Two-Dimensional Supramolecular Polymerization of a Bis-Urea Macrocycle into a Brick-Like Hydrogen-Bonded Network

We report on a dendronized bis-urea macrocycle 1 self-assembling via a cooperative mechanism into two-dimensional (2D) nanosheets formed solely by alternated urea-urea hydrogen bonding interactions. The pure macrocycle self-assembles in bulk into one-dimensional liquid-crystalline columnar phases. In contrast, its self-assembly mode drastically changes in CHCl₃ or tetrachloroethane, leading to 2D hydrogen-bonded networks. Theoretical calculations, complemented by previously reported crystalline structures, indicate that the 2D assembly is formed by a brick-like hydrogen bonding pattern between bis-urea macrocycles. This assembly is promoted by the swelling of the trisdodecyloxyphenyl groups upon solvation, which frustrates, due to steric effects, the formation of the thermodynamically more stable columnar macrocycle stacks. This work proposes a new design strategy to access 2D supramolecular polymers by means of a single non-covalent interaction motif, which is of great interest for materials development.     

Understanding Conformational Properties and Role of Hydrogen Bonds in Glycosaminoglycans-Interleukin8 Complexes in Aqueous Medium by Molecular Dynamics Simulation

Atomistic molecular dynamics simulations were performed under ambient conditions to explore the conformational features and binding affinities of hexameric glycosaminoglycans (GAGs) with chemokine Interleukin8 (IL8) in an aqueous medium. We tried to understand the role of hydrogen bonds (HBs) involving conserved water in mediating the interactions. The Luzar-Chandler model was adopted to study the kinetics of HB breaking and formation concerning different water-mediated HBs. The conformational flexibilities of bound GAGs are due to the flexible glycosidic linkages than the occasional/rare ring pucker conformation. The free energy landscape constructed with ϕ, and ψ, depicted that different conformational minima associated with the glycosidic linkage flexibility of the GAGs in bound states are separated by energy barriers. The binding affinities of IL8 towards GAGs are favored through the electrostatic and non-polar solvation interactions. 4-different types of conserved water were explored in the solvent-mediated binding of GAGs with IL8. The average lifetime of the IL8-GAG direct HB pairs was ∼ten times less than the IL8-GAG-shared water HBs. This is due to the rapid establishment of HB breaking and reformation kinetics involving water of a shared layer. We find that despite the highly negatively charged surface of GAGs, the IL8 surface populated by non-cationic amino acids could serve as a promising binding site in addition to the cationic surface of the protein.     

A Series of Low-Coordinate Iron Selenido Complexes: Reactivity of a Linear Iron(I) Silylamide towards Selenium

A variety of different low-coordinate iron selenide complexes is reported. These are obtained by reaction of the linear iron(I) silylamide K{18c6}[Fe(N(Dipp)SiMe₃)₂] (Dipp=2,6-diisopropylphenyl) with red selenium. Careful adjustment of the reaction conditions results in the formation of unique low-coordinate selenido iron complexes, namely a monoselenide bridged [2Fe−1Se]²⁺ complex, as well as mononuclear iron per- and triselenides. Further, C−H bond activation of one of the silylamide ligands by a putative terminal iron monoselenide is observed.     

1,3-Sulfinate Migration Triggered by α-Imino Carbene and Divergent Zwitterion Cyclization: Synthesis of Cyclopropane,Dihydropyrrole, and Azepane Ring Systems

Cyclopropane, dihydropyrrole, and azepane ring systems were synthesized conveniently from sulfinate-tethered triazoles. The divergent synthetic strategy started with the unique 1,3-sulfinate migration of an α-imino carbene. The efficient reaction allowed control of the zwitterion bearing multiple reactive sites depending on the increased stability of the resulting carbocation and anion. The sulfinate was converted to a sulfone after the group migration, and a stable anion bearing two electron-withdrawing groups was thus formed. Catalytic amounts of iodide acted as a switch for the synthesis of cyclopropanes and dihydropyrroles. The reaction merits including readily available substrates, mild reaction conditions, and excellent functional group compatibility qualified this protocol a possible synthetic tool for cyclic compounds, especially for N-heterocycles.     

Synthetic K+ Channels Constructed by Rebuilding the Core Modules of Natural K+ Channels in an Artificial System

Different types of natural K⁺ channels share similar core modules and cation permeability characteristics. In this study, we have developed novel artificial K⁺ channels by rebuilding the core modules of natural K⁺ channels in artificial systems. All the channels displayed high selectivity for K⁺ over Na⁺ and exhibited a selectivity sequence of K⁺≈Rb⁺ during the transport process, which is highly consistent with the cation permeability characteristics of natural K⁺ channels. More importantly, these artificial channels could be efficiently inserted into cell membranes and mediate the transmembrane transport of K⁺, disrupting the cellular K⁺ homeostasis and eventually triggering the apoptosis of cells. These findings demonstrate that, by rebuilding the core modules of natural K⁺ channels in artificial systems, the structures, transport behaviors, and physiological functions of natural K⁺ channels can be mimicked in synthetic channels.     

