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The coordination chemistry towards silver(I) of the small-ring macrocycles [9]aneN2S (1-thia-4,7-diazacyclononane) and [9]aneNS2 (1,4-dithia-7-azacyclononane) incorporating nitrile-functionalized pendant arms is considered both in the presence and the absence of exogenous bridging ligands. The aim is to understand the influence of the number and length of the pendant arms on the nuclearity and dimensionality of the resulting complexes. The X-ray crystal structures of the complexes bis[4,7-bis(cyanomethyl)-1-thia-4,7-diazacyclononane-κ3 N,N′,S]silver(I) tetrafluoridoborate, [Ag(C10H16N4S)2]BF4 or [Ag(L1 )2]BF4, [4,7-bis(2-cyanoethyl)-1-thia-4,7-diazacyclononane-κ3 N,N′,S](thiocyanato-κS)silver(I), [Ag(C12H20N4S)(NCS)] or [Ag(L2 )(SCN)], and μ-thiocyanato-κ2 S:S-bis{[7-(2-cyanoethyl)-1,4-dithia-7-azacyclononane-κ3 N,S,S′]silver(I)} tetrafluoridoborate, [Ag2(C9H16N2S2)2(SCN)]BF4 or [Ag2(L3 )2(μ-SCN)]BF4, are discussed in relation to analogous compounds in the literature.

Ruthenium complexes of hemilabile phosphinocarboxamide ligands, and their use to form metallacycles using halide abstraction/deprotonation reactions are reported. Thus, [Ru(p-cym){PPh2C(=O)NHR}Cl2; R = iPr (1), Ph (2), p-tol (3)] and [Ru(p-cym){PPh2C(=O)N(R)C(=O)N(H)R}Cl2; R = Ph (4), p-tol (5)] were synthesized from [(p-cym)RuCl2]2 (p-cym = para-cymene) and phosphinocarboxamides or phosphinodicarboxamides, respectively. Single crystal X-ray diffraction measurements on 1–5 reveal coordination to ruthenium through the phosphorus donor, with an intramolecular hydrogen bond between the amine-bound proton and a metal-bound chloride. Six-membered metallacycles formed by halide abstraction/deprotonation of complexes 4 and 5 afforded [Ru(p-cym){κ2-P,N-PPh2C(=O)N(R)C(=O)NR}Cl] [R = Ph (6), p-tol (7)]. These species exist as a mixture of two rotational isomers in solution, as demonstrated by NMR spectroscopy.

We report the reversible adsorption of ammonia (NH3) up to 9.9 mmol g–1 in a robust Al-based metal–organic framework, MFM-303(Al), which is functionalized with free carboxylic acid and hydroxyl groups. The unique pore environment decorated with these acidic sites results in an exceptional packing density of NH3 at 293 K (0.801 g cm–3) comparable to that of solid NH3 at 193 K (0.817 g cm–3). In situ synchrotron X-ray diffraction and inelastic neutron scattering reveal the critical role of free −COOH and −OH groups in immobilizing NH3 molecules. Breakthrough experiments confirm the excellent performance of MFM-303(Al) for the capture of NH3 at low concentrations under both dry and wet conditions.

The synthesis and coordination properties of two fluorescent chemosensors, featuring [9]aneN3 (1,4,7-triazacyclononane; L1) and [12]aneNS3 (1-aza-4,7,10-trithiacyclododecane; L2) as receptor units, and a quinoline pendant arm with an amide group as a functional group spacer are described. The optical responses of L1 and L2 in the presence of several metal ions were analysed in MeCN/H2 O (1 : 4 v/v) solutions. A selective chelation enhancement of fluorescence (CHEF) effect was observed in the presence of Zn2+ in the case of L1, and in the presence of Cd2+ in the case of L2, following the formation of a 1 : 1 and a 1 : 2 metal/ligand complex, respectively, which was also confirmed by potentiometric measurements. 1 H and 13 C NMR measurements in CD3 CN/CDCl3 in combination with molecular mechanics calculations show that for both complexes of L1 and L2 with Zn2+ and Cd2+ , respectively, the coordination of the carbonyl group from the pendant arm could be the origin of the observed optical selectivity.

Herein we report the synthesis of three heteroleptic first‐row transition metal(II) complexes containing carbazolido NNN pincer ligands and conversion to the corresponding metal(I)‐carbonyl complexes via a reductive carbonylation route. These complexes are precatalysts for the hydrophosphination of activated alkenes, affording a cobalt‐catalysed hydrophosphination process that solely and selectively yields the β addition (anti‐Markovnikov) product. The scope of this transformation has been investigated using a variety of activated alkenes. Isolation and characterisation of substrate‐coordinated intermediates reveal available coordination sites, which provide insight into the proposed catalytic cycle., This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/R004064/1]; The Leverhulme Trust [grant number RPG‐2014‐317]; CONACYT (Mexican Council for Science and Technology) [grant number CVU 600474] and the University of Nottingham.

