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首页> 外文期刊>Crystal growth & design >Modulating supramolecular reactivity using covalent 'switches' on a pyrazole platform
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Modulating supramolecular reactivity using covalent 'switches' on a pyrazole platform

机译：在吡唑平台上使用共价“开关”调节超分子反应性

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Systematic co-crystallizations of halogen- methyl- and nitro-substituted pyrazoles with a library of 20 aromatic carboxylic acids have been carried out using melt and solution-based experiments. The solids resulting from all reactions were screened using infrared spectroscopy in order to determine if a reaction (co-crystal or salt) had taken place. The halogenated pyrazoles, including their dimethyl analogues, gave a supramolecular yield of 55-70%. Replacing a halogen atom (R-X, X = Cl, Br, I) with a nitro (R-NO_2) group drops the success rate significantly to 10% due to the reduced charge on the basic nitrogen atom of the pyrazole. Eleven crystal structures were obtained: six were co-crystals and five were salts (including one hydrate). In all six co-crystals, dimeric pyrazole?acid assemblies were constructed via a combination of O-H - -N(pyz) and N-H - -O hydrogen bonds corresponding to a 100% supramolecular yield. A variety of weaker halogen-bonds CN - -I, I - -I and X - -O~- connect dimers into infinite one-dimensional chains. In contrast, the salts displayed a variety of stoichiometries and a much wider range of noncovalent interactions, although a charge-assisted N~+-H - -O~- hydrogen bond was present in all five structures. In general, the salts lack structural and stoichiometric predictability and stability as compared to the co-crystals. Furthermore, the overall electrostatic charge on the key binding sites on the pyrazole backbone can be modulated by using specific covalent switches, which in turn can increase (or decrease) the success rate for a reaction.
机译：卤素-甲基-和硝基取代的吡唑与20种芳香族羧酸的文库的系统共结晶已经使用基于熔融和溶液的实验进行了。使用红外光谱法筛选所有反应产生的固体，以确定是否发生了反应（共晶体或盐）。卤代吡唑包括其二甲基类似物的超分子产率为55-70％。由于吡唑碱性氮原子上电荷的减少，用硝基（R-NO_2）取代卤素原子（R-X，X = Cl，Br，I）会使成功率显着下降至10％。获得了十一种晶体结构：六种为共晶体，五种为盐（包括一种水合物）。在所有六个共晶体中，通过O-H--N（pyz）和N-H--O氢键的组合（相当于100％的超分子产率）构建了二聚吡唑酸组装体。各种较弱的卤素键CN--I，I--I和X--O〜-将二聚体连接成无限的一维链。相反，尽管在所有五个结构中均存在电荷辅助的N〜+ -H--O〜-氢键，但盐显示出各种化学计量比和更广泛的非共价相互作用。通常，与共晶体相比，盐缺乏结构和化学计量的可预测性和稳定性。此外，可以通过使用特定的共价开关来调节吡唑主链上关键结合位点上的总静电荷，这反过来又可以增加（或减少）反应的成功率。

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