In supramolecular architectures, the interactions between host and guest molecules are governed by non-covalent forces such as hydrogen (H) bonding, hydrophobic and electrostatic interactions. We alter here the cavity microenvironment to control the interactions between guest and host molecules and study the effects of introducing axial chlorido ligands through the use of an octahedral building block in M(μ-L)4M' architectures. We prepared the heterodimetallic Pd(μ-L)4Pt C4 Pt and Pd(μ-L)4RuCl2C4 Ru architectures and demonstrated the role of 'classic' non-covalent forces in their host-guest chemistry with anionic and neutral molecules, while the cages also underwent disassembly and reassembly upon addition of external stimuli. This culminated in the isolation of a 1 : 1 host-guest complex between C4 Pt and the dianionic 1,5-naphthalenedisulfonate which was characterized by single crystal X-ray diffraction studies. These showed the guest occupied the central cavity and was held in place by H bonding. The endo-chlorido ligand in C4 Ru played an important role in the capture of neutral guest molecules. In particular, it allowed for finetuning of the cavity properties of the supramolecular architectures by limiting the formation of H bonds and restricting the cavity size while offering alternative interactions.

Metallosupramolecular architectures formed from metal ions and bridging ligands are increasing in popularity due to their range of applications and ease of self-assembly. Many are able to readily change their shape and/or function in response to an external stimulus and have the ability to encapsulate guest molecules within their internal cavities. Ferrocenyl groups (Fc) have been incorporated previously within the bridging ligands of metallosupramolecular structures due to their ideal attributes brought about by the structural and rotational flexiblity of the two cyclopentadienyl (Cp) rings coordinated to the Fe(ii) centre. However, the majority of these Fc-based structures contain symmetrically substituted Cp rings. We report the synthesis and characterisation of non-symmetrically functionalised Fc-based ligands incorporating both N,N ' and NHC-donor groups chosen for their differing coordination properties. Both substituents were designed to coordinate to a single metal centre with the dissimilar coordination properties of each donor group facilitating stimulus-induced dissociation/association of one of the substituents as an opening/closing mechanism. Preliminary investigations into the coordination of these Fc-based ligands to a [Ru(eta 6-p-cymene)]2+ moiety indicated complexation through a mixture of either a bi- or tridentate fashion, as alluded by 1H NMR spectroscopy and mass spectrometry. Density functional theory (DFT) calculations revealed the Fc-based ligands adopt a syn conformation driven by H-bonding and pi-interactions between the two Cp substituents, which facilitate coordination of both donor groups towards the metal centre. Ferrocene-based ligands with NHC and N,N ' donor systems were designed to undergo stimulus-induced dissociation from coordinated metal centres. Studies with Ru(p-cymene) indicate coordination to the metal with the coordination mode to be elucidated.

A series of iridium pentamethylcyclopentadienyl (Cp*) complexes, [Cp*Ir(κ2-RLp/m)Cl], that contain the strongly coordinating bidentate ligands RLp/m were synthesized. The donor groups of the bidentate ligands were an N-amidate and either a para-pyridinylidene remote N-heterocyclic carbene (RLp) or a meta-pyridinylidene remote N-heterocyclic carbene (RLm). For each type of bidentate ligand, a set of iridium complexes was synthesized, which differed only according to the substituents (R) on the phenyl ring associated with the amidate group. The iridium complexes were all fully characterized and molecular structures were obtained by single-crystal X-ray diffraction studies for representative examples. The complexes were found to be good precatalysts in iso-propanol for the transfer hydrogenation of benzaldehyde to give benzyl alcohol. The catalytic activity correlated with the Hammett σm/p parameters of the phenyl ring substituents, with more electron-donating substituents leading to increased catalytic activity. In all cases, the meta-pyridinylidene complexes, [Cp*Ir(κ2-RLm)Cl], performed better than the corresponding para analogues, [Cp*Ir(κ2-RLp)Cl].

A dynamic covalent approach was exploited to generate a family of homometallic [PtnL2 n]2 n + cage (predominantly [Pt2L4]4+ systems) architectures. The family of platinum(ii) architectures were characterized using 1H nuclear magnetic resonance (NMR) and diffusion ordered spectroscopy (DOSY), electrospray ionization mass spectrometry (ESI-MS) and the molecular structures of two cages were determined by X-ray crystallography.