The reaction between a two-coordinate Co(ii) diaryl complex and "GaI" affords 2,6-Pmp2C6H3CoGa3I5, in a new geometry for a heavier group 13-transition metal cluster. Experimental and computational investigations show that this compound is best described as a nido metalla-group 13 cluster.

A two-coordinate Fe(II) m-terphenyl complex acts as a precatalyst for the hydroamination of isocyanates, affording urea and biuret derivatives, with product selectivity accomplished via modificatio...

Co-crystals of thiocyanuric acid (TCA) and five multitopic bases are reported, and their structures are compared. The adducts of all five co-crystals form two-dimensional hydrogen-bonded sheets tha...

In this paper, we describe experimental evidence of a change in the emission energy as a function of the Au-Au distance. We have employed a luminescent complex exhibiting an aurophilic interaction, which is weak enough to allow its length to be modified by external pressure but rigid enough to confer structural stability on the complex. By determining the crystal structures and emission characteristics over a range of pressures, we have identified an exponential relationship between the energy of the emitted light and the metal-metal distances under pressure. This result can be indirectly related to the repulsive branch of the fitted function representing the energy of the system in the ground state at different Au-Au distances. The relativistic nature of gold appears to play an important role in the behavior of this complex.

We describe here the synthesis and coordination properties of three new derivatives of [9]aneN3 containing phenyl/quinoline pendant arm derivatives (L1, L2 and L3, respectively) also featuring urea (L1–L2) or amide (L3) functions as “non-innocent” spacers. At first, L1, L2 and L3 were studied considering the interaction with a series of anions (AcO−, BzO−, H2PO4−, F−, and Cl−) by means of 1H NMR measurements. Subsequently, the optical responses of L2 and L3 in the presence of several metal ions Cd2+, Co2+, Cu2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Ni2+, Zn2+ and Pb2 were analysed in MeCN/H2O (4 : 1 v/v). As observed by spectrophotometric and spectrofluorimetric titrations, there were significant changes in the absorbance and fluorescent emission of L2 upon addition of increasing amounts of Cd2+, Zn2+, Pb2+ and Cu2+ in MeCN/H2O (4 : 1 v/v). In particular, titrations of L2 with Cd2+, Zn2+ or Pb2+ showed an almost comparable CHEF effect up to an M2+/L2 molar ratio of 1. Overall, no significant optical selectivity was observed in the case of L2. Conversely, L3 revealed an OFF–ON selective response only in the presence of the Zn2+ ion in MeCN/H2O (4 : 1 v/v), which can be attributed to the formation of both 1 : 1 and 1 : 2 metal-to-ligand complexes, as also confirmed by potentiometric measurements. Finally, crystals of [ZnL1(Ac)](Ac) (1), [CuL1(Cl)](Cl)·H2O (2) and [CuL3](NO3) (3) were grown and analysed by X-ray diffraction. 1 and 3 feature the metal center in a pseudo-octahedral coordination geometry coordinated also by the carbonyl group from one pendant arm, while in the case of 2, one of the six coordination sites in the final distorted octahedral geometry is occupied by the nitrogen donor from the urea group of one pendant arm.

The reactions of 1,1′-bis(3-methyl-4-imidazolin-2-selone)methane (L1) and 1,2-bis(3-methyl-4-imidazolin-2-selone)ethane (L2) with mesityltellurenyl iodide (MesTeI) [Mes = 2,4,6-Me3C6H2] yielded the neutral [L1·2MesTeI]·2CH2Cl2 and the ionic [L2·MesTe]2(MesTeI2)2 compounds, respectively, which were characterized by X-ray diffraction analysis. DFT (mPW1PW//LANL08d/def2-SVP) and NBO calculations, supported by structural and FT-Raman measurements, show that the latter compound represents the first example of an authentic mesityltellurenyl cation, [MesTe]+, stabilized within a [MesTe(B)2]+ (B = Lewis base) charge transfer adduct featuring a 3c-4e Se→Te←Se three-body system.

