Bond Order Research Articles

Balancing volumetric and gravimetric capacity for hydrogen in supramolecular crystals.

The storage of hydrogen is key to its applications. Developing adsorbent materials with high volumetric and gravimetric storage capacities, both of which are essential for the efficient use of hydrogen as a fuel, is challenging. Here we report a controlled catenation strategy in hydrogen-bonded organic frameworks (RP-H100 and RP-H101) that depends on multiple hydrogen bonds to guide catenation in a point-contact manner, resulting in high volumetric and gravimetric surface areas, robustness and ideal pore diameters (~1.2-1.9 nm) for hydrogen storage. This approach involves assembling nine imidazole-annulated triptycene hexaacids into a secondary hexagonal superstructure containing three open channels through which seven of the hexagons interpenetrate to form a seven-fold catenated superstructure. RP-H101 exhibits high deliverable volumetric (53.7 g l-1) and gravimetric (9.3 wt%) capacities for hydrogen under a combined temperature and pressure swing (77 K/100 bar → 160 K/5 bar). This work illustrates the virtues of supramolecular crystals as promising candidates for hydrogen storage.

Structure and Characterization of Catanionic Complexes and Biocompatible Vesicles of N-Acyltaurine and Sarcosine Alkyl Ester: Encapsulation and Release Studies with 5-Fluorouracil.

Hydrated dispersions containing equimolar mixtures of cationic and anionic amphiphiles, referred to as catanionic systems, exhibit synergistic physicochemical properties, and mixing single-chain cationic and anionic lipids can lead to the spontaneous formation of vesicles as well as other phase structures. In the present work, we have characterized two catanionic systems prepared by mixing N-acyltaurines (NATs) and sarcosine alkyl esters (SAEs) bearing 11 and 12 C atoms in the acyl/alkyl chains. Turbidimetric and isothermal titration calorimetric studies revealed that both NATs form equimolar complexes with SAEs having matching acyl/alkyl chains. The three-dimensional structure of the sarcosine lauryl ester (lauryl sarcosinate, LS)-N-lauroyltaurine (NLT) equimolar complex has been determined by single-crystal X-ray diffraction. The LS-NLT equimolar complex is stabilized by electrostatic attraction and multiple hydrogen bonds, including classical, strong N-H···O hydrogen bonds as well as several C-H···O hydrogen bonds between the two amphiphiles. DSC studies showed that both equimolar complexes show single sharp phase transitions. Transmission electron microscopy and dynamic light scattering studies have demonstrated that the LS-NLT catanionic complex assemblies yield stable medium-sized vesicles (diameter 280-350 nm). These liposomes were disrupted at high pH, suggesting that the designed catanionic complexes can be used to develop base-labile drug delivery systems. In vitro studies with these catanionic liposomes showed efficient entrapment (73% loading) and release of the anticancer drug 5-fluorouracil in the physiologically relevant pH range of 6.0-8.0. The release rate was highest at pH 8.0, reaching about 78%, 90%, and 100% drug release at 2, 6, and 12 h, respectively. These observations indicate that LS-NLT catanionic vesicles will be useful for designing drug delivery systems, particularly for targeting organs such as the colon, which are inherently at basic pH.

Hierarchical porous ACNF/MIL-68(In)–NH2 composites for rapid and efficient removal of losartan from water: Unveiling adsorption mechanisms and superior performance

Losartan (LP), a medication commonly used to treat hypertension, has emerged as a potential environmental pollutant. Despite its widespread use, research on the efficient and rapid removal of LP from the environment remains very scarce. The limited studies on LP adsorption indicate that the adsorption capacity and rate of LP need improvement. In this study, we successfully prepared a hierarchical porous nitric acid-treated carbon nanofiber (ACNF)/MIL-68(In)–NH2 composite with a robust three-dimensional support structure using a simple hydrothermal method for the first time to adsorb LP. The resulting ACNF/MIL-68(In)–NH2 composite demonstrated exceptional adsorption capabilities, achieving an equilibrium absorption capacity of 259.87 mg/g within just 64 min, significantly outperforming previously reported results. Langmuir fitting indicated a maximum theoretical adsorption capacity exceeding 630 mg/g at 55 °C. For actual wastewater with low LP concentrations, complete removal was achieved with a minimal dose of the ACNF/MIL-68(In)–NH2 adsorbent. DFT calculations and Multiwfn wavefunction analysis revealed that the adsorption behavior of LP onto ACNF/MIL-68(In)–NH2 is primarily driven by electrostatic interactions, multiple hydrogen bonds, π-π stacking interactions, and van der Waals forces. This work presents an innovative strategy for the efficient and rapid removal of residual LP from water environments.

