The Sensitivity of Structure to Ionic Radius and Reaction Stoichiometry: A Crystallographic Study of Metal Coordination and Hydrogen Bonding in Barbiturate Complexes of All Five Alkali Metals Li-Cs.

A systematic study has been conducted on barbiturate complexes of all five alkali metals, Li-Cs, prepared from metal carbonates or hydroxides in an aqueous solution without other potential ligands present, varying the stoichiometric ratio of metal ion to barbituric acid (BAH). Eight polymeric coordination compounds (two each for Na, K, and Rb and one each for Li and Cs) have been characterised by single-crystal X-ray diffraction. All contain some combination of barbiturate anion BA- (necessarily in a 1:1 ratio with the metal cation M+), barbituric acid, and water. All organic species and water molecules are coordinated to the metal centres via oxygen atoms as either terminal or bridging ligands. Coordination numbers range from 4 (for the Li complex) to 8 (for the Cs complex). Extensive hydrogen bonding plays a significant role in all the crystal structures, almost all of which include pairs of N-H···O hydrogen bonds linking BA- and/or BAH components into ribbons extending in one dimension. Factors influencing the structure adopted by each compound include cation size and reaction stoichiometry as well as hydrogen bonding.

Synthesis and crystal structure of a silver(I) 6-methylmercaptopurine riboside complex.

Silver nitrate reacts with 6-methylmercaptopurine riboside (6-MMPR) in aqueous solution containing methanol and dimethyl sulfoxide at room temperature to give a colourless crystalline complex, namely, bis(6-methylmercaptopurine riboside-κN7)(nitrato-κ2O,O')silver(I) 2.32-hydrate, [Ag(NO3)(C11H14N4O4S)2]·2.32H2O. The crystal structure, determined from synchrotron diffraction data, shows a central AgI ion on a crystallographic twofold rotation axis, coordinated in an almost linear fashion by two 6-MMPR ligands via atom N7 (purine numbering), with the nitrate counter-ion loosely coordinated as a bidentate ligand, forming a discrete molecular complex as an approximate dihydrate. The complex and water molecules are connected in a three-dimensional network by hydrogen bonding.

Expanding Luminescence Horizons in Macropolyhedral Heteroboranes.

Luminescence is observed in three novel macropolyhedral nineteen- and eighteen-vertex chalcogenaboranes: Se2B17H17 (1), SeB17H19 (3) and SeB18H20 (4). This led us to the recognition that previously published macropolyhedral heteroborane species might also exhibit luminescence. Thus, the known nineteen- and eighteen-vertex dithiaboranes S2B17H17 (2), n-S2B16H16 (5) and i-S2B16H16 (6) were synthesised and also found to exhibit a range of luminescent properties. These macropolyhedral species are very different from the previously unique fluorescent binary borane B18H22 in terms of their structural architectures, by the presence of borane cluster hetero atoms, and, as in the cases of 5 and 6, that their synthetic origins are not derived simply through the modification of B18H22 itself. They consequently greatly expand the possibilities of finding new luminescent inorganic borane species.

A Window into the Workings of anti-B18H22 Luminescence-Blue-Fluorescent Isomeric Pair 3,3'-Cl2-B18H20 and 3,4'-Cl2-B18H20 (and Others).

The action of AlCl3 on room-temperature tetrachloromethane solutions of anti-B18H22 (1) results in a mixture of fluorescent isomers, 3,3'-Cl2-B18H20 (2) and 3,4'-Cl2-B18H20 (3), together isolated in a 76% yield. Compounds 2 and 3 are capable of the stable emission of blue light under UV-excitation. In addition, small amounts of other dichlorinated isomers, 4,4'-Cl2-B18H20 (4), 3,1'-Cl2-B18H20 (5), and 7,3'-Cl2-B18H20 (6) were isolated, along with blue-fluorescent monochlorinated derivatives, 3-Cl-B18H21 (7) and 4-Cl-B18H21 (8), and trichlorinated species 3,4,3'-Cl3-B18H19 (9) and 3,4,4'-Cl3-B18H19 (10). The molecular structures of these new chlorinated derivatives of octadecaborane are delineated, and the photophysics of some of these species are discussed in the context of the influence that chlorination bears on the luminescence of anti-B18H22. In particular, this study produces important information on the effect that the cluster position of these substitutions has on luminescence quantum yields and excited-state lifetimes.

