Large Stabilization Energy Research Articles

London Dispersion Effects in a Distannene/Tristannane Equilibrium: Energies of their Interconversion and the Suppression of the Monomeric Stannylene Intermediate.

Reaction of {LiC6 H2 -2,4,6-Cyp3 ⋅Et2 O}2 (Cyp=cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6-triscyclopentylphenyl with SnCl2 afforded a mixture of the distannene {Sn(C6 H2 -2,4,6-Cyp3 )2 }2 (2), and the cyclotristannane {Sn(C6 H2 -2,4,6-Cyp3 )2 }3 (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH=33.36 kcal mol-1 and ΔS=0.102 kcal mol-1 K-1 , which gives a ΔG300 K =+2.86 kcal mol-1 , showing that the conversion of 3 to 2 is an endergonic process. Computational studies show that DED stabilization in 3 is -28.5 kcal mol-1 per {Sn(C6 H2 -2,4,6-Cyp3 )2 unit, which exceeds the DED energy in 2 of -16.3 kcal mol-1 per unit. The data clearly show that dispersion interactions are the main arbiter of the 3 to 2 equilibrium. Both 2 and 3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results).

London Dispersion Effects in a Distannene/Tristannane Equilibrium: Energies of their Interconversion and the Suppression of the Monomeric Stannylene Intermediate

AbstractReaction of {LiC6H2−2,4,6‐Cyp3⋅Et2O}2 (Cyp=cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6‐triscyclopentylphenyl with SnCl2 afforded a mixture of the distannene {Sn(C6H2−2,4,6‐Cyp3)2}2 (2), and the cyclotristannane {Sn(C6H2−2,4,6‐Cyp3)2}3 (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH=33.36 kcal mol−1 and ΔS=0.102 kcal mol−1 K−1, which gives a ΔG300 K=+2.86 kcal mol−1, showing that the conversion of 3 to 2 is an endergonic process. Computational studies show that DED stabilization in 3 is −28.5 kcal mol−1 per {Sn(C6H2−2,4,6‐Cyp3)2 unit, which exceeds the DED energy in 2 of −16.3 kcal mol−1 per unit. The data clearly show that dispersion interactions are the main arbiter of the 3 to 2 equilibrium. Both 2 and 3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results).

Spectroscopic investigation and density functional theory prediction of first and second order hyperpolarizabilities of 1-(4-bromophenyl)-3-(2,4-dichlorophenyl)‑prop-2-en-1-one

This work presents the spectroscopic analysis and nonlinear optical (NLO) behaviour of 1-(4-Bromophenyl)-3-(2,4-dichlorophenyl)‑prop-2-en-1-one (DCBC). The motivation behind choosing chalcone derivative DCBC for NLO studies is its crystallization in non-centrosymmetric structure, excellent second harmonic generation efficiency (SHG) and flexibility in structure of chalcones due to donor-acceptor groups. The compound was characterized by FT-IR, FT-Raman, UV–vis and NMR techniques. The structural and spectroscopic features of the molecule were calculated using density functional theory (DFT) employing B3LYP/6–311++G(d,p) basis set and compared with the experimental values. The complete vibrational assignments were made on the basis of potential energy distribution (PED). The Natural Bond Orbital (NBO) analysis of DCBC has been done in order to provide the detailed insight into the nature of electronic conjugation between the bonds in this molecule. The second-order perturbation theory analysis of Fock matrix in the NBO basis of the molecule shows the strong intramolecular hyperconjugative interactions between σ (Cl3-C28) to σ*(C26-C28), n(1)(Cl3) to σ*(C26-C28) and π(C6-C8) to π*(C5-C13) resulting in large stabilization energies leading to large delocalization. A time-dependant variant of DFT (TD-DFT) is applied to calculate the electronic properties such as oscillator strengths, absorption maxima and HOMO and LUMO energies. The HOMO-LUMO energy gap is found to be 3.882 eV and is used to calculate global reactivity parameters. Isotropic chemical shifts were calculated using gauge invariant atomic orbital (GIAO) method and these matched well with the experimental results, indicating the accuracy of calculation method. Molecular Electrostatic Potential (MEP) surface has been depicted to know the chemically active regions of the molecule. The nonlinear optical properties of title molecule were addressed theoretically by the determination of two contributions, vibrational and electronic, to polarizability (α) and the first and the second order hyperpolarizabilities (β and γ). The electronic first and second order hyperpolarizabilities of DCBC determined by Finite Field approach method are found to be 17.805 × 10−30 and 6.0 × 10−41 e.s.u. respectively. These values are comparable to other chalcones and organic NLO materials which indicate that the studied molecule is responsive to nonlinear optical (NLO) effect and has enhanced applicability in the development of nonlinear optical devices.

