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The AgI ion is coordinated by two heterocyclic N atoms from two ligands in a linear configuration, forming a discrete coordination complex. There is an O—H⋯O hydrogen bond between 2-tza− and 2tzaH of adjacent complexes. The hydrogen atom is shared between the two oxygen atoms., The linear two-coordinate silver (I) complex [Ag(C4H2NO2S)(C4H3NO2S)] or [Ag(2-Htza)(2-tza)] is reported (2-Htza = 1,3-thia­zole-2-carb­oxy­lic acid). The AgI ion is coordinated by two heterocyclic N atoms from two ligands in a linear configuration, forming a discrete coordination complex. There is an O—H⋯O hydrogen bond between 2-tza− and 2tzaH of adjacent complexes. The hydrogen atom is shared between the two oxygen atoms. This inter­action produces a hydrogen-bonded tape parallel to the [110] direction, which is augmented through inter­molecular C—H⋯O hydrogen-bonding inter­actions between the bound thia­zole groups. There is a further rather long Ag⋯O inter­action [2.8401 (13) Å, compared with a mean of 2.54 (11) Å for 23 structures in the CSD] that assembles these tapes into columns, between which there are C—H⋯π inter­actions, leading to the formation of a three-dimensional supra­molecular architecture.

Homo-dinuclear Co and Zn complexes derived from the macrocycle LH2, {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][CH2CH2(2-C6H4N)2]}2 (R = Me, tBu), revealed near inactivity for the ring opening polymerization (ROP) of the cyclic esters δ-valerolactone (δ-VL) and ε-caprolactone (ε-CL). By contrast, the hetero-bimetallic complexes [LCo(NCMe)(μ-Br)ZnBr]·nMeCN (n = 3 or 3.25) were found to be efficient catalysts for the ROP of ε-CL and δ-VL.

The mono-oxo aryloxide complexes [M(O)(L1)2] (M = Mo (1·hexane), W(2·2MeCN)) have been prepared from [Mo(O)(Cl)4] or [W(O)(Ot-Bu)4] and two equivalents of the di-phenol 2,2'-ethylidenebis(4,6-di-tert-butylphenol) L1H2, respectively. Use of in situ generated [Mo(O)(Ot-Bu)4] with two equivalents of L1H2 also led to the isolation of 1·2MeCN. In the presence of adventitious oxygen, attempts to generate in situ [Mo(O)(Ot-Bu)4] and reaction with one equivalent of L1H2 afforded the bi-metallic complex [Mo(O)(L1)(μ-O)Li(THF)(MeCN)]2·2MeCN (3·2MeCN). Use of the tetra-phenol α,α,α',α'-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p-xyleneH4 (L2H4) with [Mo(O)(Oi-Pr)4] led to the isolation of {[Mo(O)]L2}2 (4), whilst the analogous tungsten complex {[W(O)]L2}2 (5) was isolated from the reaction of L2H4 with [W(O)(Ot-Bu)4]. Similar reaction of p-tert-butylcalix[4]areneH4 (L3H4) with [Mo(O)(Oi-Pr)4] afforded ([Mo(O)L3(NCMe)]·3MeCN (6). Modifications of known routes were employed to access complexes [W(Cl)2L3]·3.5MeCN (7·3.5MeCN) and [W(O)L3(NCMe)] (8), whilst use of [WO(Ot-Bu)4] with L3H4 unexpectedly afforded [W(Ot-Bu)2L3]·MeCN (9·MeCN). The molecular crystal structures for 1-9 are reported, and the ability of these complexes to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and ω-pentadecalactone (ω-PDL) has been investigated. The molybdenum complexes 1 and 4 were the best performers for ε-Cl and δ-VL, but all complexes exhibited poor control and were also inactive toward the ROP of PDL.

Ancient and recent terrestrial carbonate-precipitating systems are characterised by a heterogeneous array of deposits volumetrically dominated by calcite. In these environments, calcite precipitates display an extraordinary morphological diversity, from single crystal rhombohedral prisms, to blocky crystalline encrustations, or spherulitic to dendritic aggregates. Despite many decades of thorough descriptive and interpretative work on these fabrics, relating calcite micro-morphology with sedimentary hydrogeochemical conditions remains a challenge. Environmental interpretations have been hampered by the fact that calcite morphogenesis results from the complex interaction between different physico-chemical parameters which often act simultaneously (e.g., carbonate mineral supersaturation, Mg/Ca ratio of the parental fluid, organic and inorganic additives). To try to experimentally address the sedimentological causes of calcite morphogenesis, an experimental approach yielding a first attempt at a calcite growth-form phase diagram is presented here. The initial aim was to account for the carbonate products experimentally nucleated in alkaline, saline lake settings. These are the result of at least two competing calcite precipitation ‘driving forces’ that affect morphogenesis: the calcite supersaturation level of the parental fluid, and the concentration of microbial-derived organic molecules (alginic acid). A key finding of this study is that common naturally-occurring calcite products such as calcite floating rafts, rhombohedral prismatic forms, di-pyramid calcite crystals, spherulitic calcite grains, or vertically stacked spheroidal calcite aggregates, can be related to specific hydrogeochemical contexts, and their physical transitions pinpointed in a phase diagram. By exploring binary or ternary responses to forcing in morphological phase-space, links between calcite growth forms and (palaeo)environmental conditions can be determined. This provides a truly process-oriented means of navigating questions around carbonate precipitate morphogenesis for the future.

Manganese‐based contrast agents (MnCAs) have emerged as suitable alternatives to gadolinium‐based contrast agents (GdCAs). However, due to their kinetic lability and laborious synthetic procedures, only a few MnCAs have found clinical MRI application. In this work, we have employed a highly innovative single‐pot template synthetic strategy to develop a MnCA, MnLMe, and studied the most important physicochemical properties in vitro. MnLMe displays optimized r 1 relaxivities at both medium (20 and 64 MHz) and high magnetic fields (300 and 400 MHz) and an enhanced r 1 b=21.1 mM−1 s−1 (20 MHz, 298 K, pH 7.4) upon binding to BSA (K a=4.2×103 M−1). In vivo studies show that MnLMe is cleared intact into the bladder through renal excretion and has a prolonged blood half‐life compared to the commercial GdCA Magnevist. MnLMe shows great promise as a novel MRI contrast agent., We present a single‐pot template synthesis strategy for a manganese‐based MRI contrast agent, MnLMe. MnLMe is highly inert toward zinc‐transmetallation and displays enhanced T 1 relaxivity upon non‐covalent interaction with serum albumin. In vivo studies show higher contrast enhancement in the liver and longer blood half‐life than that of the commercially available contrast agent Magnevist. MnLMe shows great potential for use as a blood pool agent.

Interaction of [Sc(OR)3] (R = iPr or triflate) with p-tert-butylcalix[n]arenes, where n = 4, 6, or 8, affords a number of intriguing structural motifs, which are relatively non-toxic (cytotoxicity evaluated against cell lines HCT116 and HT-29) and a number were capable of the ring opening polymerization (ROP) of cyclohexene oxide.