The desolvated (3,24)-connected metal-organic framework (MOF) material, MFM-160a, [Cu3(L)(H2O)3] [H6L = 1,3,5-triazine-2,4,6-tris(aminophenyl-4-isophthalic acid)], exhibits excellent high-pressure uptake of CO2 (110 wt% at 20 bar, 298 K) and highly selective separation of C2 hydrocarbons from CH4 at 1 bar pressure. Henry's law selectivities of 79:1 for C2H2:CH4 and 70:1 for C2H4:CH4 at 298 K are observed, consistent with ideal adsorption solution theory (IAST) predictions. Significantly, MFM-160a shows a selectivity of 16:1 for C2H2:CO2. Solid-state 2H NMR spectroscopic studies on partially deuterated MFM-160-d12 confirm an ultra-low barrier (∼2 kJ mol-1) to rotation of the phenyl group in the activated MOF and a rotation rate 5 orders of magnitude slower than usually observed for solid-state materials (1.4 × 106 Hz cf. 1011-1013 Hz). Upon introduction of CO2 or C2H2 into desolvated MFM-160a, this rate of rotation was found to increase with increasing gas pressure, a phenomenon attributed to the weakening of an intramolecular hydrogen bond in the triazine-containing linker upon gas binding. DFT calculations of binding energies and interactions of CO2 and C2H2 around the triazine core are entirely consistent with the 2H NMR spectroscopic observations.

Structural transitions of host systems in response to guest binding dominate many chemical processes. We report an unprecedented type of structural flexibility within a meta-rigid material, MFM-520, which exhibits a reversible periodic-to-aperiodic structural transition resulting from a drastic distortion of a [ZnO4N] node controlled by the specific host-guest interactions. The aperiodic crystal structure of MFM-520 has no three-dimensional (3D) lattice periodicity but shows translational symmetry in higher-dimensional (3 + 2)D space. We have directly visualized the aperiodic state which is induced by incommensurate modulation of the periodic framework of MFM-520·H2O upon dehydration to give MFM-520. Filling MFM-520 with CO2 and SO2 reveals that, while CO2 has a minimal structural influence, SO2 can further modulate the structure incommensurately. MFM-520 shows exceptional selectivity for SO2 under flue-gas desulfurization conditions, and the facile release of captured SO2 from MFM-520 enabled the conversion to valuable sulfonamide products. MFM-520 can thus be used as a highly efficient capture and delivery system for SO2.

The past decade has seen a diverse range of breakthrough inventions that are derived from gold complexes, including the application of aurophilic interactions in the preparation of stimuli-responsive materials. Examples of these gold-based materials include aurophilicity-induced metallogelators, mechanochromic, thermochromic, vapochromic, and solvatochromic luminescent compounds, as well as sensory materials for the detection of metal ions. Sophisticated properties of gold complexes with Au···Au contacts have been explored at the edge of several disciplines including chemistry, crystallography, molecular engineering and advanced materials. As science paves its way to innovation, cross-disciplinary research moves from being a luxury to becoming a necessity. Development of the concept of aurophilicity and its use in designing novel materials is a true example of innovation on a multidisciplinary platform. As miniaturization continues to influence the next generation of technological advancement, using the properties of molecules as chemical tools to enable such developments becomes extremely important. In this Review, recent examples of gold complexes which exhibit a response to external stimuli have been collected and some of their potential applications discussed for selected cases.

A magnesium complex (1) featuring a bidentate aminopyridinato ligand is a remarkably selective catalyst for the dehydrocoupling of amine‐boranes. This reaction proceeds to completion with low catalyst loadings (1 mol %) under mild conditions (60 °C), exceeding previously reported s‐block systems in terms of selectivity, rate, and turnover number (TON). Mechanistic studies by in situ NMR analysis reveals the reaction to be first order in both catalyst and substrate. A reaction mechanism is proposed to account for these findings, with the high TON of the catalyst attributed to the bidentate nature of the ligand, which allows for reversible deprotonation of the substrate and regeneration of 1 as a stable resting state.

Designing porous materials which can selectively adsorb CO2 or CH4 is an important environmental and industrial goal which requires an understanding of the host–guest interactions involved at the atomic scale. Metal–organic polyhedra (MOPs) showing permanent porosity upon desolvation are rarely observed. We report a family of MOPs (Cu-1a, Cu-1b, Cu-2), which derive their permanent porosity from cavities between packed cages rather than from within the polyhedra. Thus, for Cu-1a, the void fraction outside the cages totals 56% with only 2% within. The relative stabilities of these MOP structures are rationalized by considering their weak nondirectional packing interactions using Hirshfeld surface analyses. The exceptional stability of Cu-1a enables a detailed structural investigation into the adsorption of CO2 and CH4 using in situ X-ray and neutron diffraction, coupled with DFT calculations. The primary binding sites for adsorbed CO2 and CH4 in Cu-1a are found to be the open metal sites and pockets defined by the faces of phenyl rings. More importantly, the structural analysis of a hydrated sample of Cu-1a reveals a strong hydrogen bond between the adsorbed CO2 molecule and the Cu(II)-bound water molecule, shedding light on previous empirical and theoretical observations that partial hydration of metal−organic framework (MOF) materials containing open metal sites increases their uptake of CO2. The results of the crystallographic study on MOP–gas binding have been rationalized using DFT calculations, yielding individual binding energies for the various pore environments of Cu-1a., We report a family of metal−organic polyhedra (MOP), which derive their permanent porosity from cavities between packed cages rather than from within the polyhedra. The relative stabilities of these MOP structures are rationalized by considering their weak nondirectional packing interactions using Hirshfeld surface analysis. A detailed structural investigation into the adsorption of CO2 and CH4 is reported using in situ X-ray and neutron diffraction, coupled with DFT calculations.

