Experimental and theoretical studies on the nature of weak nonbonded interactions between divalent selenium and halogen atoms
Experimental and theoretical studies on the nature of weak nonbonded interactions between divalent selenium and halogen atoms
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DOI：
10.1021/jo048436a
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发表时间：
2005-01-07
影响因子：
3.6
通讯作者：
Tomoda, S
中科院分区：
文献类型：
--
作者：
Iwaoka, M;Katsuda, T;Tomoda, S
为了研究弱非键合硒(...)卤素相互作用（(SeX)-X-...相互作用；X = F Cl 和 Br）的性质，三种类型的模型化合物 [2-(CH2X)C6H4SeY (1-3)、3-(CH2X)-2-C10H6-SeY (4-6) 和 2-XC6H4CH2SeY (7-9)；合成了 Y = CN、Cl、Br、SeAr 和 Me]，并在 CDCl3 中分析了它们的 Se-77 NMR 光谱行为。系列 1-3 和 4-6 观察到的 Se-77 NMR 吸收的逐渐上场位移表明 (SeX)-X-... 相互作用的强度按 (SeF)-F-... > (SeCl)-Cl-... > (SeBr)-Br-... 的顺序降低。使用可极化连续介质模型 (PCM) 在 B3LYP/631H 水平上进行的量子化学计算表明，1-3 最稳定的构象异构体是具有CHCl3 中的分子内短 (SeX)-X-... 原子接触 (epsilon = 4.9) 以及 n(x) --> sigma*(se-y) 轨道相互作用 (E-Se...X) 可以合理地解释 (SeX)-X-... 相互作用的强度顺序。另一方面，系列 7-9 观察到的 Se-77 NMR 吸收与参考化合物 (C6H5CH2SeY) 相比没有显着变化，这表明 7-9 不存在 (SeX)-X-... 相互作用，这可能是由于直接取代芳环的卤素原子的碱性减弱所致。这些观察结果表明 n(x) --> sigma*(se-y) 轨道相互作用是形成弱 (SeX)-X-... 相互作用的主导因素。电子相关性也被认为对于稳定性很重要。
To investigate the nature of weak nonbonded selenium(...)halogen interactions ((SeX)-X-... interactions; X = F Cl, and Br), three types of model compounds [2-(CH2X)C6H4SeY (1-3), 3-(CH2X)-2-C10H6-SeY (4-6), and 2-XC6H4CH2SeY (7-9); Y = CN, Cl, Br, SeAr, and Me] were synthesized, and their Se-77 NMR spectroscopic behaviors were analyzed in CDCl3. The gradual upfield shifts of Se-77 NMR absorptions observed for series 1-3 and 4-6 suggested that the strength of (SeX)-X-... interaction decreases in the order of (SeF)-F-... > (SeCl)-Cl-... > (SeBr)-Br-.... The quantum chemical calculations at the B3LYP/631H level using the polarizable continuum model (PCM) revealed that the most stable conformer for 1-3 is the one with an intramolecular short (SeX)-X-... atomic contact in CHCl3 (epsilon = 4.9) and also that the n(x) --> sigma*(se-y) orbital interaction (E-Se...X) can reasonably explain the order of strength for the (SeX)-X-... interactions. On the other hand, the Se-77 NMR absorptions observed for series 7-9 did not shift significantly from the reference compounds (C6H5CH2SeY), indicating the absence of the (SeX)-X-... interaction for 7-9 presumably due to attenuation of basicity for the halogen atom that is substituted directly to the aromatic ring. These observations suggested that the n(x) --> sigma*(se-y) orbital interaction is a dominant factor for formation of weak (SeX)-X-... interactions. Electron correlation was also suggested to be important for the stability.