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Interfacial ion transfer from organic phase to aqueous phase is employed as the basis for formation of barium sulfate crystals close to the interface.

Driven by an interest in the impact of the para-substituent of calix[4]arenes on metal complexation and structural chemistry, studies of p-cyclohexylcalix[4]arene (L) have been carried out. The 1:1 dichloromethane and dimethylformamide solvates were found to be isostructural, and different to the typical bilayer structure often observed for p-t-butylcalix[4]arene solvates. The methanol solvate, in contrast, does form a bilayered structure but is also a 1:1 solvate, unlike the p-t-butylcalix[4]arene·2MeOH system. Lanthanoid complexation was investigated, resulting in the structural characterisation of two different DMF solvates of a 2:2 dimeric europium complex, Eu2(L–3H)2(DMF)4. A tetrazole derivative, 5,11,17,23-tetracyclohexyl-25,27-dihydroxy-26,28-bis(tetrazole-5-ylmethoxy)calix[4]arene, has been synthesised via the intermediate 5,11,17,23-tetracyclohexyl-25,27-dihydroxy-26,28-dicyanomethoxycalix[4]arene, with the latter compound being structurally characterised. Attempts to isolate lanthanoid clusters supported by the tetrazole derivative under conditions known to form Ln19 clusters with the p-t-butyl analogue were unsuccessful, resulting only in isolation of the ligand from the reaction mixture.

Leaving a mixture of excess N,N,N′,N′-tetramethyl-1,4-butanediamine (Me4BDA) with p-t-butylcalix[8]arene (L) and [(UO2)(dmso)5](ClO4)2 in a 1:2 ratio in acetonitrile solution to stand for an extended period resulted in the deposition of a mixture of three different crystalline materials. Single crystal X-ray structural studies were carried out to determine that the three materials were the solvated uncomplexed macrocycle L.1.5MeCN, and two uranyl complexes. These were formulated as (Me4BDAH2)2+[(HO)(UO2)2(L-5H)]2–·9MeCN·H2O and (Me4BDAH2)2+[HO(UO2)2{L-5H)]2–·(Me3BDAH)+[H2O(UO2)2(L-5H)]−·Me4BDA·14MeCN·H2O·CH3OH respectively. In contrast to analogous systems based on 1,2-ethanediamine and 1,3-propanediamine derivatives, extension of the chain length separating the N-centres to (CH2)4 in the present systems has resulted in the formation of polymeric chains where the calixuranate anions are linked by H-bond acceptance from diammonium units. These links are still not completely direct and pass in part through solvent bridges. Direct double interactions do occur in the inverse situation where the calixarene acts as an H-bond donor to neutral 1,4-butanediamine species but lead only to dimerisation.

The synthesis of the Rh(I)-aryl complex, Rh(I)(nbd)(BiPh)(P(4-FC

Enhanced near-infrared (NIR) luminescence from two structurally related heterobinuclear NaYb eight-cooridnate and heterobinuclear YbNa eight-coordinate (CN = 8) complexes is reported and compared to a nine-coordinate (CN = 9) homoleptic complex. For the heteroleptic complex, [Yb(MPQ)(acac)], the Yb cation is coordinated to two tridentate 2-(5-methylpyridin-2-yl)-8-quinolinate (MPQ) anions, with a bidentate acetylacetonate (acac) anion completing the coordination sphere. Instead, the heterobinuclear [NaYb(MPQ)] complex comprises a total of four anionic MPQ ligands, two of which exhibit κ-coordination to the Yb cation. The remaining two MPQ anions are unidentate toward the lanthanide and form μ-bridges via the deprotonated quinolinate oxygens to a bound Na cation which is also coordinated to the remaining nitrogen donor atoms. The structural properties of these complexes were evaluated by single-crystal X-ray diffraction (SXRD), continuous shape measure (CShM) analysis, and H NMR spectroscopy using a diamagnetic Lu analogue. The corresponding photophysical properties were examined in CHCl solution by using absorption and emission spectroscopy. For both the complexes, characteristic Yb emission is observed at ca. 980 nm, with recorded photoluminescence quantum yields (Φ) and NIR luminescence lifetimes (τ) of 2.0% and 14.0 μs vs 1.5% and 11.6 μs for the [NaYb(MPQ)] and [Yb(MPQ)(acac)] complexes, respectively. Interestingly, the eight-coordinate Yb complexes both have higher photoluminescence quantum yields when compared to the homoleptic [Yb(MPQ)] complex, which has a reported quantum yield of 1.0% and a NIR lifetime determined herein of 13.3 μs under identical conditions. These results have been rationalized by considering the overall efficiency of the ligand-centered sensitization process (η = Φ × Φ), together with subsequent radiative () and nonradiative () deactivation of the Yb cation. Moreover, the efficiency of the intersystem crossing (Φ) and electronic energy transfer (Φ) processes involved in the antennae effect have been quantified for the new complexes using a combination of nanosecond and femtosecond transient absorption techniques and have been compared to our previous results using [Ln(MPQ)] complexes with Ln = Yb and Lu.

