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.

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.

Crystal Structure and Catalytic Activity of Poly[bis(3-bromo-2-hydroxybenzaldehyde)-2-aminopyrimidinemagnesium(II)] for Hydrogenation of 1,3-Butadiene

A new six-coordinated Mn(II) coordination polymer, [Mn(L1)(L2)2]n (L1 = 2-aminopyrimidine, HL2 = 3-bromo-2-hydroxybenzaldehyde) was synthesized by 3-bromo-2-hydroxybenzaldehyde, NaOH, 2-aminopyrimidine and manganese(II) acetate dihydrate. The Mn(II) coordination polymer was structural characterized by elemental analysis and single crystal X-ray diffraction. The results show that each Mn(II) ion is six-coordinated with two phenolic hydroxyl O atoms from two 3-bromo-2-hydroxybenzaldehyde ligands (O1 and O4), two formyl group O atoms from two 3-bromo-2-hydroxybenzaldehyde ligands (O2 and O3), and two N atoms from two 2-aminopyrimidine molecules (N1A and N2), and forms a distorted octahedral coordination geometry. The Mn(II) coordination polymer displays a 1D chained structure by the bridge effect of 2-aminopyrimidine N atoms. The catalytic activities of Mn(II) coordination polymer and Pd@Mn(II) coordination polymer for hydrogenation of 1,3-butadiene have been investigated. The Pd@Mn(II) coordination polymer catalyst shows the good catalytic activity and selectivity in  the hydrogenation of 1,3-butadiene. The 1,3-butadiene conversion is 61.3% at 70 °C, and the selectivity to total butene is close to 100%. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Structural elucidation of microcrystalline MOFs from powder X-ray diffraction

Ab initio powder XRD structure solution and MOFs.