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首页> 外文期刊>Crystal growth & design >Tuning molecular structures using weak noncovalent interactions: Theoretical study and structure of trans -bis(2-chloropyridine)dihalocopper(II) and trans -bis(3-chloropyridine)dibromocopper(II)
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Tuning molecular structures using weak noncovalent interactions: Theoretical study and structure of trans -bis(2-chloropyridine)dihalocopper(II) and trans -bis(3-chloropyridine)dibromocopper(II)

机译：使用弱的非共价相互作用调节分子结构：反式-双（2-氯吡啶）二卤铜（II）和反式-双（3-氯吡啶）二溴铜（II）的理论研究和结构

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摘要

The effect of the weak noncovalent interactions (C-H???X-Cu, C-Y???Cu, and C-Y???H-C) on the molecular structure of Cu(nYP)_2X_2 (where nYP denotes the n-halopyridine ligand, n = 2 or 3, X = Cl~- or Br~-, and Y = H, F, Cl, or Br) has been investigated using the DFT/B3LYP method. The molecular structure of Cu(nYP)_2X_2 was optimized using two different starting geometries; the two Y groups are (a) L-cis arrangement and (b) L-trans arrangement with respect to each other, L for ligand. The optimized molecular structures of the Cu(nYP)_2X_2 structures indicate that the L-cis isomer is more stable than corresponding L-trans one by avg = 9.45 kJ/mol (range 4.29-13.15 kJ/mol). The analysis of theoretical results indicates the strength of the noncovalent interactions follows the order C-Y???H-C < C-Y???Cu < C- H???X-Cu. The L-cis isomer is stabilized by C- H???X-Cu interactions, in contrast, the L-trans isomer is stabilized by C-Y???H-C and C-Y???Cu. There is no perfect agreement (L-trans and L-cis-isomerism) between the optimized structures and the solid-state molecular structures. This is possibly because the optimization process ignores the effect of intermolecular interactions, and the energy difference between each L-trans and L-cis corresponding isomer is quite small. The structures of Cu(2CP)_2X_2 and Cu(3CP) _2Br_2 have been determined. An infinite [Cu(3CP) _2Br_2]n chain structure forms based on the Cu???Br semicoordinate bond, whereas the semicoordinate bond connects the molecular species of Cu(2CP)_2X_2 to form a dimer structure. The chains of Cu(3CP)_2Br_2 are subsequently linked via C-Cl???Br-Cu halogen bonding interactions besides the weak C-H???X-Cu hydrogen bonding interactions in the three-dimensional structure. The C-Cl???X-Cu interactions are absent in Cu(2CP)_2X_2, and the dimer structures of Cu(2CP)_2X_2 are linked via C-Cl???Cl-C interactions to form chain structures. This competition would indicate that C-Cl???X-Cu and C-Cl???Cl-C are of comparable strength. Another interesting observation, even though the two Cu(2CP) _2X_2 structures are isomorphous, is that the symmetrical C-Cl???Cl-C halogen bonding interactions play the dominant role in developing Cu(2CP)_2Br_2 crystal structures. In contrast, the perpendicular C-Cl???Cl-C halogen bonding interactions play the dominant role in the case of Cu(2CP)_2Cl_2.
机译：弱的非共价相互作用（CH-X-Cu，CY-Cu和CY-HC）对Cu（nYP）_2X_2的分子结构的影响（其中nYP表示n-卤代吡啶配体，n使用DFT / B3LYP方法研究了X = 2或3，X = Cl--或Br-，Y = H，F，Cl或Br）。 Cu（nYP）_2X_2的分子结构使用两种不同的起始几何结构进行了优化。两个Y基团是（a）L-顺式排列和（b）相对于彼此的L-反式排列，L表示配体。 Cu（nYP）_2X_2结构的优化分子结构表明，L-顺式异构体比相应的L-反式更稳定，平均avg = 9.45 kJ / mol（范围4.29-13.15 kJ / mol）。对理论结果的分析表明，非共价相互作用的强度遵循C-Y 18 H-C ＜C-Y 18 Cu ＜C-H 12 X-Cu的顺序。 L-顺式异构体通过C-H 12 X-Cu相互作用而稳定，相反，L-反式异构体通过C-Y 1-4 H-C和C-Y-Cu稳定。在优化的结构和固态分子结构之间没有完美的一致性（L-反式和L-顺式异构）。这可能是因为优化过程忽略了分子间相互作用的影响，并且每个L-反式和L-顺式对应异构体之间的能量差都很小。已经确定了Cu（2CP）_2X_2和Cu（3CP）_2Br_2的结构。基于Cu 18 Br半配位键形成无限的[Cu（3CP）_2Br_2] n链结构，而半配位键连接Cu（2CP）_2X_2的分子种类以形成二聚体结构。 Cu（3CP）_2Br_2的链随后通过三维结构中除弱的C-H18X-Cu氢键相互作用外还通过C-Cl-6Br-Cu卤素键相互作用连接。 Cu（2CP）_2X_2中不存在C-Cl ??? X-Cu相互作用，而Cu（2CP）_2X_2的二聚体结构通过C-Cl ??? Cl-C相互作用连接形成链结构。这种竞争表明C-Cl 2 X-Cu和C-Cl 3 Cl-C具有相当的强度。即使两个Cu（2CP）_2X_2结构是同构的，另一个有趣的观察结果是对称的C-Cl ??? Cl-C卤素键相互作用在形成Cu（2CP）_2Br_2晶体结构中起主要作用。相反，在Cu（2CP）_2Cl_2的情况下，垂直的C-Cl2Cl-C-C卤素键相互作用起主要作用。

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