Human Papillomavirus (HPV) is the leading cause of cervical cancer, with only some HPV types prevented with vaccines and no treatments for the viral infection itself. One way to target viral infect...

Trinuclear lanthanoid clusters have been synthesised and investigated as toroidal spin systems. A pyridyl functionalised β-diketonate, 1,3-bis(pyridin-2-yl)propane-1,3-dione (o-dppdH) has been used to synthesise a family of clusters of the form [Dy3(OH)2(o-dppd)3Cl2(H2O)4]Cl2·7H2O (1), [Tb3(o-dppd)3(μ3-OH)2(CH3CH2OH)3Cl3][Tb3(o-dppd)3(μ3-OH)2(H2O)(CH3CH2OH)2Cl3]Cl2·H2O (2), [Ho3(OH)2(o-dppd)3Cl(H2O)5]Cl3·3H2O (3) and [Er3(OH)2(o-dppd)3Cl2(H2O)3(CH3OH)]Cl2·3H2O·CH3OH (4). Despite the previous occurrence of this structural motif in the literature, these systems have not been widely investigated in terms of torodic behaviour. Magnetic studies were used to further characterise the complexes. DC susceptibility studies support weak antiferromagnetic exchange in the complexes. Slow magnetic relaxation behaviour is observed in the dynamic AC magnetic studies for complex 1. Theoretical studies predict that complex 1 and 3 have a non-magnetic ground state based on a toroidal arrangement of spins. Changes to the coordination environment in 2 do not support a toroic spin state. The prolate nature of the ErIII centres in complex 4 and large transverse anisotropy do not support the toroidal arrangement of lanthanoid spins in the complex.

The synthesis of the Rh(I)-aryl complex, Rh(I)(nbd)(BiPh)(P(4-FC6H4)3) is reported and its efficacy as an initiator for the (co)polymerization of phenylacetylenes established. The X-ray crystal str...

While tetrazole derivatives are well established as anionic ligands for d-block elements, there is a growing interest in lanthanoid complexes of these compounds. Diverse structural chemistry results from the presence of four potential donor N atoms, and the conjugated nature of the heterocycle can impact on the photophysical properties of the complexes. This review examines the range of structurally characterised lanthanoid–tetrazolato complexes, focussing on the structural features of the ligand that impact on the tendency to interact with the first or second coordination spheres.

The synthesis and characterization of an amide-functionalized axially chiral resorcinarene, 14,36,56,76-tetra-2-oxo-2-(2-hydroxyethylamino)ethoxy-16,34,54,74-tetramethoxy-2,4,6,8- tetrapropylresorcin[4]arene, is reported. Metal complexation with picrate salts gave crystalline products that could be structurally characterised for calcium, lanthanum, praseodymium, and ytterbium. While the details of these structures vary, the metal–ligand interactions are remarkably consistent, with coordination polymers formed through interaction between three of the amide O atoms, each binding to a different metal atom. No other potential donor atom of the macrocycle is bound to the metal atoms, with the coordination spheres completed by solvent or picrate donor O atoms.

The synthesis, characterization, photophysical and photocatalytic studies of anionic platinum(II) tetrazolato complexes, with the general structure [TBA][Pt(CNC)TzR], are reported, where CNC2- represents a doubly cyclometalated 2,4,6-triphenylpyridine, TzR- is an anionic 5-substituted tetrazolato ligand (with a variable R functional group), and TBA+ is the tetrabutylammonium countercation. The complexes were prepared by substitution of the DMSO ligand in [Pt(CNC)(DMSO)] with the corresponding tetrazolato ligand. No emission from the platinum(II) complexes was detected at room temperature in solution, but the photophysical properties could be assessed in the solid state, where all the complexes display emission bands attributed to aggregates. The platinum(II) complexes were found to facilitate a range of fundamental classes of visible-light-mediated photoredox-catalyzed reactions, including α-amino C-H functionalization processes, such as Povarov-type reactions and the addition of α-amino C-H bonds across Michael acceptors, in addition to ATRA chemistry, and a hydrodeiodination. With the exception of the hydrodeiodination process, the best Pt(II) catalysts provided turnover numbers of 150-175 in each of these transformations.