Bromination of (AsPh2)2S leads to cleavage of the sulfide bridge to give AsPh2Br when 1 mol of bromine is used but with 2 mols the product is the polybromide, [AsPh2Br2]2[Br8], containing the previously unknown [AsPh2Br2]+ cation and a rare [(Br3)−…(Br2)…(Br3)−] ensemble whose short (yet not covalent) Br2…Br3 contacts have previously supported tentative description as an octabromide Br82− anion. X-ray crystallography shows that the compound has a three dimensional supramolecular structure based on cooperativity of weak intermolecular Csingle bondH…π, Csingle bondH…Br hydrogen bonds and secondary Br…Br interactions in the solid state. The electronic structure and the stability of the [AsPh2Br2]2[Br8] are rationalized using DFT and HF calculations and molecular orbital considerations.

The development of synthetic analogs of the active sites of [NiFe] hydrogenases remains challenging, and, in spite of the number of complexes featuring a [NiFe] center, those featuring CO and CN- ligands at the Fe center are under-represented. We report herein the synthesis of three bimetallic [NiFe] complexes [Ni(N2S2)Fe(CO)2(CN)2], [Ni(S4)Fe(CO)2(CN)2], and [Ni(N2S3)Fe(CO)2(CN)2] that each contain a Ni center that bridges through two thiolato S donors to a {Fe(CO)2(CN)2} unit. X-ray crystallographic studies on [Ni(N2S3)Fe(CO)2(CN)2], supported by DFT calculations, are consistent with a solid-state structure containing distinct molecules in the singlet (S = 0) and triplet (S = 1) states. Each cluster exhibits irreversible reduction processes between -1.45 and -1.67 V vs Fc+/Fc and [Ni(N2S3)Fe(CO)2(CN)2] possesses a reversible oxidation process at 0.17 V vs Fc+/Fc. Spectroelectrochemical infrared (IR) and electron paramagnetic resonance (EPR) studies, supported by density functional theory (DFT) calculations, are consistent with a NiIIIFeII formulation for [Ni(N2S3)Fe(CO)2(CN)2]+. The singly occupied molecular orbital (SOMO) in [Ni(N2S3)Fe(CO)2(CN)2]+ is based on Ni 3dz2 and 3p S with the S contributions deriving principally from the apical S-donor. The nature of the SOMO corresponds to that proposed for the Ni-C state of the [NiFe] hydrogenases for which a NiIIIFeII formulation has also been proposed. A comparison of the experimental structures, and the electrochemical and spectroscopic properties of [Ni(N2S3)Fe(CO)2(CN)2] and its [Ni(N2S3)] precursor, together with calculations on the oxidized [Ni(N2S3)Fe(CO)2(CN)2]+ and [Ni(N2S3)]+ forms suggests that the binding of the {Fe(CO)(CN)2} unit to the {Ni(CysS)4} center at the active site of the [NiFe] hydrogenases suppresses thiolate-based oxidative chemistry involving the bridging thiolate S donors. This is in addition to the role of the Fe center in modulating the redox potential and geometry and supporting a bridging hydride species between the Ni and Fe centers in the Ni-C state.

The structural characterization of single crystals of di-4-pyridyl-substituted 3,4,9,10-perylenetetracarboxylic diimide reveals a surprising triple helical arrangement. The intermolecular interactions that lead to such an arrangement are investigated by Hirshfeld surface analysis and indicate that the supramolecular structure arises due to a combination of C–H···O interactions and π–π stacking interactions between adjacent perylene diimide (PDI) species. The interplay of these interactions leads to the formation of a tubular structure enclosed by the triple helix of PDI molecules. In contrast, the analogous phenyl-substituted molecule forms a simple one-dimensional stack of PDI molecules which is also unusual in that the perylene core adopts an essentially planar arrangement despite bay substitution.

Two new Cu(II) complexes [Cu(L1)(N3)](1) and [Cu(L1)(NCS)]n(2), where HL1 ((E)-4-((2(dimethylamino)ethylimino)methyl)-5-(hydroxymethyl)-2-methylpyridin-3-ol) is a N,N,O-donor Schiff base ligand, have been synthesized. These complexes were characterized on the basis of spectroscopic, electrochemical, and other physicochemical properties. X-ray crystal structure determination reveals that in complex 1, Cu(II) is in a square planar geometry with the N,N,O-donor ligand and a terminally coordinated azide ion. In complex 2, however, Cu(II) assumes a square pyramidal geometry, and apart from the tridentate Schiff base ligand there is a thiocyanate ion, which acts in a μ1,3-bridging mode, connecting adjacent Cu(II) atoms in an axial-equatorial fashion forming an one dimensional chain. Cyclic voltammetry shows that complexes undergo Cu(II)/Cu(I) reductions at −0.40 to −0.55V followed by imine reduction at around −0.7V. Cu(I)/Cu(0) reduction is observed at approximately −0.9V. Complex 1 also shows appreciable catalytic activity for the aerial oxidation of 3,5 DTBCH2 to DTBQ (catecholase activity). Both the complexes also show strong binding affinity towards calf-thymus DNA.

