Molecular design of antimicrobial conjugated oligoelectrolytes with enhanced selectivity toward bacterial cells

A series of cationic conjugated oligoelectrolytes (COEs) was designed to understand how variations in molecular dimensions impact the relative activity against bacteria and mammalian cells. These COEs kept a consistent distyrylbenzene framework but differed in the length of linker between the core and the cationic site and the length of substitute on the quaternary ammonium functioned group. Their antimicrobial efficacy, mammalian cell cytotoxicity, hemolytic activity, and cell association were determined. We find that hydrophobicity is a factor that controls the degree of COE association to cells, but in vitro efficacy and cytotoxicity depend on more subtle structural features. COE2-3C-C4butyl was found to be the optimal structure with a minimum inhibitory concentration (MIC) of 4 μg mL⁻¹ against E. coli K12, low cytotoxicity against HepG2 cells and negligible hemolysis of red blood cells, even at 1024 μg mL⁻¹. A time-kill kinetics study of COE2-3C-C4butyl against E. coli K12 demonstrates bactericidal activity. These findings provide the first systematic investigation of how COEs may be modulated to achieve low mammalian cell cytotoxicity with the long-range perspective of finding candidates suitable for developing a broad-spectrum antimicrobial agent.

A series of cationic conjugated oligoelectrolytes (COEs) was designed to understand how variations in molecular dimensions impact the relative activity against bacteria and mammalian cells.     

Improved broad-spectrum antibiotics against Gram-negative pathogens via darobactin biosynthetic pathway engineering

The development of new antibiotics is imperative to fight increasing mortality rates connected to infections caused by multidrug-resistant (MDR) bacteria. In this context, Gram-negative pathogens listed in the WHO priority list are particularly problematic. Darobactin is a ribosomally produced and post-translationally modified bicyclic heptapeptide antibiotic selectively killing Gram-negative bacteria by targeting the outer membrane protein BamA. The native darobactin A producer Photorhabdus khanii HGB1456 shows very limited production under laboratory cultivation conditions. Herein, we present the design and heterologous expression of a synthetically engineered darobactin biosynthetic gene cluster (BGC) in Escherichia coli to reach an average darobactin A production titre of 13.4 mg L⁻¹. Rational design of darA variants, encoding the darobactin precursor peptide with altered core sequences, resulted in the production of 13 new ‘non-natural’ darobactin derivatives and 4 previously hypothetical natural darobactins. One of the non-natural compounds, darobactin 9, was more potent than darobactin A, and showed significantly improved activity especially against Pseudomonas aeruginosa (0.125 μg mL⁻¹) and Acinetobacter baumannii (1–2 μg mL⁻¹). Importantly, it also displayed superior activity against MDR clinical isolates of E. coli (1–2 μg mL⁻¹) and Klebsiella pneumoniae (1–4 μg mL⁻¹). Independent deletions of genes from the darobactin BGC showed that only darA and darE, encoding a radical forming S-adenosyl-l-methionine-dependent enzyme, are required for darobactin formation. Co-expression of two additional genes associated with the BGCs in hypothetical producer strains identified a proteolytic detoxification mechanism as a potential self-resistance strategy in native producers. Taken together, we describe a versatile heterologous darobactin platform allowing the production of unprecedented active derivatives in good yields, and we provide first experimental evidence for darobactin biosynthesis processes.

Heterologous expression of a synthetically engineered darobactin gene cluster in E. coli yields new darobactin derivatives with improved anti-Gram-negative activity. Targeted gene deletions provide first insights into biosynthetic steps.     

Triazole-based osmium(ii) complexes displaying red/near-IR luminescence: antimicrobial activity and super-resolution imaging

Cellular uptake, luminescence imaging and antimicrobial activity against clinically relevant methicillin-resistant S. aureus (MRSA) bacteria are reported. The osmium(ii) complexes [Os(N^N)₃]²⁺ (N^N = 1-benzyl-4-(pyrid-2-yl)-1,2,3-triazole (1²⁺); 1-benzyl-4-(pyrimidin-2-yl)-1,2,3-triazole (2²⁺); 1-benzyl-4-(pyrazin-2-yl)-1,2,3-triazole (3²⁺)) were prepared and isolated as the chloride salts of their meridional and facial isomers. The complexes display prominent spin-forbidden ground state to triplet metal-to-ligand charge transfer (³MLCT) state absorption bands enabling excitation as low as 600 nm for fac/mer-3²⁺ and observation of emission in aqueous solution in the deep-red/near-IR regions of the spectrum. Cellular uptake studies within MRSA cells show antimicrobial activity for 1²⁺ and 2²⁺ with greater toxicity for the meridional isomers in each case and mer-1²⁺ showing the greatest potency (32 μg mL⁻¹ in defined minimal media). Super-resolution imaging experiments demonstrate binding of mer- and fac-1²⁺ to bacterial DNA with high Pearson''s colocalisation coefficients (up to 0.95 using DAPI). Phototoxicity studies showed the complexes exhibited a higher antimicrobial activity upon irradiation with light.

