldehyde (4-MBA) and 4-methoxyphenol (4-MP) were identified. Experimental studies were enriched with DFT and MP2 calculations. We found that reactions of 4-MCA, 4-MBA and 4-MP with Cl2 and HOCl were in all cases thermodynamically favorable. However, reactivity indices provide a better explanation of the formation of particular chloroorganic compounds. Generally, those isomeric forms of mono- and dichlorinated compounds which exhibits the highest hardness were identified. Nucleophilicity of the chloroorganic compounds precursors were examined by means of the Fukui function.