Simultaneous Interactions of Anions and Cations with Cyclohexane and Adamantane: Aliphatic Cyclic Hydrocarbons as Charge Insulators

Amidation-Reaction Strategy Constructs Versatile Mixed Matrix Composite Membranes towards Efficient Volatile Organic Compounds Adsorption and CO2 Separation

Mixed matrix composite membranes (MMCMs) have shown advantages in reducing VOCs and CO2 emissions. Suitable composite layer, substrate, and good compatibility between the filler and the matrix in the composite layer are critical issues in designing MMCMs. This work develops a high-performance UiO-66-NA@PDMS/MCE for VOCs adsorption and CO2 permea-selectivity, based on a simple and facile fabrication of composite layer using amidation-reaction approach on the substrate. The composite layer shows a continuous morphological appearance without interface voids. This outstanding compatibility interaction between UiO-66-NH2 and PDMS is confirmed by molecular simulations. The Si─O functional group and UiO-66-NH2 in the layer leads to improved VOCs adsorption via active sites, skeleton interaction, electrostatic interaction, and van der Waals force. The layer and ─CONH─ also facilitate CO2 transport. The MMCMs show strong four VOCs adsorption and high CO2 permeance of 276.5 GPU with a selectivity of 36.2. The existence of VOCs in UiO-66-NA@PDMS/MCE increases the polarity and fine-tunes the pore size of UiO-66-NH2, improving the affinity towards CO2 and thus promoting the permea-selectivity for CO2, which is further verified by GCMC and EMD methods. This work is expected to offer a facile composite layer manufacturing method for MMCMs with high VOC adsorption and CO2 permea-selectivity.

Exploring alkali metal cation⋯hydrogen interaction in the formation half sandwich complexes with cycloalkanes: a DFT approach

Gas and solvent phase stability of half sandwich complexes between cycloalkanes viz. cyclopropane, cyclobutane, cyclopentane, cyclohexane, bicyclo[2.2.2]octane and adamantane with alkali metal cations (Li+, Na+ and K+) are analysed using density functional theory (DFT). M06-2X/6-31++G(d,p) level is primarily used for the study. The studied half sandwich complexes are stable in gas phase (stabilization energy upto 26.55 kcal mol−1). Presence of solvent phase irrespective of its dielectric, imparts negative impact on the stability of the chosen complexes. The formation of the complexes is exothermic in nature. The process of complexation is both enthalpy (ΔH) and free energy (ΔG) driven. Variation in HOMO (highest occupied molecular orbital) energy also indicates towards the chemical stability of complexes. The interaction is non-covalent with primary contribution from induction component. NBO analysis indicates that C–H bond is the donor and antibonding metal orbital is the acceptor site in the process of complexation. Stability of the complexes depends on the size of the interacting monomers.

Highly Polar Insertion Complexes with Focused IR Spectra and Internal Field-Inhibited Isomerization

Complexes of a polar molecule (benzene trioxide) and alkali halide diatoms are predicted to form stable conformers through not only a common attachment, but also trapping the molecule between the counterions. Two possible low- and no-barrier routes of formation of such an insertion complex are identified, and stability and other properties of this and other conformers are analyzed, including polarity and charge distribution. Calculated IR spectra indicate a bright feature specific for the insertion complex, facilitating its reliable experimental detection. Isomerization of the ion-pair-trapped molecule shows a nonobvious inhibition effect (through an increased potential energy barrier) compared to the free molecule due to the reduction of its polarity in the isomerization. Formation of a flatter isomer, trioxonine, is clearly "reported" by a sharp alteration of the IR spectrum, distinguishable also from its variation for the nonreactive relaxation of the insertion complex into an attached one.

Counterion-Trapped-Molecules: From High Polarity and Enriched IR Spectra to Induced Isomerization

We report extensive computational studies of some novel intermolecular systems and their properties. Recombination of alkali-halide counterions separated by a noncovalently trapped hydrocarbon molecule is prevented by significant potential energy barriers, resulting in unusual metastable insertion complexes. These systems are extremely polar, while the inserted molecule is strongly counter-polarized, leading to significant cooperative nonadditivity effects. The compression and electric field produced by the counterions favours isomerization of the trapped molecule via a significant reduction of the barriers to bond rearrangement, in a field-induced mechanochemical process. The predicted IR intensity spectra clearly reflect (1) formation of the insertion complex, rather than simple attachment of alkali halide, and (2) isomerization of the trapped molecule, thus allowing experimental access to these events.

Inside-protonated 1-azaadamantane: computational studies on the structure, stability, and generation

Post Hartree–Fock and density functional theory methods have been employed to study inside-protonated 1-azaadamantane 7 and its complexes with the fluoride counterion (contact ion pairs) 10 and 11. The study also involved 1-azaadamantane 4, its outside-protonated form 8, and 1-azaadamantane radical cation 17. Inside-protonated 1-azaadamantane 7 is more than 82 kcal mol−1less stable than out-isomer 8. The repulsive interaction between the internal N+–H group and the azaadamantane cage and a substantial deformation of this cage greatly weaken the C–N and C–C bonds and, consequently, lead to a low kinetic stability of in-ion 7 in the studied unimolecular and bimolecular reactions involving the removal of the encapsulated proton from the cage. Among these reactions, a 7 → 8 rearrangement through a reversible cage opening at the C–N bond was found to be the main transformation channel ([Formula: see text] < 16 kcal mol−1) for in-ion 7. This rearrangement can be catalyzed by an external base, e.g., the fluoride anion. A 1,4-hydrogen migration in 1-azaadamantane radical cation 17 as a possible pathway to the inside-protonated 1-azaadamantane 7 was explored. It was found that this process has a prohibitively high activation barrier, [Formula: see text] > 104 kcal mol−1, and is not able to compete with the α-C–C cleavage of the azaadamantane cage ([Formula: see text] < 26 kcal mol−1).

Noncovalently bound complexes of polar molecules: dipole-inside-of-dipole vs. dipole–dipole systems

Complexes of polar molecules framed by counter-ions exhibit significant stabilities, huge dipole moments, prominent IR-spectral signatures and feasible anion-mediated formation.

Unique cation–cyclohexane interactions in tri- and hexa-fluorocyclohexane multidecker complexes in the gas phase: a DFT study

The formation of stable sandwich and multidecker complexes through electrostatic interaction in tri- and hexa-fluorocyclohexane has been analyzed in the light of density functional theory.

Interplay between Beryllium Bonds and Anion-π Interactions in BeR2:C6X6:Y- Complexes (R = H, F and Cl, X = H and F, and Y = Cl and Br)

A theoretical study of the beryllium bonds in BeR₂:C₆X₆ (R = H, F, Cl and X = H and F) has been carried out by means of MP2/aug′-cc-pVDZ computational methods. In addition, the ternary complexes BeR₂:C₆X₆:Y⁻ (Y = Cl and Br) have been analyzed. Geometric, energetic and electronic aspects of the complexes have been taken into account. All the parameters analyzed provide a clear indication of favorable cooperativity in both interactions observed, beryllium bond and aromatic ring:anion interaction.