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[Image: see text] To improve the metabolic stability profile of BMS-741672 (1a), we undertook a structure–activity relationship study in our trisubstituted cyclohexylamine series. This ultimately led to the identification of 2d (BMS-753426) as a potent and orally bioavailable antagonist of CCR2. Compared to previous clinical candidate 1a, the tert-butyl amine 2d showed significant improvements in pharmacokinetic properties, with lower clearance and higher oral bioavailability. Furthermore, compound 2d exhibited improved affinity for CCR5 and good activity in models of both monocyte migration and multiple sclerosis in the hCCR2 knock-in mouse. The synthesis of 2d was facilitated by the development of a simplified approach to key intermediate (4R)-9b that deployed a stereoselective reductive amination which may prove to be of general interest.

The use of the unprecedented annulating reagents methyl N-(tert-butylsulfinyl)-4-chlorobutanimidate and methyl N-(tert-butylsulfinyl)-5-bromopentanimidate enables the diastereoselective preparation of 5- and 6-membered carbocycles bearing three contiguous stereocenters. These synthons undergo cycloaddition with a variety of Michael acceptors to form cyclopentane/cyclohexane rings with excellent stereochemical control, generating only one of the eight possible diastereomers. This novel methodology has enabled the highly enantioselective and high yielding synthesis of novel chemotypes of pharmacological relevance.

We describe an efficient synthetic route to differentially protected diester, 1-(tert-butyl) 4-methyl (1R,2S,4R)-2-methylcyclohexane-1,4-dicarboxylate (+)-1, via palladium-catalyzed methoxycarbonylation of an enol triflate derived from a Hagemann's ester derivative followed by a stereoselective Crabtree hydrogenation. Diester 1 is a novel chiral synthon useful in drug discovery and was instrumental in the generation of useful SAR during a RORγt inverse agonist program. In addition, we describe a second-generation synthesis of the clinical candidate BMS-986251, using diester 1 as a critical component.

Owing to their participation in Click reactions, bifunctional azides are valuable intermediates in the preparation of medicines and biochemical tool compounds. Despite the privileged nature of pyridines among pharmaceutical scaffolds, reports of the synthesis and characterization of azidopyridines bearing a halogen substituent for further elaboration are almost completely unknown in the literature. As azidopyridines carry nearly equal numbers of nitrogen and carbon atoms, we hypothesized that safety concerns limited the application of these useful bifunctional building blocks in medicinal and biological chemistry. To address this concern, we prepared and characterized nine azidopyridines bearing a single fluorine, chlorine, or bromine atom. All were examined by differential scanning calorimetry (DSC), in which they demonstrated exotherms of 228-326 kJ/mol and onset temperatures between 119 and 135 °C. Selected azidopyridines were advanced to mechanical stress testing, in which impact sensitivity was noted for one regioisomer of C5H3FN4. The utility of these versatile intermediates was demonstrated through their use in a variety of Click reactions and the diversification of the halogen handles.

We describe a stereodefined synthesis of the newly identified non-natural phosphorothioate cyclic dinucleotide (CDN) STING agonist, BMT-390025. The new route avoids the low-yielding racemic approach using P(III)-based reagents, and the stereospecific assembly of the phosphorothioate linkages are forged via the recently invented P(V)-based platform of the so-called PSI (Ψ) reagent system. This P(V) approach allows for the complete control of chirality of the P-based linkages and enabled conclusive evidence of the absolute configuration. The new approach offers robust procedures for preparing the stereodefined CDN in eight steps starting from advanced nucelosides, with late-stage direct drop isolations and telescoped steps enabling an efficient scale-up that proceeded in an overall 15% yield to produce multigram amounts of the CDN.