Simple quantum computation composition, DFT modeling, spectroscopic characterization, and charge, NLO analysis of the novel pyridopyrimidineamide

Reaction of 6-amino-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxaldehyde (1) with 2-cyano-N-phenylacetamide (2) in boiling DMF containing TEA afforded the novel 7-amino-1,3-dimethyl-2,4-dioxo-N-phenyl-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidine-6-carboxamide (3, ADDPPC). The Spectroscopic profile of ADDPPC was examined using FT-IR, UV, 1H and 13C NMR techniques. DFT/B3LYP method simulations with 6–311++G (d,p) basis sets provided the geometrical parameters and global energy. The PES technique was employed for structural confirmation of ADDPPC by considering the geometry around C6–C14 bond using Gaussian software, and the computational results detect the stable structure of ADDPPC to be conformer II which has the lowest energy. The molecule's geometry was adjusted to perfection, and the vibrational spectral data was calculated. The delocalization of electrons and the accompanying attraction between orbitals demonstrates that the lone pair transition has larger stabilization energy than the remaining electrons, according to the NBO study. The 1H and 13C NMR chemical shifts were calculated using the GIAO method, and the experimental chemical shifts were compared with the theoretical values for the stable conformer. The electronic properties, HOMO and LUMO energies, are performed with TD-DFT, that agree well with the experimental findings. Besides, the highly reactive nature of the molecule in the frontier molecular orbitals (FMO) is identified with MEP and global reactivity descriptor analysis.

Experimental and Density Functional Theory Studies on a Zinc(II) Coordination Polymer Constructed with 1,3,5-Benzenetricarboxylic Acid and the Derived Nanocomposites from Activated Carbon.

A coordination polymer with the composition C12H20O16Zn2 (ZnBTC) (BTC = benzene-1,3,5-tricarboxylate) was synthesized under hydrothermal conditions at 120 °C, and its crystal structure was determined using single-crystal X-ray crystallography. First-principles electronic structure investigation of the compound was carried out using the density functional theory computational approach. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, the energy gap, and the global reactivity descriptors of ZnBTC were investigated in both the gas phase and the solvent phase using the implicit solvation model, while the donor–acceptor interactions were studied using natural bond orbital analyses. The results revealed that ZnBTC is more stable but less reactive in solvent medium. The larger stabilization energy E(2) indicates a greater interaction of ZnBTC in the solvent than in the gas phase. Orange peel activated carbon and banana peel activated carbon chemically treated with ZnCl2 and/or KOH were used to modify the synthesis of ZnBTC to obtain nanocomposites. ZnBTC and the nanocomposites were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis, and Fourier transform infrared. The specific surface area (SBET) and the average pore diameter of the materials were determined by nitrogen sorption measurements using the Brunauer–Emmett–Teller (BET) method, while scanning electron microscopy and transmission electron microscopy were used to observe their morphology and particle size, respectively. The PXRD of all the activated carbon materials exhibited peaks at 2θ values of 12.7 and 13.9° corresponding to a d-spacing of 6.94 and 6.32 Å, respectively. The N2 adsorption–desorption isotherm of the materials are of type II with nanocomposites showing enhanced SBET compared to the pristine ZnBTC. The results also revealed that activated carbons from the banana peel and the derived nanocomposites exhibited better porous structure parameters than those obtained from orange peel. The degradation efficiency of methyl orange in aqueous solutions using ZnBTC as a photocatalyst was found to be 52 %, while that of the nanocomposites were enhanced up to 79 %.