A dynamic covalent approach was exploited to generate a family of homometallic [PtnL2n]2n+ cage (predominantly [Pt2L4]4+ systems) architectures.

Heterobimetallic cages built from Pd and either octahedral Ru or square-planar Pt moieties and bridged by ligands with H bonding-accepting or -donating properties are reported. They showed stimulus-responsive dis- and reassembly, while guest binding was found to be dependent on the complementary properties of the guest to the host in terms of charge, size and H bonding properties.

Graphical Abstract The depicted macrocyclic iron complex is a highly active, biomimetic oxidation catalyst in water at pH 7. The iron centre is coordinated by four unique, hybrid, pyridinium amidate/amidate nitrogen donors. Upon activation by the green oxidant hydrogen peroxide, the iron complex is converted to an aggressive intermediate (represented by the piranha) that very rapidly oxidises the surrogate pollutant orange II to colourless products, with the iron returning to its FeIII resting state. More information can be found in the Research Article by L. J. Wright and co-workers (DOI: 10.1002/chem.202301548).

The macrocyclic proligand [H4L][OTf]2, which contains four carboxamide functions and two conjugated pyridinium groups, is easily deprotonated by the weak base sodium acetate to give the corresponding neutral proligand [H2L]. Metallation of [H2L] with iron(II) chloride proceeds rapidly to form the macrocyclic complex, [FeIIICl(L)]. This is an effective catalyst for the oxidation of the organic dye orange II by hydrogen peroxide in aqueous solution, and the kinetic parameters for this reaction have been determined. In striking contrast to an analogous iron-TAML complex that contains two phenyl groups in place of the two pyridinium groups, [FeIIICl(L)] is a very active oxidation catalyst at pH 7 and is also highly stable towards acid-promoted demetallation at pH 5 or above. The results show that the two pyridinium groups bring greatly enhanced catalytic properties to [FeIIICl(L)]. The incorporation of four mixed or "hybrid" pyridinium amidate/amidate donors into a macrocyclic ligand leads to a superior iron catalyst that resists acid-induced demetallation and rapidly catalyses hydrogen peroxide oxidation of the surrogate organic pollutant orange II in water at pH 7 and at ambient temperature.image

Using ferrocene-based ligand systems, a series of heterobimetallic architectures of the general formula [PdmLn]x+ were designed with the aim of installing an opening and closing mechanism that would allow the release and binding of guest molecules. Palladium complex formation was achieved through coordination to pyridyl groups, and using 2-, 3-, and 4-pyridyl derivatives provided access to defined PdL, PdL2, and Pd2L4 structures, respectively. The supramolecular complexes were characterized using nuclear magnetic resonance (NMR) and infrared spectroscopy, mass spectrometry, and elemental analysis, and for some examples density functional theory calculations and single-crystal X-ray diffraction analysis. 1H NMR spectroscopy was used to investigate disassembly and reassembly of the metallosupramolecular structures. The former was induced by cleavage of the relatively labile Pd-Npyridyl bonds with the introduction of the competing ligands N,N'-dimethylaminopyridine (DMAP) and Cl- (using tetrabutylammonium chloride) to yield [Pd(DMAP)4]2+ and [PdCl4]2-, respectively. The process was found to be reversible for several of the heterodimetallic compounds, with the addition of H+ or Ag+ triggering complex reassembly. Guest binding studies with several architectures revealed interactions with the anionic guests p-toluenesulfonate and octyl sulfate, but not with neutral molecules. Furthermore, the release of guests was reversibly induced with Cl- ions as a stimulus.