The treatment of CuX2 (X = Cl, Br) with an equimolar amount of 2-2ʹ-diphenylglycine (DpgH) in EtOH at reflux afforded, after work up, the complexes [CuCl(Dpg)(EtOH)]2 (1) and [(CuBr2)2(Dpg)2Cu(EtOH)4] (2), respectively. The compounds were obtained microanalytically pure in low to moderate yield (13 and 27%, respectively) and were fully characterised. Synthetic attempts towards Cu-alkoxide species led to the isolation of the heterobimetallic species [(CuCl2)(Dpg)Li(THF)]·THF (3·THF). Finally, complex 4, bearing an imine ligand derived from the decarboxylation of DpgH, was serendipitously obtained from the synthesis of 3. These complexes were found to be inactive in the homo- and co-ring opening polymerization (ROP) of cyclic esters (e-caprolactone and rac-lactide) and epoxides (propylene oxide and cyclohexene oxide). Compounds 1 and 2 were shown to be non-toxic against cancerous cell lines HCT116 and HT-29.

Growth of the library of tetraaza macrocyclic pyridinophane ligands is a result of the potential to treat neurodegenerative diseases by binding unregulated redox active metal-ions, scavenging radicals, and reducing oxidative stress. As part of this work, the copper complex of (OH)PyN(3)Cu (3,6,9,15-tetraazabicyclo[9.3.1]penta-deca-1(15),11,13-trien-13-ol) was previously identified as a discrete molecule in the solid state when isolated at lower pH values. However, here we report that (OH)PyN(3)Cu forms a helical structure upon crystallization around pH 6.5. Several properties of the ligand and complex were evaluated to understand the driving forces that led to the concatenation and formation of this solid-state helix. DFT studies along with a comparison of keto/enol tautomerization stability and bond lengths were used to determine the keto-character of the C=O within each subunit. This pH dependent keto-enol tautomerization is responsible for the solid state intermolecular C=O···Cu bonds observed in this metallohelix (Cu1(H)) when produced around pH 6.5. Perchlorate templating that occurs through hydrogen bonding between perchlorate counter ions and each Cu1(H) unit is the primary driving factor for the twist that leads to the helix structure. Cu1(H) does not exhibit the typical factors that stabilize the formation of helices, such as intra-strand hydrogen bonding or π-stacking. The helix structure further highlights the diversity of inorganic metallohelices and demonstrates the importance of tautomerization and pH that occurs with the pyridinophane ligand used in this study. To our knowledge and although these phenomenon have been observed individually, this is the first example of a pH dependent keto-enol tautomerization in an azamacrocycle being the driving force for the formation of a metallohelix solid state structure and is a particularly unique observation for pyridinophane complexes.

Co‐crystallisation is widely explored as a route to improve the physical properties of pharmaceutical active ingredients, but little is known about the fundamental mechanisms of the process. Herein, we apply a hyphenated differential scanning calorimetry—X‐ray diffraction technique to mimic the commercial hot melt extrusion process, and explore the heat‐induced synthesis of a series of new co‐crystals containing isonicotinamide. These comprise a 1:1 co‐crystal with 4‐hydroxybenzoic acid, 2:1 and 1:2 systems with 4‐hydroxyphenylacetic acid and a 1:1 crystal with 3,4‐dihydroxyphenylactic acid. The formation of co‐crystals during heating is complex mechanistically. In addition to co‐crystallisation, conversions between polymorphs of the co‐former starting materials and co‐crystal products are also observed. A subsequent study exploring the use of inkjet printing and milling to generate co‐crystals revealed that the synthetic approach has a major effect on the co‐crystal species and polymorphs produced., Co‐crystallisation is widely explored as a route to improve the physical properties of pharmaceutical active ingredients, but little is known about the fundamental mechanisms of the process. In this study, X‐ray diffraction was used to provide an unprecedented insight into pharmaceutical co‐crystallisation processes (see figure).

Rigid and topologically constrained ethylene cross-bridged tetraazamacrocycles have been increasingly utilised for thirty years as they form remarkably stable transition metal complexes for catalysis, biomedical imaging, and inorganic drug molecule applications. Extending these benefits to pentaazamacrocycles has been achieved and a first transition metal complex prepared and structurally characterized.

Reaction of [ReOCl

Metallation of biomacromolecular species forms the basis for the anticancer activity of many metallodrugs. A major limitation of these compounds is that their reactivity is indiscriminate and can, in principle, occur in healthy tissue as well as cancerous tissue, potentially leading to side effects in vivo. Here we present pH-dependent intramolecular coordination of an arene-tethered sulfonamide functionality in organometallic ruthenium(II) ethylenediamine complexes as a route to controlling the coordination environment about the central metal atom. Through variation of the sulfonamide R group and the length of the tether linking it to the arene ligand the acidity of the sulfonamide NH group, and hence the pH-region over which regulation of metal coordination occurs, can be modulated. Intramolecular sulfonamide ligation controlled the reactivity of complex 4 within the physiologically relevant pH-region, rendering it more reactive towards 5ʹ-GMP in mildly acidic pH-conditions typical of tumour tissue compared to the mildly alkaline pH-conditions typical of healthy tissue. However, the activation of 4 by ring-opening of the chelate was found to be a slow process relative to the timescale of typical cell culture assays and members of this series of complexes were found not to be cytotoxic towards the HT-29 cell line. These complexes provide the basis for the development of analogues of increased potency where intramolecular sulfonamide ligation regulates reactivity and therefore cytotoxicity in a pH-dependent, and potentially, tissue-dependent manner.

Macrocyclic ligands have been explored extensively as scaffolds for transition metal catalysts for oxygen and hydrogen atom transfer reactions. C-C reactions facilitated using earth abundant metals bound to macrocyclic ligands have not been well-understood but could be a green alternative to replacing the current expensive and toxic precious metal systems most commonly used for these processes. Therefore, the yields from direct Suzuki-Miyaura C-C coupling of phenylboronic acid and pyrrole to produce 2-phenylpyrrole facilitated by eight high-spin iron complexes ([Fe(3+)L1(Cl)(2)](+), [Fe(3+)L4(Cl)(2)](+), [Fe(2+)L5(Cl)](+), [Fe(2+)L6(Cl)(2)], [Fe(3+)L7(Cl)(2)](+), [Fe(3+)L8(Cl)(2)](+), [Fe(2+)L9(Cl)](+), and [Fe(2+)L10(Cl)](+)) were compared to identify the effect of structural and electronic properties on catalytic efficiency. Specifically, catalyst complexes were compared to evaluate the effect of five properties on catalyst reaction yields: 1. the coordination requirements of the catalyst, 2. Redox half-potential of each complex, 3. topological constraint/rigidity, 4. N-atom modification(s) increasing oxidative stability of the complex, and 5. geometric parameters. The need for two labile cis-coordination sites was confirmed based on a 42% decrease in catalytic reaction yield observed when complexes containing penta-dentate ligands were used in place of complexes with tetra-dentate ligands. A strong correlation between iron(III/II) redox potential and catalytic reaction yields was also observed, with [Fe(2+)L6(Cl)(2)] providing the highest yield (81%, −405 mV). A Lorentzian fitting of redox potential versus yields predicts that these catalysts can undergo more fine tuning to further increase yields. Interestingly, the remaining properties explored did not show a direct, strong relationship to catalytic reaction yields. Altogether, these results show that modifications to the ligand scaffold using fundamental concepts of inorganic coordination chemistry can be used to control the catalytic activity of macrocyclic iron complexes by controlling redox chemistry of the iron center. Furthermore, the data provides direction for the design of improved catalysts for this reaction and strategies to understand the impact of a ligand scaffolds on catalytic activity of other reactions.

