Energy ΔE Research Articles

Thermal, optical and electrical properties of MnO2-doped mixed sodium potassium phosphate glasses

Glasses in the system (1 − x)(0.5NaPO3–0.5KPO3)–xMnO2, with 0 ≤ x ≤ 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn2+ and Mn3+ ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (Tg) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (ρ) as a structural index is found to increase while the corresponding molar volume decreases with MnO2 content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn2+ centers in the glasses. The UV–Visible absorption is utilized to estimate the values of the optical band gap (Eg) and Urbach energy (ΔE). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc’s methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (Ec) and the Avrami parameter (n) were determined.

Palladium-catalyzed synthesis of pyrimidine substituted diaryl ethers through Suzuki Miyaura coupling reactions: Experimental and DFT studies

Aryl and hetero-aryl substituted pyrimidine derivatives demonstrate widespread applications in nonlinear optics (NLO), agrochemical and therapeutic drugs. Therefore, 2-(4-phenoxyphenyl)pyrimidine (2-PPP) and 5-(4-phenoxyphenyl) pyrimidine (5-PPP) were synthesized by palladium-catalyzed Suzuki coupling approach. The structure elucidation of synthesized products was done by 1H-NMR, 13C-NMR, and UV–vis spectroscopic analyses. The natural bond orbital (NBO) analysis was performed using density functional theory (DFT) assisted M06/6-311G** functional, which confirmed the existence of delocalization process and the hyper-conjugative interaction with representative transitions as π(C10-N16)→π*(C14-N17) and π(C26-N30)→π*(C9-N31) having stabilization energies of 36.30 and 36.55 kcal/mol for 2-PPP and 5-PPP, respectively. The small energy ΔE LUMO HOMO gap as 5.330 eV in 2-PPP and 4.975 eV in 5-PPP was evident from the frontier molecular orbital (FMO) analysis, computed at TD-DFT/M06/6-311G** level, Both the NBO and the FMO analysis predicted promising NLO molecular response. Furthermore, HF, LC-BLYP, CAM-B3LYP, M06-2X, and M06 methods, along with the 6-311G** basis set, were utilized to acquire the NLO findings of 2-PPP and 5-PPP. M06 and HF methods indicated the largest and lowest values of average polarizability ⟨α⟩ and first hyperpolarizability (βtot), respectively for both the compounds 2-PPP and 5-PPP. The ⟨α⟩ and βtot values of 2-PPP and 5-PPP were observed as 7.0 and 7.3 times and 15 and 36 times higher than the urea molecule, respectively. Both compounds hold fine NLO characteristics, thus recommended for future NLO applications.

Exfoliated Clay Decorated with Magnetic Iron Nanoparticles for Crystal Violet Adsorption: Modeling and Physicochemical Interpretation.

Surfactant–modified exfoliated Fayum clay (CTAB–EC) obtained after chemical treatment with a CTAB/H2O2 solution was further decorated with magnetic Fe3O4 nanoparticles (MNP). The final nanocomposite (MNP/CTAB–EC) was characterized by XRD, SEM, FTIR, TEM and its adsorptive capability against a model cationic dye, crystal violet (CV), was evaluated. A comparison of the adsorption performance of the raw clay and its modified counterparts using H2O2, CTAB, CTAB/H2O2 or MNP indicated that the adsorption capacity of MNP/CTAB–EC was the highest for CV removal at pH 8.0. The pseudo‒second order for the kinetics and Freundlich model for adsorption equilibrium fitted well the CV removal experimental data at all tested temperatures (25, 40 and 55 °C). The enhancement of the Langmuir adsorption capacity from 447.1 to 499.4 mg g−1 with increasing the temperature from 25 to 55 °C revealed an endothermic nature of the removal process. The interactions between CV and MNP/CTAB–EC were interpreted using advanced statistical physics models (ASPM) in order to elucidate the adsorption mechanism. Multilayer model fitted the adsorption process and therefore, the steric and energetic factors that impacted the CV adsorption were also interpreted using this model. The aggregated number of CV molecules per MNP/CTAB–EC active site () was more than unity at all temperatures, representing thus a vertical adsorption orientation and a multi‒interactions mechanism. It was determined that the increase of CV uptake with temperature was mainly controlled by the increase of the number of active sites (NM). Calculated adsorption energies (ΔE) revealed that CV removal was an endothermic and a physisorption process (ΔE < 40 kJ mol −1). MNP/CTAB–EC was magnetically separated, regenerated by NaOH, and reused without significant decrease in its adsorption efficiency, supporting a prosperity of its utilization as an effective adsorbent against hazardous dyes from wastewaters.