Two- and three-coordinate manganese m-terphenyl complexes are precatalysts for the dehydrogenation of dimethylamine-borane (Me2NH·BH3) affording one equivalent of molecular hydrogen and half an equivalent of [Me2N–BH2]2. Experimental studies into the nature of the catalyst indicate that small changes in the coordination environment give rise to significant differences in the reaction mechanism, occurring through a homogeneous mechanism for two-coordinate precatalysts, whilst for the three-coordinate species a heterogeneous mechanism takes place where nanoparticles are responsible for the catalysis.

Group 1 salts containing carbazolido NNN pincer ligands are precatalysts for the dehydrogenation of Me2NH·BH3. NMR monitoring and DOSY studies show a heavy dependence on the metal and solvent, allowing in some cases selective formation of dehydrogenation products consistent with hydrogen liberation.

With an exceptional portfolio of properties such as high water content and cross-linked nature, hydrogels can provide an ideal and compatible environment not only to encapsulate but also to control the delivery of biological therapeutics. However, uncontrollable degradation, release and especially swelling impose limitations on our ability to engineer these gels. Herein a zirconium metallogel is proposed that utilizes zirconyl tetramers as the metal component in conjunction with a nucleic acid (adenine). The variable gel-formation temperature as a simple step of gel formation allows the tuning of gel formation and properties by controlling the adenine-nucleobase interactions. Reconstitution, entrapment, degradation, cytotoxicity, and release of bovine serum albumin (BSA) as a negatively charged macromolecular therapeutic agent were investigated. The controllable and sustained release of BSA, offers a route to new tailorable protein delivery applications.

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The first transition metal catalyzed hydrophosphination of isocyanates is presented. The use of low-coordinate iron(II) precatalysts leads to an unprecedented catalytic double insertion of isocyanates into the P−H bond of diphenylphosphine to yield phosphinodicarboxamides [Ph2PC(=O)N(R)C(=O)N(H)R], a new family of derivatized organophosphorus compounds. This remarkable result can be attributed to the low-coordinate nature of the iron(II) centers whose inherent electron deficiency enables a Lewis-acid mechanism in which a combination of the steric pocket of the metal center and substrate size determines the reaction products and regioselectivity.

The phosphinimine, trimethylsilyl-substituted BIPM ligand [BIPM = bis(iminophosphorano)methanide] has been used to stabilise CH(Ph2PNSiMe3)2MgFe(η5-C5H5)(CO)2 (1), which is a structurally authenticated complex exhibiting a direct, unsupported bond between an alkaline earth metal and a transition metal. The FTIR-measured carbonyl stretching frequencies for this complex suggest that there is a polarisation of charge from the transition metal fragment to the magnesium centre. The presence of a polar metal-metal bond in 1 is confirmed by DFT calculations, which suggest that the Mg−Fe bond is predominantly ionic in nature.

Nine dioxidomolybdenum(VI) complexes were synthesized by the ?reaction of MoO3 with tridentate hydrazone Schiff base ligands ?obtained from the reaction of aromatic acid hydrazides (3-hydroxy-2-?naphthoic acid hydrazide, 4-pyridine carboxylic acid hydrazide or 2-?furane carboxylic acid hydrazide) and ortho-hydroxy aldehyde ?derivatives (5-iodo-2-hydroxybenzaldehyde, 2-hydroxy-1-?naphthaldehyde or 2-hydroxy-3-methoxybenzaldehyde). All ligands ?and complexes were characterized by elemental analysis and ?spectroscopic methods. The structures of seven complexes were ?further elucidated by single-crystal X-ray diffraction analysis which ?indicated a distorted octahedral geometry at the metal centre. ?Spectroscopic and X-ray analyses indicated that the ligands are ?coordinated to the molybdenum(VI) ion as dinegative ligands due to ?deprotonation of phenolic OH and amidic NH groups upon ?complexation. These complexes were used as catalyst in ?the oxidation of cyclooctene and thioanisol in the presence of ?hydrogen peroxide as environmental friendly oxidant. In order to ?achieve the highest catalytic activity, the effects of important ?parameters such as solvent, temperature and the molar ratio of ?oxidant to substrate were optimized. The results indicate that ?electron-withdrawing substituents on the ligands increase the ?catalytic activity of dioxidomolybdenum(VI)-hydrazone complexes.?

