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A new biomimetic model complex of the active site of acireductone dioxygenase (ARD) was synthesized and crystallographically characterized ( [Ni( ii )( N -(ethyl- N 'Me 2 )(Py)(2- t -ButPhOH))(OTf)]- 1). 1 displays carbon-carbon oxidative cleavage activity in the presence of O 2 towards the substrate 2-hydroxyacetophenone. This reactivity was monitored via UV-Visible and NMR spectroscopy. We postulate that the reactivity of 1 with O 2 leads to the formation of a putative Ni(III)-superoxo transient species resulting from the direct activation of O 2 via the nickel center during the oxidative reaction. This proposed intermediate and reaction mechanism were studied in detail using DFT calculations. 1 and its substrate bound derivatives display reactivity toward mild outer sphere oxidants, suggesting ease of access to high valent Ni coordination complexes, consistent with our calculations. If confirmed, the direct activation of O 2 at a nickel center could have implications for the mechanism of action of ARD and other nickel-based dioxygenases and their respective non-traditional, enzymatic moonlighting functions, as well as contribute to a general understanding of direct oxidation of nickel(II) coordination complexes by O 2 .

Herein, we report mechanistic investigations into the Cu-catalyzed three-component carboamination of alkenes with α-halo carbonyls and aryl amines via an oxocarbenium intermediate. Monitoring the reaction reveals the formation of transient atom transfer radical addition (ATRA) intermediates with both electron-neutral and deficient vinyl arenes as well as unactivated alkenes. Based on our experimental studies and density functional theory calculations, the oxocarbenium is generated through atom transfer and subsequent intramolecular substitution. Further, mechanistic factors that dictate the regioselectivity of the nucleophilic attack onto the oxocarbenium to afford the γ-amino ester, γ-iminolactone, or γ-lactone are discussed. A strategy to overcome scope limitation with respect to unactivated alkenes is developed using the mechanistic insights gained herein. Finally, we demonstrate that under modified conditions, our Cu catalyst enables the ATRA reaction between a variety of alkyl halides and vinyl arenes/α-olefins, and we present a one-pot, two-step carbofunctionalization with an array of nucleophiles through ATRA/S N 2.

We report the reactivity, structures and spectroscopic characterization of reactions of phosphine-based ligands (mono-, di- and tri-dentate) with iron-carbide carbonyl clusters. Historically, the archetype of this cluster class, namely [Fe 6 (μ 6 -C)(μ 2 -CO) 4 (CO) 12 ] 2- , can be prepared on a gram-scale but is resistant to simple ligand substitution reactions. This limitation has precluded the relevance of iron-carbide clusters relating to organometallics, catalysis and the nitrogenase active site cluster. Herein, we aimed to derive a simple and reliable method to accomplish CO → L (where L = phosphine or other general ligands) substitution reactions without harsh reagents or multi-step synthetic strategies. Ultimately, our goal was ligand-based chelation of an Fe n (μ n -C) core to achieve more synthetic control over multi-iron-carbide motifs relevant to the nitrogenase active site. We report that the key intermediate is the PSEPT-non-conforming cluster [Fe 6 (μ 6 -C)(CO) 16 ] (2: 84 electrons), which can be generated in situ by the outer-sphere oxidation of [Fe 6 (μ 6 -C)(CO) 16 ] 2- (1: closo , 86 electrons) with 2 equiv. of [Fc]PF 6 . The reaction of 2 with excess PPh 3 generates a singly substituted neutral cluster [Fe 5 (μ 5 -C)(CO) 14 PPh 3 ] (4), similar to the reported reactivity of the substitutionally active cluster [Fe 5 (μ 5 -C)(CO) 15 ] with monodentate phosphines (Cooke & Mays, 1990). In contrast, the reaction of 2 with flexible, bidentate phosphines (DPPE and DPPP) generates a wide range of unisolable products. However, the rigid bidentate phosphine bis(diphenylphosphino)benzene (bdpb) disproportionates the cluster into non-ligated Fe 3 -carbide anions paired with a bdpb-supported Fe(ii) cation, which co-crystallize in [Fe 3 (μ 3 -CH)(μ 3 -CO)(CO) 9 ] 2 [Fe(MeCN) 2 (bdpb) 2 ] (6). A successful reaction of 2 with the tripodal ligand Triphos generates the first multi-iron-chelated, authentic carbide cluster of the formula [Fe 4 (μ 4 -C)(κ3-Triphos)(CO) 10 ] (9). DFT analysis of the key (oxidized) intermediate 2 suggests that its (μ 6 -C)Fe 6 framework remains fully intact but is distorted into an axially compressed, 'ruffled' octahedron distinct from the parent closo cluster 1. Oxidation of the cluster in non-coordinating solvent allows for the isolation and crystallization of the CO-saturated, intact closo -analogue [Fe 6 (μ 6 -C)(CO) 17 ] (3), indicating that the intact (μ 6 -C)Fe 6 motif is retained during initial oxidation with [Fc]PF 6 . Overall, we demonstrate that redox modulation beneficially 'bends' Wade-Mingo's rules via the generation of electron-starved (non-PSEPT) intermediates, which are the key intermediates in promoting facile CO → L substitution reactions in iron-carbide-carbonyl clusters., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Although chemical methods for the selective derivatization of amino acid (AA) side chains in peptides and proteins are available, selective N-terminal labeling is challenging, especially for glycine, which has no side chain at the α-carbon position. We report here a double activation at glycine's α-methylene group that allows this AA to be differentiated from the other 19 AAs. A condensation reaction of dibenzoylmethane with glycine results in the formation of an imine, and subsequent tautomerization is followed by intramolecular cyclization, leading to the formation of a fluorescent pyrrole ring. Additionally, the approach exhibits compatibility with AAs possessing reactive side chains. Further, the method allows for selective pull-down assays of N-terminal glycine peptides from mixtures without prior knowledge of the N-terminal peptide distribution.

Carbaporphyrin dimers, investigated for their distinctive electronic structures and exceptional properties, have predominantly consisted of systems containing identical subunits. This study addresses the associated knowledge gap by focusing on asymmetric carbaporphyrin dimers with Janus-like characteristics. The synthesis of a Janus-type carbaporphyrin pseudo-dimer 5 is presented. It displays antiaromatic characteristics on the fused side and nonaromatic behavior on the unfused side. A newly synthesized tetraphenylene (TPE) linked bis-dibenzihomoporphyrin 8 and a previously reported dibenzo[g,p]chrysene (DBC) linked bis-dicarbacorrole 9 were prepared as controls. Comprehensive analyses, including 1 H NMR spectral studies, single crystal X-ray diffraction analyses, and DFT calculations, validate the mixed character of 5. A further feature of the Janus pseudo-dimer 5 is that it may be transformed into a heterometallic complex, with one side coordinating a Cu(III) center and the other stabilizing a BODIPY complex. This disparate regiochemical reactivity underscores the potential of carbaporphyrin dimers as versatile frameworks, with electronic features and site-specific coordination chemistry controlled through asymmetry. These findings position carbaporphyrin dimers as promising candidates for advances in electronic structure studies, coordination chemistry, materials science, and beyond., (© 2024. The Author(s).)

