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kmhaijun

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[交流] 求助段落翻译有效期至2009年3月13日

We investigated the ion pairs in [Hbet][Tf2N] extracted from
the crystal structure with a single-point calculation and after
optimization. Furthermore, conformers were randomly generated.
We selected from the random conformers some examples
of ion pairs that show the least similarities with the experimental
structures to gain a comparison. In Figure 8, some investigated
structures are depicted. The perspective is always chosen such
that the S-N-S motif of the anion lies in the same plane, except
for structure 5, which is shown from a different angle, since
from the same point of view as shown for the other structures
(see inlet) the interaction pattern is not obvious. We observe
that in the experimental structures 1 and 2 the betaine cation
only interacts with the anion via the carboxylate group. The
three methyl groups stay furthest away. This is also evident
from the N-N distances listed in Table 4. These structures resultfrom environmental effects. Since no neighbor is present in the
isolated clusters, it is obvious that the ion pair tries to build
conformers where as many contacts as possible are formed to
gain most of the attractive interaction energy. Ion pair 3 is a
special case, because it is the only conformer where the
carboxylate group of the betaine is further away from the anion
than the nitrogen atom. This conformer is expected to be less
stable than the others for the reason that it lacks the strong
hydrogen bond of the carboxylate group but also is the most
positive atom furthest away, and thus, it will lack Coulombic
attraction as compared to the other conformers

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1楼 2009-03-12 08:44:57

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morphine

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这么难的论文6个有点少啊

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2楼2009-03-12 17:10:06

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mayong11

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kmhaijun(金币+6,VIP+0):非常感谢 3-13 20:07

我们调查了从单点计算和优化的晶体结构中提取的[ Hbet ] [ Tf2N ]离子对。而且，他们的构像是随机产生的，我们从随机构像中选择了一些与经验结构最不相似的离子对进行比较。在图8中，罗列了一些被调查的随机构象结构。一般的选择观点始终是选择SNS序的阴离子位于同一平面，但构象5除外，因为从其他结构（见入口）的同一个角度来看，构象5的互动模式并不明显。我们注意观察在经验结构1和2中，甜菜碱的阳离子仅仅通过羧酸基团与阴离子的相互作用，三个甲基处在位置最远的地方，这可以从表4中N-N键的距离明显的判断出。这些构象是由周围环境引起的。因为在孤立的基团中，我们明显可以观察到离子对试图在可能获得最大吸引力的能量的地方建立构像。离子对3是一种特殊情况，因为它是唯一的特征为甜菜碱的羧基距离阴离子比氮原子远的构象。这种构象被认为不如别的构象稳定，理由是这种构象中的羧基缺乏强有力的氢键而且相对于其它构象，由于其极性原子离得最远，因此，这将缺乏库仑引力。

不好意思，昨天没翻译完，没影响你吧！我也不太专业，不对之处多多包涵，金币看着给吧，呵呵...

[ Last edited by mayong11 on 2009-3-13 at 10:09 ]

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学海无涯，重在交流

3楼2009-03-12 17:46:50

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