The tetranuclear heterometallic complex [Li2Zn2(piv)6(py)2] (1, where piv– = pivalate and py = pyridine) has been successfully employed as a presynthesized node for the construction of four porous metal–organic frameworks (MOFs) [Li2Zn2(R-bdc)3(bpy)]·solv (2-R, R-bdc2–; R = H, Br, NH2, NO2) by reaction with 4,4′-bipyridine (bpy) and terephthalate anionic linkers. The [Li2Zn2] node is retained in the products, representing a rare example of the rational step-by-step design of isoreticular MOFs based on complex heterometallic building units. The permanent porosity of the activated frameworks was confirmed by gas adsorption isotherm measurements (N2, CO2, CH4). Three compounds, 2-H, 2-Br, and 2-NH2 (but not 2-NO2), feature extensive hysteresis between the adsorption and desorption curves in the N2 isotherms at low pressures. The substituents R decorate the inner surface and also control the aperture of the channels, the volume of the micropores, and the overall surface area, thus affecting both the gas uptak...

Chromeazurol B (Na2HL) is a pH-sensitive (halochromic) dye based on a hydroxytriarylmethane core and two carboxylate functional groups, which makes it suitable for the synthesis of coordination polymers. Two new coordination polymers [NaZn4(H2O)3(L)3]·3THF·3H2O (1) and [Zn3(H2O)3(μ2- OH2)(μ3-OH)(HL)2(H2L)]·2THF·3H2O (2) incorporating Chromeazurol B linkers have been prepared and characterised. The structure of 1 comprises pentanuclear heterometallic {Zn4Na} nodes linked by six L3– anions to give a layered structure with a honeycomb topology. 2 crystallizes as a double-chain ribbon (ladder) structure with two types of metal node: a mononuclear Zn(II) cation and tetranuclear {Zn(II)}4 cluster. Chromeazurol B anions link each tetranuclear cluster to four individual Zn(II) cations and each Zn(II) cation with four tetranuclear clusters. Both compounds show pH-sensitivity in water solution which can be observed visually, giving the first example of a halochromic coordination polymer. The halochromic properties of 1 towards HCl vapors were systematically investigated. As-synthesized violet-grey 1 reversibly changes color from orange to pink in the presence of vapors of 2M and 7M HCl, respectively. The coordination of the Chromeazurol B anion at each color stage was examined by diffuse reflectance spectroscopy and FT-IR measurements. The remarkable stability of 1 to acid and the observed reversible and reproducible color changes provide a new design for multifunctional sensor materials.

In two binuclear complexes of formula [Cu 2 (AnthenMe 2 ) 2 (μ 1,3 -SCN) 2 (NCS) 2 ] ( 1 ) and [Cu 2 (AnthenMe 2 ) 2 (μ 1,1 -N 3 ) 2 (N 3 ) 2 ] ( 2 ), where AnthenMe 2 is the bidentate N , N -donor Schiff base formed by anthracene-9-aldehyde and N , N -dimethylethylenediamine, each Cu(II) center adopts a square pyramidal geometry with N 4 S and N 5 coordination environments for 1 and 2 , respectively. In spite of the very different Cu⋯Cu separations in these two complexes (5.141 A in 1 and 3.4744 A in 2 ), the molecules show very similar catalytic efficiency for the aerial oxidation of 3,5-ditertiarybutyl catechol (DTBCH 2 ) to the corresponding quinone (DTBQ), probably because similar mononuclear complexes are involved in the catalytic reaction in both the cases. The k cat and k cat / K M values of 1.53(0.20) × 10 4 h −1 and 5.71(0.15) × 10 7 M −1 h −1 for 1 and 1.56(0.12) × 10 4 h −1 and 5.61(0.12) × 10 7 M −1 h −1 for 2 are comparable to the best values reported in the literature for Cu(II) model complexes of catecholase.