The reaction between Th(IV) dipyriamethyrin dichloride and sodium cyclopentadienyl (Cp) results in the formation of a cyclopentadienyl capped thorium dipyriamethyrin complex, which to our knowledge represents the first expanded porphyrin f-element Cp complex.

A nanographene-fused expanded carbaporphyrin ( 5 ) and its BF 2 complex ( 6 ) were synthesized. Single-crystal X-ray structures revealed that 5 and 6 are connected by two hexa- peri -hexabenzocoronene (HBC) units and two dipyrromethene or BODIPY units, respectively. As prepared, 5 and 6 both show nonaromatic character with figure-of-eight carbaoctaphyrin (1.1.1.0.1.1.1.0) cores and adopt tweezers-like conformations characterized by a partially confined space between the two constituent HBC units. The distance between the HBC centers is >10 Å, while the dihedral angles between the two HBC planes are 30.5 and 35.2° for 5 and 6 , respectively. The interactions between 5 and 6 and fullerene C 60 were studied both in organic media and in the solid state. Proton NMR spectral titrations of 5 and 6 with C 60 revealed a 1:1 binding mode for both macrocycles. In toluene- d 8 , the corresponding binding constants were determined to be 1141 ± 17 and 994 ± 10 M -1 for 5 and 6 , respectively. Single-crystal X-ray diffraction structural analyses confirmed the formation of 1:1 fullerene inclusion complexes in the solid state. The C 60 guests in both complexes are found within triangular pockets composed of two HBC units from the tweezers-like receptor most closely associated with the bound fullerene, as well as an HBC unit from an adjacent host. Femtosecond transient absorption measurements revealed subpicosecond ultrafast charge separation between 5 (and 6 ) and C 60 in the complexes. To the best of our knowledge, the present report provides the first example wherein a nanographene building block is incorporated into the core of a porphyrinic framework.

The anion binding features of diphenylpyrrole-strapped calix[4]pyrrole 1 have been investigated by means of 1 H NMR spectroscopy and ITC (isothermal titration calorimetry), as well as single crystal X-ray diffraction analyses. Receptor 1 bearing an auxiliary pyrrolic NH donor and solubilizing phenyl groups on the strap was found to bind F - , Cl - , and Br - as their tetrabutylammonium salts with high affinity in DMSO-d 6 . In addition, receptor 1 was found to extract the fluoride anion (as both its tetraethylammonium (TEA + ) and tetrabutylammonium (TBA + ) salts), as well as the chloride anion into chloroform-d from an aqueous source phase. Cation metathesis using TBAI or the use of a dual host approach involving crown ethers enabled receptor 1 to extract simple alkali metal fluoride or chloride salts from water. Quantitative binding of NaF by receptor 1 was observed in 20 % D 2 O-DMSO-d 6 allowing for the direct determination of the NaF concentration in an unknown sample., (© 2023 Wiley-VCH GmbH.)

Deferasirox is an FDA-approved iron chelator used in the treatment of iron toxicity. In this work, we report the use of several deferasirox derivatives as lanthanide chelators. Solid-state structural studies of three representative trivalent lanthanide cations, La(III), Eu(III), and Lu(III), revealed the formation of 2:2 complexes in the solid state. A 1:1 stoichiometry dominates in DMSO solution, with K a values of 472 ± 14, 477 ± 11, and 496 ± 15 M -1 being obtained in the case of these three cations, respectively. Under the conditions of competitive precipitation in the presence of triethylamine, high selectivity (up to 80%) for lutetium(III) was observed in competition with La(III), Ce(III), and Eu(III). Theoretical calculations provided support for the observed selective crystallization.

A heteroleptic copper(I) bis(phenanthroline) complex with aldehyde groups at the 4,7 positions of the phenanthroline ligand was synthesized. The complex is responsive to alcohol, resulting in a distinct colour change caused by the facile reaction of the aldehyde group with alcohol, forming a hemiacetal product. The aldehyde species can be regenerated after heating the intermediate at 80 °C for 10 minutes, demonstrating the reusability of the complex for alcohol detection. This work presents a new strategy for applying transition metal complexes in small molecule sensing by installing functional groups in the secondary coordination sphere which reversibly react with analytes.

A key challenge to the effective utilization of solar energy is to promote efficient photoinduced charge transfer, specifically avoiding unproductive, circuitous electron-transfer pathways and optimizing the kinetics of charge separation and recombination. We hypothesize that one way to address this challenge is to develop a fundamental understanding of how to initiate and control directional photoinduced charge transfer, particularly for earth-abundant first-row transition-metal coordination complexes, which typically suffer from relatively short excited-state lifetimes. Here, we report a series of functionalized heteroleptic copper(I)bis(phenanthroline) complexes, which have allowed us to investigate the directionality of intramolecular photoinduced metal-to-ligand charge transfer (MLCT) as a function of the substituent Hammett parameter. Ultrafast transient absorption suggests a complicated interplay of MLCT localization and solvent interaction with the Cu(II) center of the MLCT state. This work provides a set of design principles for directional charge transfer in earth-abundant complexes and can be used to efficiently design pathways for connecting the molecular modules to catalysts or electrodes and integration into systems for light-driven catalysis.

Developing efficient photocatalysts that perform multi electron redox reactions is critical to achieving solar energy conversion. One can reach this goal by developing systems which mimic natural photosynthesis and exploit strategies such as proton-coupled electron transfer (PCET) to achieve photochemical charge accumulation. We report herein a heteroleptic Cu(i)bis(phenanthroline) complex, Cu-AnQ, featuring a fused phenazine-anthraquinone moiety that photochemically accumulates two electrons in the anthraquinone unit via PCET. Full spectroscopic and electrochemical analyses allowed us to identify the reduced species and revealed that up to three electrons can be accumulated in the phenazine-anthraquinone ring system under electrochemical conditions. Continuous photolysis of Cu-AnQ in the presence of sacrificial electron donor produced doubly reduced monoprotonated photoproduct confirmed unambiguously by X-ray crystallography. Formation of this photoproduct indicates that a PCET process occurred during illumination and two electrons were accumulated in the system. The role of the heteroleptic Cu(i)bis(phenanthroline) moiety participating in the photochemical charge accumulation as a light absorber was evidenced by comparing the photolysis of Cu-AnQ and the free AnQ ligand with less reductive triethylamine as a sacrificial electron donor, in which photogenerated doubly reduced species was observed with Cu-AnQ, but not with the free ligand. The thermodynamic properties of Cu-AnQ were examined by DFT which mapped the probable reaction pathway for photochemical charge accumulation and the capacity for solar energy stored in the process. This study presents a unique system built on earth-abundant transition metal complex to store electrons, and tune the storage of solar energy by the degree of protonation of the electron acceptor., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

2,3-Dihydro-4-hydroxy-chromene-4( N )-ethyl thiosemicarbazone (probe F4 ) is used as a chemosensor, and it selectively detected Cu 2+ ions among the metal ions by showing fluorescence "TURN ON" behavior. The stoichiometric binding of the probe with Cu 2+ ( CF4 ) was confirmed by Job's plot and mass spectroscopy. Further, CF4 was used as a sensor for the detection of l-amino acids and N-heterocyclic compounds. Among them, CF4 selectively detected l-histidine by showing fluorescence " TURN-OFF " behavior and selectively detected indazole by showing fluorescence " TURN-ON " behavior. These behaviors were further confirmed by in vivo live cell imaging studies by using Caenorhabditis elegans as a model. In vitro cytotoxicity was assayed for probe F4 , complex CF4 , and CF4 with l-histidine and indazole. The IC 50 concentration was used for confocal imaging studies by using the MDA-MB-231 cell line (breast cancer cell line).

