Organic superalkalis with closed-shell structure and aromaticity

Benzene (C₆H₆) and polycyclic hydrocarbons such as naphthalene (C₁₀H₈), anthracene (C₁₄H₁₀) and coronene (C₂₄H₁₂) are well known aromatic organic compounds. We study the substitution of Li replacing all H-atoms in these hydrocarbons using density functional method. The vertical ionisation energy of such lithiated species, i.e. C₆Li₆, C₁₀Li₈, C₁₄Li₁₀ and C₂₄Li₁₂ ranges 4.24–4.50 eV, which is lower than the ionisation energy (IE) of Li atom. Thus, these species may behave as superalkalis due to their lower IE than alkali metal. However, these lithiated species possess planar and closed-shell structure, unlike typical superalkalis. Furthermore, all Li-substituted species are aromatic although their degree of aromaticity is reduced as compared to corresponding hydrocarbon analogues. We have further explored the structure of C₆Li₆ as star-like, unlike its inorganic analogue B₃N₃Li₆, which appears as fan-like structure. We have also demonstrated that the interaction of C₆Li₆ with a superhalogen (such as BF₄) is similar to that of a typical superalkali (such as OLi₃). This may further suggest that the proposed lithiated species may form a new class of closed-shell organic superalkalis with aromaticity.     

Use of HPHT Autoclave to Determine Corrosion Inhibition Effect of Poly（methyl methacrylate-co-N-vinyl-2-pyrrolidone） on Carbon Steels in 3.5% NaCl Solution Saturated with CO2

The influence of poly(methylmethacrylate-co-N-vinyl-2-pyrrolidone), P(MMA-co-VP), on corrosion of carbon steels(J55, N80, P110 SS and C110 steels) in 3.5 wt% NaCl solution saturated with CO2 was evaluated using static high pressure and high temperature(HPHT) autoclave. The surface was further evaluated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and contact angle measurements. Quantum chemical calculations have been used to evaluate the structural, electronic and reactivity parameters of the inhibitor on the steels surface. SEM, XRD and contact angle measurement studies reveal that the surface of metals are quite unaffected after use of inhibitor in 3.5% NaCl solution saturated with CO2.     

Inhibition effect of pomelo peel extract for N80 steel in 3.5% NaCl saturated with CO2 solution

Research on Chemical Intermediates - Pomelo peel extract (PPE) has been evaluated as a corrosion inhibitor for N80 steel in 3.5% NaCl saturated with CO2 solution using weight loss measurements,...     

Theoretical investigations on the superhalogen properties and interaction of PdOn (n = 1–5) species

Density functional calculations on the ground state geometries and stabilities of PdO_n species (n = 1–5) are performed in neutral as well as anionic forms. Calculations reveal that Pd can bind stably with four O atoms indicating the maximum oxidation state of Pd as high as +8. The electron affinities of PdO_n suggest that these species behave as superhalogens for n ≥ 2. The large electron affinities of PdO_n species along with stability of their anions point toward the synthesis of new class of compounds having unusual oxidizing capabilities. This possibility is explored by considering the interaction of PdO₂ superhalogen with Ca atom which forms a stable CaPdO₂ complex. In this complex, PdO₂ unit closely mimics the behavior of O atom when compared with CaO molecule. © 2013 Wiley Periodicals, Inc.     

Structures and basicity of LiNOH (N = 1 − 5) species

LiOH is one of the strong bases among neutral molecules. What about hydroxides of small Li_n (n = 2 ? 5) clusters? The addition of a single atom to a cluster sometimes has dramatic effects on its reactivity. This fact motivated us to perform an ab initio MP2/6‐311++G(d, p) investigation on Li_nOH species (n = 1 ? 5). These Li_nOH species are stabilized by both ionic as well as covalent interactions, and are found to be stable against elimination of LiOH and OH. We have determined their gas and aqueous phase basicity by considering hypothetical protonation reactions. The calculated proton affinities of Li_nOH (n ≥ 2) suggest their reduced basicity as compared to LiOH by 50–100 kJ/mol. The NBO charges and the highest occupied molecular orbitals also reveal the electride and alkalide characteristics of Li₂OH and Li₃OH, respectively. © 2016 Wiley Periodicals, Inc.     