Pressure and temperature diagram of C60 from atomistic simulations.

Although widely studied experimentally in the 1990s, the structure and properties of low-dimensional or high-pressure phases of fullerenes have recently been re-examined. Remarkably, recent experiments have shown that transparent, nearly pure amorphous sp3-bonded carbon phases can be obtained by heating a C60 molecular crystal at a high pressure. With the additional aim of testing the ability of three classical carbon potentials reactive empirical bond order, environment-dependent interatomic potential, and reactive force-field to reproduce these results, we investigate the details of the structural transformations undergone by fullerene crystals over a wide range of pressures and temperatures. All the potentials tested show that the initial polymerization of fullerenes is accompanied by negative thermal expansion, albeit in slightly different ranges. However, more significant differences in structural and mechanical properties are observed in the amorphous phases, in particular the sp3 carbon fraction and the existence of layered amorphous carbon. Overall, these results indicate to which extent classical reactive potentials can be used to explore phase transitions over a wide range of pressures and temperatures.

QSAR Studies on a Class of Benzofuranene Cyanide Derivatives as Potential Inhibitors Targeting Staphylococcus aureus Sortase A.

Staphylococcus aureus is a widely distributed and highly pathogenic zoonotic bacterium. Sortase A represents a crucial target for the research and development of novel antibacterial drugs. This study aims to establish quantitative structure-activity relationship models based on the chemical structures of a class of benzofuranene cyanide derivatives. The models will be used to screen new antibacterial agents and predict the properties of these molecules. The compounds were randomly divided into a training set and a test set. A large number of descriptors were calculated using the software, and then the appropriate descriptors were selected to build the models through the heuristic method and the gene expression programming algorithm. In the heuristic method, the determination coefficient, determination coefficient of cross-validation, F-test, and mean squared error values were 0.530, 0.395, 9.006, and 0.047, respectively. In the gene expression programming algorithm, the determination coefficient and the mean squared error values in the training set were 0.937 and 0.008, respectively, while in the test set, they were 0.849 and 0.035. The results showed that the minimum bond order of a C atom and the relative number of benzene rings had a significant positive contribution to the activity of compounds. In this study, two quantitative structure-activity relationship models were successfully established to predict the inhibitory activity of a series of compounds targeting Staphylococcus aureus Sortase A, providing insights for further development of novel anti-Staphylococcus aureus drugs.

Self-healing cellulose nanocrystals/fluorinated polyacrylate with double dynamic interactions of coumarin groups and multiple hydrogen bonds

In this work, self-healing cellulose nanocrystals/fluorinated polyacrylate with dual dynamic networks of photoreversible crosslinking network and high-density hydrogen bonds was prepared by Pickering emulsion polymerization. The main work was to study the effects of 7-(2-methacryloyloxy)-4-methylcoumarin (CMA) and 2-ureido-4[1H]-pyrimidinone methyl methacrylate (UPyMA) monomer dosage on emulsion polymerization and latex film properties. The monomer conversion increased first and then decreased as the CMA and UPyMA monomer dosage increased, while a reverse trend was noted for the particle size and particle size distribution. Incorporating UPyMA allowed the rapid formation of hydrogen bonds at the crosslinking sites, which increased the interaction force between the healing surfaces. Besides, reversible photocrosslinking reaction of coumarin groups provided another support for self-healing performance. Moreover, the influence of self-healing temperature, self-healing time and UV irradiation on the self-healing ability was also systematically investigated The tensile strength of the prepared cellulose nanocrystals/fluorinated polyacrylate latex film exhibited a self-healing efficiency of 91.4 % under 365 nm UV irradiation and 80 °C for 12 h. The latex film had excellent thermal stability as was shown by TG and DTG analyses. The outstanding self-healing capability of latex film was attributed to the reversible photodimerization of coumarin groups and multiple hydrogen bonds. In addition, the water-oil repellent and mechanical properties of the latex films were improved as the CMA and UPyMA monomer dosage increased.

AgNP Composite Silicone-Based Polymer Self-Healing Antifouling Coatings.