Lacustrine carbonate chimneys are striking, metre-scale constructions. If these were bioinfluenced constructions, they could be priority targets in the search for early and extraterrestrial microbial life. However, there are questions over whether such chimneys are built on a geobiological framework or are solely abiotic geomorphological features produced by mixing of lake and spring waters. Here, we use correlative microscopy to show that microbes were living around Pleistocene Mono Lake carbonate chimneys during their growth. A plausible interpretation, in line with some recent works by others on other lacustrine carbonates, is that benthic cyanobacteria and their associated extracellular organic material (EOM) formed tubular biofilms around rising sublacustrine spring vent waters, binding calcium ions and trapping and binding detrital silicate sediment. Decay of these biofilms would locally have increased calcium and carbonate ion activity, inducing calcite precipitation on and around the biofilms. Early manganese carbonate mineralisation was directly associated with cell walls, potentially related to microbial activity though the precise mechanism remains to be elucidated. Much of the calcite crystal growth was likely abiotic, and no strong evidence for either authigenic silicate growth or a clay mineral precursor framework was observed. Nevertheless, it seems likely that the biofilms provided initial sites for calcite nucleation and encouraged the primary organised crystal growth. We suggest that the nano-, micro- and macroscale fabrics of these Pleistocene Mono Lake chimneys were affected by the presence of centimetre-thick tubular and vertically stacked calcifying microbial mats. Such carbonate chimneys represent a promising macroscale target in the exploration for ancient or extraterrestrial life.

The pH-dependent intramolecular chelation of a tethered sulfonamide ligand in ruthenium(II) arene complexes is demonstrated, a process shown to modulate metal-centered reactivity toward the model ligand guanosine 5′-monophosphate within the physiologically relevant pH region.

The interaction between inverted cucuribit[6]uril (iQ[6]) and a series of symmetric viologens bearing aliphatic substituents, namely dicationic dialkyl-4,4′-bipyridinium guests where the alkyl substituent is CH3(CH2)n (n = 1, 3 and 5) or benzyl, has been studied in aqueous solution by 1H NMR spectroscopy, electronic absorption spectroscopy, isothermal titration calorimetry and mass spectrometry. The viologen bearing C6H5CH2 substituents has also been investigated. In the case of the dialkyl-derived guests, single crystal X-ray diffraction, on crystals grown in the presence of CdCl2, revealed the compositions to be 2(C36H36N24O12), 4(C14H18N2), Cd5Br9.56Cl10.442(H2O)·2(H3O); 2(C36H36N24O12), C18H26N2,2(CdCl4), 36H2O and 2(C36H36N24O12), 2(C11H17N), 2(CdCl4), 20H2O for the use of n = 1, 3 or 5 respectively. Thus, in the solid state, in the case of both BV2+ (n = 3) and HV2+ (n = 5), an interaction of viologen with iQ[6] was observed and the structure adopted is an external ‘dumbbell-type’ structure.

Six new lanthanide metal organic complexes, i.e. [La2(NO2-BDC)3(H2O)4] (1) [Ln(L)0.5(NO2-BDC) (H2O)]·3H2O (Ln = Eu (2), Tb (3), Dy (4) and Ho (5); L = BDC2− or BDC2−/NO2-BDC2-) and [Tm(NO2-BDC)1.5(H2O)]·H2O (6), have been synthesized using mixed ligands of benzene-1,4-dicarboxylic acid (H2BDC) and the in situ generated 2-nitro-benzene-1,4-dicarboxylic acid (NO2-BDC2-). Single crystal structures and topologies of the complexes are presented based on the single crystal X-ray diffraction and spectroscopic data. Whilst the structures of 1 and 6 contain negligible voids, the frameworks of 2–5 are microporous in nature and stable upon the removal of all the water molecules from the structures and thermal treatment to over 400 °C. Based on the study of 2, significant adsorption capacities for carbon dioxide (95 cm3·g−1 or 4.2 mmol·g−1) and hydrogen (79 cm3·g−1 or 4 mmol·g−1), as well as the remarkable stability of the framework upon the sorption/desorption experiments are revealed.

Two new tricyclic β-aminoacrylate derivatives (2e and 3e) have been found to be inhibitors of Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) with Ki 0.037 and 0.15 μM respectively. 1H and 13C NMR spectroscopic data show that these compounds undergo ready cis-trans isomerisation at room temperature in polar solvents. In silico docking studies indicate that for both molecules there is neither conformation nor double bond configuration which bind preferentially to PfDHODH. This flexibility is favourable for inhibitors of this channel that require extensive positioning to reach their binding site.

Lacustrine carbonate deposits with spherulitic facies are poorly understood, but are key to understanding the economically important “Pre-Salt” Mesozoic strata of the South Atlantic. A major barrier to research into these unique and spectacular facies is the lack of good lacustrine spherulite-dominated deposits which are known in outcrop. Stratigraphy and petrography suggest one of the best analogue systems is found in the Carboniferous of Scotland: the East Kirkton Limestone. Here we propose a hydrogeochemical model that explains why the CaCO3, SiO2, Mg-Si-Al mineral suite associated with spherular radial calcite facies forms in alkaline lakes above basaltic bedrock. Demonstrating links between igneous bedrock chemistry, lake and spring water chemistry and mineral precipitation, this model has implications for studies of lacustrine sediments in rift basins of all ages. Using empirical and theoretical approaches, we analyze the relationship between metal mobilization from sub-surface volcaniclastic rocks and the potential for precipitation of carbonate minerals, various Mg-bearing minerals and chalcedony in a lacustrine spherulitic carbonate setting. This suite of minerals is most likely formed by in-gassing of CO2 to a carbon-limited alkaline spring water, consistent with the reaction of alkali igneous rocks in the subsurface with meteoric groundwater. We suggest that an analogous system to that at East Kirkton caused development of the ‘Pre-Salt’ spherulitic carbonate deposits.

In the crystal structures of N′-amino­pyridine-2-carboximidamide (C6H8N4), 1, and N′-{[1-(pyridin-2-yl)ethyl­idene]amino}­pyridine-2-carboximidamide (C13H13N5), 2, mol­ecules are linked by inter­molecular N—H⋯N hydrogen-bonding inter­actions, forming a two-dimensional network in 1 and a chain in 2., The crystal structures of N′-amino­pyridine-2-carboximidamide (C6H8N4), 1, and N′-{[1-(pyridin-2-yl)ethyl­idene]amino}­pyridine-2-carboximidamide (C13H13N5), 2, are described. The non-H atoms in compound 1 are nearly planar (r.m.s. deviation from planarity = 0.0108 Å), while 2 is twisted about the central N—N bond by 17.8 (2)°. Both mol­ecules are linked by inter­molecular N—H⋯N hydrogen-bonding inter­actions; 1 forms a two-dimensional hydrogen-bonding network and for 2 the network is a one-dimensional chain. The bond lengths of these mol­ecules are similar to those in other literature reports of azine and di­imine systems.