Cellular uptake, luminescence imaging and antimicrobial activity of facial and meridional isomers of Os(ii) triazole-based complexes against methicillin-resistant S. aureus, MRSA.     

Modulation of the superficial electronic structure via metal–support interaction for H2 evolution over Pd catalysts

Electronic interactions can radically enhance the performance of supported metal catalysts and are critical for fundamentally understanding the nature of catalysts. However, at the microscopic level, the details of such interactions tuning the electronic properties of the sites on the metal particle''s surface and metal–support interface remain obscure. Herein, we found polarized electronic metal–support interaction (pEMSI) in oxide-supported Pd nanoparticles (NPs) describing the enhanced accumulation of electrons at the surface of NPs (superficial Pd^δ−) with positive Pd atoms distributed on the interface (interfacial Pd^δ+). More superficial Pd^δ− species mean stronger pEMSI resulting from the synergistic effect of moderate Pd–oxide interaction, high structural fluxionality and electron transport activity of Pd NPs. The surface Pd^δ− species are responsible for improved catalytic performance for H₂ evolution from metal hydrides and formates. These extensive insights into the nature of supported-metal NPs may open new avenues for regulating a metal particle''s electronic structure precisely and exploiting high-performance catalysts.

A new type of electronic effect, polarized metal-support interaction (pEMSI), in oxide-supported Pd nanoparticles describing the enhanced accumulation of electrons at the superficial surface is responsible for improved catalytic H₂ evolution.     

A reconstructed porous copper surface promotes selectivity and efficiency toward C2 products by electrocatalytic CO2 reduction

Electrocatalytic synthesis of multicarbon (C₂₊) products from CO₂ reduction suffers from poor selectivity and low energy efficiency. Herein, a facile oxidation–reduction cycling method is adopted to reconstruct the Cu electrode surface with the help of halide anions. The surface composed of entangled Cu nanowires with hierarchical pores is synthesized in the presence of I⁻, exhibiting a C₂ faradaic efficiency (FE) of 80% at −1.09 V vs. RHE. A partial current density of 21 mA cm⁻² is achieved with a C₂ half-cell power conversion efficiency (PCE) of 39% on this electrode. Such high selective C₂ production is found to mainly originate from CO intermediate enrichment inside hierarchical pores rather than the surface lattice effect of the Cu electrode.

The Cu electrode surface is reconstructed by a halide anion assisted method for promoting CO₂ reduction.     

Acyclic diaminocarbene-based Thiele,Chichibabin, and Müller hydrocarbons

Thiele, Chichibabin and Müller hydrocarbons are considered as classical Kekulé diradicaloids. Herein we report the synthesis and characterization of acyclic diaminocarbene (ADC)-based Thiele, Chichibabin, and Müller hydrocarbons. The calculated singlet–triplet energy gaps are ΔE_S–T = −27.96, −3.70, −0.37 kcal mol⁻¹, respectively, and gradually decrease with the increasing length of the π-conjugated spacer (p-phenylene vs. p,p′-biphenylene vs. p,p′′-terphenylene) between the two ADC-scaffolds. In agreement with the calculations, we also experimentally observed the enhancement of paramagnetic diradical character as a function of the length of the π-conjugated spacer. ADC-based Thiele''s hydrocarbon is EPR silent and exhibits very well resolved NMR spectra, whereas ADC-based Müller''s hydrocarbon displays EPR signals and featureless NMR spectra at room temperature. The spacer also has a strong influence on the UV-Vis-NIR spectra of these compounds. Considering that our methodology is modular, these results provide a convenient platform for the synthesis of an electronically modified new class of carbon-centered Kekulé diradicaloids.

We report the synthesis of acyclic diaminocarbene (ADC)-scaffold based Thiele, Chichibabin, and Müller hydrocarbons. Studies support that the singlet-triplet energy gap depends on the π-conjugated spacer between the ADC scaffolds.     

