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Building on the MOF approach to prepare porous materials, herein we report the engineering of porous BN‐doped materials using tricarboxylic hexaarylborazine ligands, which are laterally decorated with functional groups at the full‐carbon ‘inner shell’. Whilst an open porous 3D entangled structure could be obtained from the double interpenetration of two identical metal frameworks derived from the methyl substituted borazine, the chlorine‐functionalised linker undergoes formation of a porous layered 2D honeycomb structure, as shown by single‐crystal X‐ray diffraction analysis. In this architecture, the borazine cores are rotated by 60° in alternating layers, thus generating large rhombohedral channels running perpendicular to the planes of the networks. An analogous unsubstituted full‐carbon metal framework was synthesised for comparison. The resulting MOF revealed a crystalline 3D entangled porous structure, composed by three mutually interpenetrating networks, hence denser than those obtained from the borazine linkers. Their microporosity and CO2 uptake were investigated, with the porous 3D BN‐MOF entangled structure exhibiting a large apparent BET specific surface area (1091 m2 g−1) and significant CO2 reversible adsorption (3.31 mmol g−1) at 1 bar and 273 K., The borazine unit was used to prepare crystalline porous MOFs from specifically designed borazine carboxylate linkers. To evaluate the influence of the borazine rings on the gas adsorption properties, the analogous full‐carbon carboxylate linker and the corresponding MOF were also prepared. The structure of the three MOFs was unambiguously determined by single crystal X‐ray analysis.

The asymmetric n-type Ph-BTBT-C10 derivative 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene S,S,S′,S′-tetraoxide is structurally investigated in the thin film regime. After film preparation by spin coating and physical vapor deposition, a rather disordered structure is observed, with a strong change of its internal degree of order upon heating. At 95 °C, a transition into a layered structure of upright standing molecules without any in-plane order appears, and at 135 °C, crystallization takes place. This phase information is combined with surface morphological studies and charge carrier mobility measurements to describe the structure and thin film transistor applicability of this molecule.

This work is focused on a polymorphic and crystallographic study of a novel p-type organic semiconductor 2,7-bis(2-(2-methoxyethoxy)ethoxy)benzo[b]benzo[4,5]thieno[2,3-d]thiophene (OEG-BTBT). The well-known BTBT core is functionalized by eight-atom-long oligoethylene glycol side chains. Our results demonstrate the discovery of three crystal forms of the OEG-BTBT molecule, namely, Form I, Form II, and Form III, in different experimental conditions. Crystal structures of Form I and Form III are reported, while only unit cell indexing of Form II could be determined. Form I and Form II are enantiotropically related, and Form II is stable at temperatures higher than 127 °C. The kinetics of transformation to Form II was studied by the Avrami equation. Form III is a solvate crystal form which is rarely observed in the field of organic electronics, and upon release of dichloromethane, it converts to Form I. Furthermore, we studied the mechanical properties of the Form I crystals, which exhibit plastic bending upon applying mechanical stress in the [100] direction. This distinct mechanical behavior is rationalized by the slip layer topology, the intermolecular interactions energies from energy frameworks, and the Hirshfeld surface analysis.

Herein, we describe the synthesis of the first boron nitride-doped polyphenylenic material obtained through a [4 + 2] cycloaddition reaction between a triethynyl borazine unit and a biscyclopentadienone derivative, which undergoes organogel formation in chlorinated solvents (the critical jellification concentration is 4% w/w in CHCl3). The polymer has been characterized extensively by Fourier-transform infrared spectroscopy, solid-state 13C NMR, solid-state 11B NMR, and by comparison with the isolated monomeric unit. Furthermore, the polymer gels formed in chlorinated solvents have been thoroughly characterized and studied, showing rheological properties comparable to those of polyacrylamide gels with a low crosslinker percentage. Given the thermal and chemical stability, the material was studied as a potential support for solid-state electrolytes. showing properties comparable to those of polyethylene glycol-based electrolytes, thus presenting great potential for the application of this new class of material in lithium-ion batteries.