Discovery, isolation, heterologous expression and mode-of-action studies of the antibiotic polyketide tatiomicin from Amycolatopsis sp. DEM30355.

A genomic and bioactivity informed analysis of the metabolome of the extremophile Amycolatopsis sp. DEM30355 has allowed for the discovery and isolation of the polyketide antibiotic tatiomicin. Identification of the biosynthetic gene cluster was confirmed by heterologous expression in Streptomyces coelicolor M1152. Structural elucidation, including absolute stereochemical assignment, was performed using complementary crystallographic, spectroscopic and computational methods. Tatiomicin shows antibiotic activity against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Cytological profiling experiments suggest a putative antibiotic mode-of-action, involving membrane depolarisation and chromosomal decondensation of the target bacteria.

Influence of the methyl group in isoprene epoxides on reactivity compared to butadiene epoxides: Biological significance.

Reactions of the epoxides of 1,3-butadiene and isoprene (2-methyl-1,3-butadiene) with oxygen, nitrogen and sulfur nucleophiles have been compared to enable a better molecular understanding of the relative human toxicities of these epoxides. Hydrolysis of rac.-ethenyloxirane in (18O)water gave 77% (2-18O)but-3-ene-1,2-diol and 23% (1-18O)but-3-ene-1,2-diol. The R:S ratio for but-3-ene-1,2-diol from hydrolysis of (S)-ethenyloxirane was 75:25. Hence, hydrolysis of ethenyloxirane occurs by competing SN2 attack at C-2 and C-3 in 3:1 ratio, with no SN1 component. Hydrolysis of rac.-2-ethenyl-2-methyloxirane gave 2-hydroxy-2-methylbut-3-en-1-ol (73%) and 27% of a 2:1 mixture of the E- and Z-isomers of 4-hydroxy-2-methylbut-2-en-1-ol. In (18O)water (2-18O)2-hydroxy-2-methylbut-3-en-1-ol was obtained. Formation of these products occurs via SN1 ionisation to resonance-stabilised allylic cations which are captured by water. Reaction of rac.-ethenyloxirane with l-valine methyl ester gave diastereoisomeric adducts from SN2 attack of the valine amino at both C-2 (substituted position) and C-3 of the oxirane. The corresponding reaction of rac.-2-methyl-2-ethenyloxirane gave diastereoisomeric adducts, (R, S)- and (S, S)-N-(2-hydroxy-2-methyl-3-buten-1-yl)-l-valine methyl ester, from SN2 attack of the valine amino solely at C-3. Reactions of rac.-2-ethenyl-2-methyloxirane with cysteine derivatives occurred at C-2 in neutral polar media (SN1 reaction) or at C-3 in basic media (SN2), whereas for ethenyloxirane products arose from attack at both C-2 and C-3. Reaction of meso-butadiene diepoxide (meso-2,2'-bioxirane) with l-valine methyl ester gave mainly 2:1 adducts, dimethyl 2,2'-(((2R,3S)-2,3-dihydroxybutane-1,4-diyl)bis(azanediyl))-(2S,2'S)-bis(3-methyl-butanoates), whereas 2-methyl-2,2'-bioxirane gave a mixture of 1:1 [methyl 2-(3,4-dihydroxy-3-methylpyrrolidin-1-yl)-3-methylbutanoates] and 2:1 adducts. Meso-2,2'-bioxirane reacted with N-acetylcysteine methyl ester in methanol to afford meso-thiolane-3,4-diol, by elimination of N-acetyldehydroalanine methyl ester from a precursor cyclic adduct. Similarly, 2-methyl-2,2'-bioxirane gave solely 3-methylthiolane-3,4-diols. Thus, the methyl group of isoprene has a subtle effect on the reactivity of its epoxides relative to those of butadiene and therefore, in the context of their toxicology, could abrogate crosslinking of nitrogen functions in biomolecules related to mutagenicity and carcinogenicity.

Antiureolytic activity of new water-soluble thiadiazole derivatives: Spectroscopic, DFT, and molecular docking studies.

