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)

Abstract

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)2X2 (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)2X2 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)2X2 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 o...