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The vital role of triel bonding (TrB) has been highlighted in two new thallium compounds i.e. Tl+[{(4-C2H5)C6H4O}2PS2]2- (1) and Tl[{(4-(CH)CH3)2C6H4O}2PS2]2 (2). These new compounds have been characterized by elemental and spectral analyses. The crystal structure of 1 and 2 belongs to monoclinic and triclinic system with space group P21/c and Pī, respectively. Interestingly, compound 1 exists in ionic form and stabilized through intramolecular Tl⋯S (TrBs) interactions wherein thallium atom is symmetrically positioned in the cleft of ligand with longer Tl–S distances. In compound 2, the thallium atom is coordinated to one sulfur atom and other sulfur atom participates in TrB interactions. Both the compounds also exhibit intermolecular Tl⋯S, Tl⋯π (TrBs) and C-H⋯Tl (anagostic) interactions which assist to form unique supramolecular architectures owing to large size as well as coordinative unsaturation on the thallium. These non-covalent TrB interactions were authenticated by Hirshfeld surface analysis (HSA) and Density functional theory (DFT) calculations using the quantum theory of atoms-in-molecules (QTAIM) and non-covalent interaction plot (NCI Plot) index methods. TrBs involving Tl have been scarcely described in the literature; therefore this manuscript provides valuable insight into the importance of these unprecedented TrBs in the solid state.

The vital role of non-covalent interactions in the supramolecular organization of two mercury(II) complexes with sulfur donor ligands have been investigated. These new complexes of mercury(II) diphenyldithiophosphates were synthesized in purely aqueous media and characterized, which corresponds to [Hg(L1)2] (1) and [Hg(L2)2]n (2), {L1 = O,O-bis(4-tert-butylphenyl) phosphorodithioate and L2 = O,O-bis(3,4-dimethylphenyl) phosphorodithioate}. These complexes have been characterized by NMR (1H, 13C and 31P), IR, UV-visible, TGA and elemental analysis. The molecular structure of 1 and 2 belong to the triclinic and monoclinic system of the space group P and P21/c, respectively, as revealed by single crystal diffraction analysis. Interestingly, complex 1 consists of a monomer unit while complex 2 consists of a polymer unit with an additional Hg⋯S bond. The supramolecular network including hydrogen bonds, spodium bonds and CH⋯π interactions in both the complexes have been identified and confirmed using theoretical analysis. A thorough analysis of the Hirshfeld surface has also been carried out to examine the intermolecular contacts in the crystal structure. Bader's Quantum Theory of Atoms-in-Molecules (QTAIM) has been applied extensively in order to acquire the quantitative and qualitative insight into the physical nature of weak non-covalent interactions. Additionally, the non-covalent interactions reduced density gradient (NCI-RDG) methods support nicely the presence of such non-covalent intermolecular interactions.

Three tetraphenylarsonium dithiophosphate salts [Ph4As]+[S2P(OAr)2]−, where Ar = 2,4-(CH3)2C6H3 (1), 3,5-(CH3)2C6H3 (2), {4-(CH3)3C}C6H4 (3), were crystallized in the monoclinic space group P21 (1), triclinic space group P¯1 (2) and monoclinic space group P21/c (3), respectively. These salts are stabilized by various non-covalent interactions resulting in the extension of their molecular structure along different axis. The cationic and anionic species are interconnected by various C—H•••X, C—H•••π (X = O, S) interactions leading the molecules as one-dimensional and two-dimensional supramolecular structures. A thorough Hirshfeld surface analysis elegantly quantifies the various non-covalent interactions present within the molecules. This analysis reveals that the main contributions in all the three salts are because of H…H and C…H/H…C interactions that represent 82.1%, 82.9% and 84.1% of the total contribution to the Hirshfeld surface for 1, 2 and 3, respectively. Further, the coordinates were optimized by DFT calculations with B3LYP hybrid functional along with LANL2DZ basis set. Experimental values of bond lengths and bond angles are in good agreement with the optimized structural parameters. HOMO-LUMO of the molecules were calculated using corresponding methods with the same basis set. Other computational data pertaining to chemical reactivity have indicated potential sites for nucleophilic and eletrophilic attack in the molecules.