Macrocyclic compounds such as DOTP (1,4,7,10-tetraazacyclododecanetetrakis(methylenephosphonic acid)) and NOTP (1,4,7,-triazacyclononanetri(methylenephosphonic acid)) are found to inhibit precipitation of barium sulfate just as potently as their non-cyclic counterparts depending on the ionisation state of the molecule. Morphologically, DOTP has a more significant influence on the shape of barium sulfate particles formed than NOTP while turbidity results show that NOTP does not significantly affect the induction time observed, unlike DOTP, which does impact the induction time at higher concentrations. Overall, the inhibition of these macrocyclic compounds can be explained by the number of de-protonated phosphonate groups and is not significantly impacted by the presence of the ring. The presence of calcium ions during barium sulfate crystallization lowers the degree of inhibition for both NOTP and DOTP. Molecular modelling showed that an uncomplexed DOTP molecule could lattice match to the barium sulfate lattice but had fewer Ba⋯Ophos interactions than the equivalent non-macrocyclic molecule. The comparison of uncomplexed with complexed DOTP shows that the final configuration is similar for these two situations, thus in this case it is not the Ba⋯Ophos interactions but the overall replacement energy that is important.

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. Here, organometallic molecular probes have been developed and assessed for bacterial imaging, designed to have the potential to support multiple imaging modalities. The chemical structure of the probes is designed around a metal-naphthalimide structure. The 4-amino-1,8-naphthalimide moiety, covalently appended through a pyridine ancillary ligand, acts as a luminescent probe for super-resolution microscopy. On the other hand, the metal centre, rhenium(I) or platinum(II) in the current study, enables techniques such as nanoSIMS. While the rhenium(I) complex was not sufficiently stable to be used as probe, the platinum(II) analogue showed good chemical and biological stability. Structured illumination microscopy (SIM) imaging on live Bacillus cereus confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis was used to monitor the uptake of the platinum(II) complex within the bacteria and demonstrate the potential of this chemical architecture to enable multimodal imaging. The successful combination of these two moieties introduces a platform that could lead to a versatile range of multi-functional probes for bacteria.

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. A platinum(II)-naphthalimide molecule has been developed as a small molecule probe for bacterial imaging, designed to have the potential for correlative imaging. The naphthalimide moiety acts as a luminescent probe for super-resolution microscopy, functioning independently of the platinum(II) centre which enabled visualisation of the complex with ion nanoscopy. Structured illumination microscopy (SIM) imaging on live Bacillus cereus confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the multimodal action of the probe. The successful combination of these two probe moieties introduces a platform that could lead to a versatile range of correlative probes for bacteria.

In this manuscript we investigate the impact of oxalate ions on the crystallization of barium sulfate. The organic anion, oxalate, was found to inhibit both nucleation and growth according to atomic force microscopy measurements and dynamic light scattering data. Raman confocal imaging was used to try and determine how the oxalate interacts with the barium sulfate surface. It was found that barium oxalate is only seen at very high oxalate concentrations. At lower concentrations no direct evidence for the presence of oxalate was observed, however, the most probable mode of action for oxalate is via adsorption onto the barium sulfate surface including into key kink or step sites, impacting growth.

An aspartic acid functionalised azobenzene derivative is found to be a light-switchable crystal growth modifier of calcite. UV irradiation of the molecule reversibly switches it to the cis isomer, which is a significantly less effective crystal growth inhibitor than the trans isomer. Visible light, or heat switches the inhibitor back “on”. Extended irradiation degrades the inhibitor such that it is irreversibly switched “off”. It was shown that the trans isomer is preferentially absorbed on to the crystal surface, which is consistent with its greater efficacy as an inhibitor.

A new tool has been developed to help elucidate the differences in packing between different polymorphs, especially when the differences of interest are small. The technique builds upon the Hirshfeld fingerprint plot pioneered by Spackman and co-workers by subtracting the value at every point in a fingerprint plot from the value at every point in another. This is found to reveal differences that are not readily apparent to the eye. By summing the absolute values of these differences, a quantitative measure of the difference between two fingerprint plots can be obtained. The technique was applied to Ni and Cu trans-bis(2-hydroxy-5-methylphenonethanoneoximato) complexes determined at two temperatures, with the Ni complex displaying temperature-dependent polymorphism. Difference Hirshfeld fingerprint plots were also generated for calculated structures from DFT simulations that were performed on the experimental structures. These demonstrated that the simulations reproduced the fine detail of the packing.