Indole and indoline rings are important pharmacophoric scaffolds found in marketed drugs, agrochemicals, and biologically active molecules. The [2 + 2] cycloaddition reaction is a versatile strategy for constructing architecturally interesting, sp3-rich cyclobutane-fused scaffolds with potential applications in drug discovery programs. A general platform for visible-light mediated intermolecular [2 + 2] cycloaddition of indoles with alkenes has been realized. A substrate-based screening approach led to the discovery of tert-butyloxycarbonyl (Boc)-protected indole-2-carboxyesters as suitable motifs for the intermolecular [2 + 2] cycloaddition reaction. Significantly, the reaction proceeds in good yield with a wide variety of both activated and unactivated alkenes, including those containing free amines and alcohols, and the transformation exhibits excellent regio- and diastereoselectivity. Moreover, the scope of the indole substrate is very broad, extending to previously unexplored azaindole heterocycles that collectively afford fused cyclobutane containing scaffolds that offer unique properties with functional handles and vectors suitable for further derivatization. DFT computational studies provide insights into the mechanism of this [2 + 2] cycloaddition, which is initiated by a triplet-triplet energy transfer process. The photocatalytic reaction was successfully performed on a 100 g scale to provide the dihydroindole analog.

We describe an efficient synthetic route to differentially protected diester, 1-(

The design and synthesis of new metal–organic frameworks (MOFs) is important from both a fundamental and application standpoint. In this work, a novel, highly‐connected rare‐earth (RE) MOF with shp topology is reported, named RE‐CU‐10 (RE = rare‐earth, CU = Concordia University), comprised of nonanuclear RE(III)‐cluster nodes and tetratopic pyrene‐based linkers. This represents the first time that the 1,3,6,8‐tetrakis(p‐benzoic acid)pyrene (H4TBAPy) linker is integrated in the shp topology. Y‐CU‐10 was explored as a heterogeneous photocatalyst for the selective oxidation and detoxification of a sulfur mustard simulant, 2‐chloroethyl ethyl sulfide (2‐CEES), showing a halflife for conversion to the less toxic 2‐chloroethyl ethyl sulfoxide (2‐CEESO) of 6.0 min.

Herein, we report an unprecedented mixed-valence crystal superstructure that consists of a 2:1 host–guest complex [MV⊂(CBPQT)_2]^(2/3+) [MV = methyl viologen, CBPQT = cyclobis(paraquat-p-phenylene)]. One electron is distributed statistically between three [MV⊂(CBPQT)_2]•+ composed of a total of 15 viologen units. The mixed-valence state is validated by single-crystal X-ray crystallography, which supports an empirical formula of [MV⊂(CBPQT)_2]_3·(PF_6)_2 for the body-centered cubic superstructure. Electron paramagnetic resonance provides further evidence of electron delocalization. Quantum chemistry calculations confirm the mixed-valence state in the crystal superstructure. Our findings demonstrate that precise tuning of the redox states in host–guest systems can lead to a promising supramolecular strategy for achieving long-range electron delocalization in solid-state devices.

The crystal structure of tricaesium citrate monohydrate, 3Cs+·C6H5O73−·H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. This compound is isostructural to the K+and Rb+compounds with the same formula. The three independent Cs cations are eight-, eight-, and seven-coordinate, with bond-valence sums of 0.91, 1.22, and 1.12 valence units. The coordination polyhedra link into a three-dimensional framework. The hydroxy group forms the usualS(5) hydrogen bond with the central carboxylate group, and the water molecule acts as a donor in two strong hydrogen bonds.

Communicating science is hard. This is particularly true for a lot of structural science concepts which are inherently three dimensional in nature such as molecular geometry, symmetry, intermolecular interactions and the packing of crystal structures. One of the most effective ways to get around this difficulty is to use physical 3D models for communication, whether it is in an outreach setting, through classroom education or even presenting research results at a conference. Recent studies have shown how to generate instruction files to 3D print experimentally accurate models. Here we present for the first time how scientists can do this from any standard structural model file (incl. MOL2, XYZ, SDF, PDB, CIF, RES) easily using the well-known, freely available structure visualisation program, Mercury.

