Size-Selective Supramolecular Chemistry in a Hydrocarbon Nanoring

Formation and reactivity of NHC-boryl radicals: insight into substituent effect from theoretical calculations

Substituent modification effects of N-heterocyclic carbene (NHC) boranes on their hydrogen atom abstraction (HAA) reactions and the chemical reactivities of corresponding NHC-boryl radicals have been investigated by density functional theory calculations. The substituent modification of NHC-boranes may notably affect the HAA reaction, both kinetically and thermodynamically, and shows remarkable substitution position dependence. The multi-site-modification of NHC-boranes is proved to be more effective for reduction of the B-H bond dissociation energy (BDE), promotion of the HAA reaction, and the reactivity regulation of their corresponding NHC-boryl radicals. Computational screening reveals that the spin density and the charge population of the radical boron center have good correlation with the B-H BDEs of NHC-boranes and the chemical reactivities of NHC-boryl radicals, and they can be considered as property and reactivity descriptors of these boron-based systems. The present results and established scaling relationships are beneficial to promote the advancement of design of NHC-boryl radical catalysis.

A DFT study on effective detection of ClCN gas by functionalized, decorated, and doped nanocone strategies

Density Functional Theory (DFT) was employed to investigate the interaction between cyanogen chloride (ClCN) and the surface of a carbon nanocone (CNC). The findings of this research revealed that pristine CNC is not an ideal material to detect ClCN gas due to its minimal alterations in electronic properties. In order to enhance the properties of carbon nanocones, multiple methods were implemented. These included functionalizing the nanocones with pyridinol (Pyr) and pyridinol oxide (PyrO) as well as decorating them with metals such as boron (B), aluminium (Al) and gallium (Ga). Additionally, the nanocones were also doped with the same third-group metal (B, Al and Ga). The simulation results indicated that doping it with aluminium and gallium atoms yielded promising results. After a comprehensive optimization process, two stable configurations were obtained between the ClCN gas and the CNC-Al, and CNC-Ga structures (configurations S21, and S22) with E _ads values of -29.11, and -23.70 kcal mol^-1 respectively, using M06-2X/6-311G(d) level. The adsorption of ClCN on CNC-Al and CNC-Ga surfaces leads to a marked alteration in the electrical properties of these structures. Calculations reveal that the energy gap between the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels (E _g) of these configurations increased in the range of 9.03% and 12.54%, respectively, thereby giving off a chemical signal. An analysis conducted by the NCI confirms that there is a strong interaction between ClCN and Al and Ga atoms in CNC-Al and CNC-Ga structures, which is represented by the red color in the RDG isosurfaces. Additionally, the NBO charge analysis reveals that significant charge transfer is present in S21 and S22 configurations (190 and 191 |me|, respectively). These findings suggest that the adsorption of ClCN on these surfaces impacts the electron-hole interaction, which subsequently alters the electrical properties of the structures. Based on the DFT results, the CNC-Al and CNC-Ga structures, which have been doped with aluminium and gallium atoms, respectively, have the potential to serve as good candidates for detecting ClCN gas. Among these two structures, the CNC-Ga structure emerged as the most desirable one for this purpose.

Microsolvation of lithium cation in xenon clusters: An octahedral growth pattern

The structural and energetic proprieties for the Li ⁺ Xe_n (n = 1-18) clusters are investigated using both Basin-Hopping combined with Potential Model description (BH-PM) and DFT methods. A structural transition from tetrahedral (4 coordination) form to octahedral (6 coordination) one is observed for n = 6. Above this size, all structures have an octahedral core. The cubic-face-centered arrangement for xenon atoms is detected for Li ⁺ Xe₁₄. To the best of our knowledge, the Li ⁺ Xe_n (n = 1-18) clusters are studied in the present work for the first time using the DFT theoretical approach. The M062X functional combined with aug-cc-pVDZ (for Li) and def2-TZVP (for Xe) basis sets reproduces accurately the CCSD(T) potential energy curve of Li + Xe system. Atom-Centered Density Matrix Propagation (ADMP) molecular dynamic calculations have been carried. Moreover, we investigate the larger sizes n = 31-35, 44, and 55 for the first time using the BH-PM theoretical approach. The closing of the first and second octahedron shells are proved for the n = 6 and 34 sizes, respectively. The relative stabilities of the Li ⁺ Xe_n molecules are also studied by computing the total energy, the binding energy per atoms for each size n. Then, the second energy difference between the size n and its two near neighbors allows identifying the magic number series. Our present data are analyzed, discussed and compared with the available theoretical and experimental data.

