Abbas Washeel Salman

Sterically tuned Ag(I)- and Pd(II)-N-heterocyclic carbene complexes of imidazol-2-ylidenes: synthesis, crystal structures, and in vitro antibacterial and anticancer studies

Unsymmetrically substituted sterically tuned Pd(II)–NHC complexes of the general formula [PdCl2(NHC)2] (NHC = 1-allyl-3-methylimidazolin-2-ylidene, 7; 1-allyl-3-butylimidazol-2-ylidene, 8; 1-benzyl-3-butyl imidazolin-2-ylidene, 9) were prepared through transmetallation from their corresponding Ag(I)–NHC complexes. The Pd complexes were structurally characterized by different spectroscopic and X-ray diffraction methods. Complexes 7 and 9 adopted a trans–anti arrangement of the NHC ligands, whereas complex 8 adopted a cis–syn arrangement. Preliminary antibiogram studies using Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria showed that Ag(I)–NHC complexes demonstrate higher activity compared with Pd(I)–NHC complexes. Furthermore, Pd(II)–NHC complexes were evaluated for their anticancer potential using the human colorectal cancer cell line. A higher anticancer activity was observed for complexes 8 and 9, with 26.5 and 6.6 mM IC50 values, respectively.

Potassium bis-[bis-(1-benzyl-3-methyl-imidazolium)silver(I)] tris-(hexa-fluoridophosphate).

In the title compound, K[Ag(C11H12N2)2]2(PF6)3, the 12-coordinate potassium cation lies on a crystallographic twofold axis and one of the hexafluorophosphate anions is generated by symmetry. In the complex cation, the AgI ion is coordinated by two C atoms; the two imidazolium rings are orientated at a dihedral angle of 8.14 (14)°. In the 1-benzyl-3-methylimidazolium units, the dihedral angles between imidazolium and phenyl rings are 80.47 (15) and 76.53 (14)°. The F atoms of the general-position hexafluorophosphate anion are disordered over two sets of sites in a 0.767 (17):0.233 (17) ratio. In the crystal, the hexafluorophosphate anions link the cations into three-dimensional networks via intermolecular C—H⋯F hydrogen bonds and are further consolidated by π–π stacking [centroid–centroid distances = 3.5518 (15) Å] interactions.

3,3'-Dibenzyl-1,1'-(2,4,6-trimethyl-m-phenyl-enedimethyl-ene)diimidazol-3-ium dibromide.

In the title molecular salt, C31H34N4 2+·2Br−, the central benzene ring makes dihedral angles of 80.47 (12) and 82.78 (12)° with the adjacent imidazole rings. The dihedral angle between the two terminal phenyl rings is 79.16 (13)°. In the crystal, the cations and anions are linked via C—H⋯Br hydrogen bonds, forming supramolecular chains along the c axis.

3-(3-Cyano­benz­yl)-1-methyl-1H-imidazol-3-ium hexa­fluoro­phosphate

In the title compound, C12H12N3 +·PF6 −, the hexafluorophosphate anion is disordered over two orientations with refined site occupancies of 0.8071 (17) and 0.1929 (17). The dihedral angle between the imidazole and benzene rings in the cation is 71.26 (7)°. In the crystal, the cations and anions are linked by C—H⋯F and C—H⋯N hydrogen bonds into a three-dimensional network.

2,4-Bis[(3-butyl­imidazol-3-ium-1-yl)meth­yl]-1,3,5-trimethyl­benzene bis­(hexa­fluoro­phosphate)

In the title molecular salt, C25H38N4 2+·2PF6 −, one of the butyl groups and four F atoms in the basal plane of one of the PF6 − octahedra are disordered over two sets of sites, with occupancy ratios of 0.704 (5):0.296 (5) and 0.71 (3):0.29 (3), respectively. The central benzene ring makes dihedral angles of 85.17 (12) and 81.97 (12)° with the terminal imidazole rings. In the crystal, cations and anions are linked together via intermolecular C—H⋯F hydrogen bonds forming a three-dimensional network.

Bis(1-benzyl-3-methyl­imidazolium-κC 2)mercury(II) bis­(hexa­fluoridophosphate)

The asymmetric unit of the title complex, [Hg(C11H12N2)2](PF6)2, consists of one bis(1-benzyl-3-methylimidazolium)mercury(II) cation, one half of the cation and an additional HgII atom, which lies on an inversion centre, and three hexafluoridophosphate anions. The HgII atoms exist in a linear coordination geometry [C—Hg—C = 178.9 (2) and 180°] formed by two carbene C atoms from the imidazole rings. In the crystal, the cations and anions are connected via C—H⋯F hydrogen bonds, forming a three-dimensional network.