We report a copolymeric fluorescent sensor that is selective for lithium chloride. The two constituent polymers comprise pendent triphenylethylene (TPE) moieties for aggregate induced emission (AIE) along with either strapped-calix[4]pyrrole or secondary ammonium groups that drive aggregation via self-assembly upon polymer mixing. Addition of LiCl in acetonitrile disrupts the strapped-calix[4]pyrrole/secondary ammonium chloride salt host-guest crosslinks leading to disaggregation of the polymer chains and a decrease in TPE emission. The lack of AIE perturbation upon addition of NaCl, KCl, MgCl 2 or CaCl 2 provides for high selectivity for LiCl relative to potential interferants. This supramolecular dual polymer approach could serve as a complement to more traditional sensor systems., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Two cyclic carbaporphyrin arrays (trimer 6 and tetramer 7 ) were synthesized from a dibrominated carbaporphyrin precursor ( 5 ) via a one-pot Yamamoto-type coupling. Single-crystal X-ray diffraction analyses revealed that 6 and 7 contain three and four covalently linked carbaporphyrin (formally dicarbacorrole) units, respectively. Trimer 6 adopts a roughly planar conformation and tetramer 7 adopts an up-and-down zig-zag conformation. Both 6 and 7 contain a [n]cyclo-meta-phenylene ([n]CMP) core, namely, [6]- and [8]CMP for 6 and 7 , respectively. Transient absorption (TA) anisotropy and pump-power-dependent excited-state decay studies provided evidence for excitation energy transfer (EET) within both trimer 6 and tetramer 7 . The exciton energy hopping (EEH) times were estimated to be 18 and 35 ps for 6 and 7 , respectively, as inferred from pump-power-dependent TA measurements. Since the center-to-center distances between adjacent carbaporphyrin units are similar in 6 and 7 , the different EEH times are attributed to differences in the orientation of the transition dipoles in these two congeneric arrays. The orientation factor κ 2 , the key parameter defining the Förster resonance energy transfer efficiency, was calculated to be 2.15 and 1.03 for 6 and 7 , respectively, a finding that supports the shorter excitation energy hopping time seen in the case of trimer 6 . To our knowledge, this is the first time that covalently linked cyclic carbaporphyrin arrays were synthesized using a single carbaporphyrin as the starting point and that EET between carbaporphyrin subunits constrained within a well-defined polycyclic framework has been correlated with structural differences.

We report here a nanosized "buckytrap", 1 , constructed from two bis-zinc(II) expanded-TTF (exTTF) porphyrin subunits. Two forms, 1a and 1b , differing in the axial ligands, H 2 O vs tetrahydrofuran (THF), were isolated and characterized. Discrete host-guest inclusion complexes are formed upon treatment with fullerenes as inferred from a single-crystal X-ray structural analyses of 1a with C 70 . The fullerene is found to be encapsulated within the inner pseudohexagonal cavity of 1a . In contrast, the corresponding free-base derivative ( 2 ) was found to form infinite ball-and-socket type supramolecular organic frameworks (3D-SOFs) with fullerenes, ( 2• C 60 ) n or ( 2 •C 70 ) n . This difference is ascribed to the fact that in 1a and 1b the axial positions are blocked by a H 2 O or THF ligand. Emission spectroscopic studies supported a 1:1 host-guest binding stoichiometry, allowing association constants of (2.0 ± 0.5) × 10 4 M -1 and (4.3 ± 0.9) × 10 4 M -1 to be calculated for C 60 and C 70 , respectively. Flash-photolysis time-resolved microwave conductivity (FP-TRMC) studies of solid films of the Zn-complex 1a revealed that the intrinsic charge carrier transport, i.e., pseudo-photoconductivity (ϕ∑μ), increases upon fullerene inclusion (e.g., ϕ∑μ = 1.53 × 10 -4 cm 2 V -1 s -1 for C 60 ⊂( 1a ) 2 and ϕ∑μ = 1.45 × 10 -4 cm 2 V -1 s -1 for C 70 ⊂( 1a ) 2 vs ϕ∑μ = 2.49 × 10 -5 cm 2 V -1 s -1 for 1a ) at 298 K. These findings provide support for the notion that controlling the nature of self-assembly supramolecular constructs formed from exTTF-porphyrin dimers through metalation or choice of fullerene can be used to regulate key functional features, including photoconductivity.

A cyclo[2]carbazole[2]pyrrole (2) consisting of two carbazoles and two pyrroles has been synthesized by directly linking the carbazole 1- and 8-carbon atoms to the pyrrole α-carbon atoms. Macrocycle 2 is an extensively conjugated 16-membered macrocyclic ring that is fixed in a pseudo-1,3-alternate conformation. This provides a preorganized anion binding site consisting of two pyrrole subunits. 1 H NMR spectroscopic analysis revealed that only the two diagonally opposed pyrrole NH protons, as opposed to the carbazole protons, take part in anion binding. Nevertheless, cyclo[2]carbazole[2]pyrrole 2 binds representative anions with higher affinity in CD 2 Cl 2 than calix[4]pyrrole (1), a well-studied non-conjugated tetrapyrrole macrocycle that binds anions via four pyrrolic NH hydrogen bond interactions. On the basis of computational studies, the higher chloride anion affinity of receptor 2 relative to 1 is rationalized in terms of a larger binding energy and a lower host strain energy associated with anion complexation. In the presence of excess fluoride or bicarbonate anions, compound 2 loses two pyrrolic NH protons to produce a stable dianionic macrocycle [2-2H] 2- displaying a quenched fluorescence., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The environmentally benign metal-organic framework (MOF) CUK-1 based on 2,4-pyridine dicarboxylate has been prepared for the first time using Mn(II) as the inorganic node and water as the only solvent. Mn-CUK-1 shows reversible and efficient capture of H 2 O, SO 2 , and H 2 S. Compared to previously studied Co(II) and Mg(II) versions of the same MOF, Mn-CUK-1 also exhibited unique temperature-induced structural flexibility due to organic linker torsion, as detailed by variable-temperature single-crystal X-ray diffraction studies. Owing to this inherent solid-state flexibility, Mn-CUK-1 showed stepwise adsorption for polar gases, which induce structural deformations upon adsorption, while the nonpolar guest adsorbates were reversibly sorbed in a more classical manner. Notably, Mn-CUK-1 demonstrates the highest reported H 2 S capacity-to-surface area ratio among MOFs that are chemically stable toward this reactive acidic molecule. Moreover, Mn-CUK-1 displays exceptional structural stability in the presence of high relative humidity and corrosive gases and shows soft crystalline behavior triggered by changes in both the adsorption temperature and guest molecule identity.