Diffusion Monte Carlo Studies on the Detection of Structural Changes in the Water Hexamer upon Isotopic Substitution.

The ground-state structures of water hexamer and several deuterated variants are studied by using the diffusion Monte Carlo (DMC) method. We demonstrate that a recently developed guided DMC approach allows us to study these systems using substantially smaller ensembles than are required for standard DMC approaches. DMC calculations of the ground states of (H2O)6 and (D2O)6 using the MB-pol potential with 50 000 walkers and a 1 au time step show that for (H2O)6 the cage structure is 51 ± 7 cm-1 lower in energy than the prism structure. In the case of (D2O)6, the two structures have nearly equal energies (ΔE = 9 ± 11 cm-1). The structures of the singly substituted, (H2O)(D2O)5 and (H2O)5(D2O), variants of water hexamer are also explored to identify the impact of the location of the unique water molecule on the relative stability of the possible structure. The effect on the stability of the hydrogen bond on whether a hydrogen bond has an OD or OH bond as the donor is also explored.

Theoretical Investigation on Molecular Structure and Electronic Properties of BxLiy Cluster for Lithium-Ion Batteries with Quantum ESPRESSO Program.

In this study, molecular structure and electronic properties of eleven BxLiy (x = 1–3, y = 1–3) clusters are examined using the Perdew, Burke and Ernezerhof (PBE) method in the Quantum ESPRESSO program. Three main groups, consisting of two atoms, three atoms and four atoms, are selected as the starting points. The stable configurations, their binding energies per atom (Eb), dissociation energy (ΔE), and the second difference in energy (Δ2E), HOMO-LUMO (HOMO: Highest Occupied Molecular Orbital LUMO: Lowest Occupied Molecular Orbital) gaps, total energy, frequency, force on atom, point group, bond length, density of state (DOS) and band structures are investigated for BxLiy (x = 1–3, y = 1–3) clusters. The results of binding energies (Eb), dissociation energy (ΔE) and the second difference in energy (Δ2E) show that BLi, BLi2 first isomer, BLi2 second isomer, B2Li2 first isomer, B2Li2 second isomer and BLi3 are the most stable among all 11 molecules of BxLiy (x = 1–3, y = 1–3). The stability of BxLiy (x = 1–3, y = 1–3) clusters depend on both the formation of geometrical structures on the number of Li atoms. As the number of Li atoms in the group increases, the stability of BxLiy clusters also increases. Within each group formation of geometrical structures, the stability of BxLiy clusters changes. It is observed that they may change the capability of chemical reactions in BxLiy clusters.

How the ascorbic acid and hesperidin do improve the biological activities of the cinnamon: theoretical investigation.

DFT/B3LYP calculations have been performed on series of molecules of natural products containing cinnamon and citrus, namely, cinnamic aldehyd, ascorbic acid and hesperidin. This theoretical investigation predicts the biological activities of mixtures between cinnamon and ascorbic acid and between cinnamon and hesperidin based on already proven values for these molecules. The strength of the intermolecular interactions is evaluated in term of energy decomposition of the total interaction energy ΔEint between molecules, which are mainly governed by electrostatic interactions. The HOMO–LUMO gaps explain that the possible charge transfer interactions that take place within the molecules are responsible for the molecular reactivity of the studied molecules. The chemical hardness, the chemical potential and the electrophilicity indexes are good indicators for biological activities showing their improvement to that of cinnamon itself. The mixture of hesperidin and cinnamon could be an excellent blood thinner with the regard to its polarity’s enhancement.