MC6Li6 (M = Li,Na and K): a new series of aromatic superalkalis

Organic superalkalis are carbon-based species possessing lower ionisation energy than alkali atom. We study the MC₆Li₆ (M?=?Li, Na, and K) complexes and their cations by decorating hexalithiobenzene with an alkali atom using density functional theory. All MC₆Li₆ complexes are stable against dissociation into M?+?C₆Li₆ fragments, irrespective of their charge. Furthermore, their degree of aromaticity increases monotonically from M?=?Li to K, unlike MC₆Li₆ ⁺ cations, which are not aromatic as suggested by their NICS values. The adiabatic ionisation energies of MC₆Li₆ (2.60–2.78?eV) and vertical electron affinities of MC₆Li₆ ⁺ (2.32–2.62?eV) suggest that MC₆Li₆ species form a new series of aromatic superalkalis. The superalkali nature of MC₆Li₆ ⁺ and its relation with NICS values are explained on the basis of the positive charge delocalisation. We believe that these species will not only enrich the aromatic superalkalis but also their possible applications will be explored.     

Novel (Li2X)+(LiX2)− supersalts (X = F,Cl) with aromaticity: a journey towards the design of a new class of salts

LiF₂ and Li₂F can be considered as representatives of main group superhalogens and superalkali species, respectively. For the first time, we present a study on the interactions between LiX₂ and Li₂X, for X = F, Cl. Our findings show that this interaction leads to the formation of ring-shaped Li₃X₃ supersalts. The quantum theory of atoms in molecule (QTAIM) approach is used to discuss superatomic bonding in these novel species. The aromatic character of Li₃X₃ rings is established by QTAIM in addition to various chemical-reactivity-based measures. Thus, the present work opens up an avenue to further investigate these new classes of aromatic species, theoretically as well as to synthesise them, experimentally.     

Structures,stabilities and electronic properties of manganese oxyfluoride (MnOxFy) species (x + y = 1–4; x,y = 0–4)

In this work, a density functional survey on manganese oxyfluoride (MnO_xF_y) species for x + y = 1–4 is performed, in which an Mn atom interacts simultaneously with O as well as F atoms. The stabilities of all these species are established against dissociation to manganese oxides as well as fluorides and their relative stabilities are also discussed. It is revealed that the most favourable oxidation state of Mn is +4 in its oxyfluorides, same as in fluorides. For the first time, the superhalogen properties of MnOF₃, MnO₃F and MnO₂F₂ species are introduced on the basis of their high electron affinities as compared to halogens. The interaction of MnO₂F₂ superhalogen with an alkali metal (K) is considered via F atoms as well as O atoms which is similar to that in KF and leads to the formation of stable KMnO₂F₂ complex. Thus, this study is expected to motivate theorist to design a new series of superhalogen species using transition metals with mixed F and O ligands, as well as experimentalists to synthesise such novel complex compounds.     

Inhibition effect of environmentally benign Karanj (Pongamia pinnata) seed extract on corrosion of mild steel in hydrochloric acid solution

The inhibition of the corrosion of mild steel in hydrochloric acid solution by the seed extract of Karanj (Pongamia pinnata) has been studied using weight loss, electrochemical impedance spectroscopy, potentiodynamic polarization, and linear polarization techniques. Inhibition was found to increase with increasing concentration of the extract. The effect of temperature, immersion time, and acid concentration on the corrosion behavior of mild steel in 1 M HCl with addition of extract was also studied. The adsorption of the extract on the mild steel surface obeyed the Langmuir adsorption isotherm. Values of inhibition efficiency calculated from weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy are in good agreement. Polarization curves showed that Karanj (P. pinnata) seed extract behaves as a mixed-type inhibitor in hydrochloric acid. The activation energy as well as other thermodynamic parameters for the inhibition process was calculated. The adsorbed film on mild steel surface containing Karanj (P. pinnata) seed extract inhibitor was also measured by Fourier transform infrared spectroscopy. The results obtained showed that the seed extract of Karanj (P. pinnata) could serve as an effective inhibitor of the corrosion of mild steel in hydrochloric acid media.     

Fluorinated ferromagnetic metal clusters and their superhalogen behaviour

Density functional theory calculations on the ground-state geometries and spin multiplicities of neutral and anionic ferromagnetic metal fluoride clusters, MF_n (M = Fe, Co and Ni; n = 1–7), have been performed. The results show that in the case of FeF_n and CoF_n clusters, a maximum of five F atoms can be bound atomically to metal atoms while four in the case of NiF_n. The remaining F atoms bind either very weakly or molecularly. The stabilities of all MF_n clusters are discussed by calculating dissociation energies to F atoms and F₂ molecules. We notice that the anionic species are relatively more stable than corresponding neutrals. The electron affinities of these clusters are very large, reaching values as high as 7.98 eV. Therefore, these clusters can be regarded as superhalogens.