Biofouling poses a significant challenge to the marine industry, and silicone anti-biofouling coatings have garnered extensive attention owing to their environmental friendliness and low surface energy. However, their widespread application is hindered by their low substrate adhesion and weak static antifouling capabilities. In this study, a novel silicone polymer polydimethylsiloxane (PDMS)-based poly(urea-thiourea-imine) (PDMS-PUTI) was synthesized via stepwise reactions of aminopropyl-terminated polydimethylsiloxane (APT-PDMS) with isophorone diisocyanate (IPDI), isophthalaldehyde (IPAL), and carbon disulfide (CS2). Subsequently, a nanocomposite coating (AgNPs-x/PDMS-PUTI) was prepared by adding silver nanoparticles (AgNPs) to the polymer PDMS-PUTI. The dynamic multiple hydrogen bonds formed between urea and thiourea linkages, along with dynamic imine bonds in the polymer network, endowed the coating with outstanding self-healing properties, enabling complete scratch healing within 10 min at room temperature. Moreover, uniformly dispersed AgNPs not only reduced the surface energy of the coating but also significantly enhanced its antifouling performance. The antibacterial efficiency against common marine bacteria Pseudomonas aeruginosa (P.sp) and Staphylococcus aureus (S.sp) was reduced by 97.08% and 96.71%, respectively, whilst the diatom settlement density on the coating surface was as low as approximately 59 ± 3 diatom cells/mm2. This study presents a novel approach to developing high-performance silicone antifouling coatings.

A hydrophobic phase-locking strategy enabling ultrarobust and water-stable self-healing elastomers for underwater ionotronics

Water-resistant conductive elastomers can endow soft electronic devices with reliable sensing performance for motion monitoring and real-time communication in aquatic environments. Nevertheless, traditional conductive elastomers typically suffer from notable shortcomings in terms of inferior mechanical robustness, weak stability, and self-healing capabilities in wet conditions and even underwater, significantly restricting their practical utility. Drawing inspiration from the optimization of multiphase structure, an ultrarobust underwater healable elastomer is constructed by incorporating biomass-derived long-chain segments with a large number of amide/benzene groups into a hierarchical H-bonding supramolecular network. The locking of multiple dynamic bonds by uniformly distributed hard-phase domains with dense hydrophobic barriers leads to the resultant elastomer gaining remarkably enhanced mechanical properties (stretchability, 2217.2 %; toughness, 272.97 MJ m−3) and outstanding capability to autonomously self-heal even underwater with a high ultimate strength over 10 MPa (aqueous healing for 24 h). Notably, it boasts exceptional healing stability to all types of harsh aqueous environments, such as strong acid/alkali, high temperature, and salty water. The application of the developed elastomer is also demonstrated by creating a multifunctional wearable sensor that can accurately detect and transmit information for a variety of human motions in both atmospheric and aquatic environments. The viable strategy reported herein for designing advanced multifunctional healable materials can be applicable for all-environment flexible iontronic devices.

Comparative Study of Neutral and Cationic Sn2H2: Toward Laboratory Detection of the Cation.

Group 14 M2H2 isomers (M = Si, Ge, Sn, and Pb) have attracted interest due to their radically differing electronic structures from acetylene. To better understand the Sn-H interactions of the neutral and cationic Sn2H2 structures, we present the most rigorous study of these systems to date. CCSD(T)/cc-pwCVTZ harmonic frequencies are presented as the first predictions for the neutral and cationic species to date. CCSDT(Q)/CBS relative energies are reported using the focal point approach, confirming the butterfly isomer as the global minimum on the potential energy surface for both the neutral and cationic species. In all, there exist 7 minima and 15 transition states. NBO analysis is also performed to elucidate the changes in bond order going from neutral to cation across all isomers of Sn2H2. Our results provide insights into the important Sn-H interaction and provide guidance for future work that may detect in the laboratory for the first time.

Synthesis, Reactivity, and Bonding Analysis of a Tetracoordinated Nickel Carbene.

Nickel carbenes are key reactive intermediates in the catalytic cyclopropanation of olefins and other reactions, but isolated examples are scarce and generally rely on low coordination numbers (≤ 3) to stabilize the metal-ligand multiple bond. Here we report the isolation and characterization of a stable tetracoordinated nickel carbene bearing a triphosphine pincer ligand. Its nucleophilic character is evidenced by reaction with acids, and it can transfer the carbene fragment to CO to form a ketene. A computational study of the Ni=C chemical bond sheds light on the role of the third phosphine in the pincer framework to the stabilization of the nickel carbene fragment.