Photoredox-Enabled Self-(3+2) Cyclization of Vinyldiazo Reagents: Synthesis of Cyclopentenyl α-Diazo Compounds

A photocatalytic self-(3+2) cycloaddition of vinyldiazo compounds is described, which provides cyclopentene derivatives with conservation of one diazo functional group. Experimental insights and density functional theory indicate that the reaction is triggered by an unusual single electron oxidation of vinyldiazo compounds, while the photolysis for the generation of free carbene species is not involved. The synthetic applications of the resulting cyclopentenyl α-diazo compounds were demonstrated based on the rich chemistry of the diazo functional group.     

Perturbing π-clouds with Substituents to Study the Effects on Reaction Dynamics of gauche-1,3-Butadiene to Bicyclobutane Electrocyclization

The conical intersection (CI) governs the ultra-fast relaxation of excited states in a radiationless manner and are observed mainly in photochemical processes. In the current work, we investigated the effects of substituents on the reaction dynamics for the conversion of gauche-1,3-butadiene to bicyclobutane via photochemical electrocyclization. We incorporated both electron withdrawing (−F) and donating (−CH₃) groups in the conjugated system. In our study, we optimized the minimum energy conical intersection (MECI) geometries using the multi-configurational state-averaged CASSCF approach, whereas, to study the ground state reaction pathways for the substituted derivatives, dispersion corrected, B3LYP-D3 functional was used. The non-adiabatic surface hopping molecular dynamics simulations were performed to observe the behaviour of electronic states involved throughout the photoconversion process. The results obtained from the multi-reference second-order perturbation correction of energy at the XMS-CASPT2 level of theory, topography analysis, and non-adiabatic dynamics suggest that the −CH₃ substituted derivatives can undergo faster thermal conversion to the product in the ground state with a smaller activation energy barrier compared to −F substituted derivative. Our study also reveals that the GBUT to BIBUT conversion follows both conrotatory and disrotatory pathways, whereas, on substitution with −F or −CH₃, the conversion proceeds via the conrotatory pathway.     

Heteroleptic Square Planar Cobalt(I/II) Complexes

Reduction of the cobalt(II) chloride complex, Ph₂B(^tBuIm)₂Co(THF)Cl ( 1 ) in the presence of ^tBuN≡C affords the diamagnetic, square planar cobalt(I) complex Ph₂B(^tBuIm)₂Co(C≡N^tBu)₂ ( 2 ). This is a rare example of a 16-electron cobalt(I) complex that is structurally related to square planar noble metal complexes. Accordingly, the electronic structure of 2 , as calculated by DFT, reveals that the HOMO is largely d_z² in character. Complex 2 is readily oxidized to its cobalt(II) congener [Ph₂B(^tBuIm)₂Co(C=N^tBu)₂]BPh₄ ( 3 -BPh₄), whose EPR spectral parameters are characteristic of low-spin d⁷ with an unpaired electron in an orbital of d_z² parentage. This is also consistent with the results of DFT calculations. Despite its 16-electron configuration and the d_z² parentage of the HOMO, the only tractable reactions of 2 involve one electron oxidation to afford 3 .     

Rhodium-Catalyzed C8-Alkenylation of Isoquinolones with Maleimides

An efficient Rh(III)-catalyzed C−H alkenylation of N-protected isoquinolone with maleimides is reported. The carbonyl group of isoquinolone acts as an inherent directing group. Various N-substituents in the maleimide, including alkyl, aryl, and even H and −OH, were well tolerated under the developed reaction condition. This protocol showed broad substrate scope, good selectivity, and excellent yields. Hammett plot is also drawn to check the effect of substituents on the reaction progress.     

Surface-Degenerate Semiconductor Photocatalysis for Efficient Water Splitting without Sacrificial Agents via a Reticular Chemistry Approach

The production of green hydrogen through photocatalytic water splitting is crucial for a sustainable hydrogen economy and chemical manufacturing. However, current approaches suffer from slow hydrogen production (<70 μmol ⋅ g_cat⁻¹ ⋅ h⁻¹) due to the sluggish four-electrons oxygen evolution reaction (OER) and limited catalyst activity. Herein, we achieve efficient photocatalytic water splitting by exploiting a multifunctional interface between a nano-photocatalyst and metal–organic framework (MOF) layer. The functional interface plays two critical roles: (1) enriching electron density directly on photocatalyst surface to promote catalytic activity, and (2) delocalizing photogenerated holes into MOF to enhance OER. Our photocatalytic ensemble boosts hydrogen evolution by ≈100-fold over pristine photocatalyst and concurrently produces oxygen at ideal stoichiometric ratio, even without using sacrificial agents. Notably, this unique design attains superior hydrogen production (519 μmol ⋅ g_cat⁻¹ ⋅ h⁻¹) and apparent quantum efficiency up to 13-fold and 8-fold better than emerging photocatalytic designs utilizing hole scavengers. Comprehensive investigations underscore the vital role of the interfacial design in generating high-energy photoelectrons on surface-degenerate photocatalyst to thermodynamically drive hydrogen evolution, while leveraging the nanoporous MOF scaffold as an effective photohole sink to enhance OER. Our interfacial approach creates vast opportunities for designing next-generation, multifunctional photocatalytic ensembles using reticular chemistry with diverse energy and environmental applications.