We describe here the synthesis and coordination properties of three new derivatives of [9]aneN3 containing phenyl/quinoline pendant arm derivatives (L1, L2 and L3, respectively) also featuring urea (L1-L2) or amide (L3) functions as "non-innocent" spacers. At first, L1, L2 and L3 were studied considering the interaction with a series of anions (AcO-, BzO-, H2PO4-, F-, and Cl-) by means of 1H NMR measurements. Subsequently, the optical responses of L2 and L3 in the presence of several metal ions Cd2+, Co2+, Cu2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Ni2+, Zn2+ and Pb2 were analysed in MeCN/H2O (4 : 1 v/v). As observed by spectrophotometric and spectrofluorimetric titrations, there were significant changes in the absorbance and fluorescent emission of L2 upon addition of increasing amounts of Cd2+, Zn2+, Pb2+ and Cu2+ in MeCN/H2O (4 : 1 v/v). In particular, titrations of L2 with Cd2+, Zn2+ or Pb2+ showed an almost comparable CHEF effect up to an M2+/L2 molar ratio of 1. Overall, no significant optical selectivity was observed in the case of L2. Conversely, L3 revealed an OFF-ON selective response only in the presence of the Zn2+ ion in MeCN/H2O (4 : 1 v/v), which can be attributed to the formation of both 1 : 1 and 1 : 2 metal-to-ligand complexes, as also confirmed by potentiometric measurements. Finally, crystals of [ZnL1(Ac)](Ac) (1), [CuL1(Cl)](Cl)·H2O (2) and [CuL3](NO3) (3) were grown and analysed by X-ray diffraction. 1 and 3 feature the metal center in a pseudo-octahedral coordination geometry coordinated also by the carbonyl group from one pendant arm, while in the case of 2, one of the six coordination sites in the final distorted octahedral geometry is occupied by the nitrogen donor from the urea group of one pendant arm.

A magnesium complex (1) featuring a bidentate aminopyridinato ligand is a remarkably selective catalyst for the dehydrocoupling of amine-boranes. This reaction proceeds to completion with low catalyst loadings (1 mol %) under mild conditions (60 °C), exceeding previously reported s-block systems in terms of selectivity, rate, and turnover number (TON). Mechanistic studies by in situ NMR analysis reveals the reaction to be first order in both catalyst and substrate. A reaction mechanism is proposed to account for these findings, with the high TON of the catalyst attributed to the bidentate nature of the ligand, which allows for reversible deprotonation of the substrate and regeneration of 1 as a stable resting state.

We report a series of six isoreticular metal–organic frameworks (MOFs) for selective gas adsorption, specifically for selective adsorption of CO2 and C2H2., In order to develop new porous materials for applications in gas separations such as natural gas upgrading, landfill gas processing and acetylene purification it is vital to gain understanding of host–substrate interactions at a molecular level. Herein we report a series of six isoreticular metal–organic frameworks (MOFs) for selective gas adsorption. These materials do not incorporate open metal sites and thus provide an excellent platform to investigate the effect of the incorporation of ligand functionality via amide and alkyne groups on substrate binding. By reducing the length of the linker in our previously reported MFM-136, we report much improved CO2/CH4 (50 : 50) and CO2/N2 (15 : 85) selectivity values of 20.2 and 65.4, respectively (1 bar and 273 K), in the new amide-decorated MOF, MFM-126. The CO2 separation performance of MFM-126 has been confirmed by dynamic breakthrough experiments. In situ inelastic neutron scattering and synchrotron FT-IR microspectroscopy were employed to elucidate dynamic interactions of adsorbed CO2 molecules within MFM-126. Upon changing the functionality to an alkyne group in MFM-127, the CO2 uptake decreases but the C2H2 uptake increases by 68%, leading to excellent C2H2/CO2 and C2H2/CH4 selectivities of 3.7 and 21.2, respectively. Neutron powder diffraction enabled the direct observation of the preferred binding domains in MFM-126 and MFM-127, and, to the best of our knowledge, we report the first example of acetylene binding to an alkyne moiety in a porous material, with over 50% of the acetylene observed within MFM-127 displaying interactions (

This study investigates the coordination chemistry of the tetradentate pyridine-containing 12-membered macrocycles L1-L3 towards Platinum Group metal ions PdII, PtII, and RhIII. The reactions between the chloride salts of these metal ions and the three ligands in MeCN/H2O or MeOH/H2O (1:1 v/v) are shown, and the isolated solid compounds are characterized, where possible, by mass spectroscopy and 1H- and 13C-NMR spectroscopic measurements. Structural characterization of the 1:1 metal-to-ligand complexes [Pd(L1)Cl]2[Pd2Cl6], [Pt(L1)Cl](BF4), [Rh(L1)Cl2](PF6), and [Rh(L3)Cl2](BF4)·MeCN shows the coordinated macrocyclic ligands adopting a folded conformation, and occupying four coordination sites of a distorted square-based pyramidal and octahedral coordination environment for the PdII/PtII, and RhIII complexes, respectively. The remaining coordination site(s) are occupied by chlorido ligands. The reaction of L3 with PtCl2 in MeCN/H2O gave by serendipity the complex [Pt(L3)(m-1,3-MeCONH)PtCl(MeCN)](BF4)2·H2O, in which two metal centers are bridged by an amidate ligand at a Pt1-Pt2 distance of 2.5798(3) Å and feature one square-planar and one octahedral coordination environment. Density Functional Theory (DFT) calculations, which utilize the broken symmetry approach (DFT-BS), indicate a singlet d8-d8 PtII-PtII ground-state nature for this compound, rather than the alleged d9-d7 PtI-PtIII mixed-valence character reported for related dinuclear Pt-complexes.