A molecular capsule ( 1 ) consisting of two calix[4]pyrroles connected via ethylene diamide linkers has been prepared as an anion receptor. 1 H NMR spectroscopic studies carried out in CD 2 Cl 2 revealed that receptor 1 recognizes a variety of anions with different binding modes and stoichiometries. For instance, receptor 1 binds fluoride and acetate with 1:2 receptor/anion stoichiometry and other test anions with 1:1 stoichiometry in solution when their respective tetrabutylammonium (TBA + ) salts were used. In contrast, with tetraethylammnium (TEA + ) salts, receptor 1 forms 1:2 complexes with chloride and bromide in addition to fluoride, overcoming expected Columbic repulsions between the anions co-bound in close proximity. Receptor 1 is also able to bind oxoanions, such as oxalate (C 2 O 4 2- ), dihydrogen phosphate (H 2 PO 4 - ), sulfate (SO 4 2- ), and hydrogen pyrophosphate (HP 2 O 7 3- ), in the form of 1:1 complexes as the result of presumed cooperation between the two calix[4]pyrrole subunits. The selectivity of receptor 1 for fluoride versus dihydrogen phosphate varies depending on their relative concentrations. For instance, in the presence of less than 1.0 equiv of an equimolar mixture of fluoride and dihydrogen phosphate, receptor 1 shows high selectivity for dihydrogen phosphate. In contrast, in the presence of ≥2.0 anion equiv, receptor 1 binds fluoride preferentially, forming a 1:2 complex. Moreover, when treated with F - , the preformed 1:1 H 2 PO 4 - complex of receptor 1 is converted to the corresponding 1:2 receptor/fluoride complex with the release of the prebound dihydrogen phosphate anion. As inferred from gas-phase computations, this seemingly counterintuitive behavior is rationalized in terms of the precomplexed dihydrogen phosphate serving to reduce the reorganization energy required to bind two fluoride anions. The presence of a water molecule in addition to the bound fluoride anions may also favor the formation of the 1:2 F - complex. The present study provides a new approach for fine-tuning the binding selectivity of polytopic anion receptors.

Two belt-like expanded carbaporphyrins ( NB1 and NB2 ) were prepared via a one-pot procedure that involves a [6 + 3] condensation between a pyrene-bearing tetrapyrrole precursor ( 2 ) and pentafluorobenzaldehyde, followed by oxidation. Single crystal X-ray diffraction analyses revealed that NB1 and NB2 both contain six dipyrromethene moieties and three bridging pyrene units. In the structure of NB1 , there are two vertically orientated pyrene units and one transverse orientated pyrene unit; however, in NB2 all three pyrene units are vertically orientated. The structural differences between NB1 and NB2 are reflected in their respective physical properties as revealed by proton NMR, UV-vis, and fluorescence spectroscopies. In contrast to all-carbon nanobelts, NB1 and NB2 contain multiple pyrrolic nitrogen donors that could serve as potential metal coordination sites. As a test of this possibility, NB2 was used to prepare an unprecedented Zn complex containing 7 Zn 2+ metal centers connected by a network of bridging atoms, as confirmed by a single crystal X-ray diffraction analysis. To the best of our knowledge, this is the first example of a belt-like molecular system that can coordinate multiple metal ions both along the backbone and within its central cavity.

Palladium metallates containing 4-oxo-4 H -chromene-3-carbaldehyde derived ONS donor Schiff bases were synthesized and their efficacy was tested in the direct amination of diosgenin - a phyto steroid. Based on the pharmacological importance of diosgenin, the obtained derivatives were exposed to study their effect on breast cancer cells where they significantly reduced the growth of cancer cells and left non-malignant breast epithelial cells unaffected. Among the derivatives, D3, D4 and D6 showed a better anti-proliferative effect and further analysis revealed that the D3, D4 and D6 derivatives markedly promoted cell cycle arrest and apoptosis by attenuation of the AKT1 signalling pathway.

Deferasirox, an FDA-approved iron chelator, has gained increasing attention for use in anticancer and antimicrobial applications. Recent efforts by our group led to the identification of this core as an easy-to-visualize aggregation-induced emission platform, or AIEgen, that provides a therapeutic effect equivalent to deferasirox ( J. Am. Chem. Soc. 2021 , 143 , 3, 1278-1283). However, the emission wavelength of the first-generation system overlapped with that of Syto9, a green emissive dye used to indicate live cells. Here, we report a library of deferasirox derivatives with various fluorescence emission profiles designed to overcome this limitation. We propose referring to systems that show promise as both therapeutic and optical imaging agents as "illuminoceuticals". The color differences between the derivatives were observable to the unaided eye (solid- and solution-state) and were in accord with the Commission Internationale de L'Eclairage (CIE) chromaticity diagram 1913. Each fluorescent derivative successfully imaged the respective spherical and rod shapes of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa . They also displayed iron-dependent antibiotic activity. Three derivatives, ExNMe 2 ( 3 ), ExTrisT ( 11 ), and ExDCM ( 13 ), display emission features that are sufficiently distinct so as to permit the multiplex (triplex) imaging of both MRSA and P. aeruginosa via stimulated emission depletion microscopy. The present deferasirox derivatives allowed for the construction of a multi-fluorophore sensor array. This array enabled the successful discrimination between Gram-positive/Gram-negative and drug-sensitive/drug-resistant bacteria. Antibiotic sensitivity and drug-resistant mutants from clinically isolated strains could also be identified and differentiated.

Inspired by the tetracationic "Texas-sized" molecular box, a neutral analogue containing four iodotriazole halogen bond-promoting subunits ("Ibox") was synthesized. This new macrocycle was prepared by means of azide-alkyne click chemistry. It was found to recognize Cl - , Br - and I - anions (as their tetrabutylammonium salts) in CDCl 3 . 1 H NMR spectroscopic titrations revealed a higher affinity for the heavier halide anions and provided support for a preferred 1 : 2 binding stoichiometry.

High-energy X-ray scattering and pair distribution function analysis (HEXS/PDF) is a powerful method to reveal the structure of materials lacking long-range order, but is underutilized for molecular complexes in solution. We demonstrate the application of HEXS/PDF with 0.26 Å resolution to uncover the solution structure of five bimetallic Cu I /Ru II /Os II complexes. HEXS/PDF of each complex in acetonitrile solution confirms the pairwise distances in the local coordination sphere of each metal center as well as the metal⋅⋅⋅metal distances separated by over 12 Å. The metal⋅⋅⋅metal distance detected in solution is compared with that from the crystal structure and molecular models to confirm that distortions to the metal bridging ligand are unique to the solid state. This work presents the first example of observing sub-Ångström conformational differences by direct comparison of solution phase and solid-state structures and shows the potential for HEXS/PDF in the determination of solution structure of single molecules., (© 2021 Wiley-VCH GmbH.)