The synthesis of a novel Rh(I)-aryl complex is detailed and its ability to serve as an initiator in the stereospecific polymerisation of phenylacetylene evaluated. Targeting the Rh(I) species, (2-phenylnaphthalen-1-yl)rhodium(I)(2,5-norbornadiene)tris(para-fluorophenylphosphine), Rh(nbd)(P(4-FC6H4)3)(2-PhNapth), following recrystallization we obtained the isomeric (2-(naphthalen-2-yl)phenyl)rhodium(I) complex, Rh(nbd)(P(4-FC6H4)3)(2-NapthPh), as determined by X-ray single-crystal structure analysis, and confirmed by X-ray powder diffraction. The isolation of the latter species was proposed to occur from the target (2-PhNapth) derivative via an intramolecular 1,4-Rh atom migration. This supposition was supported by density functional theory (DFT) calculations that indicated the isolated (2-NapthPh) derivative has lower energy (−19 kJ mol−1) than the targeted complex. The structure of the isolated (2-NapthPh) species was confirmed by multinuclear NMR spectroscopy including 2D 31P–103Rh{1H, 103Rh}, heteronuclear multiple-quantum correlation (HMQC) experiments; however, NMR analysis indicated the presence of a second, minor species in solution in an approximate 1 : 4 ratio with the 2-NapthPh complex. The minor species was identified as a second structural isomer, the 3-phenylnaphthyl derivative, proposed to be formed under a dynamic equilibrium with the 2-NapthPh derivative via a second 1,4-Rh atom migration. DFT calculations indicate that this 1,4-migration proceeds through a low-energy pathway involved in the oxidative addition of a C–H bond to Rh followed by a reductive elimination with the distribution of the products being thermodynamically controlled. The recrystallized Rh(nbd)(P(4-FC6H4)3)(2-NapthPh) complex was subsequently evaluated as an initiator in the polymerisation of phenylacetylene (PA); gratifyingly, the Rh(I) species was an active initiating species with the pseudo-first-order kinetic and molecular weight evolution vs time plots both linear implying a controlled polymerisation while yielding (co)polymers with low dispersities (Đ = Mw/Mn typically ≤1.25) and high cis-transoidal stereoregularity (>95%). Typical initiation efficiencies, while not quantitative (as judged by size exclusion chromatography), were nonetheless high at ca. 0.8. The presence of the minor 3-phenylnaphthyl species when in solution is proposed to be the cause of the observed non-quantitative initiation.

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. This is especially so for correlative probes, which are proving to be powerful tools for enhancing the imaging of live cells. In this work a platinum(II)-naphthalimide molecule has been developed to extend small molecule correlative probes to bacterial imaging. The probe was designed to exploit the naphthalimide moiety as a luminescent probe for super-resolution microscopy, with the platinum(II) centre enabling visualisation of the complex with ion nanoscopy. Photophysical characterisation and theoretical studies confirmed that the emission properties of the naphthalimide are not altered by the platinum(II) centre. Structured illumination microscopy (SIM) imaging on live Bacillus cereusrevealed that the platinum(II) centre does not change the sub-cellular localisation of the naphthalimide, and confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis of the sample was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the correlative action of the probe. The successful combination of these two probe moieties with no perturbation of their individual detection introduces a platform for a versatile range of new correlative probes for bacteria.

A family of three neutral iridium(III) tetrazolato complexes are investigated as bacterial imaging agents. The complexes offer a facile tuning of the emission colour from green (520 nm) to red (600 nm) in aqueous media, while keeping the excitation wavelength unchanged. The three complexes do not inhibit the bacterial growth of Bacillus Cereus, used as a model in this study, and exhibit extremely fast cellular uptake. After a minute incubation time, the nontoxic complexes show subcellular localisation in spherical structures identified as lipid vacuoles. Confocal Raman imaging has been exploited for the first time on live bacteria, to provide direct and label-free mapping of the lipid-enriched organelles within B. cereus, complementing the use of luminescent probes. Examination of the Raman spectra not only confirmed the presence of lipophilic inclusions in B. cereus but offered additional information about their chemical composition, suggesting that the lipid vacuoles may contain polyhydroxybutyrate (PHB).