Improved understanding of fundamental structure–property relationships, particularly the effects of molecular shape and intermolecular packing on film morphology and active layer charge transport characteristics, enables more rational synthesis of new p-type small molecules. Here we investigate a series of small molecules consisting of an acene-based electron-rich core flanked by one or two electron-deficient diketopyrrolopyrrole (DPP) moieties. Through minor changes in the molecule structures, measurable variations in the crystal structure and sizable differences in macroscopic properties are achieved. The molecular symmetry as well as the conformation of the side chains affects the unit cell packing density and strength of the intermolecular electronic coupling in single crystals of all molecules in this series. The addition of a second DPP unit to the benzodithiophene (BDT) core increases molecular planarity leading to decreased reorganization energy, strong cofacial coupling, and moderate hole mobility (2.7 × 10−4 cm2 V−1 s−1). Increasing the length of the acene core from benzodithiophene to naphthodithiophene (NDT) results in a further reduction in reorganization energy and formation of smaller crystalline domains (∼11 nm) when mixed with PCBM. Decreasing the aspect ratio of the core using a “zig-zag” naphthodithiophene (zNDT) isomer results in the highest hole mobility of 1.3 × 10−3 cm2 V−1 s−1 due in part to tight lamellar (d = 13.5 A) and π–π stacking (d = 3.9 A). The hole mobility is directly correlated with the short-circuit current (11.7 mA cm−2) and solar cell efficiency (4.4%) of the highest performing zNDT:PCBM device. For each of these small molecules the calculated π-coupling constant is correlated with the hole mobility as a function of crystal structure and orientation indicating the importance of designing molecules that create extended crystalline networks with maximal π-orbital overlap.

The synthesis, characterization, and catalytic activity of bis(2-pyridylmethyl)amine (BPMA) copper complexes incorporating olefinic pendent arms are reported. Four copper(I) and four copper(II) complexes were synthesized employing four different counterions [chloride (Cl−), perchlorate (ClO4−), trifluoromethanesulfonate (CF3SO3−), and tetraphenylborate (BPh4−)]. The counterions used ranged from coordinating (Cl−) to non-coordinating (BPh4−), producing different coordination modes in respective complexes. Solid state results obtained for the copper(I) complex incorporating the non-coordinating (BPh4−) counterion displayed an associative bond between the metal center and the C C group in the olefinic arm of a neighboring complex. This interaction led to augmentation of the C C bond due to back-bonding from the metal center. Five solid state structures were obtained for the copper(II) complexes with two also displaying intermolecular associative bonding between olefinic pendent arms and the metal center. X-ray crystallography studies showed that the olefinic arm motifs incorporated were hemilabile. Solution studies indicated that the copper complexes had some inherent reducing power and could be potential candidates for use as catalysts in atom transfer radical processes. However, only moderate conversions and yields were obtained in atom transfer radical addition (ATRA) reaction studies performed utilizing the copper complexes due to the presence of a competing reaction.

The crystal structure of disodium hydrogen citrate sesquihydrate has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques., The crystal structure of disodium hydrogen citrate sesquihydrate, 2Na2 +·C6H6O7 2−·1.5H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. The asymmetric unit contains two independent hydrogen citrate anions, four sodium cations and three water molecules. The coordination polyhedra of the cations (three with a coordination number of six, one with seven) share edges to form isolated 8-rings. The un-ionized terminal carb­oxy­lic acid groups form very strong hydrogen bonds to non-coordinating O atoms, with O⋯O distances of 2.46 Å.

Methods and outcomes for teaching crystallography in graduate, post-graduate and secondary school environments are presented. This is an extended report based on the ideas presented in the MS92 Microsymposium at the IUCr 23rd Congress and General Assembly in Montreal., There are many methods that can be used to incorporate concepts of crystallography into the learning experiences of students, whether they are in elementary school, at university or part of the public at large. It is not always critical that those who teach crystallography have immediate access to diffraction equipment to be able to introduce the concepts of symmetry, packing or molecular structure in an age- and audience-appropriate manner. Crystallography can be used as a tool for teaching general chemistry concepts as well as general research techniques without ever having a student determine a crystal structure. Thus, methods for younger students to perform crystal growth experiments of simple inorganic salts, organic compounds and even metals are presented. For settings where crystallographic instrumentation is accessible (proximally or remotely), students can be involved in all steps of the process, from crystal growth, to data collection, through structure solution and refinement, to final publication. Several approaches based on the presentations in the MS92 Microsymposium at the IUCr 23rd Congress and General Assembly are reported. The topics cover methods for introducing crystallography to undergraduate students as part of a core chemistry curriculum; a successful short-course workshop intended to bootstrap researchers who rely on crystallography for their work; and efforts to bring crystallography to secondary school children and non-science majors. In addition to these workshops, demonstrations and long-format courses, open-format crystallographic databases and three-dimensional printed models as tools that can be used to excite target audiences and inspire them to pursue a deeper understanding of crystallography are described.