A novel black organoammonium iodoplumbate semiconductor, namely phenyl viologen lead iodide C22H18N2(PbI3)2 (PhVPI), was successfully synthesized and characterized. This material showed physical and chemical properties suitable for photovoltaic applications. Indeed, low direct allowed band gap energy (Eg = 1.32 eV) and high thermal stability (up to at least 300 °C) compared to methylammonium lead iodide CH3NH3PbI3 (MAPI, Eg = 1.5 eV) render PhVPI potentially attractive for solar cell fabrication. The compound was extensively characterized by means of X-ray diffraction (performed on both powder and single crystals), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), UV-photoelectron spectroscopy (UPS), FT-IR spectroscopy, TG-DTA, and CHNS analysis. Reactivity towards water was monitored through X-ray powder diffraction carried out after prolonged immersion of the material in water at room temperature. Unlike its methyl ammonium counterpart, PhVPI proved to be unaffected by water exposure. The lack of reactivity towards water is to be attributed to the quaternary nature of the nitrogen atoms of the phenyl viologen units that prevents the formation of acid-base equilibria when in contact with water. On the other hand, PhVPI's thermal stability was evaluated by temperature-controlled powder XRD measurements following an hour-long isothermal treatment at 250 and 300 °C. In both cases no signs of decomposition could be detected. However, the compound melted incongruently at 332 °C producing, upon cooling, a mostly amorphous material. PhVPI was found to be slightly soluble in DMF (∼5 mM) and highly soluble in DMSO. Nevertheless, its solubility in DMF can be dramatically increased by adding an equimolar amount of DMSO. Therefore, phenyl viologen lead iodide can be amenable for the fabrication of solar devices by spin coating as actually done for MAPI-based cells. The crystal structure, determined by means of single crystal X-ray diffraction using synchrotron radiation, turned out to be triclinic and consequently differs from the prototypal perovskite structure. In fact, it comprises infinite double chains of corner-sharing PbI6 octahedra along the a-axis direction with phenyl viologen cations positioned between the columns. Finally, the present determination of PhVPI's electronic band structure achieved through UPS and UV-Vis DRS is instrumental in using the material for solar cells.

It is widely accepted that drug-target association and dissociation rates directly affect drug efficacy and safety. To rationally optimize drug binding kinetics, one must know the atomic arrangement of the protein-ligand complex during the binding/unbinding process in order to detect stable and metastable states. Whereas experimental approaches can determine kinetic constants with fairly good accuracy, computational approaches based on molecular dynamics (MD) simulations can deliver the atomistic details of the unbinding process. Furthermore, they can also be utilized prospectively to predict residence time (i.e., the inverse of unbinding kinetics constant, koff) with an acceptable level of accuracy. Here, we report a novel method based on adiabatic bias MD with an electrostatics-like collective variable (dubbed elABMD) for sampling protein-ligand dissociation events in two kinases. elABMD correctly ranked a ligand series on glucokinase, in agreement with experimental data and previous calculations. Subsequently, we applied the new method prospectively to a congeneric series of GSK-3β inhibitors. For this series, new crystal structures were generated and the residence time was experimentally measured with surface plasmon resonance (SPR). There was good agreement between computational predictions and experimental measures, suggesting that elABMD is an innovative and efficient tool for calculating residence times.

Tetraphenylmethane appended with four pyridylpyridinium units works as a scaffold to self-assemble four ruthenium porphyrins in a tetrahedral shape-persistent giant architecture. The resulting supramolecular structure has been characterised in the solid state by X-ray single crystal analysis and in solution by various techniques. Multinuclear NMR spectroscopy confirms the 1 : 4 stoichiometry with the formation of a highly symmetric structure. The self-assembly process can be monitored by changes of the redox potentials, as well as by modifications in the visible absorption spectrum of the ruthenium porphyrin and by a complete quenching of both the bright fluorescence of the tetracationic scaffold and the weak phosphorescence of the ruthenium porphyrin. An ultrafast photoinduced electron transfer is responsible for this quenching process. The lifetime of the resulting charge separated state (800 ps) is about four times longer in the giant supramolecular structure compared to the model 1 : 1 complex formed by the ruthenium porphyrin and a single pyridylpyridinium unit. Electron delocalization over the tetrameric pyridinium structure is likely to be responsible for this effect.

