We report a systematic study of phenanthroline-Pd(II) complexes featuring electronically tuned amide substituents (alkyl: L1; carboxylic: L2/L3) for the transfer hydrogenation (TH) of trans-cinnamic acid (trans-CA) to hydrocinnamic acid (HCA) in imidazolium-based ionic liquids (ILs). The electronic effects of ligand substituents, hydrogen source (FA/TEA mixtures vs ammonium formate), and solvent environment on catalytic activity were evaluated. Alkylamide-substituted [Pd(L1)Cl2] displayed superior performance with FA/TEA via solution-phase hydride transfer, whereas electron-deficient [Pd(L2-L3)Cl2] were more effective with ammonium formate under a mixed homogeneous/heterogeneous regime. Ionic liquids significantly enhanced catalyst performance compared to the conventional organic solvent DMF, with minor changes in IL cations or anion causing substantial variations in conversion. Mechanistic studies, including MS, UV-Vis, NMR, electrochemistry (using Pt(II) analogues), and gas-evolution analyses, revealed that monoformate Pd intermediates and their evolution depend on the electronic properties of the ligands and the hydrogen donor, directing productive or unproductive pathways. This work highlights the delicate interplay between ligand design, hydrogen source, and ionic liquid microenvironment in controlling Pd-catalyzed transfer hydrogenation and provides a platform for designing efficient, tunable Pd-based TH systems.

The dibenzo-annulated six-membered ring of 9(10H)-phenanthrenone- and the dibenzo-annulated five-membered ring in 1-acenaphthenone-derived alpha, beta-unsaturated ketones were chosen to study the influence of the ring size on the reactivity of the exocyclic electron-deficient pi-system. The kinetics of nucleophilic addition of carbanions to both Michael acceptors in DMSO at 20 degrees C was monitored by UV-Vis spectroscopy to determine the second-order rate constants k(2) of the carbon-carbon bond-forming reactions. The Mayr-Patz equation, lg k(2) = s(N)(N + E), along with reported reactivity parameters (N and s(N)) of the carbanions were used to calculate the electrophilicity parameter E for both electrophiles. The higher electrophilicity of the phenanthrenone-derived Michael acceptor was further scrutinized by quantum chemical calculations, which showed a less advanced bond formation in the transition state and a greater thermodynamic driving force for adduct formation for the phenanthrenone (E = -15.93) than for the acenaphthenone-derived alpha, beta-unsaturated ketone (E = -18.72). Thus, the phenanthrenone derivative is located on the electrophilicity scale in the reactivity range of structurally related ortho-quinone methides. The acenaphthenone derivative has similar electrophilicity as cyclic alpha, beta-unsaturated lactones with an exocyclic methylene group. Further nucleophilic reaction partners for both studied electrophiles can now be systematically selected by using the Mayr reactivity scales.

The capture and immobilization of radioactive iodine remain significant challenges due to its high volatility and radiotoxicity. Herein, we report a series of five low-dimensional, nonporous Ag(I) coordination polymers based on a methimazole-derived sulfur-donor ligand, designed to investigate the role of coordinated anions in iodine adsorption. The compounds were synthesized via a controlled branched-tube method and structurally characterized by single-crystal X-ray diffraction, revealing one- and two-dimensional architectures depending on the coordinated anion (NO3-, Cl-, I-, SCN-, and N3-). Iodine uptake was systematically evaluated in both the vapor and solution phases. Despite the absence of permanent porosity, all materials exhibit substantial iodine adsorption, with the azide-containing polymer (CP-5) showing the highest uptake (up to 4171 mg g-1 in solution and 545 wt % in the vapor phase). A clear dependence of adsorption performance on the coordinated anion was observed (NO3- < Cl- < I- < SCN- < N3-), indicating that anion-dependent electronic properties contribute to iodine affinity. Postadsorption PXRD and Raman analyses reveal distinct iodine capture pathways across the series: the nitrate-containing framework undergoes partial transformation to AgI, whereas the remaining coordination polymers retain their structural integrity and stabilize iodine predominantly as polyiodide species. These findings demonstrate that iodine uptake in nonporous Ag(I) coordination polymers is governed primarily by anion-dependent stabilization of iodine species and charge-transfer interactions rather than by porosity alone, highlighting anion selection as an effective strategy for tuning iodine capture performance.