Although current human papillomavirus (HPV) vaccines can protect well against infection, they are effective only for a limited number of subtypes. Coupled with the dilemma that no efficient prescription is currently clinically available for therapy, there is an urgent need to develop new anti-HPV agents. In the present study l- and d-Proline modified calix[4]arenes (Pro-C4 A) were investigated to determine any differences in their effect on the assembly of HPV 16 L1 pentamer (L1-p). The mechanism of action using model peptides was investigated by Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) and Nuclear Magnetic Resonance (NMR) and revealed that the binding was targeting the basic residues at L1 interface. This was also well supported by the trypsin digestion experiments and molecular simulations performed on the full-length L1. The large energy and morphology differences revealed by molecular simulations explain the binding disparity of l- and d-Pro-C4 A to L1, and consequently the selective inhibition of them on L1-p formation. The present study opens a way to develop enantioselective and cost-effective inhibitors for L1-p formation, which might be used as a new kind of anti-HPV agent and could be extended to other viruses based on similar mechanisms.

The synthesis and characterization of 5,11,17,23-tetra-tert-butyl-25-hydroxy-26,27,28-tris(tetrazol-5-ylmethoxy)calix[4]arene is reported. Purification of the macrocycle required the use of preparative HPLC techniques. The macrocycle was found to be a poorer ligand for complexation of lanthanoid cations than the bis(tetrazole) analogue, but somewhat more effective than the tetrakis(tetrazole)-substituted derivative. Two metal complexes of the tris(tetrazole)–calixarene were structurally characterised. A polymeric sodium salt of the tris(tetrazole)–calixarene was isolated from a solution containing yttrium and a sodium acetate buffer. A praseodymium complex was isolated in the presence of an ammonium acetate buffer, where the calixarene acts as a unidentate ligand, bound to the metal atom through one tetrazole N-atom. Increasing the amount of buffer resulted in the crystallisation of a metal-free ammonium salt of the calixarene.

Lanthanoid complexes of a tetra-amide substituted calix[4]arene in the cone conformation are characterised by single crystal X-ray structure determination. The structural analysis shows that the metal ions are coordinated to the calixarene through the eight O donor atoms, along with one aqua ligand which is located within the cavity of the calixarene. The calixarene ligand was covalently incorporated into a polymethylmethacrylate monolith through p-allyl functional groups, followed by loading with a range of lanthanoid cations giving rise to light-emitting materials. The emission from the hydrid materials was found to be comparable to the solution phase emission.

The syntheses and single crystal X-ray structure determinations of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(cyanomethoxy)calix[4]arene (partial-cone conformer), 5,11,17,23-tetra-tert-butyl-25,27-bis(diethylcarbamoylmethoxy)-26,28-bis(cyanomethoxy)calix[4]arene (cone and partial-cone conformers), 5,11,17,23-tetra-tert-butyl-25,26,27-tris(cyanomethoxy)-28-hydroxycalix[4]arene, and 5,11,17,23-tetra-tert-butyl-25-diethylcarbamoylmethoxy-26,27,28-tris(cyanomethoxy)calix[4]arene (cone conformer) are reported. The calixarenes are found to be conformationally mobile when heated in DMSO, favouring the partial-cone conformer at equilibrium. The tris-substituted cyanomethoxy derivative was found to assume the partial-cone conformation in the solid state. Attempts to convert nitrile groups to tetrazole moieties in derivatives containing both amide and nitrile groups were unsuccessful.

Dinuclear silver, di- and tetra-nuclear gold, and mononuclear palladium complexes with chelating C,N,C diethylaminotriazinyl-bridged bis(NHC) pincer ligands were prepared and characterised. The silver and gold complexes exist in a twisted, helical conformation in both the solution- and the solid state. In contrast, an analogous dinuclear gold complex with pyridyl-bridged NHCs exists in a linear conformation. Computational studies have been performed to rationalise the formation of twisted/helical vs. linear forms.

Lanthanoid picrate (pic) complexes of 5,11,17,23-tetra-tert-butyl-25-hydroxy-26,27,28-tris(diethylcarbamoylmethoxy)calix[4]arene (LH) have been synthesised and structurally characterised, to complete this series for all lanthanoids (other than promethium). From cerium to lutetium, three structural types are observed: Type I, [Ln(L)(O,O′-pic)](pic), Ln=Ce–Dy; Type II, [Ln(L)(O-pic)](pic), Ln=Tb, Ho; Type III, [Ln(L)(HOEt)](pic)2, Ln=Er–Lu. With lanthanum, three different ten-coordinate complexes were characterised; [Ln(L)(O,O′-pic)(HOEt)](pic), [Ln(L)(O,O′-pic)(OH2)](pic), and [Ln(L)(O,O′-pic)(HOMe)](pic). The crystallisation of Type I and II observed for terbium shows that the stability of the different structures are sensitively poised at the transition points. Nevertheless, the structures show that the vacant space in the coordination sphere left by the trisamide L tends to reduce across the series as expected. It is occupied by a bidentate picrate anion and unidentate solvent molecule with lanthanum, a bidentate picrate anion for cerium to dysprosium (Type I), a unidentate picrate anion for terbium and holmium (Type II), and finally a unidentate solvent molecule from erbium to lutetium (Type III). The coordination number thus reduces from 10 to 8 across the series.