Two new water-soluble thiadiazole compounds are prepared and characterized with various techniques. These compounds, 5-amino-1,3,4-thiadiazole hydrochloride (1) and 5-amino-3-(N-propane-2-imine)-1,3,4-thiadiazole chloride salt (2) were synthesized via Mannich reaction, and characterized by microelemental analysis, and some spectroscopic means (FTIR, UV-Vis, 1H NMR, 13C NMR and mass), in addition to single-crystal X-ray diffraction for compound 2. DFT calculations were conducted to study their geometry optimization, vibrational spectra, MEP maps, and NBO analysis. In addition, TD-DFT calculations were performed to study their absorption spectra. The prepared compounds were tested against Jack beans urease enzyme (in vitro) to indicate their antiureolytic activity potency. The activity of the enzyme was measured under optimal conditions, before and after mixing with the prepared organic compounds. The results showed that both compounds have potentially inhibited the enzyme activity with respect to their IC50 values: 13.76 µM ± 0.15 for 1, and 18.81 µM ± 0.18 for 2. These values are even lower than that of thiourea (21.40 ± 0.21 µM) as a standard inhibitor. The inhibition activity of urease enzyme was confirmed by a Lineweaver-Burk plot. According to the kinetic parameters obtained from the Lineweaver-Burk plot, the inhibition of urease enzyme by compounds 1 and 2 seems to be non-competitive. Molecular docking studies of the prepared compounds 1 and 2 were performed in order to interpret the obtained biological results and to investigate their interactions with the urease enzyme active site. These studies reveal that compounds 1 and 2 are good candidates as inhibitors for urease enzyme. Moreover, compound 1 exhibits a higher promising inhibition activity.

Macropolyhedral Chalcogenaboranes: Insertion of Selenium into the Isomers of B18H22.

High yields of novel macropolyhedral selenaboranes are reported. Reactions of the monoanions of the syn- and anti-isomers of B18H22 with powdered selenium in THF variously give new macropolyhedral selenaboranes: 19-vertex [SeB18H19]- anion 1, 19-vertex [SeB18H21]- anion 2, 20-vertex [Se2B18H19]- anion 3, and 19-vertex [Se2B17H18]- anion 4. Single-cluster [hypho-Se2B6H9]- anion 5 and neutral arachno-Se2B7H9 6 also result. All of the macropolyhedrals 1, 2, 3, and 4 are characterized by NMR spectroscopy and mass spectrometry, and by single-crystal X-ray diffraction analyses. Anions 1 and 2 each consist of an 11-vertex subcluster joined by a common two-boron edge to a 10-vertex subcluster. Anion 3 consists of an 11-vertex subcluster joined by a common boron atom and an interboron link to an arachno-type 10-vertex subcluster. Unusually, anion 3 incorporates a hexagonal pyramidal intracluster structural motif in its 11-vertex subcluster. Anion 4 entails two arachno-type 10-vertex subclusters joined by a common boron atom, and with an additional intercluster boron-boron link. NMR data for syn-B18H22 and its mono- and dianions 7 and 8 and single-crystal X-ray diffraction results for these anions and also the monoanion 9 of anti-B18H22 are also reported. The oxaborane [µ-(8,9)-O-syn-B18H20]2- dianion 10 was serendipitously formed during the work and also characterized by a single-crystal X-ray diffraction study. Experimental NMR and structural findings are supported by DFT calculations throughout.

A simple and high-yield route to iridium, rhodium, osmium and ruthenium nido-6-metalladecaborane compounds.

