The S···P noncovalent interaction: diverse chalcogen bonds

Synergy Effects in Heavy Metal Ion Chelation with Aryl- and Aroyl-Substituted Thiourea Derivatives

Detection and removal of metal ion contaminants have attracted great interest due to the health risks that they represent for humans and wildlife. Among the proposed compounds developed for these purposes, thiourea derivatives have been shown as quite efficient chelating agents of metal cations and have been proposed for heavy metal ion removal and for components of high-selectivity sensors. Understanding the nature of metal-ionophore activity for these compounds is thus of high relevance. We present a theoretical study on the interaction between substituted thioureas and metal cations, namely, Cd²⁺, Hg²⁺, and Pb²⁺. Two substituent groups have been chosen: 2-furoyl and m-trifluoromethylphenyl. Combining density functional theory simulations with wave function analysis techniques, we study the nature of the metal-thiourea interaction and characterize the bonding properties. Here, it is shown how the N,N'-disubstituted derivative has a strong affinity for Hg²⁺, through cation-hydrogen interactions, due to its greater oxidizing capacity.

Post-synthetic modification of supramolecular assemblies of β-diketonato Cu(ii) complexes: comparing and contrasting the molecular topology by crystal structure and quantum computational studies

Solvent-induced structural transformations on the metal coordination sphere in homoleptic (1 and 2) and heteroleptic (3 and 4) Cu(ii) complexes were analyzed and investigated by crystallographic and quantum computational studies.

σ-Hole interactions in small-molecule compounds containing divalent sulfur groups R1-S-R2

Hydrogen bonds, aromatic stacking contacts and σ-hole interactions are all noncovalent interactions commonly observed in biological systems. Structural data derived from the Protein Data Bank showed that methionine residues can interact with oxygen atoms through directional S...O contacts in the protein core. In the present work, the Cambridge Structural Database (CSD) was used in conjunction with ab initio calculations to explore the σ-hole interaction properties of small-molecule compounds containing divalent sulfur. CSD surveys showed that 7095 structures contained R₁-S-R₂ groups that interact with electronegative atoms like N, O, S and Cl. Frequencies of occurrence and geometries of the interaction were dependent on the nature of R₁ and R₂, and the hybridization of carbon atoms in C,C-S, and C,S-S fragments. The most common interactions in terms of frequency of occurrence were C,C-S...O, C,C-S...N and C,C-S...S with predominance of Csp². The strength of the chalcogen interaction increased when enhancing the electron-withdrawing character of the substituents. The most positive electrostatic potentials (V_S,max; illustrating positive σ-holes) calculated on R₁-S-R₂ groups were located on the S atom, in the S-R₁ and S-R₂ extensions, and increased with electron-withdrawing R₁ and R₂ substituents like the interaction strength did. As with geometric data derived from the CSD, interaction geometries calculated for some model systems and representative CSD compounds suggested that the interactions were directed in the extensions of S-R₁ and S-R₂ bonds. The values of complexation energies supported attractive interactions between σ-hole bond donors and acceptors, enhanced by dispersion. The interactions of R₁-S-R₂ with large V_S,max and nucleophiles with large negative V_S,min coherently provided more negative energies. According to NBO analysis, chalcogen interactions consisted of charge transfer from a nucleophile lone pair to an S-R₁ or S-R₂ antibonding orbital. The directional σ-hole interactions at R₁-S-R₂ can be useful in crystal engineering and the area of supramolecular biochemistry.

Copper(i) complexes of functionalized sulfur-containing ligands: structural and theoretical insights into chalcogen bonding

Four new copper(i) thiocyanate complexes were studied using geometrical parameters and the lump–hole approach for justification of the strength and nature of chalcogen bonding.

Theoretical study on the effective dehydrochlorination of 1,2-dichloroethane catalyzed by tetraalkylphosphonium chlorides: electrostatically controlled reactivity

Herein, we report a DFT study on how and why tetraalkylphosphonium chlorides efficiently catalyze the dehydrochlorination of 1,2-dichloroethane.