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The structure and chemical bonding in the N 2 CuX and N 2 ···XCu (X = F, Cl, Br) systems studied by means of the molecular orbital and Quantum Chemical Topology methods
Author(s) -
Kisowska Karolina,
Berski Slawomir,
Latajka Zdzislaw
Publication year - 2008
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.21010
Subject(s) - natural bond orbital , crystallography , chemistry , van der waals force , molecule , bipyramid , ab initio , electron density , halogen bond , density functional theory , computational chemistry , electron , hydrogen bond , crystal structure , physics , organic chemistry , quantum mechanics
Ab initio studies carried out at the MP2(full)/6‐311+G(2df) and MP2(full)/aug‐cc‐pVTZ‐PP computational levels reveals that dinitrogen (N 2 ) and cuprous halides (CuX, X = F, Cl, Br) form three types of systems with the side‐on and end‐on coordination of N 2 : NNCuX (C ∞v ), N 2 CuX (C 2v ) stabilized by the donor–acceptor bonds and weak van der Waals complexes N 2 ···XCu (C 2v ) with dominant dispersive forces. An electron density transfer between the N 2 and CuX depends on type of the N 2 coordination and a comparison of the NPA charges yields the [NN] δ+ ‐[CuX] δ− and [N 2 ] δ− ‐[CuX] δ+ formula. According to the NBO analysis, the CuN coordinate bonds are governed by predominant LP N2 →σ*(CuX) “2e‐delocalization” in the most stable NNCuX systems, meanwhile back donation LP Cu →π*(NN) prevails in less stable N 2 CuX molecules. A topological analysis of the electron density (AIM) presents single BCP between the Cu and N nuclei in the NNCuX, two BCPs corresponding to two donor‐acceptor CuN bonds in the N 2 CuX and single BCP between electron density maximum of the NN bond and halogen nucleus in the van der Waals complexes N 2 ···XCu. In all systems values of the Laplacian ∇ 2 ρ( r )( r BCP ) are positive and they decrease following a trend of the complex stability i.e. NNCuX (C ∞v ) > N 2 CuX (C 2v ) > N 2 ···XCu (C 2v ). A topological analysis of the electron localization function (ELF) reveals strongly ionic bond in isolated CuF and a contribution of covalent character in the CuCl and CuBr bonds. The donor–acceptor bonds CuN are characterized by bonding disynaptic basins V(Cu,N) with attractors localized at positions corresponding to slightly distorted lone pairs V(N) in isolated N 2 . In the NNCuX systems, there were no creation of any new bonding attractors in regions where classically the donor–acceptor bonds are expected and there is no sign of typical covalent bond CuN with the bonding pair. Calculations carried out for the NNCuX reveal small polarization of the electron density in the NN bond, which is reflected by the bond polarity index being in range of 0.14 (F) to 0.11 (Cl). © 2008 Wiley Periodicals, Inc. J Comput Chem 2008