Competition Between the Two σ‐Holes in the Formation of a Chalcogen Bond
Competition Between the Two σ‐Holes in the Formation of a Chalcogen Bond
复制标题
硫族键形成过程中两个α孔之间的竞争
DOI：
10.1002/cphc.202200936
复制
发表时间：
2023
期刊：
影响因子：
2.9
通讯作者：
Scheiner, Steve
中科院分区：
文献类型：
--
作者：
Scheiner, Steve
当处于R1 YR 2分子键合模式时，硫族元素原子Y包含两个单独的σ-空穴。量子化学计算考虑了这两个σ-空穴之间的竞争，以与NH3碱形成硫族键（ChB）。考虑的R基团包括F、Br、I和叔丁基（tBu）。还检查了Y位于硫属唑环内的情况，其中其邻居是C和N。两个吸电子取代基R1和R2协同作用加深两个σ-空穴，但两个空穴中较深的始终与吸电子基团相反，并且也有利于形成更强的ChB。在三联体中同时形成两个ChB需要Y原子作为双电子受体，因此反协同性相对于简单的二联体削弱了每个键。这种效应使得当一个碱基占据另一个位置时，一些较浅的σ-孔根本无法形成ChB。
A chalcogen atom Y contains two separate σ‐holes when in a R1YR2molecular bonding pattern. Quantum chemical calculations consider competition between these two σ‐holes to engage in a chalcogen bond (ChB) with a NH3base. R groups considered include F, Br, I, and tert‐butyl (tBu). Also examined is the situation where the Y lies within a chalcogenazole ring, where its neighbors are C and N. Both electron‐withdrawing substituents R1and R2act cooperatively to deepen the two σ‐holes, but the deeper of the two holes consistently lies opposite to the more electron‐withdrawing group, and is also favored to form a stronger ChB. The formation of two simultaneous ChBs in a triad requires the Y atom to act as double electron acceptor, and so anti‐cooperativity weakens each bond relative to the simple dyad. This effect is such that some of the shallower σ‐holes are unable to form a ChB at all when a base occupies the other site.