Modeling the Effect of Zinc Oxide on the Electronic Properties of Polyvinyl Alcohol

A compactional study for the physical properties of polyvinyl alcohol PVA in its emeraldine base form (4PVA) was presented. Both PM6 semiempirical and DFT:B3LYP/LANL2DZ levels are conducted to elucidate the ZnO effects on the electronic and surface properties of PVA. The influence of ZnO was introduced in terms of total dipole moment (TDM), HOMO/LUMO band gap energy (ΔE) and molecular electrostatic potential (MESP). The results indicated that, TDM of 4PVA and the band gap energy were changed by changing the interaction site. Where, the band gap energy of 4PVA decreased sharply with ZnO addition and the electron density together with the reactivity was increased as presented in MESP maps. Also, the influence of ZnO addition was clearly observed from TDM and band gap energy values calculated with DFT than that at the PM6 level. The difference between both methods could be attributed to electron correlation which is included in DFT rather than PM6, this makes DFT more accurate than PM6.

Crystallization behaviors of poly(ethylene terephthalate) (PET) with monosilane isobutyl-polyhedral oligomeric silsesquioxanes (POSS)

The crystallization behaviors of poly(ethylene terephthalate) (PET) with monosilane isobutyl-polyhedral oligomeric silsesquioxanes (POSS) were investigated in detail. It is observed that POSS acts as an effective nucleating agent under appropriate concentration in the PET system. Polarized optical microscopy (POM) results showed that POSS improved the nucleation density of PET. Besides, the transmission electron microscopy (TEM) observation demonstrated POSS dispersed mostly at the nanometer scale throughout the PET matrix. The crystal structures of POSS and PET/POSS were analyzed using wide-angle X-ray diffraction (WAXD). Moreover, non-isothermal crystallization kinetics of PET and PET/POSS were studied using Mo’s method. The PET/POSS system demonstrated the lower value of F(T) than pure PET, indicating that the lower cooling rate was required to attain a specified relative crystallinity for the system. The comparison of the crystallization activation energy (ΔE) showed that the POSS nanoparticles improved the crystallization of PET through an acceleration of the nucleation process. Furthermore, the isothermal crystallization behaviors were also investigated using classic Avrami method. Overall, POSS can act as a nucleating agent and greatly improve the crystallization of PET through accelerating the nucleation process.

Structural, elastic, optical and γ-ray shielding behavior of Dy3+ ions doped heavy metal incorporated borate glasses

The effect of modifier ions in different basis have been analyzed through a new series of heavy metals incorporated borate based glasses 39H3BO3+30PbO+20MO+10Bi2O3 +1Dy2O3 (where M=Ca,Sr,Ba,Na and K) which are synthesized following melt quenching technique for radiation screening applications. The potentiality of glasses to withstand the penetration of fast moving neutrons is checked by various studies. Functional groups are identified through different stretching and bending modes of vibrations within the glass membrane through FTIR spectral analysis. In addition to that, other structural properties like Boron-Boron distance (dB−B), molar volume of oxygen (Vo), Oxygen Packing Density (OPD), optical basicity (Λth) and Bond density (nb) are calculated theoretically. The bonding nature (β) and nephelauxetic ratio (δ) values reveals that the glasses possess more of ionic linkages. The high density value exhibited by the Bismuth lead borate glasses indicates their capability to act as a good shielding material in reactors emitting hazardous radiation. Different moduli of elasticity (E, K, G, σ) values for the present glasses are calculated and the results reveal the enhancement in shielding performances when compared to other existing glasses and a comparative study is made on it. Optical studies are carried out and the absorption of Dy3+ions to different energy levels is observed and optical band gap (Eopt) values of the synthesized glasses are calculated along with the Urbach energy (ΔE) values. Radiation shielding properties of the produced glasses were investigated in terms of the mass attenuation coefficients (µm), transmission fraction (T), half value layer (HVL) and effective atomic number (Zeff) parameters. The results attained in the shielding study indicated that glass specimen with M = Ba exhibits enhanced shielding behavior as Ba owns high atomic number (Z) compared to other elements. Glass specimen with M = Na shows the poorest shielding characteristics due to the low Z of Na.