Multinuclear metal complexes have shown a unique capacity to provide interesting magnetic, chemical and electronic properties by virtue of the remarkably diverse range of structural types that they exhibit. Calix[n]arenes are now a mature synthetic platfom that provide for a diverse spatial arrangement of binding groups, making them highly suitable to use for the formation of multinuclear metal ion complexes. Increasing interest has been shown in the development and properties of magnetic materials based on calixarene macrocycles. Here, we review the magnetic properties of calixarene-supported metal clusters with emphasis on those examples exhibiting slow magnetic relaxation.

This research was partially supportedby the Australian Research Council's Discovery Projects funding scheme (project DP17010189), and a Royal Society International Exchanges Grant. EZ-C thanks EPSRC (EP/M02105X/1) for support. L.A.G thanks Curtin University for the postgraduate scholarship. β-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four β-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by in situ retro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensation reaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest that using solvents of lower polarity will mimimise the impact of the retro-Claisen condensation in these complexes. Postprint

β-Triketonates have been recently used as chelating ligands for lanthanoid ions presenting unique structures varying from assemblies to polymers. Despite their novel complexation behaviour little is known about the stability of these molecules. Indeed, two examples of possible in situretro-Claisen condensation reactions have been reported previously. To better understand this possible decomposition pathway, four new β-triketones were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media, aiming to isolate the potentially varying ligands present in solution. The X-ray diffraction studies revealed the formation of structures where one, two, or three of the molecules involved in the retro-Claisen condensation reaction were linked to the lanthanoid centres.

An isomorphous series of lanthanoid complexes containing tribenzoylmethanide (tbm) and 1,10-phenanthroline (phen) ligands has been synthesised and structurally characterised. These complexes, formulated as [Ln(phen)(tbm)3] (Ln = Eu3+, Er3+ and Yb3+), were compared with analogous dibenzoylmethanide (dbm) [Ln(phen)(dbm)3] complexes to investigate the effect of changing β-diketonate to β-triketonate ligands on the photophysical properties of the complex. The photophysical properties for the Eu3+ complexes were similar for both systems, whereas a modest enhancement was observed for Yb3+ and Er3+ moving from the dbm to the tbm complexes. A detailed study of the NIR photophysical properties was achieved by adapting the integrating sphere method for the calculation of overall quantum yields in the solid state.

Isomorphousβ-triketonate-based lanthanoid polymers containing tris(4-methylbenzoyl)methanide (mtbm) and Rb+with formula,{[Ln(Rb)(mtbm)4]2}n (Ln = Eu3+ and Nd3+) have been synthesised and structurally characterised. The photophysical properties for the Nd3+complex presented long lifetimes and relatively high quantum yields in comparison with analogous β-diketonate complexes. Mixed lanthanoid complexes were also formed and their luminescence properties studied, with effective sensitisation of the 4F3/2 of Nd3+ via the 5D0 of Eu3+, which is to the best of our knowledge the first example of Eu3+to Nd3+sensitisation in a coordination complex or polymer.

The synthesis of a C 4 dissymmetric resorcinarene tetracarboxylic acid derivative and determination of its critical micelle concentration is reported. The tetrahydroxy derivative was prepared by reduction of the tetra-acid. The low-temperature single crystal X-ray structure of the methyl ester derivative of the tetra-acid is also reported. This crystallised with two independent molecules of similar boat (flattened cone) conformation within the asymmetric unit.

The synthesis and structural characterization of a lanthanum picrate complex of the proximally-substituted calix[4]arene bisamide, 5,11,17,23-tetra-tert-butyl-25,26-bis(diethylcarbamoylmethoxy)-27,28-dihydroxycalix[4]arene (L), is reported. The complex is formulated as [La(L-H)(picrate)2]·2.75CH2Cl2 and crystallises with two inequivalent metal complexes in the unit cell. The differing dispositions of the picrate anions in the two complexes suggest that intramolecular interactions between the aromatic rings of the picrate and calixarene are less significant than the forces involved in the crystal packing of the complexes.