An isoreticular series of metal-organic frameworks (MOFs) with the ftw topology based on zirconium oxoclusters and tetracarboxylate linkers with a planar core (NU-1101 through NU-1104) has been synthesized employing a linker expansion approach. In this series, NU-1103 has a pore volume of 2.91 cc g(-1) and a geometrically calculated surface area of 5646 m(2) g(-1), which is the highest value reported to date for a zirconium-based MOF and among the largest that have been reported for any porous material. Successful activation of the MOFs was proven based on the agreement of pore volumes and BET areas obtained from simulated and experimental isotherms. Critical for practical applications, NU-1103 combines for the first time ultrahigh surface area and water stability, where this material retained complete structural integrity after soaking in water. Pressure range selection for the BET calculations on these materials was guided by the four so-called "consistency criteria". The experimental BET area of NU-1103 was 6550 m(2) g(-1). Insights obtained from molecular simulation suggest that, as a consequence of pore-filling contamination, the BET method overestimates the monolayer loading of NU-1103 by ∼16%.

Polyaromatic compounds are well-known to intercalate DNA. Numerous anticancer chemotherapeutics have been developed upon the basis of this recognition motif. The compounds have been designed such that they interfere with the role of the topoisomerases, which control the topology of DNA during the cell-division cycle. Although many promising chemotherapeutics have been developed upon the basis of polyaromatic DNA intercalating systems, these candidates did not proceed past clinical trials on account of their dose-limiting toxicity. Herein, we discuss an alternative, water-soluble class of polyaromatic compounds, the 2,9-diazaperopyrenium dications, and report in vitro cell studies for a library of these dications. These investigations reveal that a number of 2,9-diazaperopyrenium dications show similar activities as doxorubicin toward a variety of cancer cell lines. Additionally, we report the solid-state structures of these dications, and we relate their tendency to aggregate in solution to their toxicity profiles. The addition of bulky substituents to these polyaromatic dications decreases their tendency to aggregate in solution. The derivative substituted with 2,6-diisopropylphenyl groups proved to be the most cytotoxic against the majority of the cell lines tested. In the solid state, the 2,6-diisopropylphenyl-functionalized derivative does not undergo π···π stacking, while in aqueous solution, dynamic light scattering reveals that this derivative forms very small (50-100 nm) aggregates, in contrast with the larger ones formed by dications with less bulky substituents. Alteration of the aromaticitiy in the terminal heterocycles of selected dications reveals a drastic change in the toxicity of these polyaromatic species toward specific cell lines.

A series of metal–organic framework (MOF) materials containing AuI-carbon covalent bonds was prepared by solvent-assisted linker exchange (SALE) between (alkynyl)gold(phosphine)-functionalized bipyridine linkers and the bipyridyl naphthalene tetracarboxydiimide struts in Zn pillared-paddlewheel MOFs. These new materials could not be obtained by the authors through de novo synthesis or post-synthesis modification, both of which lead to the decomposition of the organometallic complex. In contrast, the SALE process occurs readily under mild conditions that preserve the integrity of both the pillared-paddlewheel structure and the organometallic complex. For bipyridine linkers with similar basicities, the rate of the SALE exhibits a strong inverse dependence on the size of the phosphine ligand in the incoming (alkynyl)gold(phosphine)-functionalized linker, with smaller ligands reacting faster.