Unprecedented platinum(II) coordination compound of sterically hindered 3,3′-bis(NH-benzimidazol-2-yl)-2,2′-bipyridine ligand

The synthesis, spectroscopic characterization, single-crystal X-ray diffraction (SCXD) analysis, and Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) studies of the coordination compound of cis-dichloroplatinum(II) with a sterically hindered N4-donor ligand, 3,3′-bis(NH-benzimidazol-2-yl)-2,2′-bipyridine (L), [Pt(L)Cl2]⋅DMSO (1) (DMSO = dimethyl sulfoxide) are reported. The Pt(II) ion adopts a slightly distorted square-planar geometry in which L coordinates in a bidentate fashion to the metal center through N atom of benzimidazole (bim) and N atom of pyridine (py) to form a seven-membered ring. The molecular units in the lattice are held together in a head to tail fashion as a dimer through intermolecular hydrogen bonding between the uncoordinated bim and py rings in the molecule through N H⋅⋅⋅N hydrogen bonds with the R22 (14) graph-set motif. The lattice DMSO solvent molecule significantly stabilizes the structure through N H⋅⋅⋅O hydrogen bond with the coordinated bim in the structure. Hirshfeld surface analysis also confirmed the hydrogen bond interactions in the crystal. DFT and TD-DFT results show that optimized geometry and UV-vis absorption spectra are consistent with the experimental results. Natural bond orbital (NBO) properties show that the hydrogen bond stability between the two monomers attributes with large stabilization energy values.

Synthesis of Diaminopyrimidine Sulfonate Derivatives and Exploration of Their Structural and Quantum Chemical Insights via SC-XRD and the DFT Approach.

Two heterocyclic compounds named 2,6-diaminopyrimidin-4-ylnaphthalene-2-sulfonate (A) and 2,6-diaminopyrimidin-4-yl4-methylbenzene sulfonate (B) were synthesized. The structures of heterocyclic molecules were established by the X-ray crystallographic technique, which showed several noncovalent interactions as N···H···N, N···H···O, and C–H···O bonding and parallel offset stacking interaction. Hydrogen-bonding interactions were further explored by the Hirshfeld surface (HS) analysis. Nonlinear optical (NLO) and natural bond orbital (NBO) properties were calculated utilizing the B3LYP/6-311G(d,p) level. Frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP) were calculated utilizing the time-dependent density functional theory (TD-DFT) at the same level. The NBO analysis showed that the molecular stabilities of compounds A and B were attributed to their large stabilization energy values. The second hyperpolarizability (γtot) values for A and B were obtained as 3.7 × 104 and 2.7 × 104 au, respectively. The experimental X-ray crystallographic and theoretical structural parameters of A and B were found to be in close correspondence. Both the molecules reveal substantial NLO responses that can be significant for their utilization in advanced applications.

Spectroscopic, quantum chemical calculations, and molecular docking analysis of 3-Chlorophenyl boronic acid

This work presents the characterization of 3-Chlorophenyl boronic acid by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by Fourier transform infrared, Fourier transform Raman, and ultra violet visible techniques. The experimental infrared and Raman spectra were obtained in the region 4000–400cm−1 and 4000 − 100 cm−1, respectively. The optimized molecular geometry, the vibrational wavenumbers, the infrared intensities, and Raman scattering were calculated using density functional theory. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital with frontier orbital gap were presented is 5.768 eV. To study donor and acceptor interactions, natural bond orbital analysis was performed with large stabilization energy of the 172.12, 192.56 kcal/mol. Molecular electrostatic potential was calculated for the title compound to predict the reactive sites for electrophilic attract at O8 and O9. Nonlinear optical behavior in terms of the first-order hyperpolarizability and dipole moment 1.6258 D and it was higher than that of Urea were calculated. Molecular docking was carried out with different proteins using the PatchDock method show that the molecule has inhibitory activity against these receptors

Study on the Electrodeposition of Trivalent Chromium Plating Bath in the Presence of Oxalate Anions

Chromium is not easily electrodeposited from aqueous solutions based on trivalent chromium. Hull cell is employed to determine the optimum bath composition, and several electroplating baths were evaluated. The new bath with oxalate and acetate anions produces very good coatings and our results are valuable for the electroplating community and electrochemists. The baths presented a current efficiency of 37%, high covering power at 8.2 cm, low deposition potential of 7.3 V, and deposition rate of 0.4 μm/min. However, the Hull cell required a high current density (30 A/dm2). After 2 h of the electrodeposition process, the pH values change by 0.2 units. In addition, the baths were analyzed after electrolysis to detect Cr(VI), and this cation was not detected. Our study not only has a technological contribution but also presents a new explanation for the nature of these baths. In the literature, the usual explanation of the performance of these baths is based on the formation of complexes between ligands and Cr(III); however, our novel explanation is based on the high stability of water in the first solvation sphere of Cr(III), and we support our suggestions with several references to chromium solvation studies. The ligand-exchange reaction explanation is replaced by the second sphere hypothesis, that is, our explanation is based on the large stabilization energy of Cr−O bonds in [Cr(H2O)6]3+. Figure 1

Stretching the P-C Bond. Variations on Carbenes and Phosphanes.