The structure, stability, and enzymatic activity of the adduct formed upon the reaction of the V–picolinato (pic) complex [VIVO(pic)2(H2O)], with an octahedral geometry and the water ligand in cis to the V=O group, with the bovine pancreatic ribonuclease (RNase A) were studied. While electrospray ionization-mass spectrometry, circular dichroism, and ultraviolet–visible absorption spectroscopy substantiate the interaction between the metal moiety and RNase A, electron paramagnetic resonance (EPR) allows us to determine that a carboxylate group, stemming from Asp or Glu residues, and imidazole nitrogen from His residues are involved in the V binding at acidic and physiological pH, respectively. Crystallographic data demonstrate that the VIVO(pic)2 moiety coordinates the side chain of Glu111 of RNase A, by substituting the equatorial water molecule at acidic pH. Computational methods confirm that Glu111 is the most affine residue and interacts favorably with the OC-6-23-Δ enantiomer establishing an extended network of hydrogen bonds and van der Waals stabilizations. By increasing the pH around neutrality, with the deprotonation of histidine side chains, the binding of the V complex to His105 and His119 could occur, with that to His105 which should be preferred when compared to that to the catalytically important His119. The binding of the V compound affects the enzymatic activity of RNase A, but it does not alter its overall structure and stability., The structure, stability, and enzymatic activity of the adduct formed upon the reaction of [VIVO(picolinato)2(H2O)] with RNase A were studied through a combination of experimental and computational techniques, including X-ray crystallography. The binding of the V compound affects the enzymatic activity of RNase A, but it does not alter its overall structure and stability.

The anisotropic thermal expansion properties of an organic semiconducting single crystal constituted by 4-hydroxycyanobenzene (4HCB) have been probed by XRD in the range 120–300 K. The anisotropic thermal expansion coefficients for the three crystallographic axes and for the crystal volume have been determined. A careful analysis of the crystal structure revealed that the two different H-bonds stemming from the two independent, differently oriented 4HCB molecules composing the unit cell have different rearrangement patterns upon temperature variations, in terms of both bond length and bond angle. Linearly Polarized Mid InfraRed (LP-MIR) measurements carried out in the same temperature range, focused on the O–H bond spectral region, confirm this finding. The same LP-MIR measurements, on the basis of a semi-empirical relation and of geometrical considerations and assumptions, allowed calculation of the –CN H–O– hydrogen bond length along the a and b axes of the crystal. In turn, the so-calculated –CN H–O– bond lengths were used to derive the thermal expansion coefficients along the corresponding crystal axes, as well as the volumetric one, using just the LP-MIR data. Reasonable to good agreement with the same values obtained from XRD m easurements was obtained. This proof-of-principle opens interesting perspectives about the possible development of a rapid, low cost and industry-friendly assessment of the thermal expansion properties of organic semiconducting single crystals (OSSCs) involving hydrogen bonds.

Biogenic crystals produced by organisms have been known for several decades to exhibit intracrystalline organic macromolecules. Here, using a reductionist approach, we tackle the question of whether the incorporation of single amino acids is driven by kinetics or by thermodynamics. We show that when calcite is grown in the presence of amino acids under nonambient conditions, extremely high loading levels of up to 6.12 mol % of aspartic acid (Asp) are achieved. This incorporation leads to marked changes in the host calcite crystal's structure and expansion coefficient. The latter is as much as twice as high as that of pure calcite. This is the first example showing that an organic molecule incorporated into an inorganic host can strongly affect the expansion coefficient. Most importantly, we show that the incorporation of amino acids in calcite is controlled by their thermodynamic solubility in calcite rather than kinetically and that hybrid amino acid-calcite crystals can indeed be considered a solid solution.