We report a high-yield heterogeneous solid/liquid phase synthetic method to a series of nido-6-metalladecaboranes. The hydridoirida- and hydridorhoda-decaboranes, [6,6,6-H(PPh3)2-nido-6-MB9H13] [M = Ir (1), Rh (2)] are isolatable in 98% yields from the reaction of the square-planar M(I) complexes, [MCl(PPh3)3] (M = Rh, Ir), with K[B9H14]. The same synthetic procedure, but using [MCl(CO)H(PPh3)3] (M = Ru, Os) as metal starting reagents produces the CO-ligated clusters, [6,6,6-(CO)(PPh3)2-nido-6-MB9H13] [M = Ru (3), Os (4)], in yields of 83% and 95%, respectively. These highly convenient syntheses permit the investigation of the reaction chemistry of the new nido-6-metalladecaboranes. Thus, the CO-ligated compounds, 3 and 4, react with the square-planar platinum(II) complex, [PtCl2(PMe2Ph)2], in the presence of potassium triethylborohydride, to give the bimetallic clusters, [1,1,1-(CO)H(PPh3)-isocloso-1-RuB9H8-µ-(1,2)-{Pt(PMe2Ph)2}] (5) and [7,7-(PMe2Ph)2-9,9,9-(CO)(PPh3)2-nido-7,9-PtOsB9H11] (6), and the monometallic nido-5-osamadecaborane, [5,5,5-(PPh3)2(CO)-nido-5-OsB9H13] (7). This reactivity illustrates the potential of polyhedral boron-based clusters as molecular scaffolds ("B-frames") for the construction of multimetallic species. Single-crystal X-ray diffraction analyses have revealed the molecular structures of 3, 5, 6 and 7; the compounds are also studied by multielement NMR spectroscopy, mass spectrometry, IR spectroscopy, and in some cases computationally. Futhermore, the rotation of the {M(X)(PR3)2} moiety (X = H, CO), as PH3-ligated models, is studied by means of DFT-calculated relaxed potential energy surface scans, giving some insight into the lability of the metal-to-borane fragment interaction and of the exo-polyhedral ligands.

Distortions, deviations and alternative facts: reliability in crystallography.

This feature article is derived from the author's presentation of the Lonsdale lecture at the BCA Spring Meeting in 2018. One of the research results for which Kathleen Lonsdale is best known was her 1929 demonstration that the benzene ring in crystalline hexa-methyl-benzene is planar and has essentially hexagonal symmetry, resolving decades of dispute among organic chemists. More recent crystallographic studies of hexa-methyl-benzene have shown that there are actually small deviations from planarity. Such deviations for aromatic compounds may be due to electronic, steric, and/or intermolecular factors. Some substituted benzene molecules display remarkably large deviations, both from a planar ring structure and from regular hexagonal angular geometry around the ring. Starting from this specific connection with Kathleen Lonsdale's research, a number of stories are recounted of structural distortions and deviations from expected results and explanations that have been suggested for them, across a wide range of chemical topics including macrocycles, metal clusters, unusual coordination geometry and isomerism. On the way we find genuine surprises and results that have led to new understanding, but also examples of poor experiments, misinterpretation of data, scientific bias and preconceived ideas, incompetence and even deliberate fraud. Some aspects of structure validation are discussed. While showcasing some interesting research in its own right, this account also serves an educational purpose.

Phosphido-bis(borane) complexes of the alkaline earth metals.

The reaction between two equivalents of {(Me3Si)2CH}(Ph)PH(BH3) (1) and Bu2Mg, followed by two equivalents of BH3·SMe2, gives the corresponding phosphido-bis(borane) complex, which may be crystallised as two distinct chemical species: the complex [{(Me3Si)2CH}(Ph)P(BH3)2]2Mg(THF)4·THF (2a), and two different THF solvates (1 : 1 and 1 : 2) of the solvent-separated ion triples [{(Me3Si)2CH}(Ph)P(BH3)2]2[Mg(THF)6]·THF (2b) and [{(Me3Si)2CH}(Ph)P(BH3)2]2[Mg(THF)6]·2THF (2c). Similar reactions between two equivalents of 1 and either (4-tBuC6H4CH2)2Ca(THF)4 or [(Me3Si)2CH]2Sr(THF)2, followed by two equivalents of BH3·SMe2, give the heavier alkali metal complexes [{(Me3Si)2CH}(Ph)P(BH3)2]2M(THF)4 [M = Ca (3), Sr (4)]. Surprisingly, compounds 2a, 3 and 4 adopt almost identical structures in the solid state, which differ only in the geometrical arrangement of the phosphido-bis(borane) ligands and the hapticity of the borane groups.

A Series of Ultra-Efficient Blue Borane Fluorophores.