Understanding the mechanism of efficient photoinduced electron-transfer processes is essential for developing molecular systems for artificial photosynthesis. Towards this goal, we describe the synthesis of a donor-acceptor dyad comprising a zinc porphyrin donor and a tetracationic cyclobis(paraquat-p-phenylene) (CBPQT(4+) ) acceptor. The X-ray crystal structure of the dyad reveals the formation of a dimeric motif through the intermolecular coordination between the triazole nitrogen and the central Zn metal of two adjacent units of the dyad. Photoinduced electron transfer within the dyad in MeCN was investigated by femtosecond and nanosecond transient absorption spectroscopy, as well as by transient EPR spectroscopy. Photoexcitation of the dyad produced a weakly coupled ZnP(+.) -CBPQT(3+.) spin-correlated radical-ion pair having a τ=146 ns lifetime and a spin-spin exchange interaction of only 0.23 mT. The long radical-ion-pair lifetime results from weak donor-acceptor electronic coupling as a consequence of having nine bonds between the donor and the acceptor, and the reduction in reorganization energy for electron transfer caused by charge dispersal over both paraquat units within CBPQT(3+.) .

Cyclophanes, especially those where pyridinium units in conjugation with each other are linked up face-to-face within platforms that are held approximately 7 Å apart by rigid linkers, are capable of forming inclusion complexes with polycyclic aromatic hydrocarbons (PAHs) with high binding affinities as a result of a combination of noncovalent bonding interactions, including face-to-face [π···π] stacking and orthogonal [C-H···π] interactions. Here, we report the template-directed, catalyst-assisted synthesis of a three-fold symmetric, extended pyridinium-based, cage-like host (ExCage(6+)) containing a total of six π-electron-deficient pyridinium units connected in a pairwise fashion by three bridging p-xylylene linkers, displayed in a trigonal (1,3,5) fashion around two opposing and parallel 1,3,5-tris(4-pyridinium)benzene platforms. The association constants (K(a)) of eight complexes have been measured by isothermal titration calorimetry (ITC) in acetonitrile and were found to span the range from 2.82 × 10(3) for naphthalene up to 5.5 × 10(6) M(-1) for perylene. The barriers to decomplexation, which were measured in DMF-d7 for phenanthrene, pyrene, triphenylene, and coronene by dynamic (1)H NMR spectroscopy undergo significant stepwise increases from 11.8 → 13.6 → 15.5 →18.7 kcal mol(-1), respectively, while complexation experiments using rapid injection (1)H NMR spectroscopy in DMF-d7 at -55 °C revealed the barriers to complexation for pyrene and coronene to be 6.7 and8 kcal mol(-1), respectively. The kinetic and thermodynamic data reveal that, in the case of ExCage(6+), while the smaller PAHs form complexes faster than the larger ones, the larger PAHs form stronger complexes than the smaller ones. It is also worthy of note that, as the complexes become stronger in the case of the larger and larger PAHs, the Rebek 55% solution formula for molecular recognition in the liquid state becomes less and less relevant.

A biomimetic, ion-regulated molecular receptor was synthesized via the Weak-Link Approach (WLA). This structure features both a calix[4]arene moiety which serves as a molecular recognition unit and an activity regulator composed of hemilabile phosphine alkyl thioether ligands (P,S) chelated to a Pt(II) center. The host-guest properties of the ion-regulated receptor were found to be highly dependent upon the coordination of the Pt(II) center, which is controlled through the reversible coordination of small molecule effectors. The environment at the regulatory site dictates the charge and the structural conformation of the entire assembly resulting in three accessible binding configurations: one closed, inactive state and two open, active states. One of the active states, the semiopen state, recognizes a neutral guest molecule, while the other, the fully open state, recognizes a cationic guest molecule. Job plots and (1)H NMR spectroscopy titrations were used to study the formation of these inclusion complexes, the receptor binding modes, and the receptor binding affinities (Ka) in solution. Single crystal X-ray diffraction studies provided insight into the solid-state structures of the receptor when complexed with each guest molecule. The dipole moments and electrostatic potential maps of the structures were generated via DFT calculations at the B97D/LANL2DZ level of theory. Finally, we describe the reversible capture and release of guests by switching the receptor between the closed and semiopen configurations via elemental anion and small molecule effectors.

Zerovalent group 6 dinitrogen phosphine complexes react with 3,3-diphenylcyclopropene to give vinylcarbyne hydride complexes that have been characterized crystallographically. Computational studies indicate that the observed products resulted from the α-migration and rearrangement of an initially formed vinylcarbene.