Signatures of polarized chiral spin disproportionation in rare earth nickelates

In rare earth nickelates (RENiO3), electron-lattice coupling drives a concurrent metal-to-insulator and bond disproportionation phase transition whose microscopic origin has long been the subject of active debate. Of several proposed mechanisms, here we test the hypothesis that pairs of self-doped ligand holes spatially condense to provide local spin moments that are antiferromagnetically coupled to Ni spins. These singlet-like states provide a basis for long-range bond and spiral spin order. Using magnetic resonant X-ray scattering on NdNiO3 thin films, we observe the chiral nature of the spin-disproportionated state, with spin spirals propagating along the crystallographic (101)ortho direction. These spin spirals are found to preferentially couple to X-ray helicity, establishing the presence of a hitherto-unobserved macroscopic chirality. The presence of this chiral magnetic configuration suggests a potential multiferroic coupling between the noncollinear magnetic arrangement and improper ferroelectric behavior as observed in prior studies on NdNiO3 (101)ortho films and RENiO3 single crystals. Experimentally-constrained theoretical double-cluster calculations confirm the presence of an energetically stable spin-disproportionated state with Zhang-Rice singlet-like combinations of Ni and ligand moments.

Rotationally invariant local bond order parameters for accurate determination of hydrate structures

Averaged local bond order parameters based on spherical harmonics, also known as Lechner and Dellago order parameters, are routinely used to determine crystal structures in molecular simulations. Among different options, the combination of the q ¯ 4 and q ¯ 6 parameters is one of the best choices in the literature since distinguishes between solid- and liquid-like particles and between different crystallographic phases, including cubic and hexagonal phases. Recently, Algaba et al. [J. Colloid Interface Sci. 623, 354, (2022)] have used the Lechner and Dellago order parameters to distinguish hydrate- and liquid-like water molecules in the context of determining the carbon dioxide hydrate-water interfacial free energy. According to the results, the preferred combination previously mentioned is not the best option to differentiate between hydrate- and liquid-like water molecules. In this work, we revisit and extend the use of these parameters to deal with systems in which clathrate hydrates phases coexist with liquid phases of water. We consider carbon dioxide, methane, tetrahydrofuran, nitrogen, and hydrogen hydrates that exhibit sI and sII crystallographic structures. We find that the q ¯ 3 – q ¯ 12 combination is the best option possible between a large number of possible different pairs to distinguish between hydrate- and liquid-like water molecules in all cases.

Self‐healing reversible network from furfuryl‐functionalized copoly(triazine‐r‐polypropylene glycol‐r‐polydimethylsiloxane)

AbstractNew shape‐memory networks composed of both reversible Diels–Alder covalent crosslinks and the hydrogen and π–π stacking bonds of triazine functional groups, with self‐healing properties as a result of the reversibility of these dynamic bonds were achieved from a furfuryl‐functionalized copoly(triazine‐r‐polypropylene glycol‐r‐polydimethylsiloxane), crosslinked with a maleimide end‐capped polycaprolactone and a long polycaprolactone‐based chain extender. The presence of multiple dynamic bonds, including the Diels–Alder and triazine‐derived π–π stacking and H‐bond interactions as well as the enhanced network mobility arising from polypropylene glycol, polydimethylsiloxane and polycaprolactone segments upon triggering the shape memory effect resulted in a material with high toughness (~200 MPa J−1) and efficient healing ability (with a recoveries of tensile strength and toughness after being cut and healed of 87% and 94%, respectively).Highlights Furfuryl dichlorotriazine was coupled with PPG and PDMS forming a copolymer. The copolymer was crosslinked with PCL‐dimaleimide and PCL‐difuran extender. Multiple dynamic bonds (Diels–Alder, π–π stacking and H‐bond) were present. The network showed high toughness and good healing performance.

Imidazole and triazine framed porous aromatic framework with rich proton transport sites for high performance high-temperature proton exchange membranes