A number of artificial cation ionophores (or transporters) have been developed for basic research and biomedical applications. However, their mechanisms of action and the putative correlations between changes in intracellular cation concentrations and induced cell death remain poorly understood. Here, we show that three hemispherand-strapped calix[4]pyrrole-based ion-pair receptors act as efficient Na + /K + exchangers in the presence of Cl - in liposomal models and promote Na + influx and K + efflux (Na + /K + exchange) in cancer cells to induce apoptosis. Mechanistic studies reveal that these cation exchangers induce endoplasmic reticulum (ER) stress in cancer cells by perturbing intracellular cation homeostasis, promote generation of reactive oxygen species, and eventually enhance mitochondria-mediated apoptosis. However, they neither induce osmotic stress nor affect autophagy. This study provides support for the notion that synthetic receptors, which perturb cellular cation homeostasis, may provide new small molecules with potentially useful apoptotic activity., Competing Interests: DECLARATION OF INTERESTS The authors declare no competing interests.

Reported herein are two functionalized crown ether strapped calix[4]pyrroles, H1 and H2 . As inferred from competitive salt binding experiments carried out in nitrobenzene- d 5 and acetonitrile- d 3 , these hosts capture LiCl selectively over four other test salts, viz . NaCl, KCl, MgCl 2 , and CaCl 2 . Support for the selectivity came from density functional theory (DFT) calculations carried out in a solvent continuum. These theoretical analyses revealed a higher innate affinity for LiCl in the case of H1 , but a greater selectivity relative to NaCl in the case of H2 , recapitulating that observed experimentally. Receptors H1 and H2 were outfitted with methacrylate handles and subject to copolymerization with acrylate monomers and cross-linkers to yield gels, G1 and G2 , respectively. These two gels were found to adsorb lithium chloride preferentially from an acetonitrile solution containing a mixture of LiCl, NaCl, KCl, MgCl 2 , and CaCl 2 and then release the lithium chloride in methanol. The gels could then be recycled for reuse in the selective adsorption of LiCl. As such, the present study highlights the use of solvent polarity switching to drive separations with potential applications in lithium purification and recycling.

We report here a set of fluorescent supramolecular organic frameworks (SOFs) that incorporate aggregation-induced emission (AIE) units within their frameworks. The fluorescent SOFs of this study were constructed by linking the tetraphenylethylene (TPE)-based tetra(amidinium) cation TPE 4+ and aromatic dicarboxylate anions through amidinium-carboxylate salt bridges. The resulting self-assembled structures are characterized by fluorescence quantum yields in the range of 4.6∼14 %. This emissive behavior is ascribed to a combination of electrostatic interactions and hydrogen bonds that operate in concert to impede motions that would otherwise lead to excited state energy dissipation. Single-crystal X-ray diffraction analyses revealed that the length of the dicarboxylate anion bridges has a considerable impact on the structural features of the resulting frameworks. Nevertheless, all SOFs prepared in the context of the present study were found to display emissive features characteristic of TPE-based AIE luminogens with only a modest dependence on the structural specifics being seen. The SOFs reported here could be reversibly "broken up" and "reformed" in response to acid/base stimuli. This reversible structural behavior is consistent with their SOF nature., (© 2021 Wiley-VCH GmbH.)

We report the synthesis and reactivity of a model of [Fe]-hydrogenase derived from an anthracene-based scaffold that includes the endogenous, organometallic acyl(methylene) donor. In comparison to other non-scaffolded acyl-containing complexes, the complex described herein retains molecularly well-defined chemistry upon addition of multiple equivalents of exogenous base. Clean deprotonation of the acyl(methylene) C-H bond with a phenolate base results in the formation of a dimeric motif that contains a new Fe-C(methine) bond resulting from coordination of the deprotonated methylene unit to an adjacent iron center. This effective second carbanion in the ligand framework was demonstrated to drive heterolytic H 2 activation across the Fe(ii) center. However, this process results in reductive elimination and liberation of the ligand to extrude a lower-valent Fe-carbonyl complex. Through a series of isotopic labelling experiments, structural characterization (XRD, XAS), and spectroscopic characterization (IR, NMR, EXAFS), a mechanistic pathway is presented for H 2 /hydride-induced loss of the organometallic acyl unit ( i.e. pyCH 2 -C[double bond, length as m-dash]O → pyCH 3 +C[triple bond, length as m-dash]O). The known reduced hydride species [HFe(CO) 4 ] - and [HFe 3 (CO) 11 ] - have been observed as products by 1 H/ 2 H NMR and IR spectroscopies, as well as independent syntheses of PNP[HFe(CO) 4 ]. The former species ( i.e. [HFe(CO) 4 ] - ) is deduced to be the actual hydride transfer agent in the hydride transfer reaction (nominally catalyzed by the title compound) to a biomimetic substrate ([ Tol Im](BAr F ) = fluorinated imidazolium as hydride acceptor). This work provides mechanistic insight into the reasons for lack of functional biomimetic behavior (hydride transfer) in acyl(methylene)pyridine based mimics of [Fe]-hydrogenase., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

PCM-102 is a new organophosphine metal-organic framework (MOF) featuring diphosphine pockets that consist of pairs of offset trans- oriented P(III) donors. Postsynthetic addition of M(I) salts (M = Cu, Ag, Au) to PCM-102 induces single-crystal to single-crystal transformations and the formation of trans -[P 2 M] + solid-state complexes (where P = framework-based triarylphosphines). While the unmetalated PCM-102 has low porosity, the addition of secondary Lewis acids to install rigid P-M-P pillars is shown to dramatically increase both stability and selective gas uptake properties, with N 2 Brunauer-Emmett-Teller surface areas >1500 m 2 g -1 . The Ag(I) analogue can also be obtained via a simple, one-pot peri-synthetic route and is an ideal sacrificial precursor for materials with mixed bimetallic M A /M B pillars via postsynthetic, solvent-assisted metal exchange. Notably, the M-PCM-102 family of MOFs contain periodic trans -[P 2 M] + sites that are free of counter anions, unlike traditional analogous molecular complexes, since the precursor PCM-102 MOF is monoanionic, enabling access to charge-neutral metal-pillared materials. Four M-PCM-102 materials were evaluated for the separation of C2 hydrocarbons. The separation performance was found to be tunable based on the metal(s) incorporated, and density functional theory was employed to elucidate the nature of the unusual observed sorption preference, C 2 H 2 > C 2 H 6 > C 2 H 4 .

