Coordination Polymer Flexibility Leads to Polymorphism and Enables a Crystalline Solid–Vapour Reaction: A Multi‐technique Mechanistic Study |
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| Authors: | Dr Iñigo J Vitórica‐Yrezábal Dr Stefano Libri Dr Jason R Loader Dr Guillermo Mínguez?Espallargas Dr Michael Hippler Dr Ashleigh J Fletcher Dr Stephen P Thompson Dr John E Warren Prof Daniele Musumeci Prof Michael D Ward Prof Lee Brammer |
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| Institution: | 1. Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF (UK), Fax: (+44)?114‐222‐9536 http://www.sheffield.ac.uk/chemistry/staff/profiles/lee_brammer;2. Current address: School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL (UK);3. Instituto de Ciencia Molecular (ICMol), Universidad de Valencia c/Catedrático José Beltrán?2, 46980 Paterna (Spain);4. Department of Chemical and Process Engineering, University of Strathclyde, 75?Montrose St, Glasgow G1 1XJ (Scotland);5. Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0DE (UK);6. School of Materials, University of Manchester, Manchester M13 9PL (UK);7. Molecular Design Institute, NYU Department of Chemistry, 100?Washington Square East, New York, NY 10003 (USA);8. Current address: Department of Chemistry, York College of The City University of New York, 94‐20?Guy R. Brewer Blvd, Jamaica, New York, NY 11451 (USA) |
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| Abstract: | Despite an absence of conventional porosity, the 1D coordination polymer Ag4(O2C(CF2)2CF3)4(TMP)3] ( 1 ; TMP=tetramethylpyrazine) can absorb small alcohols from the vapour phase, which insert into Ag?O bonds to yield coordination polymers Ag4(O2C(CF2)2CF3)4(TMP)3(ROH)2] ( 1‐ROH ; R=Me, Et, iPr). The reactions are reversible single‐crystal‐to‐single‐crystal transformations. Vapour‐solid equilibria have been examined by gas‐phase IR spectroscopy (K=5.68(9)×10?5 (MeOH), 9.5(3)×10?6 (EtOH), 6.14(5)×10?5 (iPrOH) at 295 K, 1 bar). Thermal analyses (TGA, DSC) have enabled quantitative comparison of two‐step reactions 1‐ROH → 1 → 2 , in which 2 is the 2D coordination polymer Ag4(O2C(CF2)2CF3)4(TMP)2] formed by loss of TMP ligands exclusively from singly‐bridging sites. Four polymorphic forms of 1 ( 1‐ALT , 1‐AHT , 1‐BLT and 1‐BHT ; HT=high temperature, LT=low temperature) have been identified crystallographically. In situ powder X‐ray diffraction (PXRD) studies of the 1‐ROH → 1 → 2 transformations indicate the role of the HT polymorphs in these reactions. The structural relationship between polymorphs, involving changes in conformation of perfluoroalkyl chains and a change in orientation of entire polymers (A versus B forms), suggests a mechanism for the observed reactions and a pathway for guest transport within the fluorous layers. Consistent with this pathway, optical microscopy and AFM studies on single crystals of 1‐MeOH / 1‐AHT show that cracks parallel to the layers of interdigitated perfluoroalkyl chains develop during the MeOH release/uptake process. |
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| Keywords: | coordination polymers gas‐phase spectroscopy in situ diffraction microscopy polymorphism porosity solid‐state reactions thermal analysis |
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