The stability and the structure of adducts formed between four substituted phosphanes (PX3, X:H, F, Cl, and NMe2) and 11 different carbenes have been investigated by DFT calculations. In most cases, the structure of the adducts depends strongly on the stability of the carbene itself, exhibiting a linear correlation with the increasing dissociation energy of the adduct. Carbenes of low stability form phosphorus ylides (F), which can be described as phosphane → carbene adducts supported with some back-bonding. The most stable carbenes, which have high energy lone pair, do not form stable F-type structures but carbene → phosphane adducts (E-type structure), utilizing the low-lying lowest unoccupied molecular orbital (LUMO) of the phosphane (with electronegative substituents), benefiting also from the carbene–pnictogen interaction. Especially noteworthy is the case of PCl3, which has an extremely low energy LUMO in its T-shaped form. Although this PCl3 structure is a transition state of rather high energy, the large stabilization energy of the complex makes this carbene–phosphane adduct stable. Most interestingly, in case of carbenes with medium stability both F- and E-type structures could be optimized, giving rise to bond-stretch isomerism. Likewise, for phosphorus ylides (F), the stability of the adducts G formed from carbenes with hypovalent phosphorus (PX—phosphinidene) is in a linear relationship with the stabilization of the carbene. Adducts of carbenes with hypervalent phosphorus (PX5) are the most stable when X is electronegative, and the carbene is highly nucleophilic.

Observation of paramorphic phenomenon and non-tilted orthogonal smectic phases in hydrogen bonded ferroelectric liquid crystals for photonic applications

A new class of hydrogen bonded ferroelectric liquid crystals (HBFLC) have been designed and synthesized by intermolecular hydrogen bonds between mesogenic 4-decyloxybenzoic acid (10OBA) and non-mesogenic (R)-(+)-Methylsuccinic acid (MSA) which have been confirmed through experimental and theoretical studies. Further, Mulliken population analysis clearly reveals that the existence of hydrogen bonds, strength and dynamic properties. Textural observation and its corresponding enthalpy values are analyzed by polarizing optical microscope (POM) and differential scanning calorimetry (DSC) respectively. Paramorphic changes in Sm C* phase due to the change of refractive index, which clearly reveal that the complex could be used for filtering action in photonic devices. The transition from lone pair to π* with large stabilization energy evidently exposes the chiral phases in the present HBFLC complex. Intermolecular interaction is analyzed by using natural bond orbital (NBO) studies. The highest energy in the HOMO-LUMO shows the stable phase in the HBFLC complex. Molecular structure of the HBFLC complex possesses the monoclinic which has been evinced through x-ray analysis. The randomly oriented bunch of homogeneous molecules in Sm A* phase of the HBFLC complex is reported.

Na+, F–, Br–, and Cl– Adsorptions and Penetrations on an Ice Surface

With the help of our quantum mechanical/effective fragment potential (QM/EFP) scheme, the adsorptions of Na+, F–, Br–, and Cl– ions on a hexagonal ice (0001) surface were theoretically studied. Drastically different adsorption behaviors depending upon ion signs and surface heterogeneity were observed. The positive Na+ ion forms 4–5 Na+–O interfacial bondings, regardless of the number of hydrogen dangling bonds (HDBs), yielding consistent adsorptions with large stabilization energies from −49.2 to −65.6 kcal/mol. On the other hand, the binding strengths of negative ions are sensitive to the number of HDBs. In the particular binding sites where there is no HDB, both Cl– and Br– cannot form a stable surface adsorption product. At the same binding site, more reactive F– can undergo insertion reaction into surface hydrogen bonding. A molecular HF and a hydroxide are formed on a site with one HDB, showing that the surface acid–base chemistry may depend upon the surface heterogeneity. In general, the versatile b...

Effect of Orbital Interactions between Vicinal Bonds and between Hydroxy Groups on the Conformational Stabilities of 1,2-Ethanediol and 2,3-Butanediols.

