Bispidine Based Hg(II) 1D Coordination Polymers of Helical Topology: Stability, Selective Adsorption and 1D to 2D Dimensionality Change Via SC-to-SC Transformation.

Bispidine based Hg(II) coordination polymers of helical topology CP-MeOH and CP-EtOH are almost isostructural (they mainly differ for the solvent included in their lattice and by a small % in unit cell parameters) but they differ for everything else: i) their intrinsic stability, ii) their ability to adsorb solvents upon prior evacuation, iii) their accessible structural transformations. In particular, one of the two starting materials, once evacuated, is capable to adsorb methanol from atmospheres containing binary and ternary mixtures of volatile organic compounds (MeOH, CHCl and EtOH) under ambient conditions (25 °C, 1 atm) and with a marked selectivity. The other one is not, but undergoes a 1D to 2D dimensionality change which can be monitored in situ by SC-XRD through a SC-to-SC process.

Systematic Study of Podand Molecules for Synergistic Halogen and Hydrogen Bond-Driven Anion Recognition in the Solid State.

The increasing demand of species for the efficient capture and sensing of anions benefits from a systematic study of anion binding capabilities in the solid state. This work reports a detailed crystallographic study of ten structurally related podands and shows that these charged receptors bind anions with a combination of charge-assisted halogen and hydrogen bonds. Computational tools helped in highlighting the role of the different involved interaction and afforded possible design principles for the design of improved podands.

Aryl Boronic Acids in Columnar Stacked Co-crystalline Materials: Key-Factors Governing the Assembly with Quinones.

The assembly of aryl boronic acids B with quinones Q into columnar mixed stacked materials, as previously observed in the solid-state, has been here subjected to a detailed theoretical analysis focusing on the properties of the isolated synthons (HOMO-LUMO energies, electron affinity, ionization potential, reorganization hole/electron energies, partial Hirshfeld atomic charges and conformation stabilities) as well as those of the 1 : 1 adducts (Hirshfeld analysis, IRI surfaces, Hirshfeld atomic charges, hydrogen bond and slipped stacked π-π contributions). The overall picture obtained throught this study shows an intricate pattern of interconnected factors contributing to the formation and stability of the B Q adducts, and it unveils the importance of parameters such as HOMO-LUMO gap, polarization and charge transfer, in addition to the more evident hydrogen bond and slipped-stacked π-π interactions in the formation of 1 : 1 adducts. An explanation has been also given for the presence in some B Q adducts of the rare anti-anti conformation for the BO-H group with respect to the most studied and common anti-syn conformation.

Different Topologies of Hg(II)-Bispidine 1D Coordination Polymers: Dynamic Behavior in Solvent Adsorption and Exchange Processes.

One-dimensional (1D) coordination polymers (CPs) featuring three different topologies, comprising zig-zag, ribbon-like and poly-[n]-catenane structures, were obtained by reaction of Hg(II) ions with a novel bispidine ligand L3, and structurally characterized by SC- and P-XRD methods. The CPs obtained in the form of microcrystalline powders were tested for their ability to undergo solvent adsorption and exchange by P-XRD and H NMR spectroscopy. The extent of their dynamic behavior was then correlated to their structural features, highlighting the role of interchain interactions established among their constituting linear arrays.

Tuneable solvent adsorption and exchange by 1D bispidine-based Mn(II) coordination polymers ligand design.

Here we report novel bispidine-based coordination polymers (CPs) 2·TCM, 3·TCM, 3·NB, 5·TCM and 5·TCM·NB, of compostition [Mn(Cl)2(L2)2·(TCM)2], [Mn(Cl)2(L3)2·(TCM)5], [Mn(Cl)2(L3)2·(NB)8], [Mn(Cl)2(L5)2·(TCM)4], [Mn(Cl)2(L5)2·(TCM)2·(NB)2], respectively (NB = nitrobenzene; TCM = chloroform). They were obtained starting from novel bispidine ligands L2 (dimethyl 7-isopropyl-3-methyl-9-oxo-2,4-di(pyridin-4-yl)-3,7-diazabicyclo[3.3.