Thioindigo (2-(3-Oxo-1-benzothiophen-2(3H)-ylidene)-1-benzothiophen-3(2H)-one) is a synthetic dye related to the natural compound Indigo. Notwithstanding the interest aroused recently by its employment as a functional material in a number of applications, a satisfactory characterization of its solid state is still missing. In this work, we study the occurrence of the two thioindigo α and β polymorphs under various growth conditions, and find that their structural similarity implies they often coexist. However, whereas polymorph β is certainly predominant in the bulk phase, polymorph α grows preferentially on substrates, turning out to be the surface stabilized phase in highly homogeneous and ordered films obtained by the bar‐assisted meniscus shearing method (BAMS). DFT calculations support the experimental findings, aiding in the polymorph spectroscopic identification and to the interpretation of the order in the films of polymorph α., We thank CINECA Supercomputing Center for providing computer time through the ISCRA scheme (project C – HP10CA2TWT). The authors thank the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), the DGI (Spain) project, FANCY CTQ2016-80030-R, the Generalitat de Catalunya (2017-SGR-918) and the Spanish Ministry of Economy and Competitiveness, through the ‘Severo Ochoa‘ Programme for Centres of Excellence in R&D (SEV- 2015–0496). We acknowledge the Elettra Synchrotron Trieste for beamtime allocation and thank Luisa Barba for assistance in using beamline XRD1. T.S. acknowledges the H2020-MSCA-COFUND-2014 Programme (P-SPHERE, Grant agreement 665919).

In this paper, we describe three new stereoisomers of the already known 2 + 2 metallacycle of porphyrins [trans,cis,cis-RuCl2(CO)2(4′cisDPyP)]2 (2, 4′cisDPyP = 5,10-bis(4′-pyridyl)-15,20-diphenylporphyrin), namely [{trans,cis,cis-RuCl2(CO)2}(4′cisDPyP)2{cis,cis,cis-RuCl2(CO)2}] (14) and [cis,cis,cis-RuCl2(CO)2(4′cisDPyP)]2 (15), in which the chiral {cis,cis,cis-RuCl2(CO)2} fragment has either a C or A handedness. The least abundant 15 exists as a mixture of two stereoisomers defined as alternate (15alt, both porphyrins are trans to a Cl and a CO) and pairwise (15pw, one porphyrin is trans to two chlorides and the other to two carbonyls), each one as a statistical mixture of meso (AC) and racemic (AA and CC) diastereomers. Remarkably, both 14 and 15 are—to the best of our knowledge—unprecedented examples of 2D metallacycles with octahedral chiral-at-metal connectors, and 14 is the first example of a 2 + 2 molecular square with stereoisomeric Ru(II) corners. Whereas 2 is selectively obtained by treatment of trans,cis,cis-RuCl2(CO)2(dmso-O)2 (1) with 4′cisDPyP, 14 and 15 were obtained, together with 2 (major product), using stereoisomers of 1, either cis,cis,trans-RuCl2(CO)2(dmso-S)2 (5) or cis,cis,cis-RuCl2(CO)2(dmso)2 (6), as precursors. From a general point of view, this work demonstrates that—even for the smallest 2 + 2 metallacycle and using a symmetric organic linker—several stereoisomers can be generated when using octahedral metal connectors of the type {MA2B2} that are not stereochemically rigid. As a proof-of-concept, it also opens the way to new—even though challenging—opportunities: unprecedented and yet unexplored chiral metallosupramolecular assemblies can be obtained and eventually exploited (e.g., for supramolecular catalysis) by using stereogenic octahedral metal connectors amenable to become chiral centers.