The long, linear cobalt(III) bis(dicarbollide)-based bis(isophthalic acid) anion was synthesized as a tetraphenylphosphonium salt in five steps from 8-iodo-closo-1,2-C2B10H11. The solvothermal reaction between the anionic bis(isophthalic acid) linker and copper(II) nitrate in acidified DMF yielded single crystals. Despite the tendency for copper(II) and analogous linear tetraacids to form members of an isoreticular family of metal–organic frameworks (MOFs) with the fof topology, single-crystal X-ray diffraction analysis revealed the growth of three different frameworks. These MOFs, NU-150, NU-151, and NU-152, have three distinct topologies: fof, sty, and hbk, respectively. NU-152 has a novel quadrinodal topology in which cuboctahedral coordination polyhedra are each connected to 10 neighboring polyhedra via the cobalt bis(dicarbollide) portions of the linkers. The formation of these frameworks illustrates the limitations of structure prediction in MOF chemistry and the possibility of using flexible linker...

We have successfully used a highly efficient copper-catalyzed "click" reaction for the synthesis of a new series of hexacarboxylic acid linkers with varying sizes for the construction of isoreticular (3,24)-connected metal-organic frameworks (MOFs)-namely, NU-138, NU-139, and NU-140. One of these MOFs, NU-140, exhibits a gravimetric methane uptake of 0.34 g/g at 65 bar and 298 K, corresponding to almost 70% of the DOE target (0.5 g/g), and has a working capacity (deliverable amount between 65 and 5 bar) of 0.29 g/g, which translates into a volumetric working capacity of 170 cc(STP)/cc. These values demonstrate that NU-140 performs well for methane storage purposes, from both a gravimetric and a volumetric point of view. Adsorption of CO2 and H-2 along with simulated isotherms are also reported.

Solvent-assisted linker exchange (SALE) has recently emerged as an attractive strategy for the synthesis of metal-organic frameworks (MOFs) that are unobtainable via traditional synthetic pathways. Herein we present the first example of selective SALE in which only the benzimiadazolate-containing linkers in a series of mixed-linker zeolitic imidazolate frameworks (ZIF-69, -78, and -76) are replaced. The resultant materials (SALEM-10, SALEM-10b, and SALEM-11, respectively) are isostructural to the parent framework and in each case contain trifluoromethyl moieties. We therefore evaluated each of these materials for their hydrophobicity in condensed and gas phases. We expect that selective SALE will significantly facilitate the design of improved, and potentially complex, MOF materials with new and unusual properties.

The self-assembly of two topological isomers of a handcuff catenane has been achieved by utilizing the template-directed synthesis between the π-electron-rich bis-1,5-dioxynaphtho[50]crown-14 and the precursors to two fused π-electron-deficient cyclobis(paraquat-p-phenylene) cyclophanes. Characterization of the product using 1H NMR spectroscopy and single-crystal X-ray diffraction, with supporting density functional theory (DFT) calculations, suggests that the 1,5-dioxynaphthalene units in the major topological isomer align themselves with the same relative orientations inside the cyclophanes on account of restrictions imposed by the lengths of the polyether loops. The DFT calculations also reveal that the energies of the two topological isomers are similar to each other, supporting the experimental observation that both isomers can be isolated as a mixture from a one-pot reaction. The two isomers – designated as the meta–meta and ortho–ortho isomers with different topologies that are not interconvertible – only differ in the manner in which the polyether loops wind their way around the central 1,2,4,5-tetrasubstituted benzenoid ring in the ditopic host. X-Ray crystallography proves that by far the major topological isomer in the solid state is the meta–meta one. 1H NMR spectroscopy confirms that it is also the major isomer in solution, whilst also revealing the presence of a minor isomer, which is assumed, for the time-being, to have the ortho–ortho topology. The free fused ditopic host has been obtained using a protocol similar to that employed in the template-directed synthesis of the handcuff catenane, except that the crown ether is replaced with an acyclic template which can be removed post-synthesis. The results of isothermal titration calorimetry studies shed some light on the mechanism of binding of π-electron-rich guests: they lead us to believe that when two electron-rich guests bind to the ditopic host, they do so with allosteric negative cooperativity.

