title: Interplay of Halogen and π-π Charge-Transfer Bondings in Intermolecular Associates of Bromo- or Iododinitrobenzene with Tetramethyl-p-phenylenediamine.
abstract: Two modes of intermolecular interactions (halogen and π-π charge-transfer bonding) between bromo- or iododinitrobenzene (XDNB) and tetramethyl-p-phenylenediamine (TMPD) are compared. X-ray crystallography revealed that TMPD·XDNB cocrystals comprise alternating donors/acceptors stacks formed by π-bonded (cofacial) TMPD and XDNB molecules. These structures also show two-point (C-X···O-N) halogen bonding between XDNB molecules resulting in formation of (XDNB)2 dimers. In solutions, XDNB and TMPD molecules formed 1:1 complexes showing strong absorption bands near 550 nm which followed the same Mulliken correlation as the associates of TMPD with the (halogen-free) nitro- and cyanobenzenes. In accord with the experimental data, density functional theory calculations with the M062X functional showed that TMPD·XDNB associates formed via π-π charge-transfer bonding are more stable (by 6-12 kcal/mol) than their halogen-bonded analogues. If XDNB is replaced with iodo- or bromoperfluorinated benzenes, or TMPD is replaced with pyridine, the energy gap between the π-π and halogen-bonded associates decreased. The analysis of the molecular-orbital interactions and surface electrostatic potentials of the interacting species indicated that charge-transfer contributions represent a critical component which determines variations of the strength of halogen bonding in these systems.
authors.affiliation: Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, Illinois 60605, United States.
authors.forename: Sergiy V
authors.initials: SV
authors.lastname: Rosokha
authors.affiliation: Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, Illinois 60605, United States.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Loboda
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006219:Halogens / Q000737:chemistry*; D008958:Models, Molecular; D009578:Nitrobenzenes / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D000814:Aniline Compounds; D006219:Halogens; D009578:Nitrobenzenes; C000599600:tetramethyl-p-phenylenediamine