Reaction of R1R2CHN=CH(3,5-tBu2C6H2-OH-2) (R1 = R2 = Me L1H; R1 = Me, R2 = Ph L2H; R1 = R2 = Ph L3H) with slightly greater than one equivalent of R33Al (R3 = Me, Et) afforded the complexes [(L1–3)AlR32] (L1, R3 = Me 1, R3 = Et 2; L2, R3 = Me 3, R3 = Et 4; L3 R3 = Me 5, R3 = Et 6); complex 1 has been previously reported. Use of the N,O-ligand derived from 2,2′-diphenylglycine afforded either 5 or the byproduct [Ph2NCH2(3,5-tBu2C6H2-O-2)AlMe2] (7). The known Schiff base complex [2-Ph2PC6H4CH2(3,5-tBu2C6H2-O-2)AlMe2] (8) and the product of the reaction of 2-diphenylphosphinoaniline 1-NH2,2-PPh2C6H4 with Me3Al, namely {Ph2PC6H4N[(Me2Al)2µ-Me](µ-Me2Al)} (9), were also isolated. For structural and catalytic comparisons, complexes resulting from the interaction of Me3Al with diphenylamine (or benzhydrylamine), namely {Ph2N[(Me2Al)2µ-Me]} (10) and [Ph2CHNH(µ-Me2Al)]2·MeCN (11), were prepared. The molecular structures of the Schiff proligands derived from Ph2CHNH2 and 2,2′-Ph2C(CO2H)(NH2), together with those of complexes 5, 7 and 9–11·MeCN were determined; 5 contains a chelating imino/phenoxide ligand, whereas 7 contains the imino function outside of the metallocyclic ring. Complex 9 contains three nitrogen-bound Al centres, two of which are linked by a methyl bridge, whilst the third bridges the N and P centres. In 10, the structure resembles 9 with a bridging methyl group, whereas the introduction of the extra carbon in 11 results in the formation of a dimer. All complexes have been screened for their ability to promote the ring-opening polymerization (ROP) e-caprolactone, δ-valerolactone or rac-lactide, in the presence of benzyl alcohol, with or without solvent present. Reasonable conversions were achievable at room temperature for e-caprolactone when using complexes 7, 9 and 12, whilst at higher temperatures (80–110 °C), all complexes produced good (> 65 %) to quantitative conversions over periods as short as 3 min, albeit with poor control. In the absence of solvent, conversions were nearly quantitative at 80 °C in 5 min with better agreement between observed and calculated molecular weight (Mn). For rac-lactide, conversions were typically in the range 71–86 % at 110 °C in 12 h, with poor control affording atactic polylactide (PLA), whilst for δ-valerolactone more forcing conditions (12–24 h at 110 °C) were required for high conversion. Co-polymerization of e-caprolactone with rac-lactide afforded co-polymers with appreciable lactide content (35–62.5 %); the reverse addition was ineffective, affording only (polycaprolactone) PCL.

Reaction of LiOR (R=t-Bu, Ph) with the acids 2,2/-Ph2C(X)(CO2H), X=OH (benzH), NH2 (dpgH) was investigated. For benzH, one equivalent LiOt-Bu in THF afforded [Li(benz)]2⋅2THF (1⋅2THF), which adopts a 1D chain structure. If acetonitrile is used (mild conditions), another polymorph of 1 is isolated; LiOPh also led to 1. Robust work-up afforded [Li7(benz)7(MeCN)] 2MeCN THF (2⋅2MeCN⋅THF). Use of LiOt-Bu (2 equivalents) led to {Li8(Ot-Bu)2[(benz)](OCPh2CO2CPh2CO2t-Bu)2(THF)4} (3), the core of which comprises two open cubes linked by benz ligands. For dpgH, two equivalents of LiOt-Bu in THF afforded [Li6(Ot-Bu)2(dpg)2(THF)2] (4), which contains an Li2O2 6-step ladder. Similar reaction of LiOPh afforded [Li8(PhO)4(dpg)4(MeCN)4] (5). Complexes 1–5 were screened for their potential as catalysts for ring opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL), rac-lactide (rac-LA) and δ-valerolactone (δ-VL). For ROP of ϵ-CL, conversions > 70 % were achievable at 110 °C with good control. For rac-LA and δ-VL, temperatures of at least 110 °C over 12 h were necessary for activity (conversions > 60 %). Systems employing 2 were inactive.

We have successfully prepared crystals of thiazole-5-carboxylic acid (5-Htza) (L) and three new thiazole-5-carboxylate-based Cu2+ coordination polymers with different dimensionality, namely, 1D [Cu2(5-tza)2(1,10-phenanthroline)2(NO3)2] (1), 2D [Cu(5-tza)2(MeOH)2] (2), and 3D [Cu(5-tza)2]·H2O (3). These have been characterized by single crystal X-ray diffraction and thermogravimetry. Interestingly, the 2D network structure of 2 can directly transform into the 3D framework of 3 upon removal of methanol molecules at room temperature. 2 can also undergo structural transformation to produce the same 2D network present in the known [Cu(5-tza)2]·1.5H2O upon heat treatment for 2 h. This 2D network can adsorb water and convert to 3 upon exposure to air.

Gallium-68 (68Ga) has been the subject of increasing interest for its potential in the production of radiotracers for diagnosis of diseases. In this work we report the complexation of 68Ga by the amino acid based tripodal chelate H3Dpaa, and two bifunctional derivatives, H3Dpaa.dab and H4Dpaa.ga, under a range of conditions with particular emphasis on the rapid complexation of 68Ga at pH 7.4. 100 μM H3Dpaa achieved a radiochemical yield of 95% at pH 7.4 in 5 minutes at 37 °C. The bifunctional derivatives H4Dpaa.ga and H3Dpaa.dab achieved 94% and 84% radiochemical yields, respectively, under the same conditions. The resulting Ga(III) complexes show thermodynamic stabilities of log KGaDpaa = 18.53, log KGaDpaa.dab = 22.08, log KGaDpaa.ga = 18.36. Unfortunately, the resulting radiolabelled species do not present sufficient serum stability for in vivo application. Herein we show a flexible synthesis for bifunctional chelators based on amino acids that rapidly complex 68Ga under physiological conditions.

The interaction between inverted cucuribit[7]uril (iQ[7]) and a series of symmetric viologen derivatives bearing aliphatic substituents of variable length, namely dicationic dialkyl-4,4′-bipyridinium guests where the alkyl is CH3(CH2)n with n = 0 to 6, has been studied in aqueous solution by 1H NMR spectroscopy, electronic absorption spectroscopy, isothermal titration calorimetry and mass spectrometry. In the case of both n = 5 (HV2+) and 6 (SV2+), single crystal X-ray diffraction revealed the composition to be [(iQ[7])2(HV)2][CdCl3Br][H3O+]2[H2O]12.5 and (iQ[7])2(C7-SV)1.5[CdCl4]4(H3O+)5(H2O)8, respectively, with both adopting an external B-type structure (the alkyl chains of the viologen reside within the iQ[7]).