De novo design of cyclobutadiene-iron (CBD-Fe) complexes has allowed for the synthesis of new libraries of fourmembered building blocks. The use of tetramethylpiperidinyllithium bases (TMP-Li) allows for smooth, yet highly selective metalation of those CBD-Fe complexes, providing efficient and unprecedented access to trisubstituted architectures. Perfect control of the regiochemical outcome was achieved by fine tuning of the nature of substituents, applying steric, coordinating and electronic effects during the metalation step.

Copper(II) complexes have great potential as antitumor and antimicrobial agents, and their coumarin derivatives bearing histamine substituents possess versatile structural and biological properties. The present article describes the synthesis of novel copper(II)-coumarin-histamine complexes and ligands and their characterization by IR, NMR, X-ray diffraction, and elemental analysis. Their antimicrobial activity (MIC, MBC/MFC) was tested against 11 reference strains. Cytotoxicity was evaluated using the MTT assay against 15 selected cancer cell lines and normal HMEC-1 cells. It presents three new ligands and three new complexes with copper(II) ions and selected histamine-containing coumarin derivatives. The new copper(II) complexes demonstrated markedly higher anticancer activity than their corresponding ligands across all evaluated cancer cell lines. The highest anticancer activity against the Hep3B liver cancer cell line was demonstrated by the copper(II) complex (3b), which also showed the strongest inhibition of S. epidermidis ATCC 12228 and S. aureus ATCC 6538. The copper(II) ions play a crucial role in the antitumor activity of these derivatives. Despite limited antimicrobial effects, the tested complexes, particularly 3a and 3b, demonstrate promising anticancer potential, especially against the Hep3B cancer cell line. Only 3b demonstrated antimicrobial activity against S. epidermidis ATCC 12228 and S. aureus ATCC 6538.

The electrophilic reactivities of para-quinone methides (pQMs) with functional groups (FG) at the exocyclic polarized carbon-carbon double bond were determined by photometrically monitoring the kinetics of their reactions with carbanions in dimethyl sulfoxide (DMSO) at 20 °C. The experimental second-order rate constants k2 were evaluated by the Mayr-Patz equation, that is, the linear free energy relationship lg k2 = sN(N + E), which was leveraged to determine the electrophilicity descriptors E of the pQMs. These electrophilicity parameters E were subsequently used to successfully predict the scope of the pQM reactions with C-, H-, N-, O-, and S-centered nucleophiles. Moreover, the electrophilicity parameters E correlate linearly with a linear combination of quantum-chemically calculated methyl anion affinities (MAAs) and buried volumes (%Vbur). While MAA values mainly reflect the thermodynamic driving force of the carbon-carbon bond formation, %Vbur values take account of the variable steric effects of substituents at the electrophilic δ-position of the pQMs. Knowledge of MAA and %Vbur thus enables chemists to tailor novel pQMs with predictable reactivity properties.

