A detailed analysis of a complete set of the local potentials that appear in the Euler equation for electron density is carried out for noncovalent interactions in the uracil derivative using experimental X-ray charge density. The interplay between the quantum theory of atoms in molecules and crystals and the local potentials and corresponding inner-crystal electronic forces of electrostatic and kinetic origin is explored. Novel physically grounded bonding descriptors derived within the orbitalfree quantum crystallography provided the detailed examination of π-stacking and intricate C=O•••π interactions and nonclassical hydrogen bonds. The donor-acceptor character of these interactions is revealed by analysis of Pauli and von Weizsäcker potentials together with well-known functions.Partitioning of crystal space into atomic-like potential basins led us to the definite description of the charge transfer. In this way, our analysis throws light on aspects of these closed-shell interactions hitherto hidden from the description.

Developing new, efficient catalysts that contain Earth-abundant metals and simple, robust ligands for CO 2 hydrogenation is important to create cost-effective processes of CO 2 utilization. Inspired by nature, which utilizes an ortho-OH-substituted pyridine motif in Fe-containing hydrogenases, we developed a Mn complex with a simple N-donor ligand, 6,6′-dihydroxy-2,2′-bipyridine, that acts as an efficient catalyst for CO 2 hydrogenation. Turnover numbers of 6250 for hydrogenation of CO 2 to formate in the presence of DBU were achieved. Moreover, hydrogenation of CO 2 to formamide was achieved in the presence of a secondary amine.

Intricate behaviour of one‐electron potentials from the Euler equation for electron density and corresponding gradient force fields in crystals was studied. Channels of locally enhanced kinetic potential and corresponding saddle Lagrange points were found between chemically bonded atoms. Superposition of electrostatic ϕesboldr and kinetic ϕkboldr potentials and electron density ρboldr allowed partitioning any molecules and crystals into atomic ρ ‐ and potential‐based ϕ ‐basins; ϕk ‐basins explicitly account for the electron exchange effect, which is missed for ϕes ‐ones. Phenomena of interatomic charge transfer and related electron exchange were explained in terms of space gaps between zero‐flux surfaces of ρ ‐ and ϕ ‐basins. The gap between ϕes ‐ and ρ ‐basins represents the charge transfer, while the gap between ϕk ‐ and ρ ‐basins is a real‐space manifestation of sharing the transferred electrons caused by the static exchange and kinetic effects as a response against the electron transfer. The regularity describing relative positions of ρ ‐, ϕes ‐, and ϕk ‐ basin boundaries between interacting atoms was proposed. The position of ϕk ‐boundary between ϕes ‐ and ρ ‐ones within an electron occupier atom determines the extent of transferred electron sharing. The stronger an H⋅⋅⋅O hydrogen bond is, the deeper hydrogen atom's ϕk ‐basin penetrates oxygen atom's ρ ‐basin, while for covalent bonds a ϕk ‐boundary closely approaches a ϕes ‐one indicating almost complete sharing of the transferred electrons. In the case of ionic bonds, the same region corresponds to electron pairing within the ρ ‐basin of an electron occupier atom.

Herein, we experimentally obtained and studied the inner-crystal scalar potential fields and the associated vector force fields of static and kinetic nature in picolinic acid N-oxide (PANO) and methimazole. The “through-bond” and “through-space” electronic effects were defined and distinguished via the vector fields and concurred with the penetration of the electron contributor’s electrostatic and kinetic force field pseudoatoms (φes- and φ k -basins) into the occupier’s chemical atom (ρ-basin). A special focus was given to the dipolar N+–O– bond as well as to the thioamide N–CS and carboxylic OC–OH fragments. An unusual way of interatomic charge transfer was revealed between two nonbonded hydrogen atoms [COO−]H···H[−C] in the PANO crystal. The experimental electric and kinetic force fields in the molecular crystals were compared to the theoretical ones for the free molecules and hydrogen-bonded associates, which helped figure out the natural consequences of the crystal packing effect. As expected, the appearance of neighboring attractors in a dense crystal packing requires zero-flux surfaces (ZFSs) emerging in the vector fields and the compression of the outer force field pseudoatoms of a molecule. We proposed to consider a ZFS in the kinetic force field to be a turning surface for electrons in the sense that an electron passed through the boundary is immediately affected by the redirected force attributed to another attractor. The strengthening and noticeable increase observed in the covalency of the intramolecular hydrogen bond O–H···O in the PANO crystal is a direct consequence of such compression of the hydrogen atom and pseudoatoms by the inner-crystal environment. The Pauli and fermionic scalar and vector fields were applied to locate electron lone pairs and describe their involvement in noncovalent interactions within the donor–acceptor mechanism.

The electronic and steric properties of a new class of electron-rich and sterically hindered tertamethylated PNP pincer ligands (Me 4 PNP R = 2,6-bis[(dialkylphosphino)propyl]pyridine with R = i Pr, t Bu) are discussed. Introducing the methyl groups on the pincer arm prevents dearomatization of the pincer framework and increases the bulkiness and electron-donating capacity of the ligand. Highly reactive Ni I species are thus prevented from dimerizing and can be analyzed by a wide variety of spectroscopic methods. X-ray diffraction study shows that steric bulk has an important influence on the resulting geometric and spectroscopic properties of the Ni I complexes. Complexes 5 and 6, which contain i Pr groups on the phosphorus atoms, show a very rare seesaw geometry around the metal center, while t Bu complexes 7 and 8 show a distorted square-planar geometry. Computational analysis reveals that the SOMO for all complexes has a d x 2 −y 2 character with the spin density mostly residing on the nickel.