The structure and properties of the electron donor-acceptor complexes formed between methyl viologen (MV) and purine nucleosides and nucleotides in water and the solid state have been investigated using a combination of experimental and theoretical methods. Solution studies were performed using UV-vis and 1H NMR spectroscopy. Theoretical calculations were performed within the framework of density functional theory (DFT). Energy decomposition analysis indicates that dispersion and induction (charge-transfer) interactions dominate the total binding energy, whereas electrostatic interactions are largely repulsive. The appearance of charge transfer bands in the absorption spectra of the complexes are well described by time-dependent (TD) DFT and are further explained in terms of the redox properties of purine monomers and solvation effects. Crystal structures are reported for complexes of methyl viologen with the purines 2′-deoxyguanosine 3′-monophosphate GMP (DAD′DAD′ type) and 7-deazaguanosine zG (DAD′ADAD′ type). Comparison of the structures determined in the solid state and by theoretical methods in solution provides valuable insights into the nature of charge-transfer interactions involving purine bases as electron donors.

The compound Th2GeSe5 has been synthesized by the reaction of the elements at 1273 K. From a single-crystal study Th2GeSe5 crystallizes in the Ba5Si3 structure type with four formula units in the space group D84h−P4/ncc of the tetragonal system in a cell with dimensions a=7.4968(4) A and c=13.6302(9) A at 100(2) K. From optical absorption measurements Th2GeSe5 is found to have an optical band gap of 1.92 eV (indirect) or 1.98 eV (direct), consistent with its red color. Th2GeSe5 is a wide gap semiconductor, as indicated by its electrical resistivity at 298 K of 4.37(2)×109 Ω cm measured on a single crystal.

Solvent-assisted linker exchange (SALE) was performed on a pillared-paddlewheel metal–organic framework (MOF), SALEM-5, to achieve incorporation of longer linkers into the material. The 9-A meso-1,2-di(4-pyridyl)-1,2-ethanediol pillar of SALEM-5 was successfully replaced by 11-A, 14-A, and 17-A pillars to generate daughter MOFs SALEM-6, SALEM-7, and SALEM-8. The daughter frameworks possess more open cages, as was demonstrated by structural modeling from the powder X-ray diffraction patterns, and larger solvent accessible space, as was demonstrated by thermogravimetric analysis. Finally, a study was performed to examine the effect of pKa of monoprotonated dipyridyl pillars (as an indicator of the Zn–L bond strength) on the outcome of SALE.

A Cu–carborane-based metal–organic framework (MOF), NU-135, which contains a quasi-spherical para-carborane moiety, has been synthesized and characterized. NU-135 exhibits a pore volume of 1.02 cm3/g and a gravimetric BET surface area of ca. 2600 m2/g, and thus represents the first highly porous carborane-based MOF. As a consequence of the unique geometry of the carborane unit, NU-135 has a very high volumetric BET surface area of ca. 1900 m2/cm3. CH4, CO2, and H2 adsorption isotherms were measured over a broad range of pressures and temperatures and are in good agreement with computational predictions. The methane storage capacity of NU-135 at 35 bar and 298 K is ca. 187 vSTP/v. At 298 K, the pressure required to achieve a methane storage density comparable to that of a compressed natural gas (CNG) tank pressurized to 212 bar, which is a typical storage pressure, is only 65 bar. The methane working capacity (5–65 bar) is 170 vSTP/v. The volumetric hydrogen storage capacity at 55 bar and 77 K is 49 g/L. T...

Through a combination of protecting groups, postsynthesis deprotection, and postsynthesis metallation, a homogeneously inaccessible, single-site vanadyl(monocatecholate) moiety can be incorporated into the dipyridyl struts of a Zn-based, pillared paddlewheel MOF. The resulting MOF, which has large pores, exhibits catalytic activity in the benzylic oxidation of tetralin in the presence of tert-butylhydroperoxide.

A series of isostructural noncatenated, water-stable zinc-based dipyridyl pillared-paddlewheel metal–organic frameworks (MOFs) was synthesized with tunable pore hydrophobicity. Pore hydrophobicity was engendered through dipyridyl ligands decorated with alkyl chains of varying length (methyl to hexyl). The most hydrophobic MOFs exhibited selective sorption of ethanol over water.