Iron enzymes are ubiquitous in nature. In particular, enzymes with iron-oxygen cofactors as active sites perform a vast variety of reactions. Both iron(III)-hydroxido and iron(IV)-oxido species have been observed to play a catalytically active role. In order to complement biochemical investigations, a large variety of synthetic compounds using these motifs were synthesized in past decades to study and understand their inherent reactivity. One such synthetic model complex is [FeIV(O)(Py5Me2)]2+, (Py5Me2 = 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine, henceforth labeled L1), which was used as a model complex for epigenetically relevant iron(II)/alpha-ketoglutarate-dependent ten-eleven translocation 5-methylcytosine dioxygenases (TET). Additionally, [FeIII(OH)(Py5(OH)2)]2+ (Py5(OH)2 = pyridine-2,6-diylbis [di(pyridin-2-yl)methanol, henceforth labeled L2) was tested as a lipoxygenase model. We have complemented the available complexes of these related pentapyridyl complexes to include all oxidation states II-IV and performed detailed spectroscopic and spectrometric investigations. We found that iron(II) and iron(IV)-oxido compounds (cross-)comproportionate readily to form iron(III)-hydroxido species, which represents a major side reaction for model complex investigations. We also investigated the oxidative reactivity of a new iron(IV)-oxido complex.

We report the first total synthesis of several natural products of the loline family, including the unusual chloropyrrolizidine alkaloid lolidine. We demonstrate the utility of an azide intermediate in our synthesis toward click-chemistry and late-stage functionalization. Lastly, we further explore the CO2 absorbing properties of temuline, as well as a potential application of loline as a chiral ligand in palladium chemistry.

ABSTRACT Aromaticity is a key concept in physical organic chemistry. However, as it cannot be measured directly, it is assessed indirectly via other properties (energetic, electronic, geometric and magnetic). Although these properties describe aromaticity, they are not solely related to aromaticity as the observed values also can stem from, for example, magnetically induced local currents at certain atoms or groups, or strain in the σ‐skeleton. This can lead to misinterpretations. Here, we highlight a pitfall in the (anti)aromaticity assessment of polycyclic molecules when it is mainly based on nucleus independent chemical shifts (NICSs). The NICS index can be misinterpreted to indicate ‘aromaticity’ or ‘antiaromaticity’ in nonaromatic rings as a result of paratropic or diatropic ring currents in adjacent rings. We explore if such false indications by NICS are (i) stronger in Baird‐aromatic or ‐antiaromatic excited states (mainly triplet and quintet, but also singlet) than in closed‐shell singlet ground states, and (ii) if a paratropic ring current in an adjacent ring causes stronger or weaker false ‘aromaticity’ than a diatropic one causes false ‘antiaromaticity’. Based on our computations we conclude that larger aromatic rings in all types of states (e.g., a triplet state Baird‐aromatic cyclooctatetraene ring) have greater influence than smaller ones, yet, we see no indication that the effect is stronger in excited states. Instead, annulene rings are more influential in their paratropic (antiaromatic) states, regardless if ground or excited states, than in their diatropic (aromatic) ones.

The compound described in a previous report [Ru 2 (CO) 4 ( µ -H)( µ -P t Bu 2 )( µ -dppa)] [dppa = bis(diphenylphosphanyl)amine, 1 ] crystallizes from acetone/ethanol as a solvate stabilized in the solid by an intermolecular hydrogen bonding between the NH function of the dppa ligand and an ethanol molecule (Mayer, T.; Böttcher, H.-C. Polyhedron 2013 , 50 , 507−511). Surprisingly, by the use of n -pentane as the antisolvent during crystal growth for X-ray diffraction purposes an isomer of compound 1 was obtained. A deprotonation of the NH function within the dppa ligand in 1 occurred accompanied by an intramolecular oxidative addition of the proton towards the diruthenium core resulting in the novel compound [Ru 2 (CO) 4 ( µ -H) 2 ( µ -P t Bu 2 )( µ -dppa−H)] ( 2 ), [(dppa−H) = [dppa−H + ] − = Ph 2 PNPPh 2 − , bis(diphenylphosphanyl)amide]. By dissolution of solid 2 in polar solvents a transformation back to 1 (reductive elimination) occurred as clearly indicated in solution by the NMR data for complex 1 . Therefore, compound 2 has been characterized only in the solid state by elemental analysis, IR spectroscopy, mass spectrometry and single-crystal X-ray diffraction.