The oxygen in Earth’s atmosphere is there primarily because of water oxidation performed by photosynthetic organisms using solar light and one specialized protein complex, photosystem II (PSII). High-resolution imaging of the PSII ‘core’ complex shows the ideal co-localization of multi-chromophore light-harvesting antennas with the functional reaction centre. Man-made systems are still far from replicating the complexity of PSII, as the majority of PSII mimetics have been limited to photocatalytic dyads based on a 1:1 ratio of a light absorber, generally a Ru–polypyridine complex, with a water oxidation catalyst. Here we report the self-assembly of multi-perylene-bisimide chromophores (PBI) shaped to function by interaction with a polyoxometalate water-oxidation catalyst (Ru4POM). The resulting [PBI]5Ru4POM complex shows a robust amphiphilic structure and dynamic aggregation into large two-dimensional paracrystalline domains, a redshifted light-harvesting efficiency of >40% and favourable exciton accumulation, with a peak quantum efficiency using ‘green’ photons (λ > 500 nm). The modularity of the building blocks and the simplicity of the non-covalent chemistry offer opportunities for innovation in artificial photosynthesis. In native photosystem II (PSII), multi-chromophore antennas surround the reaction centre, capturing light and triggering the quantized (four-flashes) photo-oxidation of water to oxygen. The PSII ‘quantasome’ is the most efficient photo-electrolyser built so far. An artificial quantasome has now been developed; it is specifically designed for oxygen evolution by self-assembling light-harvesting-perylene bisimides with a ruthenium polyoxometalate water-oxidation catalyst.

A series of four arrays made of a central Sn(IV) porphyrin as scaffold axially connected, via carboxylate functions, to two free-base porphyrins has been prepared and fully characterized. Three arrays in the series feature the same free-base unit and alternative tin-porphyrin macrocycles, and one consists of a second type of free-base and one chosen metallo-porphyrin. A thorough photophysical investigation has been performed on all arrays by means of time-resolved emission and absorption techniques. Specific focus has been given at identifying how structural modifications of the free-base and tin-porphyrin partners and/or variation of the solvent polarity can effectively translate into distinct photophysical behaviors. In particular, for systems SnTPP(Fb) 2 (1) and SnOEP(Fb) 2 (2), an ultrafast energy transfer process from the excited Sn(IV) porphyrin to the free-base unit occurs with unitary efficiency. For derivative SnTPP(FbR) 2 (3), the change of solvent from dichloromethane to toluene is accompanied by a neat change in the intercomponent quenching mechanism, from photoinduced electron transfer to energy transfer, upon excitation of the Sn(IV) porphyrin unit. Finally, for array SnTpFP(Fb) 2 (4), an ultrafast electron transfer quenching of both chromophores is detected in all solvents. This work provides a general outline, accompanied by clear experimental support, on possible ways to achieve a systematic fine-tuning of the quenching mechanism (from energy to electron transfer) of Sn(IV) multiporphyrin arrays.

A cyclic hexapeptide with three pyridyl moieties connected to its backbone forms a hydrogen-bonded dimer, which tightly encapsulates a single xenon atom, like a pearl in its shell. The dimer imprints its shape and symmetry to the captured xenon atom, as demonstrated by 129 Xe NMR spectroscopy, single-crystal X-ray diffraction, and computational studies. The dimers self-assemble hierarchically into tubular structures to form a porous supramolecular architecture, whose cavities are filled by small molecules and gases.

A new inherently chiral cavitand is described, in which the desymmetrization of the rigid concave cavity is achieved by introducing three different bridging groups at the upper rim, namely two inward P=O groups, one inward P=S moiety and one methylene bridge in the AABC mode. The racemic mixture of cR and cS enantiomers is resolved by semi-preparative chiral HPLC and the enantiopurity confirmed through circular dichroism. The properties of the enantiopure cR-cav in the enantioselective recognition of racemic 2-butanol is studied by co-crystallization experiments. The exclusive formation of the complex R-BuOH@cR-cav demonstrates that cR-cav is able to discriminate between the two enantiomers of the alcohol in the solid state. The enantiospecific recognition exhibited by the cR-cav towards racemic 2-butanol is particularly relevant because of the low degree of chirality of the alcohol (1.9 calculated by CCM algorithm).