Theoretical Prediction on a Novel Reduction-Responsive Nanoring Having a Disulfide Group for Facile Encapsulation and Release of Fullerenes C60 and C70

In this work, a novel reduction-responsive disulfide bond-containing cycloparaphenylene nanoring molecule (DSCPP) with a pyriform shape has been designed. In addition, the interactions between the designed nanoring (host) and fullerenes C₆₀ and C₇₀ (guests) were investigated theoretically at the M06-2X/6-31G(d,p) and M06-L/MIDI! levels of theory. By analyzing geometric characteristics and host-guest binding energies, it is revealed that the designed DSCPP is an ideal host molecule of guests C₆₀ and C₇₀. DSCPP presents excellent elastic deformation during the encapsulation of C₆₀ and C₇₀. The high binding energies suggest that both DSCPP⊃C₆₀ and DSCPP⊃C₇₀ (∼92 and 118 kJ·mol^-1 at the M06-2X/6-31G(d,p) level of theory) are stable host-guest complexes, and the guest C₇₀ is more strongly encapsulated than C₆₀ in the gas phase. The thermodynamic information indicates that the formation of the two host-guest complexes is thermodynamically spontaneous. In addition, the frontier molecular orbital (FMO) features and intermolecular weak interaction region between DSCPP and fullerenes gusts are discussed to further understand the structures and properties of the DSCPP⊃fullerene systems. Finally, the ring-opening mechanism of the DSCPP under reduction conditions is investigated.

Consistency and variability of cocrystals containing positional isomers: the self-assembly evolution mechanism of supramolecular synthons of cresol-piperazine

The disposition of functional groups can induce variations in the nature and type of interactions and hence affect the molecular recognition and self-assembly mechanism in cocrystals. To better understand the formation of cocrystals on a molecular level, the effects of disposition of functional groups on the formation of cocrystals were systematically and comprehensively investigated using cresol isomers (o-, m-, p-cresol) as model compounds. Consistency and variability in these cocrystals containing positional isomers were found and analyzed. The structures, molecular recognition and self-assembly mechanism of supramolecular synthons in solution and in their corresponding cocrystals were verified by a combined experimental and theoretical calculation approach. It was found that the heterosynthons (heterotrimer or heterodimer) combined with O-H⋯N hydrogen bonding played a significant role. Hirshfeld surface analysis and computed interaction energy values were used to determine the hierarchical ordering of the weak interactions. The quantitative analyses of charge transfers and molecular electrostatic potential were also applied to reveal and verify the reasons for consistency and variability. Finally, the molecular recognition, self-assembly and evolution process of the supramolecular synthons in solution were investigated. The results confirm that the supramolecular synthon structures formed initially in solution would be carried over to the final cocrystals, and the supramolecular synthon structures are the precursors of cocrystals and the information memory of the cocrystallization process, which is evidence for classical nucleation theory.

DNA-supramolecule conjugates in theranostics

The elegant properties of deoxyribonucleic acid (DNA), such as accurate recognition, programmability and addressability, make it a well-defined and promising material to develop various molecular probes, drug delivery carriers and theranostic systems for cancer diagnosis and therapy. In addition, supramolecular chemistry, also termed "chemistry beyond the molecule", is a promising research field that aims to develop functional chemical systems by bringing discrete molecular components together in a manner that invokes noncovalent intermolecular forces, such as hydrophobic interaction, hydrogen bonding, metal coordination, and shape or size matching. Thus, DNA-supramolecule conjugates (DSCs) combine accurate recognition, programmability and addressability of DNA with the greater toolbox of supramolecular chemistry. This review discusses the applications of DSCs in sensing, protein activity regulation, cell behavior manipulation, and biomedicine.