Sulfur-based coordination polymers have gained significant attention, yet constructing 3D sulfur-based networks remains challenging. This study presents two novel 3D water-stable silver-sulfur MOFs: {[Ag6Cl2(L3)5][BF4]4}n(SCU-1) and [AgSCN(L3)]n(SCU-2). Single crystals were synthesized using the branched tube method, and X-ray crystallography revealed SCU-1's large cationic framework with 193 atoms per unit cell and a volume of ∼10,000 Å3, exhibiting 15.1% porosity. SCU-2, with a simpler structure, showed 5.9% porosity. Leveraging the strong silver-sulfur affinity and the methimazole-based ligands' potential for iodine uptake, the iodine adsorption capabilities of SCU-1 and SCU-2 were investigated, revealing remarkable uptake capacities of 3.650 g/g and 3.749 g/g, respectively, setting a new benchmark for iodine removal. Additionally, the H2S adsorption potential of these frameworks was explored for the first time. SCU-1, with BF4-and Cl- as electron-rich sites, exhibited a higher H2S adsorption energy (Eads = -45.0 kJ mol-1) compared to SCU-2 (Eads = -39.0 kJ mol-1), where thiocyanate serves as the electron-rich component. Simulations aligned well with experimental data, highlighting the frameworks' potential for gas adsorption applications. This work advances the design of sulfur-based MOFs for environmental remediation, particularly in iodine and H2S capture.

A binuclear La(III) complex {[La2(HA)4(H2O)4(C2H5OH)2Cl2]Cl4 (C1)} with 2-aminobenzoic acid (HA) was prepared from the ligand and heptahydrated lanthanum chloride. The complex was characterised by X-ray crystallography that revealed anti-prismatic geometry around both of the lanthanum. In the complex, the four 2-aminobenzoic acid ligands are zwitter ionic and the two lanthanum(III) ions net charge is only counterbalanced by chloride ions. The complex cytotoxicity was determined against human breast (MDA-MB-231), prostate (PC-3) and bladder (T-24) cancer cells. This complex afforded cytotoxicity towards the T-24 bladder cancer cells with an IC50 value of 383.5 µg/mL (319 µM). In contrary, activities by the lanthanum complex with IC50 values of 1124 µg/mL (934 µM) and 739 µg/mL (614 µM) were, respectively, shown against the MDA-MB-231 and PC-3 cancer cells. This means the complex is more cytotoxic against the T-24 cells, despite that its activity is less compared with activities shown by classical drugs.

Molecular motors are central driving units for nanomachinery, and control of their directional motions is of fundamental importance for their functions. Light-driven variants use easy to provide, easy to dose, and waste-free fuel with high energy content, making them particularly interesting for applications. Typically, light-driven molecular motors work via rotations around dedicated chemical bonds where the directionality of the rotation is dictated by the steric effects of asymmetry in close vicinity to the rotation axis. In this work, we show how unidirectional rotation around a virtual axis can be realized by reprogramming a molecular motor. To this end, a classical light-driven motor is restricted by macrocyclization, and its intrinsic directional rotation is transformed into a directional rotation of the macrocyclic chain in the opposite direction. Further, solvent polarity changes allow to toggle the function of this molecular machine between a directional motor and a nondirectional photoswitch. In this way, a new concept for the design of molecular motors is delivered together with elaborate control over their motions and functions by simple solvent changes. The possibility of sensing the environmental polarity and correspondingly adjusting the directionality of motions opens up a next level of control and responsiveness to light-driven nanoscopic motors.

We herein successfully demonstrate the use of chiral isochalcogenoureas as Lewis Base catalysts for a variety of (4+2)-cycloaddition reactions of allenoates and different Michael acceptors. In all cases the same structural key-motive, a dihydropyran with a (Z)-configurated exocyclic double bond could be accessed as the major regio- and diastereoisomer in an enantioselective manner. Furthermore, these chiral dihydropyrans were successfully engaged in different follow-up transformations.