Green synthesis is employed to prepare cobalt/cellulose nanocomposites with cubic (α-cobalt) cobalt as a main component with antibacterial and magnetic properties. An in situ reduction of aqueous solutions of cobalt ions on a model cellulose substrate surface using hydrogen gas affords spherical, cellulose-stabilised cobalt nanoclusters with magnetic properties and an average diameter of 7 nm that are distributed evenly over the surface of the cellulose fibres. These cobalt/cellulose nanocomposites exhibit good antibacterial action against opportunistic pathogens both Gram-positive (S. aureus) and Gram-negative (E. coli, A. baumannii and P. aeruginosa), with zones of inhibition up to 15 mm, thereby encouraging the deployment of these advanced materials for the treatment of wastewater or within medical dressings. This method of preparation is compared with the analogous in situ reduction of cobalt ions on a cellulose surface using sodium borohydride as reducing agent.

The interaction of [VO(acac)2] with 2,6-bis(hydroxymethyl)-4-methylphenol (L1H3) or 6,6′-methylenebis(4-tert-butyl-2-(hydroxymethyl)phenol) (L2H4) in refluxing toluene afforded, following work-up in ethanol, the complexes [VOL1]2 (1) and {[VO(acac)(HOEt)](VO)L2]}2 (2), respectively. Use of 4-[3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl]benzoic acid (L3H2) or 4-[3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl]benzosulfonic acid (L4H2) with [VOCl3] in refluxing acetonitrile, followed by methanol and THF work-up, afforded the complexes [Et3NH][VO(OMe)L3]2 (3) and [Et3NH][VO(OMe)L4]2 (4), respectively. The interaction of [VOSO4] and L3H2 in refluxing acetonitrile afforded, with extraction into methanol, the complex [VO(OMe)L3]2 (5). The molecular structures of 2, 3 and 5 have been determined; the structure of 1 has been reported previously. The complexes in this study have been determined to be of low toxicity using in vitro cell assays with 50% cytotoxicity values (CC50) values in the range 56–126 µM.

A number of disease states including WHIM syndrome, HIV infection and cancer have been linked to the chemokine receptor CXCR4. High-affinity CXCR4 antagonist transition metal complexes of configurationally restricted bis-tetraazamacrocyclic ligands have been identified in previous studies. Recently synthesised and structurally characterised Co(2+)/Co(3+) and Ni(2+) acetate complexes of mono-macrocycle cross-bridged ligands have been used to mimic their known coordination interaction with the aspartate side chains on binding to CXCR4. Here, X-ray crystal structures for three Co(2+)/Co(3+) acetate complexes and five Ni(2+) acetate complexes are presented and demonstrate flexibility in the mode of binding to the acetate ligand concomitantly with the requisite cis-V-configured cross-bridged tetraazamacrocyle. Complexes of the smaller Co(3+) metal ion exclusively bind acetate by chelating both oxygens of acetate. Larger Co(2+) and Ni(2+) metal ions in cross-bridged tetraazamacrocycles show a clear tendency to coordinate acetate in a monodentate fashion with a coordinated water molecule completing the octahedral coordination sphere. However, in unbridged tetraazamacrocycle acetate structures reported in the literature, the coordination preference is to chelate both acetate oxygens. We conclude that the short ethylene cross-bridge restricts the equatorial bulk of the macrocycle, prompting the metal ion to fill the equator with the larger monodentate acetate plus water ligand set. In unbridged ligand examples, the flexible macrocycle expands equatorially and generally only allows chelation of the sterically smaller acetate alone. These results provide insight for generation of optimised bis-macrocyclic CXCR4 antagonists utilising cobalt and nickel ions.

Reaction of differing amounts of vanadyl sulfate with p-tert-butylthiacalix[4]areneH(4) and base allows access to the vanadyl-sulfate species [NEt4](4)[(VO)(4)((3)-OH)(4)(SO4)(4)] 1/2H(2)O (1), [HNEt3](5)[(VO)(5)((3)-O)(4)(SO4)(4)] 4MeCN (2 4MeCN) and [NEt4](2)[(VO)(6)(O)(2)(SO4)(4)(OMe)(OH2)] MeCN (3 MeCN ). Similar use of p-tert-butylsulfonylcalix[4]areneH(4), p-tert-butylcalix[8]areneH(8) or p-tert-butylhexahomotrioxacalix[3]areneH(3) led to the isolation of [HNEt3](2)[H2NEt2](2){[VO(OMe)](2)p-tert-butylcalix[8-SO2]areneH(2)} (4), [HNEt3](2)[V(O)(2)p-tert-butylcalix[8]areneH(5)] (5) and [HNEt3](2)[VIV2VV4O(11)(OMe)(8)] (6), respectively. Dc magnetic susceptibility measurements were performed on powdered microcrystalline samples of 1-3 in the T = 300-2 K temperature range. Preliminary screening for electrochemical water oxidation revealed some activity for 2 with turnover frequency (TOF) and number (TON) of 2.2 x 10(-4) s(-1) and 6.44 x 10(-6) (mmol O-2/mmol cat.), respectively. The compound 3 showed an improved electrochemical activity in the presence of water. This is related to the increased number and the rate of electrons exchanged during oxidation of V4+ species, facilitated by protons generated in the water discharge process.

Treatment of Ln(NO3)3.6H2O (Ln = La, Ce) with an equimolar amount of 2,2′-diphenylglycine (DpgH) in ethanol afforded the corresponding hexacoordinated complexes (DpgH±)3Ln(NO3)3.H2O (DpgH± = zwitterionic 2,2′-diphenylglycine, Ln = La (1), Ce (2)). The spectroscopic and structural features of these compounds have been investigated. Similar reactions with the related benzilic acid (BenzH2) were unsuccessful. The catalytic behaviour of 1 and 2 in the homo- and copolymerization of e-caprolactone (e-CL) and rac-lactide (r-LA) has been investigated herein. In the case of e-CL, the two complexes exhibited comparable activity, allowing for complete monomer conversion under aerobic and solvent-free conditions at 150 °C in 24 h. With respect to the ROP of r-LA, 1 was found to be completely inactive, while only 8% conversion was achieved in the presence of 2. Liquid oligomers were isolated during e-CL/r-LA co-polymerization in the presence of both complexes. The catalytic activity of the pre-ligands DpgH and BenzH2 (i.e. metal-free) was also examined. Interestingly, only BenzH2 was found to be active, although it required a higher catalyst loading and the presence of benzyl alcohol as co-activator.

