Solid-state synthesis of mixed trihalides via reversible absorption of dihalogens by non porous onium salts

1,6-Bis(trimethylammonium) hexane bis(trihalides) and mixed bis(trihalides) have been synthesized by treating the corresponding dihydrated halides with molecular dihalogens under gas-solid and solution conditions. Despite the starting halides being non-porous, the trihalide syntheses occur homogeneously, in quantitative yields, and reversibly. In all cases halogen bond prevails over hydrogen bond, dihalogens substitute for the hydration water of starting halide anions and trihalides are formed. The stability of the obtained trihalides is mainly due to cooperative halogen bond and cation templation effect. Hexamethonium halides are proven effective solids for the clathration and storage of molecular dihalogens. While the starting salts are not isostructural, all the formed trihalides and mixed trihalides are isostructural

Tunable Porous Organic Crystals: Structural Scope and Adsorption Properties of Nanoporous Steroidal Ureas

Previous work has shown that certain steroidal bis-(N-phenyl)ureas, derived from cholic acid, form crystals in the P61 space group with unusually wide unidimensional pores. A key feature of the nanoporous steroidal urea (NPSU) structure is that groups at either end of the steroid are directed into the channels and may in principle be altered without disturbing the crystal packing. Herein we report an expanded study of this system, which increases the structural variety of NPSUs and also examines their inclusion properties. Nineteen new NPSU crystal structures are described, to add to the six which were previously reported. The materials show wide variations in channel size, shape, and chemical nature. Minimum pore diameters vary from ∼0 up to 13.1 Å, while some of the interior surfaces are markedly corrugated. Several variants possess functional groups positioned in the channels with potential to interact with guest molecules. Inclusion studies were performed using a relatively accessible tris-(N-phenyl)urea. Solvent removal was possible without crystal degradation, and gas adsorption could be demonstrated. Organic molecules ranging from simple aromatics (e.g., aniline and chlorobenzene) to the much larger squalene (Mw = 411) could be adsorbed from the liquid state, while several dyes were taken up from solutions in ether. Some dyes gave dichroic complexes, implying alignment of the chromophores in the NPSU channels. Notably, these complexes were formed by direct adsorption rather than cocrystallization, emphasizing the unusually robust nature of these organic molecular hosts

Host-Guest Chemistry of M12L8 Poly-[n]-catenanes: Inclusion Process by Switchable ''losed-Open'' ynamic Channels

Direct guest exchange reactions in one-dimensional (1D) poly-[n]-catenanes self-assembled by elusive M12L8 large nanocages (similar to 2600 angstrom(3) of internal volume) have never been documented. Herein, we report for the first time the guest behavior of a TPB poly-[n]-catenane (1) self-assembled from M12L8 icosahedral nanocages in the absence of permanent communicating voids. High-resolution synchrotron X-ray data obtained by means of crystal-to-crystal guest exchange reactions unambiguously demonstrate the uptake of o-dichlorobenzene and p-chloroanisole. Density functional theory calculations aimed at studying local interaction energy variation among 1D chains of catenated M12L8 cages provided insights that help us further understand the intrinsic dynamic behavior of the 1D porous rods. The guest uptake by the icosahedral M12L8 nanocages is rationalized via a switchable closed-open process considering both the weak interchain interactions and the stronger intrachain mechanical bond. Mechanistic aspects of the molecular exchange consider both the sliding motion of the 1D chains of interlocked M12L8 nanocages and the dynamic aspects of single M12L8 cages within the 1D chains (i.e., cage compression/extension) in a concerted cooperative dynamic behavior. Thermal treatment of the ZnBr2-TPB poly-[n]-catenane demonstrates that the mechanical bond remains up to similar to 500 K. The exceptional structural properties of 1 have been studied for potential applications such as selectivity of chlorobenzenes. The labile nature of the Zn-N coordination bond allows the recyclability of the TPB ligand in water, thus making these materials candidates in green chemistry applications

Selective guest inclusion of linear C6 hydrocarbons in a Zn(ii) 1D coordination polymer

Trapping of volatile unbranched C6hydrocarbons (hexane, 1-hexene, and 1-hexyne) in a 1D coordination polymer is reported. The guest inclusion was studied quantitatively by1H-NMR analysis and thermogravimetric measurements, while synchrotron single-crystal diffraction data allowed advancing the view of their confinement into linear CP channels. Adsorption experiments performed through solid/vapour processes on microcrystals of CP1showed a certain degree of selectivity for 1-hexyne, which could be rationalized by its larger dipole moment

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

Diuranyl bis(salophen) complex 1 features a relatively slow conformational motion, induced by an intramolecular O═U═O···UO2 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 1, 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