Monobenzopentalenes have received moderate attention compared to dibenzopentalenes, yet their accessibility as stable, non-symmetric structures with diverse substituents could be interesting for materials applications, including molecular photonics. Recently, monobenzopentalene was considered computationally as a potential chromophore for singlet fission (SF) photovoltaics. To advance this compound class towards photonics applications, the excited state energetics must be characterized, computationally and experimentally. In this report we synthesized a series of stable substituted monobenzopentalenes and provided the first experimental exploration of their photophysical properties. Structural and opto-electronic characterization revealed that all derivatives showed 1H NMR shifts in the olefinic region, bond length alternation in the pentalene unit, low-intensity absorptions reflecting the ground-state antiaromatic character and in turn the symmetry forbidden HOMO-to-LUMO transitions of ~2 eV and redox amphotericity. This was also supported by computed aromaticity indices (NICS, ACID, HOMA). Accordingly, substituents did not affect the fulfilment of the energetic criterion of SF, as the computed excited-state energy levels satisfied the required E(S1)/E(T1)>2 relationship. Further spectroscopic measurements revealed a concentration dependent quenching of the excited state and population of the S2 state on the nanosecond timescale, providing initial evidence for unusual photophysics and an alternative entry point for singlet fission with monobenzopentalenes.

A new cadmium complex with a flexible imidazolinethione ligand has been successfully synthesized. The ligand acts as a bidentate chelating molecule, resulting in the structure being a monomer. In this monomer, cadmium has an octahedral geometry coordinated by four sulfur atoms from two mbit ligands where mbit = 3,3'-methylenebis(1-methyl-1,3-dihydro-2H-imidazole-2-thione) and two oxygen atoms from the DMF molecules. The ClO4- anions are uncoordinated and neutralize the positive charge of the cationic complex. The title complex has a good capacity for adsorbing several organic dyes from pollutant solutions.

Owing to stereoelectronic effects, lactones often deviate in reactivity from their open-chain ester analogues as demonstrated by the CH acidity (in DMSO) of 3-isochromanone (pK a = 18.8) and 2-coumaranone (pK a = 13.5), which is higher than that of ethyl phenylacetate (pK a = 22.6). We have now characterized the reactivity of the lactone enolates derived from 3-isochromanone and 2-coumaranone by following the kinetics of their Michael reactions with p-quinone methides and arylidenemalonates (reference electrophiles) in DMSO at 20 °C. Evaluation of the experimentally determined second-order rate constants k 2 by the Mayr–Patz equation, lg k 2 = s N(N + E), furnished the nucleophilicity parameters N (and s N) of the lactone enolates. By localizing their position on the Mayr nucleophilicity scale, the scope of their electrophilic reaction partners becomes predictable, and we demonstrate a novel catalytic methodology for a series of carbon–carbon bond-forming reactions of lactone enolates with chalcones under phase transfer conditions in toluene.

A series of aryl-substituted ortho-quinone methides (oQMs) was synthesised and structurally characterised. Kinetic studies of the nucleophilic additions of carbanions (reference nucleophiles) to oQMs were used to determine second-order rate constants k2 for the carbon-carbon bond forming reactions (20 °C, DMSO) at the oQMs' exocyclic π-bond. Analysing the kinetic data by the linear free energy relationship lg k2=sN(N+E) revealed the Mayr electrophilicities E of the oQMs. The electrophilicities E of oQMs correlate linearly with Hammett substituent constants and experimentally determined reduction potentials Ep red as well as with quantum-chemically calculated methyl anion affinities (MAAs), which provides valuable tools for prediciting the reactivity of further types of oQMs. Embedding the oQMs in Mayr's reactivity scales enables to predict novel nucleophilic reaction partners for oQMs and can productively be used to prepare simple Michael adducts as well as 4+2 or 4+1 cyclisation products as demonstrated in this work by several novel reactions with neutral or negatively charged C-, N-, and S-nucleophiles.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.