Coordination complexes of iron(III), cobalt(II) and zinc(II) with the ligand N′-{[1-(pyridin-2-yl)ethylidene]amino}pyridine-2-carboximidamide (pmhpa) have been synthesised and were structurally characterized by elemental analysis, mass spectrometry, X-ray diffraction and infrared spectroscopy. The mononuclear iron(III) complex, [Fe(pmhap)2][FeCl4], (1), adopts the orthorhombic non-centric space group P212121. The iron is present in an octahedral environment in the ion [Fe(pmhap)2]+. The crystallographically-determined formula of the cobalt(II) complex (2) is [Co2(pmhap)2Cl3]2[CoCl4].4MeOH. The compound crystallizes in the non-centric space group P 4 21c with a single cobalt ion in the asymmetric unit. The complex is dinuclear, with two cobalt ions bridged by chloride and the two nitrogen atoms of N=N of the pmhap ligand. The zinc(II) complex; [Zn2(pmhpa)3](NO3)4.2.75MeOH (3) crystallizes in the cubic space group Pa 3 with disordered methanol molecules present. This is dinuclear with the two zinc atoms being bridged by three N=N links from the ligand to form a threefold symmetric rotor. Infrared spectroscopy confirms that coordination occurs through the azide bridge. Measurements of magnetic susceptibility for the iron(III) and cobalt(II) complexes show that they are paramagnetic between 5 and 300 K. Mossbauer spectroscopic data supports the structure of the iron(III) complex being composed of an octahedral and a tetrahedral iron atom.

The origin of spherical-radial calcite bodies - spherulites - in sublacustrine, hyperalkaline and saline systems is unclear, and therefore their palaeoenvironmental significance as allochems is disputed. Here, we experimentally investigate two hypotheses concerning the origin of spherulites. The first is that spherulites precipitate from solutions super-saturated with respect to magnesium-silicate clays, such as stevensite. The second is that spherulite precipitation happens in the presence of dissolved, organic acid molecules. In both cases, experiments were performed under sterile conditions using large batches of a synthetic and cell-free solution replicating waters found in hyperalkaline, saline lakes (such as Mono Lake, California). Our experimental results show that a highly alkaline and highly saline solution supersaturated with respect to calcite (control solution) will precipitate euhedral to subhedral rhombic and trigonal bladed calcite crystals. The same solution supersaturated with respect to stevensite precipitates sheet-like stevensite crystals rather than a gel, and calcite precipitation is reduced by ~. 50% compared to the control solution, producing a mixture of patchy prismatic subhedral to euhedral, and minor needle-like, calcite crystals. Enhanced magnesium concentration in solution is the likely the cause of decreased volumes of calcite precipitation, as this raised equilibrium ion activity ratio in the solution. On the other hand, when alginic acid was present then the result was widespread development of micron-size calcium carbonate spherulite bodies. With further growth time, but falling supersaturation, these spherules fused into botryoidal-topped crusts made of micron-size fibro-radial calcite crystals. We conclude that the simplest tested mechanism to deposit significant spherical-radial calcite bodies is to begin with a strongly supersaturated solution that contains specific but environmentally-common organic acids. Furthermore, we found that this morphology is not a universal consequence of having organic acids dissolved in the solution, but rather spherulite development requires specific binding behaviour. Finally, we found that the location of calcite precipitation was altered from the air:water interface to the surface of the glassware when organic acids were present, implying that attached calcite precipitates reflect precipitation via metal-organic intermediaries, rather than direct forcing via gas exchange.

The interaction of a symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (TMeQ[6]) with a series of lanthanide cations (Ln3+) was investigated in neutral water and in acidic solution. Analysis by single crystal X-ray diffraction revealed that different isomorphous families formed under different synthetic conditions. Such differences in the interaction between TMeQ[6] and Ln3+ could potentially be used for isolating heavier Ln3+ from their lighter counterparts in neutral solution, and lighter lanthanide cations from their heavier counterparts in acidic solution.

A number of p-sulfonatocalix[4]arene complexes of the lanthanides (Tb, Gd, and Eu) have been prepared, some in the presence of tetraazamacrocycle 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A), and fully characterised. Crystal structure determinations reveal lanthanide coordination at the sulfonate group, bridging several calixarene units, giving coordination polymers. All complexes in this study have been determined to be relatively non-toxic using in vitro cell assays with CC50 values in the range 30–170 μM.

The vanadyl complexes [VO(OtBu)L1] (1) and {[VO(OiPr)]2(μ-p-L2p)} (2) {[VO(OR)]2(μ-p-L2m)} (R = iPr 3, tBu 4) have been prepared from [VO(OR)3] (R = nPr, iPr or tBu) and the respective phenol, namely 2,2′-ethylidenebis(4,6-di-tert-butylphenol) (L1H2) or α,α,α′,α′-tetra(3,5-di-tert-butyl-2-hydroxyphenyl–p/m-)xylene-para-tetraphenol (L2p/mH4). For comparative studies, the known complexes [VO(μ-OnPr)L1]2 (I), [VOL3]2 (II) (L3H3 = 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol) were prepared. An imido complex {[VCl(Np-tolyl)(NCMe)]2(μ-p-L2p)} (5) has been prepared following work-up from [V(Np-tolyl)Cl3], L2pH4 and Et3N. The molecular structures of complexes 1–5 are reported. Complexes 1–5 and I and II have been screened for their ability to ring open polymerise e-caprolactone, L-lactide or rac-lactide with and without solvent present. The co-polymerization of e-caprolactone with L-lactide or rac-lactide afforded co-polymers with low lactide content; the reverse addition was ineffective.

The interaction of a series of lanthanide cations (Ln3+) with inverted cucurbit[7]uril (iQ[7]) in the presence of [ZnCl4]2− anions as a structure-directing agent have been investigated.

Reaction of the bulky bi-phenols 2,2′-RCH[4,6-(t-Bu)2C6H2OH]2 (R = Me L1MeH2, Ph L1PhH2) with the bis(imido) molybdenum(VI) tert-butoxides [Mo(NR1)(NR2)(Ot-Bu)2] (R1 = R2 = 2,6-C6H3-i-Pr2, R1 = t-Bu, R2 = C6F5) afforded, following the successive removal of tert-butanol, the complexes [Mo(NC6H3i-Pr2-2,6)2L1Me] (1), [Mo(NC6H3i-Pr2-2,6)2L1Ph] (2) and [Mo(Nt-Bu)(μ-NC6F5)(L1Me)]2 (3). Similar use of the tri-phenol 2,6-bis(3,5-di-tert -butyl-2-hydroxybenzyl)-4-methylphenol (L2H3) with [Mo(NC6H3i-Pr2-2,6)2(Ot-Bu)2] afforded the oxo-bridged product [Mo(NC6H3i-Pr2-2,6)(NCMe)(μ-O)L2H]2 (4), whilst use of the tetra-phenols α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p- or -m-xylene L3pH4/L3mH4 led to {[Mo(NC6H3i-Pr2-2,6)2]2(μ-L3p)} (5) or {[Mo(NC6H3i-Pr2-2,6)2]2(μ-L3m)} (6), respectively. Similar use of [Mo(NC6F5)2(Ot-Bu)2] with L3pH4 afforded, after work-up, the complex {[Mo(NC6F5)(Ot-Bu)2]2(μ-L3p)}·6MeCN (7·6MeCN). Molecular structures of 1, 2·CH2Cl2, 3, 4·6MeCN, 6·2C6H14, and 7·6MeCN are reported and these complexes have been screened for their ability to ring open polymerize (ROP) ε-caprolactone, for comparative studies the precursor complex [Mo(NC6H3i-Pr2-2,6)2Cl2(DME)] (DME = 1,2-dimethoxyethane) has also been screened. Results revealed that good activity is only achievable at temperatures of ≥100 °C over periods of 1 h or more. Polymer polydispersities were narrow, but observed molecular weights (Mn) were much lower than calculated values.