First-principles calculations of the electronic structure, chemical bonding, and thermodynamic properties of USiO4

The density functional theory (DFT) + U method is adopted to study the electronic structure, magnetism, chemical bonding, and thermodynamic properties of USiO4. A bandgap of 3.1 eV is obtained by analyzing the band diagram of USiO4. The calculated structural parameters are consistent with the recent experimental results. The charge density and charge density differences are studied in order to analyze the chemical bonds in USiO4. The results indicate that interactions within USiO4 are mostly ionic and exhibit weak covalent character. In addition, phonon behavior is studied in detail. We predict phonon frequencies and assign and analyze the Raman-active and infrared-active modes at the Γ point. Furthermore, thermodynamic properties such as the internal energy ΔE, Helmholtz free energy ΔF, constant-volume specific heat CV, and entropy S are investigated in the region between 0 K and 1000 K. The results are expected to provide useful information for subsequent experiments on USiO4.

Quantum-Chemistry Based Design of Halobenzene Derivatives With Augmented Affinities for the HIV-1 Viral G4/C16 Base-Pair.

The HIV-1 integrase (IN) is a major target for the design of novel anti-HIV inhibitors. Among these, three inhibitors which embody a halobenzene ring derivative (HR) in their structures are presently used in clinics. High-resolution X-ray crystallography of the complexes of the IN-viral DNA transient complex bound to each of the three inhibitors showed in all cases the HR ring to interact within a confined zone of the viral DNA, limited to the highly conserved 5′CpA 3′/5′TpG 3′ step. The extension of its extracyclic CX bond is electron-depleted, owing to the existence of the “sigma-hole.” It interacts favorably with the electron-rich rings of base G4. We have sought to increase the affinity of HR derivatives for the G4/C16 base pair. We thus designed thirteen novel derivatives and computed their Quantum Chemistry (QC) intermolecular interaction energies (ΔE) with this base-pair. Most compounds had ΔE values significantly more favorable than those of the HR of the most potent halobenzene drug presently used in clinics, Dolutegravir. This should enable the improvement in a modular piece-wise fashion, the affinities of halogenated inhibitors for viral DNA (vDNA). In view of large scale polarizable molecular dynamics simulations on the entirety of the IN-vDNA-inhibitor complexes, validations of the SIBFA polarizable method are also reported, in which the evolution of each ΔE(SIBFA) contribution is compared to its QC counterpart along this series of derivatives.

A comparative multi‐reference configuration interaction study of the low‐lying states of two thione isomers of thiophenol

AbstractMulti‐reference configuration interaction, MR‐CI (including extensivity corrections, named +Q), calculations were performed on the S0–S3 states of cyclohexa‐2,4‐diene‐1‐thione (thione 24) and cyclohexa‐2,5‐diene‐1‐thione (thione 25), which are thione isomers of thiophenol. Several types of uncontracted MR‐CIS and MR‐CISD wavefunctions were employed, comprising MR‐CI expansions as large as ~365 × 106 configuration state functions. The nature of the studied excited states was characterized. Vertical excitation energies (ΔE) and oscillator strengths (f) were computed. The most intense transitions (S0 → S2 for 24 and S0 → S3 for 25) did not change with the wavefunction, although a variation as large as ~1 eV was obtained for the S3 state of 24, at the highest (MR‐CI+Q) level. On the other hand, ΔE changed at most by ~0.56 eV for 25 as the wavefunction changes, at the same level. The S1 state of both thiones was found to have nπ* character and is in the visible region. For 24, S2 and S3 are ππ* and nπ* states, respectively, while for 25 the reverse order is obtained. S2 and S3 are in the range ~3.5 to 5.2 eV, again at the highest level. It is the first time that the excited states of the title molecules are studied. The computed results agree with the experimental onset of photoreactions of thiones 24 and 25 found by Reva et al (Phys. Chem. Chem. Phys., 2015, 17, 4888).