Mechanochemical synthesis of mechanical bonds inM12L8poly-[n]-catenanes

Using mechanochemistry by grindingTPBand ZnBr2, anamorphouspoly-[n]-catenane of interlockedM12L8nanocages is obtained in good yields (∼80%) and within 15 minutes. The mechanical bond among the icosahedralM12L8cages in the amorphous phase has been demonstrated by single crystal XRD, powder XRD and FT-IR spectroscopy following anamorphous-to-crystallinetransformation by guest uptake of the amorphous phase. High-resolution solid-state13C NMR spectroscopy gives insights into the local structure of theamorphouscatenane focusing onTPBaromatic-aromatic interactions

Bidirectional Transport of Guest Molecules through the Nanoporous Tunnel Structure of a Solid Inclusion Compound

Confocal Raman microspectrometry is used to probe, for the first time, the transport of guest molecules along the one-dimensional tunnels in a crystalline urea inclusion compound under conditions of guest exchange in which new guest molecules are introduced simultaneously at both ends of the urea tunnel structure. We focus on the system comprising 1,8-dibromooctane as the original type of guest and pentadecane as the new type of guest, and results are presented for experiments in which the guest exchange process is probed both ex situ and in situ. The Raman data, recorded as a function of position along the tunnel direction and, in the case of the in situ experiments, as a function of time, demonstrate that pentadecane guest molecules enter the tunnels at both ends of the crystal and that transport of guest molecules occurs in both directions along the crystal. Mechanistic aspects of this bidirectional transport process are discussed, particularly in relation to the corresponding process for unidirectional transport of guest molecules in urea inclusion compounds reported previously

Chain-Walking Polymerization of α-Olefins by α-Diimine Ni(II) Complexes: Effect of Reducing the Steric Hindrance of Ortho- and Para-Aryl Substituents on the Catalytic Behavior, Monomer Enchainment, and Polymer Properties

With Brookhart type α-diimine Ni(II) based catalysts, it is highly challenging to tune polymers branching level and branch-type distribution, which in turn strongly affects thermal and mechanical properties, through the aryl ortho-positions modification, while maintaining high turnover frequencies (TOFs). Herein, we are interested in performing a systematic investigation on the polymerization of 1-octene, 1-decene, and 1-octadecene catalyzed by a series of α-diimine nickel(II) complexes with methyl ligand backbone and different substituents in aryl positions (Ni1-Ni6). In addition to bulky isopropyl and tert-butyl substituents described in the original Brookhart's work, complexes with different aryl ortho- and para-substituted α-diimine ligands, including the less sterically demanding methyl and ethyl substituents, are investigated. The 13C NMR spectra of the polymers have been assigned in detail, and some unique features have been identified and related to the chain-walking coordination/insertion mechanism. Changes in the ligand structure and monomer size have important effects on the numerous combinations of insertion and chain-walking paths from which different branches are installed. We have also carried out a comprehensive investigation of the mechanical behavior of the polymers by means of uniaxial stretching until failure, step-cycle, and creep tensile tests. Overall, the resulting polymers exhibited a broad spectrum of tensile properties, depending on their microstructure and crystallinity which in turn are strongly affected by monomer length and type of α-diimine ligand. 1-Octene and 1-decene polymers behave as elastomers with excellent mechanical properties, i.e., high elongation at break (up to 2000%) and good strain recovery, while 1-octadecene polymers behave as plastomers

Tuneable Solvent Adsorption and Exchange by 1D Bispidine-Based Mn(II) Coordination Polymers via Ligand Design

Here we report novel bispidine-based coordination polymers (CPs) 2\ub7TCM, 3\ub7TCM, 3\ub7NB, 5\ub7TCM and 5\ub7TCM\ub7NB, of compostition [Mn(Cl)2(L2)2\ub7(TCM)2], [Mn(Cl)2(L3)2\ub7(TCM)5], [Mn(Cl)2(L3)2\ub7(NB)8], [Mn(Cl)2(L5)2\ub7(TCM)4], [Mn(Cl)2(L5)2\ub7(TCM)2\ub7(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[3.3.1]nonane-1,5-dicarboxylate), L3 (dimethyl 7-(cyclohexylmethyl)-3-methyl-9-oxo-2,4-di(pyridin-4-yl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate) and L5 (dimethyl 7-(4-(dimethylamino)benzyl)-3-methyl-9-oxo-2,4-di(pyridin-4-yl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate), The novel CPs were characterized by single crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD) and thermal analyses (TGA). We describe their structural and dynamic properties in terms of solvent exchange and adsorption processes, and we outline the general trends observed on the basis of a total of 16 X-ray structures (4 new) and 21 microcrystalline powder phases (10 new), which have been obtained so far for CPs by coordination of ligands L1\u2013L5, having different substitution at the N7 position. This large set of CPs comprises monosolvated, bisolvated and desolvated species, and it shows a good demonstration of how small differences in the functionalization of the organic ligand can have a strong impact on the resulting structural and dynamic properties of this class of 1D CPs