Anion Recognition Based on a Combination of Double-Dentate Hydrogen Bond and Double-Side Anion-π Noncovalent Interactions

Anion recognitions between common anions and a novel pincer-like receptor (N,N'-bis(5-fluorobenzoyloxyethyl)urea, BFUR) were theoretically explored, particularly on geometric features of the BFUR@X (X = F^-, Cl^-, Br^-, I^-, CO₃^2-, NO₃^-, and SO₄^2-) systems at a molecular level in this work. Complex structures show that two N-H groups as a claw and two -C₆F₅ rings on BFUR as a pair of tweezers simultaneously interact with captured anions through cooperative double-dentate hydrogen bond and double-side anion-π interactions. The binding energies and thermodynamic information indicate that the recognitions of the seven anions by BFUR in vacuum are enthalpy-driven and entropy-opposed, which occur spontaneously. Although the binding energy ΔE_cp between F^- and BFUR is relatively high (289.30 kJ·mol^-1), ΔE_cp, ΔG, and ΔH of the recognition for CO₃^2- and SO₄^2- are much larger than the cases of F^-, Cl^-, Br^-, I^-, and NO₃^-, suggesting that BFUR is an ideal selective anion receptor for CO₃^2- and SO₄^2-. Additionally, energy decomposition analysis based on localized molecular orbital energy decomposition analysis (LMO-EDA) was performed; electronic properties and behaviors of the present systems were further discussed according to calculations on frontier molecular orbital, UV-vis spectra, total electrostatic potential, and visualized weak interaction regions. The present theoretical exploration of BFUR@X (X = F^-, Cl^-, Br^-, I^-, CO₃^2-, NO₃^-, and SO₄^2-) systems is fundamentally crucial to establish an anion recognition structure-property relationship upon combination of different noncovalent interactions, that is, double-dentate hydrogen bond and double-side anion-π interactions.

Corannulene–fullerene C70 noncovalent interactions and their effect on the behavior of charge transport and optical property

Corannulene–fullerene C₇₀ noncovalent interactions and their effect on the behavior of charge transport and optical property are investigated at a molecular level via the dispersion-corrected density functional theory calculations.

Theoretical studies on the structure and thermochemistry of cyclicparaphenylenediazenes

Comparison of thermochemistry of carbon nanoring structures.

Carbon-nanorings ([10]CPP and [6]CPPA) as fullerene (C60 and C70) receptors: a comprehensive dispersion-corrected DFT study

The good performance of [10]CPP for catching fullerenes C₆₀ and C₇₀ is made clear. The largest complexation energy corresponds to the C₇₀@[10]CPP complex: −53.32 kcal mol⁻¹ at the B97-D2/def2-TZVP level.

Enhanced anion binding by heteroatom replacement in bambusurils

Calculations predict that protonated aza-bambusurils would bind multiple anions along their main axis and may also function as synthetic anion channels.

Unraveling origins of the heterogeneous curvature dependence of polypeptide interactions with carbon nanostructures

Underlying causes of the differential polypeptide interactions on carbon nanosurfaces of varying curvatures emerge from a synchronized computational study.

Fluorine substitution effects of halide anion receptors based on the combination of a distinct hydrogen bond and anion–π noncovalent interactions: a theoretical investigation

Fluorine-substitution effects on anion–π interaction were deeply explored, and a more feasible and rational geometric criterion for halide-anion–π contact is established via three inequalities.

Oxidation of CO by N2O over Al- and Ti-doped graphene: a comparative study

In this work, we employ density functional theory calculations to investigate the CO oxidation mechanisms by N₂O molecules over Al- or Ti-doped graphene (Al–/Ti–graphene).