The Co(III) and Ni(II) complexes [Co(L2)2(bpy)]Cl (1) and [Ni(L2)2(phen)] (2) (where L2 is a monoanionic bidentate hydrazone ligand and bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) have been synthesized and characterized by infra-red, UV–Vis, ESI-MS spectroscopies and elemental analyses. Complexes 1 and 2 were structurally characterized by single crystal X-ray diffraction. Structural analysis reveals a distorted octahedral coordination environment around the metal center with an MN4O2 chromophore [M = Co(III) and Ni(II)], with the hydrazone ligand acting as a monoanionic bidentate N,O-donor. Binding of complexes 1 and 2 with calf thymus DNA (CT-DNA) was investigated by UV–Vis absorption, fluorescence spectroscopy and viscosity measurements. Complex 1 shows excellent catecholase mimicking activity with 3,5-di-tert-butylcatechol (3,5-DTBCH2) as the substrate. Kinetic measurements suggest the rate of catechol oxidation follows saturation kinetics with respect to the substrate and the kcat value was found to be quite high, with a value of 1.00 × 105 h−1.

The three reported phases of the mononuclear macrocyclic PdIIcomplex [PdCl2([9]aneS2O)] [(1); [9]aneS2O = 1-oxa-4,7-dithiacyclononane] were each studied up to pressures exceeding 9 GPa using high-pressure single-crystal X-ray diffraction. The α- and γ-phases both exhibit smooth compression of the unit-cell parameters with third-order Birch–Murnaghan bulk moduli of 14.4 (8) and 7.6 (6) GPa, respectively. Between 6.81 and 6.87 GPa β-[PdCl2([9]aneS2O)] was found to undergo a reversible transition to a phase denoted as β′ and characterized by a tripling of the unit-cell volume. Across the phase transition, rearrangement of the conformation of the bound macrocycle at two of the resulting three unique sites gives rise to an extensively disordered structure.

High pressure crystallographic studies on [1,4-C6H4{PPh2(AuCl)}2] (1) reveal the largest pressure-induced contraction of an aurophilic interaction observed for any Au(I) complex; Hirshfeld surface analysis and Raman spectroscopy reveals the presence of several types of intermolecular interaction, which play an important role in the behaviour of 1 as a function of pressure.

A binuclear Cu(II) complex of formula [Cu(L1Hpy)Cl]2(ClO4)2 (1), where L1H2 is a new tridentate ligand, formed by condensation of 2-aminomethyl pyridine and pyridoxal (one of the forms of vitamin B6), has been synthesized. X-ray crystal structure determination shows that in this complex two Cu(II) ions are interconnected by complementary hydroxymethyl bridges of the two pyridoxal moieties, which is a very rare example in the literature. However, with a Cu⋯Cu separation of 6.574(1) A and Cu–O(H)CH2– distance of 2.289 A, the bridge is very weak, and DFT calculations, as well as ESI-MS data and solution spectral studies indicate that in a MeOH solution the complex exists predominantly as a mixture of monomers [Cu(L1Hpy)Cl]+ and [Cu(L1Hpy)(MeOH)]2+ with the former being the predominant form. The DFT calculations as well as EPR spectra suggest that the SOMO is a metal dx2−y2 orbital. The complex shows highly efficient catecholase activity with kcat = 3·46 × 105 h−1 and kcat/KM = 1.00 × 108 M−1 h−1, which are the best values reported in the literature, so far, for catecholase mimicking model complexes. DFT calculations show that the reduction of the Cu(II)/Cu(I) by the coordinated catechol and the resultant structural changes is the rate determining step in the catalytic cycle. The complex also binds DNA quite strongly with a binding constant of ∼105 M−1. DFT calculations suggest that the most probable binding mode of the complex is intercalation of the pyridine ring of the complex between two adenine or adenine and cytosine base pairs. The complex shows low cytotoxicity towards HCT and HeLa cells, though cytotoxicity towards the latter cell line is much more than the former. It was also found that the complex can be used as a fluorescence probe for imaging HCT cells.

Chiral 2D and 3D metal-organic coordination polymers [Cu2(bpy)2(Hdml)2(HCOO)]-(HCOO)·2H2O (1) and [Cu(bpy)(Hphl)(HCOO)]·H2O (2) were synthesized by heating a solution of copper(ii) salts, 4,4´-bipyridine (bpy), and α-hydroxycarboxylic acids, viz., S-3,3-dimethyllactic (H2dml) or S-3-phenyllactic (H2phl) acid, in a water—N,N´-dimethylformamide mixture. The structures of compounds 1 and 2 were determined by single-crystal X-ray diffraction. Compound 2 was characterized by X-ray powder diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis.