Permittivity-dependent entropy driven complexation ability of cone and paco tetranitro-calix[4]arene toward para-substituted phenols.
Permittivity-dependent entropy driven complexation ability of cone and paco tetranitro-calix[4]arene toward para-substituted phenols.
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DOI：
10.1021/jp803498v
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发表时间：
2008-08
期刊：
影响因子：
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通讯作者：
S. Kunsági-Máté;Z. Csók;A. Tuzi;L. Kollár
中科院分区：
文献类型：
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作者：
S. Kunsági-Máté;Z. Csók;A. Tuzi;L. Kollár
考虑到杯芳烃环的极化性在熵驱动的相互作用过程中的重要性，我们研究了熵补偿对下缘具有O-乙基取代基的四硝基杯[4]芳烃的锥体和部分锥体(paco)构象异构体复合物形成的影响。两种杯芳烃构象异构体均经过全面表征，包括 X 射线晶体学。使用各种对位取代酚作为客体分子。使用光致发光（PL）测量和量子化学（QC）研究。在不同的醇作为溶剂中获得了分子相互作用的介电常数依赖性。发现标题杯芳烃衍生物的锥形构象异构体与所有对位取代系列的酚形成稳定的络合物。自由焓变化显示锥杯芳烃与对硝基和对氯取代酚的络合稳定性非常高。对于母体苯酚、对甲酚和对叔丁基苯酚，稳定性明显较低；然而，随着客体分子芳环上电子密度的增加，它略有增加。类似地，这两个单独组的熵变化也显着不同：在前一种情况下获得的熵变化几乎相同，而在后一种情况中获得的形成熵存在较大差异。实验和理论研究均表明，酚类与杯芳烃的 paco 构象异构体之间不存在显着的相互作用。这可能是由于弯曲的O-乙基链锁定了杯芳烃空腔。
Considering the importance of the polarizability of the rings of calixarenes in the entropy-driven interaction processes, we examined the effect of entropy compensation on the complex formation of cone and partial cone (paco) conformers of tetranitro-calix [4]arene, possessing O-ethyl substituents at the lower rim. Both calixarene conformers were fully characterized including X-ray crystallography. Various para-substituted phenols were used as guest molecules. Photoluminescence (PL) measurements and quantum-chemical (QC) investigations were used. A permittivity dependence of the molecular interactions was obtained in different alcohols as solvents. It was found that the cone conformer of the title calixarene derivative forms stable complexes with all phenols of the p-substituted series. The free enthalpy changes show very high complex stability of cone calixarene with p-nitro and p-chloro-substituted phenols. In the cases of parent phenol, p-cresol and p- tBu-phenol, the stability is significantly lower; however, it slightly increases with the increasing electron density on the aromatic ring of guest molecules. Similarly, the entropy changes are significantly different for these two separated groups: the entropy changes obtained in the former cases are nearly the same, while large differences in the formation entropy were obtained in the latter cases. Both the experimental and theoretical investigations revealed that no considerable interaction exists between phenols and the paco conformer of the title calixarene. It is probably due to the locking of the calixarene cavity by the bent O-ethyl chain.