Observations of tetrel bonding between sp3-carbon and THF

We report the direct observation of tetrel bonding interactions between sp³-carbons of the supramolecular synthon 3,3-dimethyl-tetracyanocyclopropane (1) and tetrahydrofuran in the gas and crystalline phase. The intermolecular contact is established via σ-holes and is driven mainly by electrostatic forces. The complex manifests distinct binding geometries when captured in the crystalline phase and in the gas phase. We elucidate these binding trends using complementary gas phase quantum chemical calculations and find a total binding energy of −11.2 kcal mol⁻¹ for the adduct. Our observations pave the way for novel strategies to engineer sp³-C centred non-covalent bonding schemes for supramolecular chemistry.

sp³-C⋯THF tetrel bonding was observed in the crystalline state and in the gas phase. Density functional calculations revealed interaction energies up to −11.2 kcal mol⁻¹ and showed that these adducts are held together mainly by electrostatics.     

Protein encapsulation: a new approach for improving the capability of small-molecule fluorogenic probes

Herein, we report a protein-based hybridization strategy that exploits the host-guest chemistry of HSA (human serum albumin) to solubilize the otherwise cell impermeable ONOO⁻ fluorescent probe Pinkment-OAc. Formation of a HSA/Pinkment-OAc supramolecular hybrid was confirmed by SAXS and solution-state analyses. This HSA/Pinkment-OAc hybrid provided an enhanced fluorescence response towards ONOO⁻versusPinkment-OAc alone, as determined by in vitro experiments. The HSA/Pinkment-OAc hybrid was also evaluated in RAW 264.7 macrophages and HeLa cancer cell lines, which displayed an enhanced cell permeability enabling the detection of SIN-1 and LPS generated ONOO⁻ and the in vivo imaging of acute inflammation in LPS-treated mice. A remarkable 5.6 fold (RAW 264.7), 8.7-fold (HeLa) and 2.7-fold increased response was seen relative to Pinkment-OAc alone at the cellular level and in vivo, respectively. We anticipate that HSA/fluorescent probe hybrids will soon become ubiquitous and routinely applied to overcome solubility issues associated with hydrophobic fluorescent imaging agents designed to detect disease related biomarkers.

Herein, we report a protein-based hybridization strategy that exploits the host–guest chemistry of HSA (human serum albumin) to solubilize the otherwise cell impermeable ONOO⁻ fluorescent probe Pinkment-OAc.     

The Biological Activity of Monarda didyma L. Essential Oil and Its Effect as a Diet Supplement in Mice and Broiler Chicken

The use of growth-promoting antibiotics in livestock faces increasing scrutiny and opposition due to concerns about the increased occurrence of antibiotic-resistant bacteria. Alternative solutions are being sought, and plants of Lamiaceae may provide an alternative to synthetic antibiotics in animal nutrition. In this study, we extracted essential oil from Monarda didyma, a member of the Lamiaceae family. We examined the chemical composition of the essential oil and then evaluated the antibacterial, antioxidant, and anti-inflammatory activities of M. didyma essential oil and its main compounds in vitro. We then evaluated the effectiveness of M. didyma essential oil in regard to growth performance, feed efficiency, and mortality in both mice and broilers. Carvacrol (49.03%) was the dominant compound in the essential oil extracts. M. didyma essential oil demonstrated antibacterial properties against Escherichia coli (MIC = 87 µg·mL⁻¹), Staphylococcus aureus (MIC = 47 µg·mL⁻¹), and Clostridium perfringens (MIC = 35 µg·mL⁻¹). Supplementing the diet of mice with essential oil at a concentration of 0.1% significantly increased body weight (+5.4%) and feed efficiency (+18.85%). In broilers, M. didyma essential oil significantly improved body weight gain (2.64%). Our results suggest that adding M. didyma essential oil to the diet of broilers offers a potential substitute for antibiotic growth promoters.     

Organocatalytic enantioselective SN1-type dehydrative nucleophilic substitution: access to bis(indolyl)methanes bearing quaternary carbon stereocenters

A highly general and straightforward approach to access chiral bis(indolyl)methanes (BIMs) bearing quaternary stereocenters has been realized via enantioconvergent dehydrative nucleophilic substitution. A broad range of 3,3′-, 3,2′- and 3,1′-BIMs were obtained under mild conditions with excellent efficiency and enantioselectivity (80 examples, up to 98% yield and >99 : 1 er). By utilizing racemic 3-indolyl tertiary alcohols as precursors of alkyl electrophiles and indoles as C–H nucleophiles, this organocatalytic strategy avoids pre-activation of substrates and produces water as the only by-product. Mechanistic studies suggest a formal S_N1-type pathway enabled by chiral phosphoric acid catalysis. The practicability of the obtained enantioenriched BIMs was further demonstrated by versatile transformation and high antimicrobial activities (3al, MIC: 1 μg mL⁻¹).

