Change of the kinetics of inclusion in cucurbit[7]uril upon hydrogenation and methylation of palmatine
作者:Zsombor Miskolczy、Mónika Megyesi、Orsolya Toke、László Biczók
DOI:10.1039/c8cp07231k
日期:——
Despite the ∼6 kJ mol−1 lower activation enthalpy, the rate constant of THP+ ingression into CB7 was about 44-fold smaller at 298 K than that of DHC+ as a consequence of the considerably negative activation entropy of the former binding. The egression rates of the two studied alkaloids differed to a much lesser extent because the lower energy barrier of THP+ release was almost compensated by the unfavourable
在不同温度下的水中,通过分光荧光法实时监测了葫芦[7] uril腔中质子化的(-)-四氢巴马汀(THP +)和脱氢钴碱素(DHC +)的天然生物碱含量。两位客人均在焓控制的过程中产生了1:1的复合物,而没有任何可检测的中间体。CB7的紧密入口对封装造成了很大的空间障碍,使得进入宿主的速度比扩散要慢几个数量级。尽管活化焓降低了约6 kJ mol -1,THP +进入CB7的速率常数在298 K时仍比CB7的速率常数小约44倍。DHC +是前结合物的相当大的负激活熵的结果。两种研究生物碱的流出速率差异较小,这是因为THP +释放的较低能垒几乎被不利的活化熵所补偿。与可逆封闭棕榈碱母体化合物的动力学相比,DHC +中芳族杂环上甲基取代基的存在几乎未改变进入CB7的速率常数,但导致CB7的解离速率提高了约10倍。 298K。