Combined structural and theoretical investigation on differently substituted bispidine ligands: predicting the properties of their corresponding coordination polymers.

Pyridine-based bispidine ligands L1-L7, which differ in the substituent at the N7 position of the bispidine scaffold, have been studied by single crystal X-ray diffraction and density functional theory (DFT) calculations, also including solid-state algorithms. Qualitative description of the packing interactions and quantitative data on the stability of each ligand in the solid-state have been employed to draw reasonable predictions on the ligand potential for the formation of linear 1D coordination polymers (CPs) with Mn(ii)Cl and on their resulting dynamic properties, in terms of adsorption and solvent exchange capabilities. The basic assumption lies in the fact that volume and polarizability of the ligands would similarly affect packing energies in both molecular solids and CP materials.

Naked-Eye Heterogeneous Sensing of Fluoride Ions by Co-Polymeric Nanosponge Systems Comprising Aromatic-Imide-Functionalized Nanocellulose and Branched Polyethyleneimine.

Heterogeneous colorimetric sensors for fluoride ions were obtained by cross-linking TEMPO-oxidized cellulose nanofibers (TOCNF) with chemically modified branched polyethyleneimine 25 kDa (bPEI). Functionalization of bPEI primary amino groups with aromatic anhydrides led to the formation of the corresponding mono- and bis-imides on the grafted polymers (f-bPEI). A microwave-assisted procedure allowed the optimization of the synthetic protocol by reducing reaction time from 17 h to 30 minutes.

Ab initio powder X-ray diffraction structural analysis of bispidine based 1D coordination polymers: insights into their guest responsive behaviour.

The first ab initio synchrotron powder X-ray diffraction (XRD) data structure solution, employing real-space global optimization strategies followed by Rietveld refinement, was obtained for a bispidine based one-dimensional ribbon-like coordination polymer (CP) 1. The structure solution of 1, a non-dynamic phase containing no solvent molecules, is crucial to obtain a more comprehensive view of the dynamic behaviour of a new family of 1D CPs, in terms of solvent adsorption and exchange processes by direct comparison among the structures, solvent-ribbon and inter-ribbon interactions of the CP materials. This work also reports novel bisolvated phases, 1·TCM·oNT, 1·TCM·pCT and 1·TCM·NB, in the form of single crystals and microcrystalline powders and shows that 1 can be thermally activated to regain dynamic selective adsorption features.

ON/OFF Control of the Flipping Motion of Diuranyl Bis(Salophen) Macrocycle by Extremely Strong Binding with Fluoride Ion.

Diuranyl bis(salophen) complex features a relatively slow conformational motion, induced by an intramolecular O═U═O···UO binding motif, which interconverts the two nonsymmetric halves of the ligand. This flipping motion, which constitutes one of the fundamental molecular motions, can be completely halted by addition of fluoride anion, which is bound to , reaching one of the highest affinities reported to date. This system represents a model to study flipping dynamics in light of the possibility of developing novel types of molecular machines based on it.

Selective Cu(ii) sensing by a versatile AIE cyanostilbene-based gel system.

Cyanostilbene-based derivatives 1-3 were designed, synthesized and fully characterized. By screening their gelating abilities, we observed that the subtle difference in the position of the pyridine nitrogen greatly affected the resulting fluorescence and gelation properties. Notably, 1 was found to be a versatile ambidextrous gelator capable of forming organo-, hydro-, and Cu(ii) specific metallogels.

Highly Dynamic and Tunable Behavior of 1D Coordination Polymers Based on the Bispidine Ligand.

