Combined analysis of chemical bonding in a Cu^IIdimer using QTAIM, Voronoi tessellation and Hirshfeld surface approaches

Abstract

Interaction of 1-(1H-pyrazol-5-yl)ethanone oxime (H2PzOx) with copper(II) chloride in the presence of pyridine afforded a binuclear discrete [Cu2(HPzOx)2Cl2py2] complex, which was characterized by Fourier transform-IR and electron paramagnetic resonance (EPR) spectra, magnetochemistry and high-resolution X-ray diffraction experiments. Multipole refinement of X-ray diffraction data and density-functional theory (DFT) calculations of an isolated molecule allowed charge and spin distributions to be obtained for this compound. Magnetochemistry data, EPR spectra and DFT calculations of an isolated molecule show antiferromagnetic coupling between copper(II) ions. The spin distribution suggests an exchange pathway via the bridging pyrazole ring in the equatorial plane of the CuN4Cl coordination polyhedron, thus providing support for the classical superexchange mechanism; the calculated value of the magnetic coupling constant -2J is equal to 220 cm(-1), which compares well with the experimental value of 203 ± 2 cm(-1). Chemical connectivity was derived by Bader's 'quantum theory of atoms in molecules' and compared with Voronoi tessellation and Hirshfeld surface representations of crystal space. All methodologies gave a similar qualitative and semi-quantitative description of intra- and intermolecular connectivity.

Solid-State Photoinitiated Cycloaddition Reaction of 4,4′-(Ethene-1,2-diyl)bis(pyridinium) Dinitrate: Charge-Density Perspective on Initial Stage of the Reaction

“…H interactions can also be found within this approximation. This result in accord with previously reported comparison of QTAIM and Voronoi approaches to describe chemical bonding in crystals [51][52][53][54]. Possibility to automatically distinguish bonding interactions among the whole set of contacts can be very helpful for comparison of bonding sets at initial and final stages of a solid-state reaction.…”

Studies of Multicenter and Intermolecular Dihydrogen B–H···H–C Bonding in [4,8,8′‐exo‐{PPh3Cu}‐4,8,8′‐(μ‐H)3‐commo‐3,3′‐Co(1,2‐C2B9H9)(1′,2′‐C2B9H10)]

“…[65] The total energy of interactions per molecule, estimated as the sum of individual E A-B values, gives a reasonable value of 40.8 kcal mol -1 , which is 2.5 times as large as the value of 17.0 kcal mol -1 for 1-phenyl-o-carborane. [66] The molecular Hirshfeld surfaces and Voronoi tessellation give the same types of intermolecular bonds, and partial contributions of various types of intermolecular contacts to the total molecular area determined by both methods are similar ( Figure 5, c), as was recently demonstrated for small organic [67] and organometallic [55,68,69] compounds. It is worth noting that in the Voronoi tessellation approach bonding H···H contacts can be distinguished from nonbonding ones by the high value of the Voronoi polyhedron face common to two hydrogen atoms (Ͼ10 % of the full solid angle of 4π steradian, Table S6 in the Supporting Information), and also that the H···H interactions can be separated into B-H···H-C, C-H···H-C, and B-H···H-B contacts, which can be helpful for investigation of dihydrogen bonding in molecular crystals.…”

“…As has previously been demonstrated for ionic conductors, [54] copper complexes, [30,55] and the zincocene family, [36] atomic Hirshfeld surfaces (AHSs) allow additional qualitative characterization of chemical bonding without timeconsuming calculations. The AHSs of Cu1 and Co3 atoms in 1 are depicted in Figure 4.…”

Contribution of Different Crystal Packing Forces in π-Stacking: From Noncovalent to Covalent Multicentric Bonding

“…Metal–ligand bonds are highly polar and usually represent a borderline case between covalent and ionic. Accurate X-ray charge density studies − of quite a few metal complexes revealed low electron density at bonding critical points (≪1 e Å –3 ) and positive Laplacians, which are not indicative of covalent bonding. Our charge density studies of two metal-quinone complexes, [Cu­(CA) 2 (H 2 O) 2 ]­Him 2 (im = imidazole) and [Mn­(CA)­(H 2 O)] n (electron densities ranging between 0.30 and 0.40 e Å –3 , positive Laplacian values) also do not support the notion of covalent metal–ligand bonds .…”