Recent decades have witnessed the emergence of Au(i) bis-N-heterocyclic carbenes (NHCs) as potential anticancer agents. However, these systems exhibit little interaction with serum proteins ( e.g. , human serum albumin), which presumably impacts their pharmacokinetic profile and tumor exposure. Anticancer drugs bound to human serum albumin (HSA) often benefit from significant advantages, including longer circulatory half-lives, tumor targeted delivery, and easier administration relative to the drug alone. In this work, we present Au(i) bis-NHCs complexes, 7 and 9 , capable of binding to HSA. Complex 7 contains a reactive maleimide moiety for covalent protein conjugation, whereas its congener 9 contains a naphthalimide fluorophore for non-covalent binding. A similar drug motif was used in both cases. Complexes 7 and 9 were prepared from a carboxylic acid functionalized Au(i) bis-NHC (complex 2 ) using a newly developed post-synthetic amide functionalization protocol that allows coupling to both aliphatic and aromatic amines. Analytical, and in vitro techniques were used to confirm protein binding, as well as cellular uptake and antiproliferative activity in A549 human lung cancer cells. The present findings highlight a hitherto unexplored approach to modifying Au(i) bis-NHC drug candidates for protein ligation and serve to showcase the relative benefits of covalent and non-covalent HSA binding., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Deferasirox, ExJade, is an FDA-approved iron chelator used for the treatment of iron overload. In this work, we report several fluorescent deferasirox derivatives that display unique photophysical properties, i.e., aggregation-induced emission (AIE), excited state intramolecular proton transfer, charge transfer, and through-bond and through-space conjugation characteristics in aqueous media. Functionalization of the phenol units on the deferasirox scaffold afforded the fluorescent responsive pro-chelator ExPhos, which enabled the detection of the disease-based biomarker alkaline phosphatase (ALP). The diagnostic potential of these deferasirox derivatives was supported by bacterial biofilm studies.

Immunogenic cell death (ICD) is a way of reengaging the tumor-specific immune system. ICD can be induced by treatment with chemotherapeutics. However, only a limited number of drugs and other treatment modalities have been shown to elicit the biomarker responses characteristic of ICD and to provide an anticancer benefit in vivo. Here, we report a rationally designed redox-active Au(I) bis-N-heterocyclic carbene that induces ICD both in vitro and in vivo. This work benefits from a synthetic pathway that allows for the facile preparation of asymmetric redox-active Au(I) bis-N-heterocyclic carbenes.

There is a recognized need in the area of explosives detection for fluorescence-based sensing systems that are capable of not only producing a turn-on response but also generating a distinctive spectral signature for a given analyte. Here, we report several supramolecular ensembles displaying efficient fluorophore displacement that give rise to an increase in fluorescence intensity upon exposure to various nitroaromatic compounds. The synthetic supramolecular constructs in question consist of a tetrathiafulvalene (TTF)-based pyrrolic macrocycle, benzo-TTF-calix[4]pyrrole (Bz-TTF-C4P), and fluorescent dyes, monomeric or dimeric naphthalenediimide (NDI) and perylenediimide (PDI) derivatives, as well as chloride or hexafluorophosphate (PF 6 - ) salts of rhodamine 6G (Rh-6G). In chloroform solution, these assemblies exist in the form of discrete supramolecular complexes or oligomeric aggregates depending on the specific dye combinations in question. Each ensemble was tested as a potential explosive-responsive fluorescence indicator displacement assay (FIDA) by challenging it with a series of di- and trinitroaromatic compounds and examining the change in fluorescence spectral characteristics. Upon addition of nitroaromatic compounds (NACs), either a "turn-on" or a "turn-off" fluorescent response was observed depending on the nature of the constituent fluorophore and, where applicable, the counteranion. The FIDAs based on the PDI derivatives were found to display not only a ratiometric fluorescence enhancement but also analyte-dependent spectral changes when treated with NACs. The NAC-induced fluorescence spectral response of each ensemble was rationalized on the basis of various solution-phase spectroscopic studies, as well as single-crystal X-ray diffraction analyses.

We report the synthesis and biomimetic activity of a family of model complexes with relevance to acireductone dioxygenase (ARD), an enzyme that displays dual function based on metal identity found in the methionine salvage pathway (MSP). Three complexes with related structural motifs were synthesized and characterized derived from phenolate, and pyridine N 4 O Schiff-base ligands. They display pseudo-octahedral Ni(II)-N 4 O ligand coordination with water at the sixth site, in close alignment to the structure in the resting state of ARD. The three featured complexes exhibit carbon‑carbon bond cleavage activation of lithium acetylacetonate, which was used as a model enzyme substrate. Computationally derived mechanistic routes for the observed reactivity consistent with experimental conditions are herein proposed. The mechanism suggests the possibility of Ni(II)-substrate interactions, followed by oxygen insertion. These results constitute only the third functional model system of ARD, in an attempt to further advance biomimetic contributions to the ongoing debate of ARD's unique metal mediated, regioselective oxidative cleavage., (Copyright © 2020 Elsevier Inc. All rights reserved.)

There is growing interest in creating solids that are responsive to various stimuli. Herein we report the first molecular-level mechanistic picture of the thermochromic polymorphic transition in a series of MAN-NI dyad crystals that turn from orange to yellow upon heating with minimal changes to the microscopic morphology following the transition. Detailed structural analyses revealed that the dyads assemble to create an alternating bilayer type structure, with horizontal alternating alkyl and stacked aromatic layers in both the orange and yellow forms. The observed dynamic behavior in the solid state moves as a yellow wavefront through the orange crystal. The overall process is critically dependent on a complex interplay between the layered structure of the starting crystal, the thermodynamics of the two differently colored forms, and similar densities of the two polymorphs. Upon heating, the orange form alkyl chain layers become disordered, allowing for some lateral diffusion of dyads within their own layer. Moving to either adjacent stack in the same layer allows a dyad to exchange a head-to-head stacking geometry (orange) for a head-to-tail stacking geometry (yellow). This transition is unique in that it involves a nucleation and growth mechanism that converts to a faster cooperative wavefront mechanism during the transition. The fastest moving of the wavefronts have an approximately 38° angle with respect to the long axis of the crystal, corresponding to a nonconventional C-H···O hydrogen bond network of dyad molecules in adjacent stacks that enables a transition with cooperative character to proceed within layers of orange crystals. The orange-to-yellow transition is triggered at a temperature that is very close to the temperature at which the orange and yellow forms exchange as the more stable, while being lower than the melting temperature of the original orange, or final yellow, solids.

Four binuclear Ni(II) complexes [[Ni 2 (H-DEAsal-tsc) 2 (μ-dppm)]·2Cl (1), [Ni 2 (DEAsal-mtsc) 2 (μ-dppm)] (2), [Ni 2 (DEAsal-etsc) 2 (μ-dppm)] (3) and [Ni 2 (DEAsal-ptsc) 2 (μ-dppm)] (4)] were synthesized from the ligands namely 4(N,N)-diethylaminosalicylaldehyde-4(N)-thiosemicarbazone [H 2 -DEAsal-tsc] H 2 L 1 /4(N,N)-diethylaminosalicylaldehyde-4(N)-methyl thiosemicarbazone [H 2 -DEAsal-mtsc] H 2 L 2 /4(N,N)-diethylaminosalicylaldehyde-4(N)-ethyl thiosemicarbazone [H 2 -DEAsal-etsc] H 2 L 3 /4(N,N)diethylaminosalicylaldehyde-4(N)-phenyl thiosemicarbazone [H 2 -DEAsal-ptsc] H 2 L 4 and 1,1'-bis(diphenylphosphino)methane (dppm) and characterized by a number of spectro analytical techniques. The molecular structure of complexes [Ni 2 (H-DEAsal-tsc) 2 (μ-dppm)]·2Cl (1) and [Ni 2 (DEAsal-ptsc) 2 (μ-dppm)] (4) have been confirmed by single crystal X-ray diffraction studies. The analysis indicated that in complex 1, the ligand [H 2 -DEAsal-tsc] coordinated as monobasic tridentate donor through phenolic oxygen, azomethine nitrogen and thione sulfur atoms. However, in complex 4, the ligand [H 2 -DEAsal-ptsc] behaved as dibasic tridentate donor with thiolate sulfur coordination. Their ability to bind with Calf Thymus Deoxyribonucleic acid (CT-DNA) and Bovine Serum Albumin (BSA) were analysed spectrometrically. Intercalative interaction of the complexes with DNA was confirmed by ethidium bromide (EB) displacement studies and DNA viscosity measurements. The interaction mechanism of the complexes with BSA was found as static. In vitro antiproliferative studies of the ligands and complexes in A549 (human lung carcinoma cancer), MCF-7 (human breast cancer) and HeLa (human cervical cancer) cell lines witnessed significant cytotoxic nature of the complexes with low IC 50 values (in μM) than the standard metallo-drug cisplatin. Further, the results of Lactate Dehydrogenase (LDH) and Nitric oxide (NO) release assays supported the effectiveness of the complexes on the above said cancer cells., Competing Interests: Declaration of competing interest There are no conflicts of interest to declare., (Copyright © 2020 Elsevier Inc. All rights reserved.)

This work explores the pivotal role that protein mobility plays in facilitating the catalytic activity of Copper-Zinc superoxide dismutase (SOD1). Through both localized active site distortions and correlated domain movement, these motions enable the enzyme to adopt the conformations necessary to achieve both substrate delivery and efficient catalytic transformation. Structural and computational studies of a biomimetic model complex are used to probe the localized interactions between substrate and secondary sphere residues that play a role in guiding substrate to the active site, as well as facilitating the conformational changes necessary for substrate turnover. Normal mode analysis (NMA) of SOD1 demonstrates how collective domain motion influences key residues of the electrostatic loop (ESL), guiding substrate to the active site and facilitating the delivery of the conserved water network necessary for proton transfer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Two-phenoxy walled calix[4]pyrroles 1 and 2 strapped with small rigid linkers containing pyridine and benzene, respectively, have been synthesized. 1 H NMR spectroscopic analyses carried out in CDCl 3 revealed that both of receptors 1 and 2 recognize only F - and HCO 3 - among various test anions with high preference for HCO 3 - (as the tetraethylammonium, TEA + salt) relative to F - (as the TBA + salt). The bound HCO 3 - 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 TEAHCO 3 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 TEAHCO 3 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., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A post-synthetic strategy is reported that allows for functionalisation of Au(i)-bis NHCs via carbonate formation. The scope of this methodology was explored using both aromatic and aliphatic alcohols. As a demonstration of potential utility, the fluorescent Au(i)-bis NHC conjugate 5 was prepared; it was found to have enhanced stability when formulated with bovine serum albumin, localise within the mitochondria of A549 cells and do so without compromising the high cytotoxicity seen for the parent Au(i)-bis NHC system.

The title compound, [Os 3 (C 6 H 12 N 3 P) 4 (CO) 8 ], crystallizes in the ortho-rhom-bic space group Pbca with Z = 8. The mol-ecule consists of a triangular triosmium(0) core surrounded by eight carbonyl ligands and four 1,3,5-tri-aza-7-phosphatri-cyclo-[3.3.1.1 3,7 ]decane (or PTA) ligands. One Os atom is coordinated by two PTA ligands and two CO ligands, while the other two Os atoms are each bonded to a single PTA ligand and three CO ligands. There is a small disorder associated with the Os 3 unit so that a minor orientation has an occupancy of 2.17 (4)%. The title compound represents the first structurally characterized triangular Os 3 carbonyl cluster with four monodentate tertiary phosphane ligands., (© Marolf et al. 2020.)

We report here a new extended tetrathiafulvalene (exTTF)-porphyrin scaffold, 2 , that acts as a ball-and-socket receptor for C 60 and C 70 . Supramolecular interactions between 2 and these fullerenes serve to stabilize 3D supramolecular organic frameworks (SOFs) in the solid state formally comprising peapod-like linear assemblies. The SOFs prepared via self-assembly in this way act as "tunable functional materials", wherein the complementary geometry of the components and the choice of fullerene play crucial roles in defining the conductance properties. The highest electrical conductivity (σ = 1.3 × 10 -8 S cm -1 at 298 K) was observed in the case of the C 70 -based SOF. In contrast, low conductivity was seen for the SOF based on pristine 2 (σ = 5.9 × 10 -11 S cm -1 at 298 K). The conductivity seen for the C 70 -based SOF approaches that seen for other TTF- and fullerene-based supramolecular materials despite the fact that the present systems are metal-free and constructed entirely from neutral building blocks. Transient absorption spectroscopic measurements corroborated the formation of charge-transfer states (i.e., 2 δ+ /C 60 δ- and 2 δ+ /C 70 δ- , respectively) rather than fully charge separated states (i.e., 2 •+ /C 60 •- and 2 •+ /C 70 •- , respectively) both in solution (toluene and benzonitrile) and in the solid state at 298 K. Such findings are considered consistent with an ability to transfer charges effectively over long distances within the present SOFs, rather than, for example, the formation of energetically trapped ionic species.

The crystal structure of 6,7-di-hydro-5 H -pyrrolo-[1,2- a ]imidazole, C 6 H 8 N 2 , at 100 K has monoclinic ( P 2 1 / n ) symmetry. The mol-ecule adopts an envelope conformation of the pyrrolidine ring, which might help for the relief torsion tension. The crystal cohesion is achieved by C-H⋯N hydrogen bonds. Inter-estingly, this fused ring system provides protection of the α-C atom (attached to the non-bridging N atom of the imidazole ring), which provides stability that is of inter-est with respect to electrochemical properties as electrolytes for fuel cells and batteries, and electrodeposition., (© Morales-Collazo et al. 2020.)