[M2L3]-type metallo-supramolecular architectures (MSAs) are widely explored for their biological activity, whereas data on non-symmetric, heterobimetallic [MM'L-3] structures is comparatively rare. [M2L3] compounds are known to form helicates and/or mesocates. Here, we report the self-assembly of a discrete non-symmetrical, heterobimetallic MSA by combination of an amine-functionalised cobalt(III)-tris((picolinamido)ethyl)amine (PICTREN) base unit with FeCl2 and 2,2'-bipyridine-5-carboxaldehyde. NMR spectroscopy in tandem with computational studies revealed the formation of a mesocate rather than a helicate. The ability of the heteromesocate to bind to DNA was examined by gel electrophoresis with pUC19 plasmid DNA, which showed DNA binding although longer incubation periods were required than found for a known DNA-interacting helicate. The mesocate displayed promising antiproliferative activity in cancer cells, including a cisplatin-resistant cell line, with IC50 values in the 17-26 mu M range. Lower biological activity of the mesocate compared to a metallocylinder reference and cisplatin may be explained by differences in the DNA interactions. This work further supports efforts to establish methods with which to construct heterobimetallic complexes, establishing the utility of the self-assembly method in [M2L3]-type assemblies using the cobalt(III)-PICTREN platform as a robust building block towards more complex assemblies of the [MM'L]-type.

A new sequential metalation strategy that enables the assembly of a new more robust reduced symmetry heterobimetallic [PdPtL4](4+) cage C is reported. By exploiting a low-symmetry ditopic ligand (L) that features imidazole and pyridine donor units we were able to selectively form a [Pt(L)(4)](2+) "open-cage" complex. When this was treated with Pd(ii) ions the cage C assembled. H-1 and DOSY nuclear magnetic resonance (NMR) spectroscopy and electrospray ionisation mass spectrometry (ESIMS) data were consistent with the quantitative formation of the cage and the heterobimetallic structure was confirmed by single crystal X-ray crystallography. The cage C was shown to bind anionic guest molecules. NMR studies suggested that these guests interacted with the cavity of the cage in a specific orientation and this was confirmed for the mesylate ion (MsO-) : C host-guest adduct using X-ray crystallography. In addition, the system was shown to be stimulus-responsive and could be opened and closed on demand when treated with appropriate stimuli. If a guest molecule was bound within the cage, the opening and closing was accompanied by the release and re-uptake of the guest molecule.

A new [PdPtL4]4+ heterobimetallic cage containing hydrazone linkages has been synthesised using the sub-component self-assembly approach. 1H and DOSY nuclear magnetic resonance (NMR) spectroscopy and electrospray ionisation mass spectrometry (ESIMS) data were consistent with the formation of the [PdPtL4]4+ architecture. The cage was stimulus-responsive and could be partially disassembled and reassembled by the addition of dimethylaminopyridine (DMAP) and p-tolenesulfonic acid (TsOH), respectively. Additionally, the stability of the hydrazone cage against hydrolysis in the presence of water and nucleophilic decomposition in the presence of guest molecules was compared to a previously synthesised imine-containing [PdPtL4]4+ cage. It was established that the hydrazone linkage was more resistant to hydrolysis. Furthermore, the host-guest (HG) chemistry with a series of drug and drug-like molecules was examined. The hydrazone cage was shown to interact with cisplatin while the smaller imine cage was shown to interact with 5-fluorouracil and oxaliplatin in CD3CN. No HG interactions were observed in the more polar d6-DMSO. In vitro antiproliferative activity studies demonstrated both cages were active against the cancer cell lines tested and displayed half-maximal inhibitory (IC50) values in the range of 25-35 μM. Most [PdPtL4]4+-drug mixtures tested had higher IC50 values than the hosts. However, the [PdPtL4]4+ cages, and [PdPtL4]4+:drug mixtures were less cytotoxic than the well established anticancer drugs cisplatin, oxaliplatin and 5-fluorouracil.

