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, CHCl3 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.

Paracetamol Inclusion in Mechanically Interlocked Nanocages

The solid-state synthesis and fast crystallization under kinetic control of poly-[n]-catenanes self-assembled of mechanically interlocked metal organic cages (MOCs) is virtually unexplored. This is in part, due to the lack of suitable crystals for single crystal X-ray diffraction (SC-XRD) analysis which limits their progress as advanced functional materials. Here we report the unprecedented inclusion of paracetamol in the cavities of amorphous materials constituted of M12L8, interlocked MOCs synthesized by mechanochemistry under kinetic control. Full structure determination of a low-crystallinity and low-resolution powders of the M12L8 poly-[n]-catenane including paracetamol has been carried out combining XRD data and Density Functional Theory (DFT) calculations using a multi-step approach. Each M12L8 cage contains six paracetamol guests which is confirmed by thermal analysis and NMR spectroscopy. The paracetamol loading has been also carried out by the instant synthesis method using a saturated paracetamol solution in which TPB and ZnI2 self-assemble immediately (i. e., 1-5 seconds) encapsulating ~7 paracetamol molecules in the M12L8 nanocages under kinetic control also giving a good selectivity. Benzaldehyde has been included in the M12L8 cages using amorphous M12L8 polycatenanes showing that the icosahedral cages can serve as potential nanoreactors for instance to study Henry reactions in the solid-state.

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 ¹H 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. Zig‐zag CPs proved to be resilient to external chemical stimuli, while they differently respond to thermal treatments, depending on the solvent originally included within the CP. In the case of polycatenated structures, we observed transformations where the original topology was maintained upon guest exchange, but also cases where it changed to zig‐zag, even under solid/vapor conditions (i. e., no complete dissolution of the CP). Given the presence of linear interconnected 1D channels, 3  ⋅  ClBz‐polycatenane^Pwd is also able to trap volatile guests such as n‐hexane when exposed to its vapors.

Dehydrohalogenation reactions in second-sphere coordination complexes

The latest advances of solid-state dehydrohalogenation and halogenation reactions of hydrogen bonded halometallate salts from the second sphere coordination perspective are reported. Since the second sphere englobes many different materials, our focus has been limited to outer sphere adducts where protonated organic cations act as outer sphere hydrogen bond donors and transition metal anions act as first sphere hydrogen bond acceptors. This is our attempt to analyze dehydrohalogenation/hydrohalogenation reactions viewed as transformations from the second sphere coordination to first sphere coordination of a complex and vice versa. The examples describe a unique solid-state chemistry and reactivity in outer sphere adducts where C-H, N-H and M-X chemical bonds are cleaved and new M-N and H-X bonds are formed (where M = Cu, Zn, Co, Pt, Pd, Hg and X = Cl, Br). The transformations are induced by external stimuli, mainly by mechanochemical and thermal methods. Different reactivities have been observed depending on the lability of the transition metals, the position of the reacting functional groups in the cations and the relative position of organic cations and metal anions. The reverse hydrohalogenation reactions (i.e., from the first sphere coordination to second sphere coordination) via the gas-solid chemisorption process occur even if the materials are non-porous implying a rather dynamic behaviour of these materials. Moreover, due to the implicit changes in the coordination sphere of transition metal ions, dehydrohalogenation/halogenation reactions allow structure-function correlation to be established, for instance involving optical, sensing and magnetic aspects.

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

Pyridine-based bispidine ligands L1–L7 have been studied by single crystal X-ray diffraction and solid-state DFT calculations in an attempt to predict the dynamic properties of their corresponding Mn(ii) coordination polymers.

Structural elucidation of microcrystalline MOFs from powder X-ray diffraction

Ab initio powder XRD structure solution and MOFs.

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

General trends on the structural and dynamic properties of bispidine-based Mn(ii) 1D coordination polymers have been outlined on the basis of both single-crystals and microcrystalline powders data and by solvent adsorption and exchange experiments.