The interaction between cucuribit[8]uril (Q[8]) and a series of 4-pyrrolidinopyridinium salts bearing aliphatic substituents at the pyridinium nitrogen, namely 4-(C4H8N)C5H5NRBr, where R = Et (g1), n-butyl (g2), n-pentyl (g3), n-hexyl (g4), n-octyl (g5), n-dodecyl (g6), has been studied in aqueous solution by 1H NMR spectroscopy, electronic absorption spectroscopy, Isothermal Titration Calorimetry and mass spectrometry. Single crystal X-ray diffraction revealed the structure of the host-guest complexes for g1, g2, g3, and g5. In each case the Q[8] contains two guest molecules in a centrosymmetric dimer. The orientation of the guest molecule changes as the alkyl chain increases in length. Interestingly, in the solid state, the inclusion complexes identified are different from those observed in solution, and furthermore, in the case of g3, Q[8] exhibits two different interactions with the guest. In solution, the length of the alkyl chain plays a significant role in determining the type of host-guest interaction present.

Steel slag is a major by-product of the steel industry and a potential resource of technology critical elements. For this study, a basic oxygen furnace (BOF) steel slag was tested for bacterial leaching and recovery of aluminium (Al), chromium (Cr), and vanadium (V). Mixed acidophilic bacteria were adapted to the steel slag up to 5% (w/v). In the batch tests, Al, Cr, and V were bioleached significantly more from steel slag than in control treatments. No statistical difference was observed arising from the duration of the leaching (3 vs 6 d) in the batch tests. Al and Cr concentrations in the leachate were higher for the smaller particle size of the steel slag (75 μm), but no difference was observed for V. In the column tests, no statistical difference was found for pH, Al, Cr and V between the live culture (one-step bioleaching) and the supernatant (two-step bioleaching). The results show that the culture supernatant can be effectively used in an upscaled industrial application for metal recovery. If bioleaching is used in the 170-250 million tonnes of steel slag produced per year globally, significant recoveries of metals (100% of Al, 84% of Cr and 8% of V) can be achieved, depending on the slag composition. The removal and recovery percentages of metals from the leachate with Amberlite

Tetracyclic bisaminals formed by condensation of tetraazamacrocycles and glyoxal have rarely been utilized as ligands for transition metal ions. Five novel Cu2+ complexes are presented to expand this set. Glyoxal derivatives of pyruvic aldehyde and butanedione were expected to further rigidify the bisaminal skeleton because of the steric requirements of the methyl groups, while the previously unutilized homocyclam was expected to increase flexibility due to the presence of a seven-membered ring. Additionally, a nitrato complex was prepared to examine the effect of more bulky monodentate ligands on the bisaminal framework. The new complexes showed similar four-coordination of Cu2+, but with significant changes in coordination geometry caused by substitution of the glyoxal bridge by one or two methyl groups. The homocyclam derivative produced a completely different coordination mode due to the flexibility of the larger macrocycle ring. Both structural and electronic properties were affected by the use of nitrato in place of the typical chlorido monodentate ligands. Overall, the electronic properties (magnetic moment, electronic spectra, and cyclic voltammetry) were only subtly affected. However, larger changes were observed when the larger homocyclam macrocycle was used or the nitrato anion was used in place of the chlorido ligand to complete the coordination. Additionally, the recently published geometric index τδ was evaluated by using this series of closely related Cu2+ complexes.

In contrast to other similar compounds, [FeCl2(C14H30N4)]PF6 is a monomer. Comparison with the mononuclear Fe2+ complex of the same ligand shows that the smaller Fe3+ ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxo dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra­aza­bicyclo­[6.6.2]hexa­decane prevent dimerization upon oxidation., The title compound, [FeCl2(C14H30N4)]PF6, contains Fe3+ coordinated by the four nitro­gen atoms of an ethyl­ene cross-bridged cyclam macrocycle and two cis chloride ligands in a distorted octa­hedral environment. In contrast to other similar compounds this is a monomer. Inter­molecular C—H⋯Cl inter­actions exist in the structure between the complex ions. Comparison with the mononuclear Fe2+ complex of the same ligand shows that the smaller Fe3+ ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra­aza­bicyclo­[6.6.2]hexa­decane prevent dimerization upon oxidation.

The first 2-pyridylmethyl pendant-armed ethylene cross-bridged cyclam ligand has been synthesized and successfully complexed to Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+) cations. X-ray crystal structures were obtained for all six complexes and demonstrate pentadentate binding of the ligand with the requisite cis-V configuration of the cross-bridged cyclam ring in all cases, leaving a potential labile binding site cis to the pyridine donor for interaction of the complex with oxidants and/or substrates. The electronic properties of the complexes were evaluated using solid-state magnetic moment determination and acetonitrile solution electronic spectroscopy, which both agree with the crystal structure determination of high-spin divalent metal complexes in all cases. Cyclic voltammetry in acetonitrile revealed reversible redox processes in all but the Ni(2+) complex, suggesting that catalytic reactivity involving electron-transfer processes is possible for complexes of this ligand. Kinetic studies of the dissociation of the ligand from the copper(II) complex under strongly acidic conditions and elevated temperatures revealed that the pyridine pendant arm actually destabilizes the complex compared to the parent cross-bridged cyclam complex. Screening for oxidation catalysis using hydrogen peroxide as the terminal oxidant for the most biologically relevant Mn(2+), Fe(2+), and Cu(2+) complexes identified the Mn(2+) complex as a potential mild oxidation catalyst worthy of continued development.