Pickering/Non-Pickering Emulsions of Nanostructured Sulfonated Lignin Derivatives.

Sulfoethylated lignin (SEKL) polymeric surfactant and sulfoethylated lignin nanoparticles (N-SEKL) with a size of 750±50 nm are produced by using a facile green process involving a solvent-free reaction and acidification-based fractionation. SEKL forms a liquid-like conventional emulsion with low viscosity that has temporary stability (5 h) at pH 7. However, N-SEKL forms a gel-like, motionless, and ultra-stable Pickering emulsion through a network of interactions between N-SEKL particles, which creates steric hindrance among the oil droplets at pH 3. The deposition of SEKL and N-SEKL on the oil surface is monitored by a using a quartz crystal microbalance. Experimentally, the formation of emulsions at pH 7 is found to be reversible owing to the low adsorption energy ΔE of SEKL on the oil droplet (ΔE≈15 kB T), which is determined with the help of three-phase contact-angle measurements. However, the high desorption energy (ΔE≈6.0×105 kB T) of N-SEKL makes it irreversibly adsorb on the oil droplets. SEKL is too hydrophilic to attach to the oil interface (ΔE≈0) and thus does not facilitate emulsion formation at pH 11. Therefore, it is feasible to apply SEKL for the formulation of Pickering or non-Pickering emulsions in the form of nanoparticles or polymeric surfactants, depending on the targeted application.

Mechanism of sonication time on structure and adsorption properties of 3D peanut shell/graphene oxide aerogel

A 3D pretreated peanut shell-supported graphene oxide (PPS/GO) aerogel has been facilely prepared through a brief sonication + freeze-shaping technique, avoiding the traditional application of hydrothermal method which suffered from high temperature and long reaction time as well as significant loss of oxygen-containing functional groups. It was then employed to efficient norfloxacin (NOR) removal from aqueous medium. The mechanism of sonication time on the structure and adsorption properties of as-obtained PPS/GO aerogels was emphatically discussed via combining instrumental analyses, batch adsorption experiments and density functional theory (DFT) calculations. Results showed that the 3D PPS/GO aerogel with a decrease in oxygen functional groups and an increase in sp2-derived sp3 hybridization regions was observed as sonication time provided in excess, causing the worse removal efficiency towards NOR. The resulting PPS/GO(5:1) aerogel obtained at sonication of 2 min and GO loading content of 200 mg/(PPS)g exhibited the optimal NOR adsorption capacity (pH 6.2, 228.83 mg g−1). DFT calculations further identified that the sp3-hybridized areas in PPS/GO aerogel had much lower adsorption energy (ΔE, −6.69 kcal/mol) towards NOR as compared with that of sp2-hybridized zones (−12.45 kcal/mol). In addition, multiple interactions were involved in the adsorption of NOR by 3D PPS/GO aerogel, including electrostatic attraction, H-bonding, π-π conjugation and hydrophobic effect.

894 Published By: Blue Eyes Intelligence Engineering &amp; Sciences Publication Retrieval Number: G5717059720/2020©BEIESP DOI: 10.35940/ijitee.G5717.059720 Journal Website: www.ijitee.org Electrical Resistivity, Thermoelectric Power and I-V Characteristics of Sb-Se Thin Films at Different Compositions.

