Combined Approach of Mechanochemistry and Electron Crystallography for the Discovery of 1D and 2D Coordination Polymers

Abstract

Mechanochemical synthesis is an attractive preparative method that combines a green approach with versatility, efficiency, and rapidity of reaction. However, it often yields microcrystalline materials, and their small crystal size is a major hindrance to structure elucidation with conventional single-crystal or powder X-ray diffraction methods. This work presents the novel approach of combining mechanochemistry with electron diffraction techniques to elucidate the crystal structure of metal–organic compounds of zinc­(II) and copper­(II) with 2,6-pyridinedicarboxylic acid and 4,4′-bipyridine.

4,4′-(Anthracene-9,10-diylbis(ethyne-2,1-diyl))bis(1-methyl-1-pyridinium) Lead Iodide C30H22N2Pb2I6: A Highly Luminescent, Chemically and Thermally Stable One-Dimensional Hybrid Iodoplumbate

“…To fully exploit the potentialities of both XRPD and 3D ED, the following protocol has been adopted: (i) any new synthesis is characterized by XRPD; (ii) if the XRPD pattern cannot be fully indexed with known structures, 3D ED data are collected from few single nanocrystals to identify the new phase present in the sample and to measure the related unit cell; and (iii) if an unknown phase is detected, its crystal structure is solved by 3D ED and refined by Rietveld refinement against XRPD. Such a combination of methods was already successfully used in several pure organic compounds − and hybrid organic–inorganic materials. ,− …”

“…Such a combination of methods was already successfully used in several pure organic compounds 32 − 35 and hybrid organic–inorganic materials. 29 , 36 − 38 …”

Selective and Reversible Solvent Uptake in Tetra‐4‐(4‐pyridyl)phenylmethane‐based Supramolecular Organic Frameworks

“…To this purpose, a batch of single crystals of TPPM ⋅ CHCl 3 was heated at 100 °C for 2 h. Part of the batch was grinded and analysed through X‐ray powder diffraction; the comparison of the diffractograms of the chloroform solvate and the activated form clearly showed the formation of a new phase showing high micro‐crystallinity, probably due to the lack of disordered solvent inside the channels. The remaining single crystals show an increased mosaicity (Figure S12) which hampers the use of single crystal X‐ray diffraction and calls for 3D electron diffraction (3D ED),[ 54 , 55 , 56 ] which can be successfully employed with nanometric samples possessing small crystalline domains. Although TPPM crystals are sensitive to the electron beam, thanks to a special low dose set up in which the electron dose is reduced below 0.05 el s −1 Å −2 and the diffraction patterns are collected with a Timepix single electron detector, [57] a full 3D ED experiment covering a 120° of reciprocal space can be performed without the amorphization of the crystals or a significant loss in resolution of the diffraction signal.…”

Stimuli‐Responsive, Dynamic Supramolecular Organic Frameworks

“…Activation of single crystals of T15•CHCl 3 at 100 °C for 2 hours afforded empty SOF crystals with increased mosaicity, which were analysed by 3D electron diffraction (3D ED). [77][78][79] The activated SOFs retains the monoclinic space group C2/c with small variations of cell parameters such as the a axis, which goes from 27.93 to 31.40 Å and the volume, which slightly decreases from 3628 to 3596 Å 3 . Despite this, the unsolvated framework presents a compact structure (Type II material), consolidated by CÀ H•••N and CÀ H•••π interactions between reorganized T15 molecules, and contains unconnected voids summing up to 4 % of the unit cell volume (Figure 5a).…”