Herein we report a new class of hemilabile ligands with boron-dipyrromethene (Bodipy) fluorophores that, when complexed to Pt(II), can signal changes in coordination mode through changes in their fluorescence. The ligands consist of phosphino-amine or phosphino-thioether coordinating moieties linked to the Bodipy's meso carbon via a phenylene spacer. Interestingly, this new class of ligands can be used to signal both ligand displacement and chelation reactions in a fluorescence "turn-on" fashion through the choice of weakly binding heteroatom in the hemilabile moiety, generating up to 10-fold fluorescence intensity increases. The Pt(II) center influences the Bodipy emission efficiency by regulating photoinduced electron transfer between the fluorophore and its meso substituent. The rates at which the excited Bodipy-species generate singlet oxygen upon excitation suggest that the heavy Pt(II) center also influences Bodipy's emission efficiency by affecting intersystem crossing from the Bodipy excited singlet to excited triplet states. This signaling strategy provides a quantitative read-out for changes in coordination mode and potentially will enable the design of new molecular systems for sensing and signal amplification.

Two are better than one: The diazaperopyrenium dication acts as both a viologen-like electron-poor and an electron-rich guest, resulting in the formation of a 1:2 complex with cucurbit[8]uril. This chameleonic binding facilitates deaggregation of the dications from aqueous solutions, leading to an increase in the fluorescence quantum yield of the diazaperopyrenium dication.

Despite being the fifth most abundant element in the atmosphere, neon has never been observed in an organic or metal–organic environment. This study shows the adsorption of this highly unreactive element within such an environment and reveals the first crystallographic observation of an interaction between neon and a transition metal.

Supporting Information, CIF file. Upon deposition to the Cambridge Structural Database (CSD), it was noted that the hydrogen atoms on the porphyrin ring of the structure were modeled incorrectly. The appropriate changes have been made, and the structure has been refined to convergence. This does not affect the chemistry reported in the publication but has small effects in the final refinement values, and a new CIF file is provided. The corrected data have also been deposited to the CSD.

A zeolitic imidazolate framework material of SOD topology possessing primarily unsubstituted imidazolate (im) linkers has been synthesized via solvent-assisted linker exchange (SALE) of ZIF-8. The structure of the new material, SALEM-2, has been confirmed through (1)H NMR and powder and single-crystal X-ray diffraction. SALEM-2 is the first example of a porous Zn(im)(2) ZIF possessing a truly zeolitic topology that can be obtained in bulk quantities. Upon treatment with n-butyllithium, the open analogue exhibits Brønsted base catalysis that cannot be accomplished by the parent material ZIF-8. Additionally, it displays a different size cutoff for uptake and release of molecular guests than does ZIF-8.

A neutral donor-acceptor [2]rotaxane, which has been synthesized using click chemistry, has had its solid-state structure and superstructure elucidated by X-ray crystallography. Both dynamic (1)H NMR spectroscopy and electrochemical investigations have been employed in an attempt to shed light on both geometrical reorganization and redox-switching processes that are occurring or can be induced within the [2]rotaxane.

Materials exhibiting a spontaneous electrical polarization that can be switched easily between antiparallel orientations are of potential value for sensors, photonics and energy-efficient memories. In this context, organic ferroelectrics are of particular interest because they promise to be lightweight, inexpensive and easily processed into devices. A recently identified family of organic ferroelectric structures is based on intermolecular charge transfer, where donor and acceptor molecules co-crystallize in an alternating fashion known as a mixed stack: in the crystalline lattice, a collective transfer of electrons from donor to acceptor molecules results in the formation of dipoles that can be realigned by an external field as molecules switch partners in the mixed stack. Although mixed stacks have been investigated extensively, only three systems are known to show ferroelectric switching, all below 71 kelvin. Here we describe supramolecular charge-transfer networks that undergo ferroelectric polarization switching with a ferroelectric Curie temperature above room temperature. These polar and switchable systems utilize a structural synergy between a hydrogen-bonded network and charge-transfer complexation of donor and acceptor molecules in a mixed stack. This supramolecular motif could help guide the development of other functional organic systems that can switch polarization under the influence of electric fields at ambient temperatures.