Calix[4]pyrrole (C4P)-based systems have been extensively explored as binding agents for anions and ion pairs. However, their capacity to act as molecular containers for neutral species remains underexplored. We report here the molecular recognition of pyrazine N , N '-dioxide ( PZDO ) using a series of aryl extended C4Ps including three α,α-diaryl substituted C4Ps (receptors 1-3 ), an α,β-diaryl substituted C4P (receptor 4 ) and an α,α,α,α-tetraaryl substituted C4P (receptor 5 ). Single crystal structural analyses of the 2 : 1 host-guest complexes between receptors 1-3 and PZDO revealed that the C4P subunits exist in an unusual partial cone conformation and that the PZDO guest is held within electron-rich cavities formed by the lower rims of the individual C4P macrocycle. In contrast, receptor 5 was seen to adopt the cone conformation in the solid state, allowing one PZDO molecule to be accommodated inside the upper-rim cavity. Evidence for guest-directed self-assembly is also seen in the solid state. Evidence for C4P- PZDO interactions in CD 3 CN/CD 3 OD solution came from 1 H NMR spectroscopic titrations. Electrostatic potential maps created by means of density functional theory calculations were constructed. Density functional theory calculations were also performed to analyse the energetics of various limiting binding modes. On the basis of these studies, it is inferred that interactions between the 'two-wall' C4P derivatives ( i.e. receptors 1-4 ) and PZDO involve a complex binding mode that differs from what has been seen in previous host-guest complexes formed between C4Ps and N -oxides. The present study thus paves the way for the further design of C4P-based receptors with novel recognition features., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The reaction between dipyriamethyrin and copper(II) acetate [Cu(OAc) 2 ] afforded what is, to our knowledge, the first transition metal-dipyriamethyrin complex. Molecular and electronic characterization of this binuclear Cu(II) complex via EPR, UV-vis, and single crystal X-ray diffraction analysis revealed marked differences between the present constructs and previously reported binuclear copper(II) hexaphyrin species. UV-vis titration analyses provided evidence for a homotropic positive allosteric effect, wherein the binuclear species is formed without significant intermediacy of a monomeric complex.

New Rh (1) and Ir (2) complexes of an N-heterocyclic carbene (NHC) featuring a terthiophene backbone were synthesized. Single crystal X-ray diffraction studies of 1 and 2 at 100 K and 298 K respectively, revealed two enantiotropic polymorphic phases with similar lattice parameters for each compound. The transition temperature between two crystalline forms for each compound was determined by measuring the percentage of reflections with a different space group ranging from 100 K to 298 K. Both 1 and 2 were also found to catalyze the hydrogen transfer reaction. The conducting metallopolymers poly-1 and poly-2 were synthesized from oxidative electropolymerization of 1 and 2, respectively, in CH 2 Cl 2 electrolyte solution on indium tin oxide-(ITO) coated glass. The electrochromic properties of synthesized conducting metallopolymers were studied by UV-vis-NIR spectroelectrochemistry.

Controlled partial decomposition of 2-selenonicotinic acid in the presence of Co2+ or Ni2+ resulted in the in situ formation of an unusual MOF based on triselenane ligands (RSeSeSeR) coordinated to M2+ centers as NSeN-pincers. Post-synthetic oxidation by treatment with aqueous H2O2 facilitates its solid-state conversion into a RSeO2- molecular coordination complex, which was tracked via powder X-ray diffraction studies and by single-crystal structural resolution of the final product.

β,β'-Phenylene bridged hexaphyrin[1.0.1.0.1.0] (naphthorosarin), an expanded porphyrin possessing C 3v -symmetry, has been shown to possess unique electronic features. We now report a bimetallic Rh(i)-complex of naphthorosarin retaining 24 π-antiaromatic characteristics. The two Rh(i) cations reside on opposite sides of the macrocyclic π-system and are separated at a distance consistent with a possible Rh(i)-Rh(i) metallic bond interaction.

Here we report the first series of in-plane thorium(IV), uranium(IV), and neptunium(IV) expanded porphyrin complexes. These actinide (An) complexes were synthesized using a hexa-aza porphyrin analogue, termed dipyriamethyrin, and the nonaqueous An(IV) precursors, ThCl 4 (DME) 2 , UCl 4 , and NpCl 4 (DME) 2 . The molecular and electronic structures of the ligand, each An(IV) complex, and a corresponding uranyl(VI) complex were characterized using nuclear magnetic resonance (NMR) and UV-vis spectroscopies as well as single-crystal X-ray diffraction analysis. Computational analyses of these complexes, coupled to their structural features, provide support for the conclusion that a greater degree of covalency in the ligand-cation orbital interactions arises as the early actinide series is traversed from Th(IV) to U(IV) and Np(IV). The axial ligands in the present An(IV) complexes proved labile, allowing for the electronic features of these complexes to be further modified.

We report here the fluorescent sensing of both aromatic and linear saturated dicarboxylate anions ( DC 2- ) (as their tetrabutylammonium salts) with different lengths and shapes in acetonitrile using a single fluorescent probe, i.e., the bis-calix[4]pyrrole-appended 9,14-diphenyl-9,14-dihydrodibenzo[ a , c ]phenazine ( DPAC-bisC4P ) incorporating a vibration-induced emission (VIE) phenazine core. Fluorescence titration studies revealed that treating DPAC-bisC4P with dicarboxylate guests capable of forming pseudomacrocyclic host-guest complexes via multiple hydrogen-bonding interactions between the dicarboxylates and calix[4]pyrrole moieties led to a blue-shift in the emission of the phenazine core. The binding-based fluorescence-tuning features of DPAC-bisC4P allow the underlying binding events and inferred structural changes to be monitored in the form of different chromaticity outputs. The analyte-induced differences in the fluorescence response to DC 2- cover a wide range within the chromaticity diagram and can be visualized readily. The present system thus functions as a rudimentary dicarboxylate anion sensor. It highlights the potential benefits associated with combining a tunable VIE core with noncovalent binding interactions and thus sets the stage for the development of new fluorescent chemosensors where a single chemical entity responds to different analytes with a high level of tunability.

Three tetranuclear (1-3) complexes and a mononuclear (4) palladium(ii) complex were synthesized from 3-acetyl-chromen-2-one Schiff base ligands [H 2 -3MAC-Rtsc] (where R = H [H 2 -3MAC-tsc]; CH 3 [H 2 -3MAC-mtsc]; C 2 H 5 [H 2 -3MAC-etsc] or C 6 H 5 [H 2 -3MAC-ptsc]) and potassium tetrachloropalladate. Their formation was confirmed by spectroscopic techniques and X-ray crystallographic analysis. Their ability to bind with DNA and albumin was analysed by using absorption and emission titrations. The MTT assay was carried out to analyze the anticancer potential of the ligands and synthesized complexes against HepG2 (human liver cancer) and HT-29 (human colon cancer) cells. In addition, the compounds were less toxic when tested against the human normal keratinocyte cells (HaCaT). Ligands and complexes displayed better cytotoxicity with lower IC 50 values than the standard drug cisplatin. Further AO-EB and DAPI staining assays were carried out to detect the mode of cell death induced by the complexes i.e. apoptosis or necrosis. The complex 3 showed better cytotoxicity and was further subjected to flow cytometric analysis. The results suggested that the complex 3 induced apoptotic cell death.