Despite the long term interest in hydroxyoximes as metal ion extractants, there is a lack of information on the possible coordination modes these ligands can assume, particularly in concert with a co-ligand. This is pertinent to the use of these extractants in synergistic systems, where a combination of extractants can achieve commercially useful results. We report here the structures of some metal complexes (M = Mn, Co, Ni, Cu, and Zn) with (1-hydroxycyclohexyl)-phenyl ketone oxime. The results demonstrate that this ligand can support complexes ranging from mononuclear to trinuclear, in association with anionic and neutral co-ligands in some cases. While these results have been obtained in the solid state, they illustrate a range of possible species that may be formed in extractant solutions.

The assembly and disassembly of supramolecular gel fibres are observed in situ using variable temperature scanning probe microscopy. The results show that fibre formation can be monitored at high resolution at a surface, and the final fibre morphologies are broadly consistent with those found by ex situ analysis of the bulk gel. The impact of a gelation inhibitor upon the fibre morphology is successfully investigated, providing direct evidence for the mechanism of inhibition as a function of additive concentration.

The thermal annealing behaviour of an electrolyte-triggered calixarene hydrogelator is found to depend strongly on the specific metal chloride used. While the lithium chloride gel showed typical gel–sol transitions as a function of temperature, the magnesium chloride gel was found to repeatedly strengthen with heat–cool cycles. Structural investigations using small-angle neutron scattering, and scanning probe microscopy, suggest that the annealing behaviour is associated with a change in morphology of the fibrous structures supporting the gel. On prolonged standing at room temperature, the magnesium chloride gel underwent a gel–crystal transition, with the collapsing gel accompanied by the deposition of crystals of a magnesium complex of the proline-functionalised calix[4]arene gelator.

α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (0 1 0) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (0 1 0) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (0 1 0) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the ( c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.

As a prospective commercial solvent extraction (SX) process, laboratory-scale continuous tests were recently undertaken to assess the use of a solution of LIX 63 hydroxyoxime (“hydroxyoxime”) and Versatic 10 to kinetically separate cobalt from a nickel-rich sulfate solution while simultaneously rejecting manganese and magnesium. A material quantity of blue precipitate observed in the strip stage cells during decommissioning has been identified as the sulfate salt of the nickel-tris hydroxyoxime complex. As precipitation during SX is undesirable, the effect of various operating parameters on precipitate formation has been investigated. Minimizing aqueous nickel and/or sulfuric acid concentration and/or increasing organic polarity can overcome this problem. Where it forms, hydroxyoxime and nickel can be recovered from the precipitate by redissolution under suitable (e.g., low acid) operating conditions. The nitrate salt counterpart of this sulfate precipitate has been crystallographically characterized using a short chained (C₈) analogue of LIX 63 hydroxyoxime, revealing the coordination of three neutral hydroxyoxime ligands around nickel, forming a monomeric coordination complex cation counterbalanced by nitrate anions.

Calix[4]arenes functionalised at the upper rim with acidic amino acid residues are found to have a significant impact on the crystal growth of model mineral systems, calcium carbonate and barium sulphate. The aspartic acid derivative is found to be most efficacious, matching or exceeding the impact of commercial phosphonate-based scale inhibitors. In some cases, the modified morphologies are found to be similar to those induced by proteins isolated from biomineralised systems.

Dipositive cation substitution in sulfate minerals has been a topic of investigation both experimentally and computationally. Here the possibility of tripositive cation substitution with accompanying vacancy formation is considered, specifically lanthanum ion substitution in barium sulfate. Experimentally, the lanthanum ions impact “bulk” crystallization in a way that is best explained by considering the solution phase ion-pair interactions. However, morphological results suggest that lanthanum ions do more than impact the free sulfate levels. Atomic force microscopy results showed that both lanthanum and calcium ions are strong inhibitors of barite growth. X-ray diffraction on bulk samples showed that lanthanum ions do indeed incorporate, as determined by lattice parameter changes. Finally, computational modeling suggests that while calcium incorporation is more energetically favorable, lanthanum ions prefer to substitute on the surface more so than calcium ions.