Ligands L1 and L2 have been designed, synthesized, and used to build for the first time bispidine-based coordination polymers (CPs) in combination with Mn . The novel CPs have been structurally characterized by single-crystal (SC) and powder X-ray diffraction (P-XRD) techniques, showing that they are composed of 1D ribbon-like chains that adopt various arrangements depending on the trapped solvent species. These materials show highly dynamic behavior as they undergo heterogeneous solid/liquid and solid/vapor multiple solvent exchange processes, comprising crystalline-amorphous-crystalline, selective adsorption and SC-to-SC transformations, where major structural reorganization of the 1D ribbons are observed.

Mechanical and Drug Release Properties of Sponges from Cross-linked Cellulose Nanofibers.

All-organic porous sponges were obtained throughout the direct and solvent-free (oven 105 °C, time>6 h) crosslinking of TEMPO-oxidized cellulose nanofibers (TOCNF) with 25 kDa branched polyethyleneimine (bPEI) in the presence of different amounts of citric acid (CA) as co-crosslinker. The chemical and mechanical stability of these materials was provided by the formation of amide bonds between the carboxylic moieties of TOCNF and CA with the primary amines of bPEI. The mechanical properties were investigated under static and dynamic loads with both dry and wet samples.

Lipophilic N-Hydroxyphthalimide Catalysts for the Aerobic Oxidation of Cumene: Towards Solvent-Free Conditions and Back.

A new class of lipophilic N-hydroxyphthalimide (NHPI) catalysts designed for the aerobic oxidation of cumene in solvent-free conditions was synthesized and tested. The specific strategy proposed for the introduction of lipophilic tails on the NHPI moiety leads to lipophilic catalysts that-while completely preserving the activity of the precursor-allow the catalytic oxidation to be conducted in neat cumene, for the first time. The corresponding cumyl hydroperoxide is obtained in good yields (28-52 %) and with high selectivity (95-97 %), under mild conditions.

Crystal Engineering of a Two-Dimensional Lead-Free Perovskite with Functional Organic Cations by Second-Sphere Coordination.

Invited for this month's cover are collaborators from the Istituto Italiano di Tecnologia, Nanyang Technological University, and Politecnico di Milano. The cover picture shows the 2 D layered nature of lead-free perovskite having a functional organic cation. Read the full text of the article at 10.

Crystal Engineering of a Two-Dimensional Lead-Free Perovskite with Functional Organic Cations by Second-Sphere Coordination.

Hybrid lead halide perovskite semiconductors are attracting increasing attention for applications in optoelectronics. However, the high lead content calls for the development of greener and smarter alternatives through crystal engineering. This is extremely challenging since the use of functional cations often results in the disruption of the metal halide framework.

X-Ray crystallographic and computational study on uranyl-salophen complexes bearing nitro groups.

In the solid state, salophen-UO complexes bearing one, two, or three NO groups lack the pronounced ligand curvature that represents a structural hallmark for this class of compounds. A detailed structural study based on single-crystal X-ray crystallography and computational methods, comprising molecular dynamics, gas-phase Hartree Fock, and DFT calculations, was carried out to investigate the coordination properties of the uranyl cation.

Selective adsorption of chlorinated volatile organic compound vapours by microcrystalline 1D coordination polymers.

Microcrystalline 1D coordination polymers 1-3 are able to adsorb vapours of chlorinated volatile organic compounds (Cl-VOCs), displaying interesting selectivity patterns, as demonstrated by H-NMR and X-ray diffraction analyses. Due to their dynamic breathing-like behavior, chemical and thermal stabilities and adsorption selectivity, these isostructural coordination polymers are promising to be used as filters for toxic Cl-VOCs.

Metallogel formation in aqueous DMSO by perfluoroalkyl decorated terpyridine ligands.

Terpyridine based ligands 1 and 2, decorated with a C8F17 perfluorinated tag, are able to form stable thermoreversible gels in the presence of several d-block metal chloride salts. The gel systems obtained have been characterized by NMR, X-ray diffraction, electron microscopies and Tgel experiments in order to gain insights into the observed different behaviour of the two similar ligands, also in terms of the effect of additional common anionic species.