We present the first examples of alkylated derivatives of the macropolyhedral boron hydride, anti-B18H22, which is the gain medium in the first borane laser. This new series of ten highly stable and colorless organic-inorganic hybrid clusters are capable of the conversion of UVA irradiation to blue light with fluorescence quantum yields of unity. This study gives a comprehensive description of their synthesis, isolation, and structural characterization together with a delineation of their photophysical properties using a combined theoretical and experimental approach. Treatment of anti-B18H22 1 with RI (where R = Me or Et) in the presence of AlCl3 gives a series of alkylated derivatives, Rx-anti-B18H22-x (where x = 2 to 6), compounds 2-6, in which the 18-vertex octadecaborane cluster architectures are preserved and yet undergo a linear "polyhedral swelling", depending on the number of cluster alkyl substituents. The use of dichloromethane solvent in the synthetic procedure leads to dichlorination of the borane cluster and increased alkylation to give Me11-anti-B18H9Cl2 11, Me12-anti-B18H8Cl2 12, and Me13-anti-B18H7Cl2 13. All new alkyl derivatives are highly stable, extremely efficient (ΦF = 0.76-1.0) blue fluorophores (λems = 423-427 nm) and are soluble in a wide range of organic solvents and also a polystyrene matrix. The Et4-anti-B18H18 derivative 4b crystallizes from pentane solution in two phases with consequent multiabsorption and multiemission photophysical properties. An ultrafast transient UV-vis absorption spectroscopic study of compounds 4a and 4b reveals that an efficient excited-state absorption at the emission wavelength inhibits the laser performance of these otherwise remarkable luminescent molecules. All these new compounds add to the growing portfolio of octadecaborane-based luminescent species, and in an effort to broaden the perspective on their highly emissive photophysical properties, we highlight emerging patterns that successive substitutions have on the molecular size of the 18-vertex borane cluster structure and the distribution of the electron density within.

A Reversible NO-Triggered Multiple Metallaborane Cluster Fusion by Ligand Expulsion/Addition from (PMe2Ph)4Pt2B10H10 to Afford (PMe2Ph)8Pt8B40H40 and (PMe2Ph)5Pt4B20H20.

The dimetallic boron hydride cluster, (PMe2Ph)4Pt2B10H10 (1-Pt2), is known to reversibly sequester small molecules (e.g., O2, CO, and SO2) across its Pt-Pt cluster vector. Here, we report the very different effect of the addition of nitric oxide (NO) to solutions of (1-Pt2) that prompts the elimination of some of its phosphine ligands and the autofusion of the resultant {(PMe2Ph)xPt2B10H10} units to afford the metallaborane conglomerates (PMe2Ph)8Pt8B40H40 (2-Pt8, 38%) and (PMe2Ph)5Pt4B20H20 (3-Pt4, 34%). Single-crystal X-ray studies of these multicluster assemblies reveal the links between the clusters to be a combination of both Pt-Pt bonds and Pt-µH-B 2-electron, 3-center bonds in (2-Pt8) and Pt-µH-B 2-electron, 3-center bonds in (3-Pt4). For compound (2-Pt8), the cluster assemblage can be effectively reversed by the addition of ethyl isonitrile (EtNC) to afford (EtNC)3(PMe2Ph)2Pt2B10H10 4 in quantitative yield. The compounds were characterized by mass spectrometry, multielement NMR spectroscopy, and single-crystal X-ray diffraction studies.

Swollen Polyhedral Volume of the anti-B18H22 Cluster via Extensive Methylation: anti-B18H8Cl2Me12.

Methylation of anti-B18H22 (1) affords the first example of alkyl substitution of terminal hydrogen atoms on the fluorescent octadecaborane-22 molecule to give highly methylated 2,2'-Cl2-1,1',3,3',4,4',7,7',8,8',10,10'-Me12-anti-B18H8 (2). This extensive chemical substitution leads to a swelling in the polyhedral volume of the 18-vertex boron atomic skeleton of the molecule and an enhancement of the absorption and solubility characteristics of this highly fluorescent molecule. We propose this "swollen polyhedral volume" to be the result of a marked increase in the relative positivity of the "cluster-only total charge" of the boron atomic skeleton caused by the combined electron-withdrawing capacity of the 12 methyl groups. Enhancement in the absorption and solubility properties may be crucial in the design of new borane-based laser materials.

A regioselectively 1,1',3,3'-tetrazincated ferrocene complex displaying core and peripheral reactivity.