A highly general and straightforward approach to access chiral bis(indolyl)methanes (BIMs) bearing quaternary stereocenters has been realized via enantioconvergent dehydrative nucleophilic substitution.     

Capture and displacement-based release of the bicarbonate anion by calix[4]pyrroles with small rigid straps

Two-phenoxy walled calix[4]pyrroles 1 and 2 strapped with small rigid linkers containing pyridine and benzene, respectively, have been synthesized. ¹H NMR spectroscopic analyses carried out in CDCl₃ revealed that both of receptors 1 and 2 recognize only F⁻ and HCO₃⁻ among various test anions with high preference for HCO₃⁻ (as the tetraethylammonium, TEA⁺ salt) relative to F⁻ (as the TBA⁺ salt). The bound HCO₃⁻ anion was completely released out of the receptors upon the addition of F⁻ (as the tetrabutylammonium, TBA⁺ salt) as a result of significantly enhanced affinities and selectivities of the receptors for F⁻ once converted to the TEAHCO₃ complexes. Consequently, relatively stable TEAF complexes of receptors 1 and 2 were formed via anion metathesis occurring within the receptor cavities. By contrast, the direct addition of TEAF to receptors 1 and 2 produces different complexation products initially, although eventually the same TEAF complexes are produced as via sequential TEAHCO₃ and TBAF addition. These findings are rationalized in terms of the formation of different ion pair complexes involving interactions both inside and outside of the core receptor framework.

The inherent selectivity of anion receptors can be reversed by ion pairing occurring both inside and outside of the receptor cavity.     

Silyloxymethanesulfinate as a sulfoxylate equivalent for the modular synthesis of sulfones and sulfonyl derivatives

An efficient protocol for the modular synthesis of sulfones and sulfonyl derivatives has been developed utilizing sodium tert-butyldimethylsilyloxymethanesulfinate (TBSOMS-Na) as a sulfoxylate (SO₂²⁻) equivalent. TBSOMS-Na, easily prepared from the commercial reagents Rongalite™ and TBSCl, serves as a potent nucleophile in S-alkylation and Cu-catalyzed S-arylation reactions with alkyl and aryl electrophiles. The sulfone products thus obtained can undergo the second bond formation at the sulfur center with various electrophiles without a separate unmasking step to afford sulfones and sulfonyl derivatives such as sulfonamides and sulfonyl fluorides.

An efficient protocol for the modular synthesis of sulfones and sulfonyl derivatives has been developed utilizing sodium tert-butyldimethylsilyloxymethanesulfinate (TBSOMS-Na) as a sulfoxylate (SO₂²⁻) equivalent.     

Switching between mono and doubly reduced odd alternant hydrocarbon: designing a redox catalyst

Since the early Hückel molecular orbital (HMO) calculations in 1950, it has been well known that the odd alternant hydrocarbon (OAH), the phenalenyl (PLY) system, can exist in three redox states: closed shell cation (12π e⁻), mono-reduced open shell neutral radical (13π e⁻) and doubly reduced closed shell anion (14π e⁻). Switching from one redox state of PLY to another leads to a slight structural change owing to its low energy of disproportionation making the electron addition or removal process facile. To date, mono-reduced PLY based radicals have been extensively studied. However, the reactivity and application of doubly reduced PLY species have not been explored so far. In this work, we report the synthesis of the doubly reduced PLY species (14π e⁻) and its application towards the development of redox catalysis via switching with the mono-reduced form (13π e⁻) for aryl halide activation and functionalization under transition metal free conditions without any external stimuli such as heat, light or cathodic current supply.

A doubly reduced redox non-innocent phenalenyl based transition metal free catalyst has been designed and utilized in the development of the C–C cross coupling reaction through the activation of aryl halides at room temperature.     