Exploring the Limit of Accuracy of the Global Hybrid Meta Density Functional for Main-Group Thermochemistry, Kinetics, and Noncovalent Interactions

The hybrid meta density functionals M05-2X and M06-2X have been shown to provide broad accuracy for main group chemistry. In the present article we make the functional form more flexible and improve the self-interaction term in the correlation functional to improve its self-consistent-field convergence. We also explore the constraint of enforcing the exact forms of the exchange and correlation functionals through second order (SO) in the reduced density gradient. This yields two new functionals called M08-HX and M08-SO, with different exact constraints. The new functionals are optimized against 267 diverse main-group energetic data consisting of atomization energies, ionization potentials, electron affinities, proton affinities, dissociation energies, isomerization energies, barrier heights, noncovalent complexation energies, and atomic energies. Then the M08-HX, M08-SO, M05-2X, and M06-2X functionals and the popular B3LYP functional are tested against 250 data that were not part of the original training data for any of the functionals, in particular 164 main-group energetic data in 7 databases, 39 bond lengths, 38 vibrational frequencies, and 9 multiplicity-changing electronic transition energies. These tests include a variety of new challenges for complex systems, including large-molecule atomization energies, organic isomerization energies, interaction energies in uracil trimers, and bond distances in crowded molecules (in particular, cyclophanes). The M08-HX functional performs slightly better than M08-SO and M06-2X on average, significantly better than M05-2X, and much better than B3LYP for a combination of main-group thermochemistry, kinetics, noncovalent interactions, and electronic spectroscopy. More important than the slight improvement in accuracy afforded by M08-HX is the conformation that the optimization procedure works well for data outside the training set. Problems for which the accuracy is especially improved by the new M08-HX functional include large-molecule atomization energies, noncovalent interaction energies, conformational energies in aromatic peptides, barrier heights, multiplicity-changing excitation energies, and bond lengths in crowded molecules.

A novel photo-responsive azobenzene-containing nanoring host for fullerene-guest facile encapsulation and release

Azobenzenes in particular have been proved to have a robust photo-response, in which their configuration can transform between the trans- and cis-form upon UV-visible irradiation. Accordingly, azobenzene-containing molecules are frequently applied in the design of the guests, involving so-called host-guest chemistry. In this paper, a novel photo-responsive nanoring host molecule ([4]AB) has been designed by introducing four azobenzene groups onto the ring, and interactions between the designed nanoring host and fullerenes C60 and C70 guests were investigated at both the M06-L/MIDI! as well as M06-2X/6-31G(d) level of theory. By analyzing the geometric characteristics and host-guest binding energies, it is revealed that the designed [4]AB with diameter ca. 13.4 Å is an ideal host molecule for the encapsulation of guests C60 and C70 fullerene. Meanwhile, inferred from UV-vis-NIR spectroscopy, the guest C60 and C70 could be facilely released from the cavity of the [4]AB via configuration transformation between trans- and cis-form of the host under 474 and 506 nm photo-irradiation, respectively. Frontier orbital features, weak interaction regions, infrared spectroscopy and (1)H NMR spectra have also been theoretically simulated. The present work would provide a new strategy for facile reversible encapsulation and release of fullerene guest by a novel nanoring host.

Theoretical exploration of the nanoscale host–guest interactions between [n]cycloparaphenylenes (n = 10, 8 and 9) and fullerene C60: from single- to three-potential well

The host–guest interactions between C₆₀ and [n]cycloparaphenylene ([n]CPP; n = 10, 8 and 9) are in the manner of single-, double- and three-potential wells, respectively.

Can Si-embedded boron nitride nanotubes act as a favorable metal-free catalyst for CO oxidation by N2O?

N₂O adsorption over Si-doped BNNT.

Electron-rich carbon nanorings as macrocyclic hosts for fullerenes

Electron-rich cycloparaphenyleneacetylenes as well as their twin "glasses-like" conjugates form stable complexes with fullerenes.