ObjectiveThe FOURIER trial showed a benefit of the PCSK9 inhibitor evolocumab over placebo with respect to cardiovascular outcomes in patients with cardiovascular disease. However, we observed some inconsistencies between the information in the Clinical Study Report (CSR) and that in the 2017 primary trial results publication. We aimed to restore the mortality data in the FOURIER trial based on the information contained in the death narratives in the CSR. MethodsMortality data in the primary results publication were compared with that in the CSR. In cases of discrepancy between the sources, an independent committee blindly readjudicated and restored the cause of death according to the information in the CSR narratives. ResultsFor 360/870 deaths (41.4%), the cause of death adjudicated by the FOURIER clinical events committee differed from that declared by the local clinical investigator. When comparing the CSR information with the 2017 primary results publication, we found 11 more deaths from myocardial infarction in the evolocumab group (36 vs 25) and 3 less deaths in the placebo group (27 vs 30, respectively). In the CSR, the number of deaths due to cardiac failure in the evolocumab group was almost double those in the placebo group (31 vs 16). While cardiac and vascular deaths were not assessed as separate outcomes in the original trial analysis, after readjudication, we noted that cardiac deaths were numerically, but non-significantly, higher in the evolocumab group (113) than in the placebo group (88; relative risk (RR) 1.28, 95%CI 0.97 to 1.69, p=0.078), whereas non-cardiac vascular deaths were similar between groups (37 in each; RR 1.00, 95% CI 0.63 to 1.58, p=0.999). The reported HR for cardiovascular mortality in the original trial analysis was 1.05 (95% CI 0.88 to 1.25); after readjudication, we found a greater (although still non-significant) relative increase in cardiovascular mortality in the evolocumab treatment group (RR 1.20, 95% CI 0.95 to 1.51, p=0.13). ConclusionAfter readjudication, deaths of cardiac origin were numerically higher in the evolocumab group than in the placebo group in the FOURIER trial, suggesting possible cardiac harm. At the time the trial was terminated early, a non-significantly higher risk of cardiovascular mortality was observed with evolocumab, which was numerically greater in our readjudication. A complete restoration of the FOURIER trial data is required. In the meantime, clinicians should be sceptical about prescribing evolocumab for patients with established atherosclerotic cardiovascular disease.Trial registration numbersNCT01764633.

A strategy for the generation of heterotrimetallic double cavity (DC) cages [Pdn Ptm L4 ]6+ (DC1: n=1, m=2; and DC2: n=2, m=1) is reported. The DC cages were generated by combining an inert platinum(II) tetrapyridylaldehyde complex with a suitably substituted pyridylamine and PdII ions. 1 H and DOSY nuclear magnetic resonance spectroscopy (NMR) and electrospray ionization mass spectrometry (ESIMS) data were consistent with the formation of the DC architectures. DC1 and DC2 were shown to interact with several different guest molecules. The structure of DC1, which features two identical cavities, binding two 2,6-diaminoanthraquinone (DAQ) guest molecules was determined by single-crystal X-ray crystallography. In addition, DC1 was shown to bind two molecules of 5-fluorouracil (5-FU) in a statistical (non-cooperative) manner. In contrast, DC2, which features two different cage cavities, was found to interact with two different guests, 5-FU and cisplatin, selectively.

Cylindrospermopsin (CYL) and anatoxin-a (ANA) are alkaloid-like potent cyanotoxins produced during cyanobacterial blooms.

Two new di(2,2′-bipyridine) ligands, 2,6-bis([2,2′-bipyridin]-5-ylethynyl)pyridine (L1) and bis(4-([2,2′-bipyridin]-5-ylethynyl)phenyl)methane (L2) were synthesized and used to generate two metallosupramolecular [Fe2(L)3](BF4)4 cylinders. The ligands and cylinders were characterized using elemental analysis, electrospray ionization mass spectrometry, UV-vis, 1H-, 13C and DOSY nuclear magnetic resonance (NMR) spectroscopies. The molecular structures of the [Fe2(L)3](BF4)4 cylinders were confirmed using X-ray crystallography. Both the [Fe2(L1)3](BF4)4 and [Fe2(L2)3](BF4)4 complexes crystallized as racemic (rac) mixtures of the ΔΔ (P) and ΛΛ (M) helicates. However, 1H NMR spectra showed that in solution the larger [Fe2(L2)3](BF4)4 was a mixture of the rac-ΔΔ/ΛΛ and meso-ΔΛ isomers. The host-guest chemistry of the helicates, which both feature a central cavity, was examined with several small drug molecules. However, none of the potential guests were found to bind within the helicates. In vitro cytotoxicity assays demonstrated that both helicates were active against four cancer cell lines. The smaller [Fe2(L1)3](BF4)4 system displayed low μM activity against the HCT116 (IC50 = 7.1 ± 0.5 μM) and NCI-H460 (IC50 = 4.9 ± 0.4 μM) cancer cells. While the antiproliferative effects against all the cell lines examined were less than the well-known anticancer drug cisplatin, their modes of action would be expected to be very different.