Phosphoric acid-doped polybenzimidazole (PA-PBI) membranes for high-temperature proton exchange membranes (HT-PEMs) exhibit low proton conductivity under low phosphoric acid loading and poor mechanical properties under high phosphoric acid loading. In order to overcome these disadvantages, a novel kind of porous aromatic framework framed with imidazole and triazine groups (PAF-227) was designed and synthesized, phosphoric acid (PA) was incorporated into PAF-227 by utilizing vacuum-assisted infusion to yield the product PAF-227-PA. Subsequently, this dopant was combined with polybenzimidazole (OPBI) to create the PAF-227-PA/OPBI composite high-temperature proton exchange membranes (HT-PEMs). The PAF-227-PA/OPBI exhibited high proton conductivity (0.24 S cm−1) at 200 °C, as well as a favorable mechanical property (6.73 MPa) and a high PA absorption rate (250.2 %), and the peak power density of the fabricated fuel cells was significantly increased to 678.21 mW cm−2 at 200 °C with the Pt loading of 0.3 mg cm−2. The basic sites of PAF-227 framed with rigid imidazole and triazine groups can anchoring the PA to achieve a high PA retention rate through the acid-basic interaction with PA, and provide sufficient proton conduction sites by forming hydrogen bonds with PA, and synergized with OPBI membranes to form a multiple hydrogen bond and proton transfer network for enhanced mechanical properties and dimensional thermal stability. Thus, this work provided a novel approach to the preparation of HT-PEMs, which exhibited excellent overall performance for HT-PEMs fuel cells.

Metal–Organic Frameworks with Axial Cobalt–Oxygen Coordination Modulate Polysulfide Redox for Lithium–Sulfur Batteries

AbstractAlthough the ultrahigh theoretical energy density and cost‐effectiveness, lithium–sulfur (Li‐S) batteries suffer from sluggish conversion kinetics and the shuttling effect of soluble lithium polysulfides (LiPSs). Herein, conductive hexagonal cobalt‐organic framework (Co‐HTP) nanosheets are anchored in situ on carboxyl graphene (CG) substrates and serve as host catalysts to modulate the polysulfide redox. Substantial characterizations identify that the local coordination environment of the quadrilateral Co–N4 units transforms into an asymmetric penta‐coordinated O–Co–N4 with axial Co─O coordination, which triggers spin polarization and remarkable electron delocalization of Co 3d orbital. The higher spin state and lower local electron density of the O–Co–N4 sites induce more active electronic states in Co‐HTP/CG and facilitate orbital hybridization with polysulfides to form more stable bond orders. Such optimized electronic structure significantly accelerates redox kinetics and enhances the adsorption strength of polysulfides. These merit the lithium–sulfur battery based on Co‐HTP/CG with a high reversible capacity, impressive rate capability, and prolonged cycling performance over 500 cycles. This work will enrich the design philosophy of modulating the spintronic structure of electrocatalysts for advanced Li–S batteries and beyond.

In Situ Formation of B═O Bond in Oxidative Dehydrogenation of Propane and as a Hunter for Alkoxyl Radicals: A Computational Study.

B═O multiple bonds are fundamentally important owing to the unique property of B and its potential as a tool in catalysis. Herein by means of DFT calculations, we investigated the in situ generation of transient -B═O species in the nonmetallic inorganic boron oxides and demonstrated its superior ability to capture alkoxyl radicals under the conditions of oxidative dehydrogenation of propane (ODHP). Boron-containing materials are emerging as promising catalysts for ODHP, while an extensive understanding of the underlying mechanisms remains challenging. Through systematic mechanistic and characterization calculations, we show the feasibility for the presence of -B═O species under ODHP conditions and propose that its π nature dictates its inertness in the C-H activation of propane (ΔG⧧ = 57 kcal/mol) but offers its strong ability in capturing alkoxyl radicals (barrierless with ΔG = -30 kcal/mol), which can then transform to the ·C3H6OH radical. This explains the observation of enol in the experimental study. This specific behavior of the -B═O species makes it one of the key players in the complex reaction network of ODHP and also implicates the rational design of scavengers for reactive oxygen species (ROS) and other active oxygenated species.

Nanoarchitectonics of Methyl and Aldehyde Group-Decorated SOD-Type Metal-Azolate Framework for SF6 Capture and Recovery.

Sulfur hexafluoride (SF6) is widely used as an insulating gas, being an etchant and contrast agent in the electrical, semiconductor, and medical industries. However, due to its long lifetime and high global warming potential in the atmosphere, SF6 must be carefully handled to prevent leakage during production and usage. Herein, we report a sod-net metal-azolate framework (MAF) named MAF-stu-111, which decorates methyl and aldehyde groups in the porous windows, showing high adsorption affinity for SF6 at low pressure. Stability tests, gas adsorption, and breakthrough experiments demonstrated that MAF-stu-111 possesses excellent water and chemical stability, fully reversible SF6 uptake, high SF6/N2 separation selectivity (10:90, 285.2), good reusability, and high SF6 recovery purity (99.03%). Theoretical calculations revealed that hydrogen atoms of methyl and aldehyde groups can form multiple hydrogen bonds with SF6 molecules, which ensure that SF6 molecules are firmly held within the MAF-stu-111 framework, playing a key role in the selective separation of SF6/N2.