The geometries of the two hydroxy groups in 1,2-ethanediol or 2,3-butanediols are more stable in a gauche orientation than those in an anti orientation. This has been generally explained in terms of the gauche effect, which is stabilization due to antiperiplanar electron delocalization between an antibonding orbital of the C-O bond (σCO*) and a bonding orbital of the C-H or C-C bond (σCH or σCC). However, a C-C single bond rotation simultaneously determines the geometries of the six vicinal bonds. Therefore, it is important to understand the effects on conformational stability of other interactions of the bond orbitals adjacent to the rotating C1-C2 bond. Bond model analysis revealed that antiperiplanar bond orbital interactions as a whole contribute to the higher stabilities of hydroxy/hydroxy gauche conformers, where the C-O/C-H or C-O/C-C combination including the σCO*/σCH or σCO*/σCC delocalization is not the dominant interaction stabilizing hydroxy/hydroxy gauche conformers. Rather, our results show that a large destabilization due to the antiperiplanar C-O/C-O combination in hydroxy/hydroxy anti conformers relatively increases the stabilities of hydroxy/hydroxy gauche conformers. This destabilization results mainly from the repulsion between the antiperiplanar bonding orbitals (σCO/σCO), which have a larger overlap compared to the synclinal σCO/σCO combination. The sum of the interbond energies between the vicinal bond orbitals of these 1,2-alkanediols is more advantageous for stability in gauche conformers. In addition, interactions between the gauche-oriented hydroxy groups provide large stabilization energies and the corresponding interactions in anti conformers are negligible. The relative conformational stabilities of 1,2-ethanediol and erythro-2,3-butanediol can be explained by the interactions between the antiperiplanar bond orbitals, between the vicinal bond orbitals, or between the hydroxy groups in addition to the combination of interactions between the vicinal bond orbitals and between the hydroxy groups. In contrast, in threo-2,3-butanediol, differences in the relative stabilities of the three conformers can be understood by the combination of the interactions between the vicinal bond orbitals and between the hydroxy groups.

Pancake Bond Orders of a Series of π‐Stacked Triangulene Radicals

AbstractConjugated radicals are capable of forming π‐stacking “pancake‐bonded” dimers. Members of the family of triangulene hydrocarbons, non‐Kekulé neutral multiradicals, can utilize more than one singly occupied molecular orbital (SOMO) to form multiple pancake‐bonded dimers with formal bond orders of up to five. The resulting dimer binding energies can be quite high and the intermolecular contacts rather small compared to the respective van der Waals values. The preferred configurations are driven by the large stabilization energy of overlapping SOMOs.

Pancake Bond Orders of a Series of π-Stacked Triangulene Radicals.

Conjugated radicals are capable of forming π-stacking "pancake-bonded" dimers. Members of the family of triangulene hydrocarbons, non-Kekulé neutral multiradicals, can utilize more than one singly occupied molecular orbital (SOMO) to form multiple pancake-bonded dimers with formal bond orders of up to five. The resulting dimer binding energies can be quite high and the intermolecular contacts rather small compared to the respective van der Waals values. The preferred configurations are driven by the large stabilization energy of overlapping SOMOs.

Dioxygen: What Makes This Triplet Diradical Kinetically Persistent?

Experimental heats of formation and enthalpies obtained from G4 calculations both find that the resonance stabilization of the two unpaired electrons in triplet O2, relative to the unpaired electrons in two hydroxyl radicals, amounts to 100 kcal/mol. The origin of this huge stabilization energy is described within the contexts of both molecular orbital (MO) and valence-bond (VB) theory. Although O2 is a triplet diradical, the thermodynamic unfavorability of both its hydrogen atom abstraction and oligomerization reactions can be attributed to its very large resonance stabilization energy. The unreactivity of O2 toward both these modes of self-destruction maintains its abundance in the ecosphere and thus its availability to support aerobic life. However, despite the resonance stabilization of the π system of triplet O2, the weakness of the O-O σ bond makes reactions of O2, which eventually lead to cleavage of this bond, very favorable thermodynamically.