Calixarenes can be used as well-defined scaffolds for investigating structure–activity relationships of additives and their impact on crystallization. In this work, we present the crystal growth modification of barium sulfate by p-phosphonic acid calix[n]arenes that vary in size (n = 4, 5, 6, and 8) and thus vary in the size of the internal cavity for the same functionality in the upper rim. The tetrameric, hexameric, and octameric macrocycles induce nanoparticle formation with clear superstructure. In the case of the hexameric calix[6]arene, the initial mesocrystalline superstructure fuses over time to form almost hollow spheres, while the mesocrystals formed in the presence of the tetramer and octamer are stable over an extended period. The pentameric calix[5]arene forms more disordered aggregates of single crystals. Thermogravimetric data shows that a significant proportion of the mass of the barium sulfate-containing solid is the macrocycle, regardless of the choice of macrocycle.

E.Z.-C. acknowledges the University of St. Andrews and EPSRC (EP/M02105X/1) for financial support. We thank Umicore AG for the gift of materials. We thank the EPSRC UK National Mass Spectrometry Facility at Swansea University for analytical services. This work is supported by a Royal Society International Exchanges Grant and by the Australian Research Council and. LAG thanks Curtin University for the postgraduate scholarship. This work used the computational resources of the CCIPL installed in Nantes. Unconventionally modified dibenzoylmethane (dbm) ligands have been synthesized and successfully utilized as ancillary ligands for neutral Ir(III) complexes of the formula [Ir(dFppy)2(LX)], where dFppyH is 2-(2,4-difluorophenyl)pyridine and LX is tribenzoylmethane ( tbm ) or 1-phenyl-3-(4-(pyridin-2-yl)phenyl)propane-1,3-dione ( pydbm ). The modification of the ligands aims to prevent or enhance possible intermolecular interactions between the dFppy and/or the LX moiety in comparison with the previously reported [Ir(dFppy)2( dbm )] complex. The aggregation induced emission (AIE) properties of these complexes are significantly modulated, as a consequence of the different π-π interactions revealed by X-ray crystallography. Postprint

Eight new redox-active di- and tri-aza crown ether macrocyclic ligands containing multiple ferrocene and quinone moieties have been prepared, including the first reported mixed ferrocene-quinone macrocyclic ligand. Solution 1H and 13C NMR complexation studies suggest these ligands form 1:1 stoichiometric complexes with ammonium as guest cation. Single-crystal structures of the hydrogen hexafluorophosphate salt of 7,16-bis(ferrocenylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane and the ammonium complex of 4,10,16-tris(ferrocenylmethyl)-1,7,13-trioxa-4,10,16-triazacyclooctadecane have also been determined. Electrochemical investigations reveal the respective ferrocene-ferrocenium redox couples of most of the ligands are perturbed to more positive potentials on co-ordination of NH4+ and K+ guest cations. The above tris(ferrocenylmethyl) ligand selectively binds and electrochemically recognises NH4+ in the presence of equimolar concentrations of K+. Secondary amide-linked ferrocene aza crown ether ligands electrochemically sense the NH4+ guest cation primarily via host ferrocenecarboxide carbonyl oxygen-H-NH3+ hydrogen-bonding electrostatic interactions.

A new library of ionophoric p-tert-butylcalix[4]diquinones containing ester (1), primary, secondary, and tertiary amide (2-4), and crown ether (5) substituents has been synthesized by treatment of the respective 1,3-bis-substituted p-tert-butylcalix[4]arene with Tl(OCOCF(3))(3) in trifluoroacetic acid. The structures of the free ligands 1 and 2, a p-tert-butylcalix[4]diquinone bridged at the lower rim by two linked veratrole groups (7), and a previously synthesized p-tert-butylcalix[4]diquinone bis(methyl ether) species (8) have been elucidated by X-ray crystallography. The X-ray crystal structures of 1-Sr(ClO(4))(2), 1-KClO(4), 2-NaClO(4), 4-n-BuNH(3)BF(4), 5-NaOCOCF(3), and 5-KPF(6) demonstrate that these complexes adopt the cone conformation in the solid state. Interestingly, cation-quinone oxygen atom coordination occurs at both the upper and lower rim of 2-NaClO(4) and 4-n-BuNH(3)BF(4). Solution coordination properties have been studied by both (1)H NMR and UV/vis techniques. The electrochemical properties of the "acyclic" p-tert-butylcalixdiquinones 1, 4, and 8 and their complexes have been studied using cyclic and square wave voltammetric techniques. The reduction potentials of the group 1 or 2 metal, ammonium, and alkylammonium complexes are significantly anodically shifted with respect to that of the free ligand. Addition of cations to electrochemical solutions of a p-tert-butylcalixdiquinone-crown-5 compound (5) caused large anodic shifts (by up to 555 mV in the presence of Ba(2+)) in a manner similar to that of the acyclic species.