Multimetallic complexes have been shown in several examples to possess greater anticancer activity than their monometallic counterparts. The increased activity has been attributed to altered modes of action. We herein report the synthesis of a series of heterodimetallic compounds based on a ditopic ligand featuring 2-pyridylimine chelating motifs and organometallic half-sandwich moieties. The complexes were characterized by a combination of 1H NMR spectroscopy, electrospray ionization mass spectrometry, elemental analysis and single crystal X-ray diffraction. Investigations into the stability of representative complexes in DMSO-d 6 and 10% DMSO-d 6 /D2O revealed the occurrence of solvent-chlorido ligand exchange. Proliferation assays in four human cancer cell lines showed that the Os-Rh complex possessed minimal activity, while all other complexes were inactive.

Hypoxia-inducible factor prolyl hydroxylase domain 2 (PHD2) is an important oxygen sensor in animals. By using the CO-releasing molecule-2 (CORM-2) as an in situ CO donor, we demonstrate that CO is an inhibitor of PHD2. This report provides further evidence about the emerging role of CO in oxygen sensing and homeostasis.

The bidentate N-(1-Alkylpyridin-4(1H)-ylidene)amide (PYA) pro-ligands [H2LBn][Cl]2 (2), and [H2LMe][TfO]2 (3) were prepared by simple alkylation reactions of the known compound, N,N-di(pyridin-4-yl)oxalamide (H2L, 1). The Pd(II) complexes, [Pd(LBn)2][Cl]2 (4), [Pd(LMe)2][Cl][TfO] (5), Pd(LBn)Cl2 (6) and Pd(LMe)Cl2 (7) were synthesized through reactions between these pro-ligands and suitable Pd(II) substrates in the presence of base. The molecular structures of 3 and 6 were obtained by single crystal X-ray structure determinations. Studies of the experimental and computational DNA binding interactions of the compounds 1-7 revealed that overall 4 and 6 have the largest values for the binding parameters Kb and Delta Gbo. The results showed a good correlation with the steric and electronic parameters obtained by quantitative structure activity relationship (QSAR) studies. In-vitro cytotoxicity studies against four different cell lines showed that the human breast cancer cell lines MCF-7, T47D and cervical cancer cell line HeLa had either higher or similar sensitivities towards 4, 6 and 2, respectively, compared to cisplatin. In general, the cytotoxicity of the compounds, represented by IC50 values, decreased in the order 4 > 6 > 2 > 5 > 3 > 1 > 7 in cancer cell lines. Apoptosis contributed significantly to the cytotoxic effects of these anticancer agents as evaluated by apoptosis studies.

In some instances, multimetallic complexes have shown higher anticancer activity than mononuclear analogues, possibly by interacting with target molecules through a different binding mode. Therefore, a series of novel bis-pyridylimine-based homodinuclear M-II/III(cym/Cp*)Cl (cym = eta(6)-p-cymene: M = Ru, Os; Cp* = eta(5)-pentamethylcyclopentadienyl: M = Rh, Ir) complexes were synthesized and studied. The dinuclear complexes were characterized by H-1, C-13{H-1}, and P-31{H-1} NMR spectroscopy, ESI-MS, and elemental analysis. Additionally, the molecular structures of several complexes were investigated by single crystal X-ray diffraction analysis. [{N,N'-(1,4-Phenylene)(bis(1-(pyridin-2-yl)(methanimine)-kappa N-2,N'))}bis{chlorido(eta(6)-p-cymene)ruthenium(II)}] hexafluorophosphate, 1a, was used in stability and binding studies to 9-ethylguanine (EtG) as a DNA nucleobase model and L-histidine (His), L-cysteine (Cys) and L-methionine (Met) as protein models. However, compared to structurally related Ru(arene) complexes, the investigations were inconclusive in terms of the nature of hydrolysis product(s) and EtG adducts formed, while reactions to His and Cys but not Met were observed for 1a. The in vitro cytotoxicity of the ligands and dinuclear complexes was determined against a small panel of human cancer cell lines. Some of the complexes showed moderate antiproliferative activity but were less potent than the bis-pyridylimine-based bridging ligands.