Institut de Química Computacional, Campus de Montilivi, Universitat de Girona, Girona, Catalonia, Spain.
Chemphyschem. 2011 Apr 18;12(6):1118-29. doi: 10.1002/cphc.201000721. Epub 2011 Mar 22.
This work presents a study of intramolecular NHN hydrogen bonds in cations of the following proton sponges: 2,7-bis(trimethylsilyl)-1,8-bis(dimethylamino)naphthalene (1), 1,6-diazabicyclo[4.4.4.]tetradecane (2), 1,9-bis(dimethylamino)dibenzoselenophene (3), 1,9-bis(dimethylamino)dibenzothiophene (4), 4,5-bis(dimethylamino)fluorene (5), quino[7,8-h]quinoline (6) 1,2-bis(dimethylamino)benzene (7), and 1,12-bis(dimethylamino)benzo[c]phenantrene (8). Three different patterns were found for proton motion: systems with a single-well potential (cations 1-2), systems with a double-well potential and low proton transfer barrier, ΔEe (cations 3-5), and those with a double-well potential and a high barrier (cations 6-8). Tests of several density functionals indicate that the PBEPBE functional reproduces the potential-energy surface (PES) obtained at the MP2 level well, whereas the B3LYP, MPWB1K, and MPW1B95 functionals overestimate the barrier. Three-dimensional PESs were constructed and the vibrational Schrödinger equation was solved for selected cases of cation 1 (with a single-well potential), cation 4 (with a ΔEe value of 0.1 kcal mol(-1) at the MP2 level), and cations 6 (ΔEe = 2.4 kcal mol(-1)) and 7 (ΔEe=3.4 kcal mol(-1)). The PES is highly anharmonic in all of these cases. The analysis of the three-dimensional ground-state vibrational wave function shows that the proton is delocalized in cations 1 and 4, but is rather localized around the energy minima for cation 7. Cation 6 is an intermediate case, with two weakly pronounced maxima and substantial tunneling. This allows for classification of proton sponge cations into those with localized and those with delocalized proton behavior, with the borderline between them at ΔEe values of about 1.5 kcal mol(-1). The excited vibrational states of proton sponge cations with a low barrier can be described within the framework of a simple particle-in-a-box model. Each cation can be assigned an effective box width.
这项工作研究了以下质子海绵体阳离子中的分子内 NHN 氢键：2,7-双（三甲基甲硅烷基）-1,8-双（二甲基氨基）萘（1）、1,6-二氮杂双环[4.4.4.]十四烷（2）、1,9-双（二甲基氨基）二苯并硒吩（3）、1,9-双（二甲基氨基）二苯并噻吩（4）、4,5-双（二甲基氨基）芴（5）、喹诺[7,8-h]喹啉（6）、1,2-双（二甲基氨基）苯（7）和 1,12-双（二甲基氨基）苯并[c]菲（8）。质子运动发现了三种不同的模式：具有单势阱的系统（阳离子 1-2）、具有双势阱和低质子转移势垒 ΔEe 的系统（阳离子 3-5）以及具有双势阱和高势垒的系统（阳离子 6-8）。对几种密度泛函的测试表明，PBEPBE 泛函很好地再现了在 MP2 水平上获得的势能面（PES），而 B3LYP、MPWB1K 和 MPW1B95 泛函高估了势垒。为阳离子 1（单势阱）、阳离子 4（在 MP2 水平上的 ΔEe 值为 0.1 kcal mol(-1)）以及阳离子 6（ΔEe = 2.4 kcal mol(-1)）和 7（ΔEe = 3.4 kcal mol(-1)）的选定情况构建了三维 PES，并求解了振动薛定谔方程。在所有这些情况下，PES 都是高度非谐的。对三维基态振动波函数的分析表明，质子在阳离子 1 和 4 中是离域的，但在阳离子 7 的能量最低点附近是相当局域的。阳离子 6 是一个中间情况，有两个微弱的显著最大值和大量的隧道。这使得质子海绵体阳离子可以分为具有局域和离域质子行为的阳离子，它们之间的边界在大约 1.5 kcal mol(-1)的 ΔEe 值。低势垒质子海绵体阳离子的激发振动态可以在简单的粒子在盒模型的框架内进行描述。每个阳离子都可以分配一个有效盒宽。
