Continua of Interactions between Pairs of Atoms in Molecular Crystals

Abstract

The electron density distributions in crystals of five previously studied DMAN complexes and five Schiff bases (two new ones) have been analysed in terms of various properties of bond critical points (BCPs) found in the pair-wise interactions in their lattices. We analysed the continua of interactions including covalent/ionic bonds as well as hydrogen bonds and all other types of weak interactions for all pairs of interacting atoms. The charge density at BCPs and local kinetic and potential energy densities vary exponentially with internuclear distance (or other measures of separation). The parameters of the dependences appear to be characteristics of particular pairs of atom types. The Laplacian and the total (sum of kinetic and potential) energy density at BCPs show similar behaviour with the dependence being of the Morse type. The components lambda1, lambda2, lambda3 of the Laplacian at BCPs vary systematically with internuclear distance according to the type of atom pair. For lambda1 and lambda2 the distribution is of the exponential type, whereas lambda3 does not seem to follow any simple functional form, consistent with previous theoretical findings. Analytical nonlinear dependences of Laplacian on charge density have been found. They agree reasonably well with those obtained by least square fit of the Laplacian to charge density data. There are four distinct regions of the [symbol: see text]2rho(BCP)/rho(BCP) space, generated by E(BCP) = 0 and G(BCP)/rho(BCP) = 1 conditions. Two regions clearly correspond to the shared-shell and closed-shell interactions and the other two to some intermediate situation.

Universal Features of the Electron Density Distribution in Hydrogen‐Bonding Regions: A Comprehensive Study Involving H⋅⋅⋅X (X=H, C, N, O, F, S, Cl, π) Interactions

“…Since then, many dependencies involving 1(r) properties at the BCP have been reported and used in theoretical analyses of complexes in the gas phase, such as those given in the detailed study of NÀH···N interactions. [16,17] Similar dependencies for HBs have been observed in crystals from experimental electron density distributions determined by using high-resolution Xray diffraction data [12,[18][19][20] of from theoretical calculations. [21] In the analysis of these dependencies, typically through least squares fits, the values of the properties at the BCP present some degree of dispersion around the fitting curves.…”

“…[33] To model the behaviours of 5 2 1 and H with d HB in the whole range of interaction distances, their dependencies have been fitted to functions containing exponential terms. [20,22,30] For closed shell interactions, the 5 2 1 dependency can be approximated to an exponential for all families but H···H (Table 2), as in this last case the effect of the transition to a shared interaction appears for shorter d HB distances. The corresponding data, represented in Figure 3, have not been fitted.…”

Experimental studies of charge density distribution in the crystals of cytisine and N-methylcytisine. Inside the Fake Tobacco

“…Figure 10 shows the plot of the chosen characteristics of the intermolecular BCPs vs. R ij distance. This plot, after removing the debatable H···H interactions, fits quite well into exp.-type dependence, as postulated, e.g., by Wozniak et al [29,30].…”

Substituent effect in para substituted Cr(CO)5–pyridine complexes

“…These changes are relatively small because of a limited possibility of the influence of substituents on the Cr-N (pyridine) bond, and can be more significant in the case of a larger spectrum of variability of a given bond. The above-described relations have a more variable, but still systematic character if following from hydrogen bond to covalent bond, as shown for the proton transfer reaction [51] or in AIM characterization of bonding in a series of DMAN complexes and Schiff bases [52]. However, if one summarize the data for the Cr-N and both cis and trans Cr-C (carbonyl) bonds, as it was done in Fig.…”