Fluorescent probe for the imaging of superoxide and peroxynitrite during drug-induced liver injury

Drug-induced liver injury (DILI) is an important cause of potentially fatal liver disease. Herein, we report the development of a molecular probe (LW-OTf) for the detection and imaging of two biomarkers involved in DILI. Initially, primary reactive oxygen species (ROS) superoxide (O₂˙⁻) selectively activates a near-infrared fluorescence (NIRF) output by generating fluorophore LW-OH. The C C linker of this hemicyanine fluorophore is subsequently oxidized by reactive nitrogen species (RNS) peroxynitrite (ONOO⁻), resulting in cleavage to release xanthene derivative LW-XTD, detected using two-photon excitation fluorescence (TPEF). An alternative fluorescence pathway can occur through cleavage of LW-OTf by ONOO⁻ to non-fluorescent LW-XTD-OTf, which can react further with the second analyte O₂˙⁻ to produce the same LW-XTD fluorescent species. By combining NIRF and TPEF, LW-OTf is capable of differential and simultaneous detection of ROS and RNS in DILI using two optically orthogonal channels. Probe LW-OTf could be used to detect O₂˙⁻ or O₂˙⁻ and ONOO⁻ in lysosomes stimulated by 2-methoxyestradiol (2-ME) or 2-ME and SIN-1 respectively. In addition, we were able to monitor the chemoprotective effects of tert-butylhydroxyanisole (BHA) against acetaminophen (APAP) toxicity in living HL-7702 cells. More importantly, TPEF and NIRF imaging confirmed an increase in levels of both O₂˙⁻ and ONOO⁻ in mouse livers during APAP-induced DILI (confirmed by hematoxylin and eosin (H&E) staining).

Drug-induced liver injury (DILI) is an important cause of potentially fatal liver disease.     

A pH-responsive ultrathin Cu-based nanoplatform for specific photothermal and chemodynamic synergistic therapy

Noninvasive tumor therapy requires a new generation of bionanomaterials towards sensitive response to the unique tumor microenvironment to achieve accurate and effective treatment. Herein, we have developed a tumor therapy nanoplatform by immobilizing natural glucose oxidase (GOD) onto Cu-based layered double hydroxide (CuFe-LDH) nanosheets, which for the first time integrates acid-enhanced photothermal therapy (PTT), and pH-responsive and heat-facilitated chemodynamic therapy (CDT) simultaneously. As demonstrated by EXAFS and HRTEM, CuFe-LDH nanosheets possess a considerable number of defects caused by different acid conditions, resulting in a significantly acid-enhanced photothermal conversion efficiency (83.2% at pH 5.4 vs. 46.0% at pH 7.4). Moreover, GOD/CuFe-LDH nanosheets can convert a cascade of glucose into hydroxyl radicals (˙OH) under tumor acid conditions, which is validated by a high maximum velocity (V_max = 2.00 × 10⁻⁷ M) and low Michaelis–Menten constant (K_M = 12.01 mM). With the combination of PTT and CDT, the tumor tissue in vivo is almost eliminated with low-dose drug injection (1 mg kg⁻¹). Therefore, this novel pH-responsive Cu-based nanoplatform holds great promise in tumor-specific CDT/PTT synergistic therapy.

A pH-responsive multifunctional nanosystem was synthesized by loading glucose oxidase (GOD) onto CuFe-layered double hydroxide (LDH) nanosheets, which exhibited synchronous acid-enhanced/responsive photothermal and chemodynamic synergistic therapy.     

Reactivity of cyano- and isothiocyanatoborylenes: metal coordination,one-electron oxidation and boron-centred Brønsted basicity

Doubly base-stabilised cyano- and isothiocyanatoborylenes of the form LL′BY (L = CAAC = cyclic alkyl(amino)carbene; L′ = NHC = N-heterocyclic carbene; Y = CN, NCS) coordinate to group 6 carbonyl complexes via the terminal donor of the pseudohalide substituent and undergo facile and fully reversible one-electron oxidation to the corresponding boryl radical cations [LL′BY]˙⁺. Furthermore, calculations show that the borylenes have very similar proton affinities, both to each other and to NHC superbases. However, while the protonation of LL′B(CN) with PhSH yielding [LL′BH(CN)⁺][PhS⁻] is fully reversible, that of LL′B(NCS) is rendered irreversible by a subsequent B-to-C_CAAC hydrogen shift and nucleophilic attack of PhS⁻ at boron.

Borylenes of the form (CAAC)(NHC)BY (Y = CN, NCS; CAAC = cyclic alkyl(amino)carbene; NHC = N-heterocyclic carbene) coordinate to group 6 carbonyl complexes via Y, and show reversible boron-centered Brønsted basicity and one-electron oxidation.     

