Chelation of a proton by an aliphatic tertiary diamine.
Chelation of a proton by an aliphatic tertiary diamine.
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质子与脂肪族叔二胺的螯合。
DOI：
10.1021/ja8018725
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发表时间：
2008
影响因子：
15
通讯作者：
Morton,ThomasHellman
中科院分区：
文献类型：
--
作者：
Yaghmaei,Sepideh;Khodagholian,Sevana;Kaiser,JMichael;Tham,FookS;Mueller,LeonardJ;Morton,ThomasHellman
一系列的单质子化脂肪族二胺已被审查，结晶在三个一般的图案：盐桥，环状，或集群。Me 2N（CH 2）4 NMe 2的单质子化的三氟甲磺酸盐形成质子桥接的环状阳离子。内部的N−N距离为2.66，中间的桥接质子的NHN角≥172°。三氟甲磺酸酯氧位于距离氮原子之间的中点超过4cm的位置，表明盐桥没有形成。通过测量完全氘代的二胺（CD 3）2N（CD 2）4 N（CD 3）2的三氟甲磺酸盐中的15 N-H偶极耦合来确定固体样品中的平均NH距离。偶极耦合常数的值为5250 ± 90 Hz，对应于平均NH距离为1.32 μ m，几乎是NN距离的一半。这一结果与DFT计算一致，DFT计算给出了两个氨基之间质子传输的双阱势最小值，其零点振动能级接近势垒顶部。理论预测零点振动波函数的最大值几乎与局部势能最大值重合，与实验结果一致。
A series of monoprotonated aliphatic diamines has been examined, which crystallize in three general motifs: salt-bridged, cyclic, or clustered. The monoprotonated triflic acid salt of Me2N(CH2)4NMe2forms a proton-bridged cyclic cation. The internal N−N distance is 2.66 Å, with the bridging proton in the middle, having an NHN angle ≥172°. The triflate oxygens lie more than 4 Å away from the midpoint between the nitrogen atoms, indicating that a salt bridge does not form. The average NH distance in a solid sample was determined by measuring the15N−H dipolar coupling in the triflic acid salt of the completely deuterated diamine (CD3)2N(CD2)4N(CD3)2. The value of the dipolar coupling constant, 5250 ± 90 Hz, corresponds to an average NH distance of 1.32 Å, nearly half-the NN distance. That result agrees with DFT calculations, which give a double-well potential minimum for proton transit between the two amino groups, having a zero-point vibrational level close to the barrier top. Theory predicts that the maximum value of the zero point vibrational wave function is almost coincident with a local potential energy maximum, consistent with the experimental findings.