SummaryA simple model for evaluation of diffusion times of small molecule into protein crystals has been developed, which takes into account the physical and chemical properties both of protein crystal and the diffusing molecules. The model also includes consideration of binding and the binding affinity of a ligand to the protein. The model has been validated by simulation of experimental set-ups of several examples found in the literature. These experiments cover a wide range of situations: from small to relatively large diffusing molecules, crystals having low, medium, or high protein density, and different size. The reproduced experiments include ligand exchange in protein crystals by soaking techniques. Despite the simplifying assumptions of the model, theoretical and experimental data are in agreement with available data, with experimental diffusion times ranging from a few seconds to several hours. The method has been used successfully for planning intermediate cryotrapping experiments in maltodextrin phosphorylase crystals.

The chemistry and biochemistry of the vitamin B(12) compounds (cobalamins, XCbl) are described, with particular emphasis on their structural aspects and their relationships with properties and function. A brief history of B(12), reveals how much the effort of chemists, biochemists and crystallographers have contributed in the past to understand the basic properties of this very complex vitamin. The properties of the two cobalamins, the two important B(12) cofactors Ado- and MeCbl are described, with particular emphasis on how the Co-C bond cleavage is involved in the enzymatic mechanisms. The main structural features of cobalamins are described, with particular reference to the axial fragment. The structure/property relationships in cobalamins are summarized. The recent studies on base-off/base-on equilibrium are emphasized for their relevance to the mode of binding of the cofactor to the protein scaffold. The absorption, transport and cellular uptake of cobalamins and the structure of the B(12) transport proteins, IF and TC, in mammals are reviewed. The B(12) transport in bacteria and the structure of the so far determined proteins are briefly described. The currently accepted mechanisms for the catalytic cycles of the AdoCbl and MeCbl enzymes are reported. The structure and function of B(12) enzymes, particularly the important mammalian enzymes methyltransferase (MetH) and methyl-malonyl-coenzyme A mutase (MMCM), are described and briefly discussed. Since fast proliferating cells require higher amount of vitamin B(12) than that required by normal cells, the study of B(12 )conjugates as targeting agents has recently gained importance. Bioconjugates have been studied as potential agents for delivering radioisotopes and NMR probes or as various cytotoxic agents towards cancer cells in humans and the most recent studies are described. Specifically, functionalized bioconjugates are used as "Trojan horses" to carry into the cell the appropriate antitumour or diagnostic label. Possible future developments of B(12) work are summarized.

Protein carbamylation is of great concern both in vivo and in vitro. Here, we report the first structural characterization of a protein carbamylated at the N-terminal proline. The unexpected carbamylation of the α-amino group of the least reactive codified amino acid has been detected in high-resolution electron density maps of a new crystal form of the HIV-1 protease/saquinavir complex. The carbamyl group is found coplanar to the proline ring with a trans conformation. The reaction of N-terminal with cyanate ion derived from the chaotropic agent urea was confirmed by mass spectra analysis on protease single crystals. Implications of carbamylation process in vitro and in vivo are discussed.

Discovery by co-crystallization: High-resolution electron-density maps of HIV-1 aspartyl protease complexed with a potent Phe–Pro isostere-based inhibitor (shown) allowed the determination of the stereochemistry of the inhibitor and an initial assessment of the inhibition properties of this compound without its purification from the epimeric mixture.

Folding can bestow macromolecules with various properties, as evident from nature's proteins. Until now complex folded molecules are the product either of evolution or of an elaborate process of design and synthesis. We now show that molecules that fold in a well-defined architecture of substantial complexity can emerge autonomously and selectively from a simple precursor. Specifically, we have identified a self-synthesizing macrocyclic foldamer with a complex and unprecedented secondary and tertiary structure that constructs itself highly selectively from 15 identical peptide-nucleobase subunits, using a dynamic combinatorial chemistry approach. Folding of the structure drives its synthesis in 95% yield from a mixture of interconverting molecules of different ring sizes in a one-step process. Single-crystal X-ray crystallography and NMR reveal a folding pattern based on an intricate network of noncovalent interactions involving residues spaced apart widely in the linear sequence. These results establish dynamic combinatorial chemistry as a powerful approach to developing synthetic molecules with folding motifs of a complexity that goes well beyond that accessible with current design approaches. The fact that such molecules can form autonomously implies that they may have played a role in the origin of life at earlier stages than previously thought possible.