Transition-metal-mediated reduction and reversible double-cyclization of cyanuric triazide to an asymmetric bitetrazolate involving cleavage of the six-membered aromatic ring

Cyanuric triazide reacts with several transition metal precursors, extruding one equivalent of N₂ and reducing the putative diazidotriazeneylnitrene species by two electrons, which rearranges to N-(1′H-[1,5′-bitetrazol]-5-yl)methanediiminate (biTzI²⁻) dianionic ligand, which ligates the metal and dimerizes, and is isolated from pyridine as [M(biTzI)]₂Py₆ (M = Mn, Fe, Zn, Cu, Ni). Reagent scope, product analysis, and quantum chemical calculations were combined to elucidate the mechanism of formation as a two-electron reduction preceding ligand rearrangement.

Cyanuric triazide reacts with transition metal precursors, extruding N₂ and reducing the ligand by two electrons, which breaks an aromatic ring and rearranges to a bitetrazolylmethanediiminate (biTzI²⁻) ligand, forming two new aromatic rings.     

Proton-conductive coordination polymer glass for solid-state anhydrous proton batteries

Designing solid-state electrolytes for proton batteries at moderate temperatures is challenging as most solid-state proton conductors suffer from poor moldability and thermal stability. Crystal–glass transformation of coordination polymers (CPs) and metal–organic frameworks (MOFs) via melt-quenching offers diverse accessibility to unique properties as well as processing abilities. Here, we synthesized a glassy-state CP, [Zn₃(H₂PO₄)₆(H₂O)₃](1,2,3-benzotriazole), that exhibited a low melting temperature (114 °C) and a high anhydrous single-ion proton conductivity (8.0 × 10⁻³ S cm⁻¹ at 120 °C). Converting crystalline CPs to their glassy-state counterparts via melt-quenching not only initiated an isotropic disordered domain that enhanced H⁺ dynamics, but also generated an immersive interface that was beneficial for solid electrolyte applications. Finally, we demonstrated the first example of a rechargeable all-solid-state H⁺ battery utilizing the new glassy-state CP, which exhibited a wide operating-temperature range of 25 to 110 °C.

Melt-quenched coordination polymer glass shows exclusive H⁺ conductivity (8.0 × 10⁻³ S cm⁻¹ at 120 °C, anhydrous) and optimal mechanical properties (42.8 Pa s at 120 °C), enables the operation of an all-solid-state proton battery from RT to 110 °C.     

Anion mediated,tunable isoguanosine self-assemblies: decoding the conformation influence and solvent effects

Systematic investigations were performed with various substituted groups at C8 purine and ribose. A series of isoG analogs, C8-phenyl substituted isoG were synthesized and applied for Cs⁺ coordination. The structural proximity between purine and ribose limited pentaplex formation for C8-phenyl substituted isoG derivatives. Based on this observation, deoxy isoG derivative with modification on ribose (tert-butyldimethylsilyl ether) was applied to assemble with the Cs⁺ cation. Critical solvent (CDCl₃ and CD₃CN) and anion (BPh₄⁻, BARF⁻, and PF₆⁻) effects were revealed, leading to the controllable formation of various stable isoG pentaplexes, including singly charged decamer, doubly charged decamer, and 15-mer, etc. Finally, the X-ray crystal structure of [isoG₂₀Cs₃]³⁺(BARF⁻)₃ was successfully obtained, which is the first example of multiple-layer deoxy isoG binding with the Cs⁺ cation, providing solid evidence of this new isoG ionophore beyond two-layer sandwich self-assembly.

The first example of multiple-layer deoxy isoG self-assembly was characterized by X-ray crystal structure. Critical solvent and anion effects were revealed, leading to the controllable formation of various stable isoG assemblies.     

Tubularenes

We report the synthesis and characterization of conjugated, conformationally rigid, and electroactive carbon-based nanotubes that we term tubularenes. These structures are constructed from a resorcin[n_b]arene base. Cyclization of the conjugated aromatic nanotube is achieved in one-pot eight-fold C–C bond formation via Suzuki–Miyaura cross-coupling. DFT calculations indicate a buildup of strain energy in excess of 90 kcal mol⁻¹. The resulting architectures contain large internal void spaces >260 ų, are fluorescent, and able to accept up to 4 electrons. This represents the first scaffolding approach that provides conjugated nanotube architectures.

First scaffolding approach to obtain tubular-shaped contorted aromatic architectures.