Sb-Se thin films of varying composition have been deposited on glass substrates at room temperature. These films were annealed at temperature interval of 50 0K. The electrical resistivity (ρ) and thermoelectric power (α) of same films were measured. The resistance of semiconducting films decreases rapidly on heating showing negative temperature coefficient of resistance (T.C.R.). The composition dependent resistivity shows exponential change, sharp fall of resistivity may be attributed due to increase of metallic ‘Sb’ in Sb-Se thin films. The composition dependent activation energy of Sb-Se thin films has been calculated. The activation energy (ΔE) of semiconducting films was found to increase with selenium concentration. For different compositions thermoelectric power (α) increases upto 70 at. wt.% of Se concentration and then slowly decreases. The I-V characteristics of Sb-Se thin films were measured using copper (Cu) contacts. The films show ohmic conduction for different applied voltages as well as various concentrations of Selenium (Se) in Sb-Se thin films.

Electronic Properties of Polyvinyl Alcohol/ TiO2/SiO2 Nanocomposites

Molecular modeling shows potential applications for calculating physical as well as chemical parameters of many molecular systems. Physical parameters such as HOMO-LUMO band gap energy (ΔE), total dipole moment (TDM) and the molecular electrostatic potential (MESP) are reflecting the reactivity of the given chemical structure. So, the effect of titanium dioxide (TiO2) and silicon dioxide (SiO2) upon Polyvinyl chloride PVC is studied in terms of physical properties. Such parameters were calculated with density functional theory: B3LYP using LANL2DZ basis set. Model molecules for PVA, TiO2, SiO2, PVA/TiO2, PVA/SiO2 and PVA/TiO2/SiO2 were optimized then ΔE, TDM and MESP were calculated at B3LYP/LANL2DZ. The results indicated that the reactivity of PVA is improved as a result of interaction with TiO2 and SiO2.

Straight Z and twisted E isomers from triphenylamine derivatives: Intramolecular charge transfer and second-order nonlinear optical response

Intramolecular charge transfer (CT) in push-pull systems plays an important role in enhancing nonlinear optical (NLO) response. The main purpose of this work is to explore the effect of straight Z and twisted E isomers on the second-order NLO properties, two types of push-pull systems (Z(E)-A and D-Z(E)-A) based on the triphenylamine are designed and investigated. Significantly, the first hyperpolarizability (βtot) results show that the βtot value of straight Z-A is larger than that of twisted E-A. It is noteworthy that Z conformation modified by acceptor units can effectively adjust the second-order NLO properties. Further, D-Z-A and D-E-A systems combining multiple donor and acceptor units exhibit large second-order NLO properties. Obviously, D3-Z-A3 shows the largest βtot values of 2.46 × 104 au. Moreover, the trend of the transition energy (ΔE) value is inconsistent with the trend of βtot value, which explains the variation tendency of the βtot value. The presented correlation between conformation and the second-order NLO properties can provide a simple predictive tool to design highly NLO material based on triphenylamine derivatives.

A novel multifunctional adsorbent of pomegranate peel extract and activated anthracite for Mn(VII) and Cr(VI) uptake from solutions: Experiments and theoretical treatment

The structure of anthracite (An) was exfoliated by H2O2 and impregnated with pomegranate peel extract (PP) to synthesize a new multifunctional (An/PP) composite. This new composite was characterized and applied for Cr(VI) and Mn(VII) adsorption at pH 3.0 and varied temperatures (i.e., 25, 40 and 55 °C). Traditional Langmuir and Freundlich models fitted well the attained data at all adsorption temperatures. The maximum adsorption capacities were 382.19, 361.50 and 339.54 mg/g for Cr(VI) and 400.49, 417.99 and 447.38 mg/g for Mn(VII) at 25, 40 and 55 °C, respectively. The steric and energetic parameters of an advanced multilayer model were interpreted to understand the adsorption mechanisms. The receptor sites (n) was <1.0 at 25 and 40 °C and higher than 1.6 at 55 °C for Cr(VI) and Mn(VII) thus revealing multi–docking and multimolecular adsorption mechanisms. The decrease of active sites number (DM) and the total adsorbed layers (Nt) resulted in decreasing the adsorption capacities (Qsat) of Cr(VI) from 888.23 to 550.28 mg/g in the temperature range of 25–55 °C. The adsorption energy (ΔE) was identified as the main factor in enhancing the Qsat of Mn(VII) from 991.87 to 1025.65 mg/g. Calculated ΔE for the studied ions varied from 21.6 to 32.48 kJ/mol with negative values for Cr(VI) and a positive one for Mn(VII). Furthermore, the calculations of ΔE confirmed the exothermic and endothermic natures for Cr(VI) and Mn(VII), respectively, where the removal of both ions was related to physical adsorption interactions. Finally, this study provided new experimental and theoretical results for the Cr(VI) and Mn(VII) adsorption onto An/PP adsorbent.