Reaction of α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p-xylene (p-L¹H₄) with two equivalents of [VO(OR)₃] (R = nPr, tBu) in refluxing toluene afforded, after work-up, the complexes {[VO(OnPr)(THF)]₂ (μ-p-L¹)}·2(THF) (1·2(THF)) or {[VO(OtBu)]₂ (μ-p-L¹)}·2MeCN (2·2MeCN), respectively in moderate to good yield. A similar reaction using the meta pro-ligand, namely α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-m-xylene (m-L²H₄) afforded the complex {[VO(OnPr)(THF)]₂ (μ-p-L²)} (3). Use of [V(Np-R¹C₆H₄)(tBuO)₃] (R¹ = Me, CF₃) with p-L¹H₄ led to the isolation of the oxo–imido complexes {[VO(tBuO)][V(Np-R¹C₆H₄) (tBuO)](μ-p-L¹)} (R¹ = Me, 4·CH2Cl₂; CF₃, 5·CH2Cl₂), whereas use of [V(Np-R¹C₆H₄)CL³] (R¹ = Me, CF₃) in combination with Et₃N/p-L¹H₄ or p-L¹Na₄ afforded the diimido complexes {[V(Np-MeC₆H₄)(THF)Cl]₂ (μ-p-L¹)}·4toluene (6·4toluene) or {[V(Np-CF₃C₆H₄)(THF)Cl]₂ (μ-p-L¹)} (7). For comparative studies, the complex [(VO)(μ-OnPr)L³]₂ (8) has also been prepared via the interaction of [VO(nPrO)₃] and 2-(α-(2-hydroxy-3,5-di-tert-butylphenyl)benzyl)-4,6-di-tert-butylphenol (L³H2). The crystal structures of 1·2THF, 2·2MeCN, 3, 4·CH2Cl₂, 5·CH2Cl₂, 6·4toluene·THF, 7 and 8 have been determined. Complexes 1–3 and 5–8 have been screened as pre-catalysts for the polymerization of ethylene in the presence of a variety of co-catalysts (with and without a re-activator), including DMAC (dimethylaluminium chloride), DEAC (diethylaluminium chloride), EADC (ethylaluminium dichloride) and EASC (ethylaluminium sesquichloride) at various temperatures and for the co-polymerization of ethylene with propylene; results are compared versus the benchmark catalyst [VO(OEt)Cl₂]. In some cases, activities as high as 243 400 g mmol⁻¹ V⁻¹ h⁻¹ (30.43 kgPE mmol V⁻¹ h⁻¹ bar⁻¹) were achievable, whilst it also proved possible to obtain higher molecular weight polymers (in comparable yields to the use of [VO(OEt)Cl₂]). In all cases with dimethylaluminium chloride (DMAC)/ethyltrichloroacetate (ETA) activation, the activities achieved surpassed those of the benchmark catalyst. In the case of the co-polymerization of ethylene with propylene, complexes 1–3 and 5–8 showed comparable or higher molecular weight than [VO(OEt)Cl₂] with comparable catalytic activities or higher in the case of the imido complexes 6 and 7.

Reaction of the pro-ligand α,α,α',α'-tetra(3,5-di-tert-butyl-2-hydroxyphenyl-p-)xylene-para-tetraphenol (p-L(1)H4) with two equivalents of [NbCl5] in refluxing toluene afforded, after work-up, the complex {[NbCl3(NCMe)]2(μ-p-L(1))}·6MeCN (1·6MeCN). When the reaction was conducted in the presence of excess ethanol, the orange complex {[NbCl2(OEt)(NCMe)]2(μ-p-L(1))}·3½MeCN·0.614toluene (2·3½MeCN·0.614toluene) was formed. A similar reaction using [TaCl5] afforded the yellow complex {[TaCl2(OEt)(NCMe)]2(μ-p-L(1))}·5MeCN (3·5MeCN). In the case of the meta pro-ligand, namely α,α,α',α'tetra(3,5-di-tert-butyl-2-hydroxyphenyl-m-)xylene-meta-tetraphenol (m-L(2)H4) only the use of [Nb(O)Cl3(NCMe)2] led to the isolation of crystalline material, namely the orange bis-chelate complex {[Nb(NCMe)Cl(m-L(2)H2)2]}·3½MeCN (4·3½MeCN) or {[Nb(NCMe)Cl(m-L(2)H2)2]}·5MeCN (4·5MeCN). The molecular structures of 1-4 and the tetraphenols L(1)H4 and m-L(2)H4·2MeCN have been determined. Complexes 1-4 have been screened as pre-catalysts for the ring opening polymerization of ε-caprolactone, both with and without benzyl alcohol or solvent present, and at various temperatures; conversion rates were mostly excellent (96%) with good control either at100 °C over 20 h (in toluene) or 1 h (neat).

Attempts to co-crystallise the nucleobases adenine, thymine, guanine, and cytosine with 1,10-phenanthroline by ball milling and solvent evaporation methods are described. A 1 : 1 co-crystal of cytosine and 1,10-phenanthroline can be obtained by grinding or by solvent evaporation. The structure contains two crystallographically independent cytosine and two independent 1,10-phenanthroline molecules (Z? = 2). The cytosine molecules form two similar but crystallographically independent hydrogen-bonded chains, while the 1,10-phenanthroline molecules are arranged in ?-stacks. Between the chains of cytosine and the ?-stacks exist N–H?N and C–H?N interactions. Crystal structure prediction (CSP) calculations were applied to all four systems to assess their potential for co-crystallisation as well as the likely structures and intermolecular interactions that could result from co-crystallisation. Calculations on the cytosine system demonstrate that co-crystallisation results in a lower energy than the crystalline forms of the two starting materials, in line with the co-crystal formation observed. For the systems which did not form a co-crystal, CSP was used to explore potential packing arrangements, but found none which were lower in energy than that of the pure crystalline forms. In these cases there is significant disruption to the nucleobase hydrogen bonding between the pure compound and the hypothetical co-crystal. For pure adenine and guanine, the hydrogen-bonded ribbons form sheets which must be broken, whereas for thymine, the lack of hydrogen bond donors does not allow the hydrogen bonding present for pure thymine to be maintained while forming thymine-1,10-phenanthroline hydrogen bonds.

An electronically active and spectral sensitive fluorescent "turn-on" chemosensor (BTP-1) based on the benzo-thiazolo-pyrimidine unit was designed and synthesized for the highly selective and sensitive detection of Fe3+ from aqueous medium. With Fe3+, the sensor BTP-1 showed a remarkable fluorescence enhancement at 554 nm (lambda(ex) = 314 nm) due to the inhibition of photo-induced electron transfer. The sensor formed a host-guest complex in 1:1 stoichiometry with the detection limit down to 0.74 nM. Further, the sensor was successfully utilized for the qualitative and quantitative intracellular detection of Fe3+ in two liver cell lines i.e., HepG2 cells (human hepatocellular liver carcinoma cell line) and HL-7701 cells (human normal liver cell line) by a confocal imaging technique. (C) 2014 Elsevier B.V. All rights reserved.

Heating a mixture of Nd(NO3)3·6H2O, KCl, Q[10] and Q[5] in HCl for 10 min affords the inclusion complex {NdQ[5]K@Q[10](H2O)4}·4NO3·20H2O. The structure of the inclusion complex has been investigated by single crystal X-ray diffraction and by X-ray Photoelectron spectroscopy (XPS).

We report a powerful new technique: hyphenating synchrotron X-ray powder diffraction (XRD) with differential scanning calorimetry (DSC). This is achieved with a simple modification to a standard laboratory DSC instrument, in contrast to previous reports which have involved extensive and complex modifications to a DSC to mount it in the synchrotron beam. The high-energy X-rays of the synchrotron permit the recording of powder diffraction patterns in as little as 2 s, meaning that thermally induced phase changes can be accurately quantified and additional insight on the nature of phase transitions obtained. Such detailed knowledge cannot be gained from existing laboratory XRD instruments, since much longer collection times are required. We demonstrate the power of our approach with two model systems, glutaric acid and sulfathiazole, both of which show enantiotropic polymorphism. The phase transformations between the low and high temperature polymorphs are revealed to be direct solid–solid processes, and sequential refinement against the diffraction patterns obtained permits phase fractions at each temperature to be calculated and unit cell parameters to be accurately quantified as a function of temperature. The combination of XRD and DSC has further allowed us to identify mixtures of phases which appeared phase-pure by DSC.