Multiple Functional Bonds Integrated Interphases for Long Cycle Sodium‐Ion Batteries

AbstractSodium‐ion batteries (SIBs) have garnered significant interest as one of the most promising energy suppliers for power grid energy storage. However, the poor electrode/electrolyte interfacial stability leads to continual electrolyte decomposition and transition metal dissolution, resulting in rapid performance degradation of SIBs. In this work, we propose a strategy integrating multiple functional bonds to regulate electrode/electrolyte interphase by triple‐coupling of succinonitrile (SN), sodium hexafluorophosphate (NaPF6) and fluorinated ethylene carbonate (FEC). Theoretical calculation and experiment results show that the solvation structure of Na+ and ClO4− is effectively reconfigured by the solvated FEC, SN and PF6− in PC‐based carbonate electrolyte. The newly developed electrolyte demonstrates increased Na+‐FEC coordination, weakened interaction of Na+‐PC and participation of SN and PF6− anions in solvation, resulting in the formation of a conformal interfacial layer comprising of sodium oxynitrides (NaNxOy), sodium fluoride (NaF) and phosphorus oxide compounds (NaPxOy). Consequently, a 3 Ah pouch full cell of hard carbon//NaNi1/3Fe1/3Mn1/3O2 exhibits an excellent capacity retention of 90.4 % after 1000 cycles. Detailed postmortem analysis of interface chemistry is further illustrated by multiple characterization methods. This study provides a new avenue for developing electrolyte formulations with multiple functional bonds integrated interphases to significantly improve the long‐term cycling stability of SIBs.

In Silico Analysis of Antibacterial Activity of Fatty Acids in Swietenia humilis Zucc. Seed Extract Against Staphylococcus aureus sortase A enzyme

This study utilised molecular docking to predict the binding affinity of various fatty acids (FAs) found in Swietenia humilis to the sortase A (SrtA) protein target from Staphylococcus aureus. Binding energies, measured in kcal/mol, indicated the strength and stability of ligand-protein interactions, with lower values signifying stronger binding. The binding affinities of eight FAs as the active constituents in n-hexane extract of S. humilis and the positive control, gentamicin, were compared to assess their theoretical antibacterial activity. Palmitoleic acid exhibited the strongest binding affinity (-5.6 kcal/mol) among the FAs, suggesting the highest potential antibacterial activity, followed by linoleic, palmitic, linolenic, arachidic, tricosanoic, stearic, and oleic acids in decreasing order of affinity. Despite having weaker binding energies than gentamicin, a common gram-positive inhibitor from aminoglycoside derivative, FAs showed multiple hydrogen bonds and van der Waals interactions with key residues like ARG197, VAL168, VAL166, and ILE182, contributing to their binding stability. Palmitoleic acid formed multiple hydrogen bonds (ARG197 and GLY119) and significant van der Waals interactions, highlighting its strong theoretical binding. Stearic and oleic acids, although having higher binding energies, also formed critical hydrogen bonds, suggesting moderate potential activity. Gentamicin's single hydrogen bond suggests a highly specific binding site, which may result in high antibacterial activity despite fewer interaction points. The study indicated that FAs like palmitoleic and oleic acid show substantial potential as supplementary antibacterial agents, especially in the context of combating antibiotic resistance. This finding can pave a path for drug design and development to address the S. aureus's resistance.

Kekulé Counts, Clar Numbers, and ZZ Polynomials for All Isomers of (5,6)-Fullerenes C52-C70.

We report an extensive tabulation of several important topological invariants for all the isomers of carbon (5,6)-fullerenes Cn with n = 52-70. The topological invariants (including Kekulé count, Clar count, and Clar number) are computed and reported in the form of the corresponding Zhang-Zhang (ZZ) polynomials. The ZZ polynomials appear to be distinct for each isomer cage, providing a unique label that allows for differentiation between various isomers. Several chemical applications of the computed invariants are reported. The results suggest rather weak correlation between the Kekulé count, Clar count, Clar number invariants, and isomer stability, calling into doubt the predictive power of these topological invariants in discriminating the most stable isomer of a given fullerene. The only exception is the Clar count/Kekulé count ratio, which seems to be the most important diagnostic discovered from our analysis. Stronger correlations are detected between Pauling bond orders computed from Kekulé structures (or Clar covers) and the corresponding equilibrium bond lengths determined from the optimized DFTB geometries of all 30,579 isomers of C20-C70.