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In aqueous medium at pH 6, cadmium acetate dihydrate combines with 4,6-dimethylpyrimidine-2-thiol to form a centrosymmetric Cl, S-bridged complex having zwitterionic terminals. The zwitterionic nature of this complex is evidenced by its pH and conductance values in methanol solution. It crystallizes in the space group P2/c (Z = 4 asymmetric units, two molecules), each molecule being uncommonly characterized by a centric Cd(II)SClN as well as two acentric and anionic Cd(II)SClN coordination chromophores with counter cationic ligands. Relevant literature reports indicate a template relation between the structural designs of this complex and hydrated cadmium acetate, the metalorganic precursor. Packing of molecular motifs through weak C-H···N and strong charge-enhanced N-H···N interactions generate the crystal structure with numerous screw-glide related small voids. Attempt has been made to rationalize the crystallochromic nature of the complex (pale green in solution, pale orange while crystalline) by time dependent DFT and ZINDO/S studies. Graphical Abstract: In aqueous medium, cadmium acetate combines with 4,6-dimethylpyrimidine-2-thiol to form a centrosymmetric, trinuclear complex with zwitterionic terminals. The crystallochromic behaviour of this complex is investigated by quantum chemical treatment.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

At pH 5.5, coordination between Cd and 4,6-dimethylpyrimidine-2-thiol was studied using CdCl and Cd(NO). For both of these, the same complex, bis-4,6-dimethylpyrimidinium-2-thiolato cadmium (II) chloride was invariably formed. It crystallized from water in the space group P2/c, Z = 4 (a = 12.955(2) Å, b = 8.429(1) Å, c = 15.727(2) Å, β = 97.19(0)°), displaying a distorted tetrahedral molecular geometry characterized by a [CdClS] chromophore. The negative charge on the coordination zone is intramolecularly compensated by protonation of one azomethine N in each of the two thiolpyrimidine ligands, resulting in a tripolar zwitterion; its aqueous solution is consequently acidic and highly conducting. The crystal structure is mainly characterized by two kinds of charge-driven H-bonding interactions generated in pairs by the inversion symmetry of the space group and translation symmetry of its periodic lattice. This ultimately results in extensive intermolecular interactions, forming left handed zigzag H-bond networks and a consequent supramolecular growth along b. Spectroscopic studies agree well with the proposed molecular structure. The aqueous solubility of the complex and a high 50% lethal dose (mice) of its ligand seem to indicate development of the pyrimidinethiol moiety into a prospective antidote to Cd toxicity. Graphical Abstract: (DMPT)ClCd(II)-a tripolar zwitterion generating zigzag supramolecules through charge-augmented H-bonds in solid state.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]