Coordination polymer flexibility leads to polymorphism and enables a crystalline solid-vapour reaction: a multi-technique mechanistic study.
Coordination polymer flexibility leads to polymorphism and enables a crystalline solid-vapour reaction: a multi-technique mechanistic study.
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DOI：
10.1002/chem.201500514
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发表时间：
2015-06-08
期刊：
影响因子：
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通讯作者：
Brammer L
中科院分区：
文献类型：
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作者：
Vitórica-Yrezábal IJ;Libri S;Loader JR;Mínguez Espallargas G;Hippler M;Fletcher AJ;Thompson SP;Warren JE;Musumeci D;Ward MD;Brammer L
尽管没有常规孔隙，1D配位聚合物[Ag4(O2C(CF2)2CF3)4(TMP)3] （1； TMP=四甲基吡嗪）可以从气相中吸收小醇，这些小醇插入Ag-O键中，生成配位聚合物[Ag4(O2C(CF2)2CF3)4(TMP)3(ROH)2] （1-ROH； R=Me, Et, iPr）。反应是可逆的单晶到单晶的转化。气相红外光谱测定了气固平衡(K=5.68(9)×10−5 (MeOH), 9.5(3)×10−6 (EtOH), 6.14（5)×10−5 (iPrOH)，温度为295 K， 1 bar）。热分析（TGA， DSC）可以定量比较两步反应1- roh→1→2，其中2是由单桥位的TMP配体损失形成的二维配位聚合物[Ag4(O2C(CF2)2CF3)4(TMP)2]。在晶体学上鉴定出了1- alt、1- aht、1- blt和1- bht的四种多晶型；HT=高温，LT=低温。1- roh→1→2转化的原位粉末x射线衍射（PXRD）研究表明，HT多晶型物在这些反应中起作用。多晶之间的结构关系，包括全氟烷基链构象的变化和整个聚合物（a型和B型）取向的变化，表明了所观察到的反应的机制和氟层内客体运输的途径。与这一途径一致的是，对1-MeOH/1-AHT单晶的光学显微镜和原子力显微镜研究表明，在MeOH释放/摄取过程中，出现了平行于交叉的全氟烷基链层的裂缝。
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.