Relationships between the normal- and supercurrents in the various sized materials

In the previous works [1-7], we suggested that in the materials with large HOMO-LUMO gaps, the Cooper pairs are formed by the large HOMO-LUMO gaps as a consequence of the quantization of the orbitals by nature, and by the attractive Coulomb interactions between two electrons with opposite momentum and spins occupying the same orbitals via the positively charged nuclei. We also suggest the reasonable mechanism of the occurrence of granular high temperature superconductivity in the graphite powder treated by water or exposed to the hydrogen plasma, discovered by Esquinazi et al. (Scheike et. al; 2012), on the basis of our previous theoretical works described above [1-7], which can be well confirmed by the recent experimental work (Wehlitz et. al; 2012). We also suggest the general guiding principle towards high temperature superconductivity. On the basis of these previous studies, we compare the normal metallic states with the superconducting states. Furthermore, in this article, we elucidate the mechanism of the Faraday’s law (experimental rule discovered in 1834) in normal metallic states and the Meissner effects (discovered in 1933) in superconductivity, on the basis of the theory suggested in our previous researches. Because of the very large stabilization energy of about 35 eV for the Bose–Einstein condensation, the Faraday’s law, Ampere’s law, and the Meissner effects can be observed. Article DOI: http://dx.doi.org/10.20319/mijst.2015.11.1257 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Template–Framework Interactions in Tetraethylammonium‐Directed Zeolite Synthesis

AbstractZeolites, having widespread applications in chemical industries, are often synthesized using organic templates. These can be cost‐prohibitive, motivating investigations into their role in promoting crystallization. Herein, the relationship between framework structure, chemical composition, synthesis conditions and the conformation of the occluded, economical template tetraethylammonium (TEA+) has been systematically examined by experimental and computational means. The results show two distinct regimes of occluded conformer tendencies: 1) In frameworks with a large stabilization energy difference, only a single conformer was found (BEA, LTA and MFI). 2) In the frameworks with small stabilization energy differences (AEI, AFI, CHA and MOR), less than the interconversion of TEA+ in solution, a heteroatom‐dependent (Al, B, Co, Mn, Ti, Zn) distribution of conformers was observed. These findings demonstrate that host–guest chemistry principles, including electrostatic interactions and coordination chemistry, are as important as ideal pore‐filling.

Template-Framework Interactions in Tetraethylammonium-Directed Zeolite Synthesis.

Zeolites, having widespread applications in chemical industries, are often synthesized using organic templates. These can be cost‐prohibitive, motivating investigations into their role in promoting crystallization. Herein, the relationship between framework structure, chemical composition, synthesis conditions and the conformation of the occluded, economical template tetraethylammonium (TEA+) has been systematically examined by experimental and computational means. The results show two distinct regimes of occluded conformer tendencies: 1) In frameworks with a large stabilization energy difference, only a single conformer was found (BEA, LTA and MFI). 2) In the frameworks with small stabilization energy differences (AEI, AFI, CHA and MOR), less than the interconversion of TEA+ in solution, a heteroatom‐dependent (Al, B, Co, Mn, Ti, Zn) distribution of conformers was observed. These findings demonstrate that host–guest chemistry principles, including electrostatic interactions and coordination chemistry, are as important as ideal pore‐filling.

Extreme Stabilization and Redox Switching of Organic Anions and Radical Anions by Large-Cavity, CH Hydrogen-Bonding Cyanostar Macrocycles.

Encapsulation of unstable guests is a powerful way to enhance their stability. The lifetimes of organic anions and their radicals produced by reduction are typically short on account of reactivity with oxygen while their larger sizes preclude use of traditional anion receptors. Here we demonstrate the encapsulation and noncovalent stabilization of organic radical anions by C-H hydrogen bonding in π-stacked pairs of cyanostar macrocycles having large cavities. Using electrogenerated tetrazine radical anions, we observe significant extension of their lifetimes, facile molecular switching, and extremely large stabilization energies. The guests form threaded pseudorotaxanes. Complexation extends the radical lifetimes from 2 h to over 20 days without altering its electronic structure. Electrochemical studies show tetrazines thread inside a pair of cyanostar macrocycles following voltage-driven reduction (+e-) of the tetrazine at -1.00 V and that the complex disassembles after reoxidation (-e-) at -0.05 V. This reoxidation is shifted 830 mV relative to the free tetrazine radical indicating it is stabilized by an unexpectedly large -80 kJ mol-1. The stabilization is general as shown using a dithiadiazolyl anion. This finding opens up a new approach to capturing and studying unstable anions and a radical anions when encapsulated by size-complementary anion receptors.