Regioselective 1,1',3,3'-tetrazincation [C-H to C-Zn(tBu)] of ferrocene has been achieved by reaction of a fourfold excess of di-t-butylzinc (tBu2Zn) with sodium 2,2,6,6-tetramethylpiperidide (NaTMP) in hexane solution manifested in the trimetallic iron-sodium-zinc complex [Na4(TMP)4Zn4(tBu)4{(C5H3)2Fe}], 1. X-ray crystallographic studies supported by DFT modelling reveal the structure to be an open inverse crown in which two [Na(TMP)Zn(tBu)Na(TMP)Zn(tBu)]2+ cationic units surround a {(C5H3)2Fe}4- tetraanion. Detailed C6D6 NMR studies have assigned the plethora of 1H and 13C chemical shifts of this complex. It exists in a major form in which capping and bridging TMP groups interchange, as well as a minor form that appears to be an intermediate in this complicated exchange phenomenon. Investigation of 1 has uncovered two distinct reactivities. Two of its peripheral t-butyl carbanions formally deprotonate toluene at the lateral methyl group to generate benzyl ligands that replace these carbanions in [Na4(TMP)4Zn4(tBu)2(CH2Ph)2{(C5H3)2Fe}], 2, which retains its tetrazincated ferrocenyl core. Benzyl-Na π-arene interactions are a notable feature of 2. In contrast, reaction with pyridine affords the crystalline product {[Na·4py][Zn(py*)2(tBu)·py]}∞, 3, where py is neutral pyridine (C5H5N) and py* is the anion (4-C5H4N), a rare example of pyridine deprotonated/metallated at the 4-position. This ferrocene-free complex appears to be a product of core reactivity in that the core-positioned ferrocenyl anions of 1, in company with TMP anions, have formally deprotonated the heterocycle.

Some reflections on symmetry: pitfalls of automation and some illustrative examples.

In the context of increasing hardware and software automation in the process of crystal structure determination by X-ray diffraction, and based on conference sessions presenting some of the experience of senior crystallographers for the benefit of younger colleagues, an outline is given here of some basic concepts and applications of symmetry in crystallography. Three specific examples of structure determinations are discussed, for which an understanding of these aspects of symmetry avoids mistakes that can readily be made by reliance on automatic procedures. Topics addressed include pseudo-symmetry, twinning, real and apparent disorder, chirality, and structure validation.

Macropolyhedral Nickelaboranes from the Metal-Assisted Fusion of KB9H14.

The reaction of K[arachno-B9H14] with [NiCl2(dppe)] produces four new 19-vertex macropolyhedral metallaboranes that result from borane cluster fusion: [9'-(dppe)-9'-Ni-anti-B18H20] (1) and isomeric [11'-(dppe)-11'-Ni-syn-B18H20] (2), together with the chlorine-substituted derivative of 1, [5'-Cl-9'-(dppe)-9'-Ni-anti-B18H19] (3), and the 18-vertex cluster compound [7'-(dppe)-7'-anti-NiB17H21] (4). Two closo 10-vertex single-cluster species, [1-(dppe)-1-closo-NiB9H7Cl2] (5) and [1-(dppe)-1-closo-NiB9H7Cl(OH)] (6), were also isolated from the reaction. The production of the metalated syn-octadecaborane isomer 2 from the fusion of two arachno-nonaborate clusters is the first such case to be observed; in all other reported cases fusion has resulted in products with the anti-octadecaboranyl bis-nido configuration.

The development and exploitation of synchrotron single-crystal diffraction for chemistry and materials.

A historical account is given of the 25-year development of dedicated synchrotron beamlines for single-crystal diffraction as applied to the so-called small-molecule fields of chemistry and materials science. Designs have drawn on previous successful models in macromolecular crystallography, with appropriate modifications in view of the different properties and behaviour of the respective sample types. Key factors in making these facilities attractive and productive for users include familiarity of operational procedures and the availability of experimental techniques and features normally found in local chemical crystallography laboratories, especially for the handling of samples and processing of diffraction data. Beamlines dedicated to single-crystal diffraction rather than shared with other techniques can be optimized for effective and efficient use. The experience gained from the original design, development and exploitation of stations 9.8 and 16.2SMX at the Daresbury Laboratory Synchrotron Radiation Source and beamline 11.3.1 at the Advanced Light Source have led to highly productive current facilities at ALS beamline 12.2.1 and Diamond Light Source beamline I19, including the recent introduction of remote-access operation. Such facilities have generated and continue to provide major impact in academic and commercial research that could otherwise not be achieved, including patents and applications in pharmaceuticals, energy and gas storage systems, and government policy. This article is part of the theme issue 'Fifty years of synchrotron science: achievements and opportunities'.