Comparative DFT and X-ray structural studies of five-coordinate, N4-donor macrocyclic ligand complexes of Cu(II) and Zn(II)

Abstract

A low-temperature single-crystal X-ray structural determination of [CuCl(L 1 )]ClO 4 ؒH 2 O [where L 1 = meso-2, 12dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene] is reported. The coordination geometry of the complex cation approximates square pyramidal, with the chloro ligand occupying an apical position. The latter group is associated with an intermolecular hydrogen bonding network involving the uncoordinated water molecule and the perchlorate counter ion. Density functional theory (DFT) has been applied to modeling the structure of this complex, both in the presence and the absence of the intermolecular hydrogen-bonding network. In the absence of this network a good fit to the X-ray structural parameters was obtained except for the Cu-Cl bond length. For this bond the calculated value (2.346 Å) was significantly shorter than the X-ray value [2.541( 2) Å] but, on incorporation of the hydrogen-bonded network, while the major portion of the computed structure remained almost identical to that obtained from the initial calculation, the Cu-Cl bond was now found to be longer at 2.572 Å, approximating the X-ray value quite closely. The study has been extended to similar/related systems for which structural data are available, confirming the wider applicability of this approach in modeling arrays of this type.

Receptor versus Counterion: Capability of N,N′‐Bis(2‐aminobenzyl)‐diazacrowns for Giving Endo‐ and/or Exocyclic Coordination of ZnII

“…Density functional theory (DFT) has emerged as the computational method of choice for the solution of many chemical problems. This is because DFT methods have relatively low computational cost, include a significant amount of the dynamic electron correlation and are applicable to a wide range of molecular types, including Zn II complexes 21. In a recent paper we reported a theoretical study of the [M(L 1 )] 2+ systems (M = Mn, Co or Ni) at the DFT (B3LYP) computational level 9.…”

Molecular modelling for coordination compounds: Cu(ii)–amine complexes

“…Coordination complexes of d 9 Cu(II) are among the most challenging to model theoretically. 1 The d electrons are highly stereochemically active 2 which leads to 'plastic' geometries 3, 4 which are easy to deform but accompanied by large structural changes.…”

A New Cryptophane Receptor Featuring Three endo‐Carboxylic Acid Groups: Synthesis, Host Behavior and Structural Study

“…The initial structures were obtained by conformation analysis by using molecular dynamics. The DFT method is applicable to the full range of molecular systems, including hydrogen‐bonded aggregates22 and transition metal complexes,23, 24 and gives results of quality comparable to ab initio level 23. Figure 3 shows the calculated “local minima” structures of 2 and 1 from the BP86 functional of the ADF software package 25.…”