Adamanzane based alkaline earthides with excellent nonlinear optical response and ultraviolet transparency

Strategies to design alkalides with excellent NLO responses are well established in the literature. On the contrary, alkaline earthides are quite scarce mainly because of low electron affinities of alkaline earth elements. Herein, we report two series of alkaline earthides M+(26Adz)M- (M+ = Li and Na; M- = Be, Mg and Ca), based on 26Adz as a complexant and alkali metals as sources of electrons for alkaline earth metals. These complexes are characterized as alkaline earthides by negatives charges on alkaline earth metals (NBO analysis) and presence of polarized-p HOMO orbital on alkaline earth meals. Presence of HOMO on alkaline earth metals is also confirmed through PDOS spectra. HOMO-LUMO gaps of the compounds are reduced significantly and range from 2.15 to 2.85 eV as compared to 5.17 eV HOMO-LUMO gap of pure cage. Besides H-L gaps, these compounds possess remarkably large nonlinear optical responses with the first hyperpolarizabilities (βo) up to 1.0 × 106 au for Na +(26Adz)Mg-. The nonlinear optical response of alkaline earthides is superior than those of alkalides and it is attributed to the presence of excess electron on alkaline earth metals in polarized p-orbitals. The hyperpolarizabilities are rationalized through two level method. The projection of hyperpolarizability on the dipole moment, βvec for both series are comparable to βo (static first hyperpolarizability) which indicate that the charge transfer is parallel to the molecular dipole moments. The alkaline earthides possess very small transition energies (ΔE) ranging from 0.6 to 2.4 eV. The UV–Vis analysis reveals that these alkaline earthides are transparent in ultraviolet region of the electromagnetic spectrum. The designed alkaline earthides are potential candidates for UV-transparent high performance NLO materials for applications in optical communication, optical computing and other laser devices. Present results will certainly inspire experimentalists and theoreticians to design and synthesize other alkaline earthides-based NLO materials with even better performance.

π-Stacking effects on acid capacity of p-aminobenzoic acid

Acidity changes of p-aminobenzoic acid (pABA) after π-stacking with substituted benzenes (SB) have been investigated using quantum mechanical calculations at the M06-2X/6-311++G(d,p) level of theory. In addition to benzene derivatives that are usually used as a model for aromatic amino acids (AA), two amino acids, tryptophan (TRP) and histidine (HIS), with different cyclic structures were also considered in this work. All substituents enhance the stacking interactions, in which enhancement is higher for electron-withdrawing substituents (EWSs). The stacking interaction (in presence of all substituents) enhances the acidity (3.42 for Br). Natural energy decomposition analysis (NEDA) shows that the polarization interactions (POL) have the largest contribution in the binding energies (ΔE) of neutral and anionic complexes, while the electrostatic effects (ES) are in better correlation with ΔE. The ΔE values are linearly dependent on the sum of electron densities (ΣρBCP) calculated at the bond critical points (BCPs) between the rings and the ΣρRCP values calculated at the ring critical points (RCPs) in the neutral and anionic SB||pABA complexes. An excellent correlation was found between the ΔE values and a combination of electrostatic (σmeta), resonance/induction (σpara), and dispersion/polarizability (molar refractivity, MR) substituent constant terms. There are good relationships between pKa and the global minimum and maximum of electrostatic potential around the O (∑Vmin-O) and H (Vmax-H) atoms, and the results of natural population analysis (NPA). Therefore, the electrostatic and charge transfer effects play a major role in acidity.