Dynamic single crystal to polycrystal transformation of a 1D-coordination polymer and its second harmonic generation.

Upon guest CHCl3 release, the one-dimensional (1D) coordination polymer ·CHCl3 gives rise to a non-porous structure, , following a unit cell volume reduction of ca. 22%. Due to the considerable structural transformation, the single crystal does not maintain its integrity, and therefore the structure determination has been carried out by combining single crystal X-ray diffraction and ab initio X-ray powder diffraction analyses.

Mixed valence mono- and hetero-metallic grid catenanes.

Here, we report on the multicomponent self-assembly and single crystal X-ray diffraction study of a series of three interlocked mixed valence mono- and hetero-metallic [2]-catenanes made of [2 × 2] metallo-grids. They show unique structural features and highlight the essential roles of both the Cu(ii)/Cu(i) pair and of the conformationally adaptable organic ligands for achieving catenation of grids.

Insights into the formation of chiral second sphere coordination complexes with aromatic tris amines: combined single crystal X-ray crystallography and molecular modeling analyses.

A family of isostructural, chiral supramolecular networks have been obtained in the solid state by exploiting second sphere coordination interactions in the self-assembly of achiral tris amines and with tetrahalometallate and halide ions. Quantum-Mechanical (QM) calculations specific for solid phases provided additional insights into the intramolecular and packing interactions which determine chirality, pointing to a direct effect of the methyl groups of the central benzene ring.

Multiple single-crystal-to-single-crystal guest exchange in a dynamic 1D coordination polymer.

A novel 1D coordination polymer that dynamically expands or shrinks upon the uptake of vapours of volatile small chlorinated molecules, such as 1,2-dichloroethane (DCE), dichloromethane (DCM) and trichloromethane (TCM), is reported. This system is robust enough to withstand multiple guest exchange via single-crystal-to-single-crystal transformation, as proved by (1)H-NMR and X-ray diffraction. The single crystal of guest-free, host framework, stable at 400 K, can also be obtained.

Cu(II)-specific metallogel formation by an amido-anthraquinone-pyridyloxalamide ligand in DMSO-water.

This study on the CuCl2-induced and water-mediated metallogel formation by a pyridine containing anthraquinone-based ligand in DMSO provides significant insights on the relationship between the coordination geometry and metallo-gelation aptitude for a series of variably substituted pyridyloxalamide ligands.

Optimization of rapid acquisition with relaxation enhancement (RARE) pulse sequence parameters for ¹⁹F-MRI studies.

Purpose: To optimize signal-to-noise ratio (SNR) in fast spin echo (rapid acquisition with relaxation enhancement [RARE]) sequences and to improve sensitivity in ¹⁹F magnetic resonance imaging (MRI) on a 7T preclinical MRI system, based on a previous experimental evaluation of T₁ and T₂ actual relaxation times.

Materials And Methods: Relative SNR changes were theoretically calculated at given relaxation times (T₁, T₂) and mapped in RARE parameter space (TR, number of echoes, flip back pulse), at fixed acquisition times. T₁ and T₂ of KPF₆ phantom samples (solution, agar mixtures, ex vivo perfused brain) were measured and experimental SNR values were compared with simulations, at optimal and suboptimal RARE parameter values.

Crystal structures and magnetic properties of a set of dihalo-bridged oxalamidato copper(II) dimers.

A set of four copper(ii) complexes, and (X = Cl, Br; = N-(l-leucine methyl ester)-N'-((2-pyridin-2-yl)methyl)oxalamide and = N-benzyl-N'-((2-pyridin-2-yl)methyl)oxalamide), have been synthesized and characterized by X-ray structural analysis, electron paramagnetic resonance (EPR) spectroscopy on single crystals and by SQUID magnetization measurements. X-ray diffraction studies show one-dimensional hydrogen bonded networks of dimeric copper(ii)-complexes bridged by two halide ions and with the two metal centers 3.44-3.