title: Convenient syntheses of cyanuric chloride-derived NHC ligands, their Ag(I) and Au(I) complexes and antimicrobial activity.
abstract: Convenient syntheses of mono- and bis-imidazolium 1,3,5-triazine derivatives bearing piperidine and morpholine substituents are reported. In situ deprotonation of the mono-imidazolium salts and reaction with Ag2O or Au(tht)Cl (tht = tetrahydrothiophene) precursors affords the corresponding Ag(NHC)Cl and Au(NHC)Cl carbene complexes. In the presence of Ag(I) or Au(I) salts the bis-imidazolium pincers eliminate the imidazolium group to afford -OMe or -NMe2 substituted triazines depending on the solvent used. In solution, the Ag(I) and Au(I) complexes show a barrier to rotation about the Ctriazine-Namine bonds, with calculated ΔG(≠) barriers in the region of 70 kJ mol(-1). Single crystal X-ray structures of several of the proligands and their corresponding Ag(I) and Au(I) complexes were obtained. These universally reveal an extended, rigidly planar π-conjugated network between the triazine core, imidazolium/imidazolylidene substituents and exocyclic amine functions, to which the origin of the rotational barrier observed in solution is attributed. Only very weak Ntriazine-metal interactions are observed in the solid state, as indicated by small deviations of the CNHC-Ag-Cl bond angles from 180° and also supported by DFT calculations on the Ag(NHC)Cl complex (NHC = 4,6-dipiperidinyl-2-methylimidazolylidene triazine). Preliminary antimicrobial susceptibility studies against five microorganisms (methicillin resistant Staphylococcus aureus NCTC 13277, S. aureus NCTC 6571, Pseudomonas aeruginosa NCTC 10662, Proteus mirabilis NCTC 11938 and Candida albicans ATCC 90028) show that the above triazine-based Ag-NHC complexes are active antimicrobial and antifungal agents.
authors.affiliation: School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.
authors.forename: Foteini
authors.initials: F
authors.lastname: Almalioti
authors.forename: James
authors.initials: J
authors.lastname: MacDougall
authors.forename: Stephen
authors.initials: S
authors.lastname: Hughes
authors.forename: Mohammed M
authors.initials: MM
authors.lastname: Hasson
authors.forename: Robert L
authors.initials: RL
authors.lastname: Jenkins
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Ward
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Tizzard
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Coles
authors.forename: David W
authors.initials: DW
authors.lastname: Williams
authors.forename: Sarah
authors.initials: S
authors.lastname: Bamford
authors.forename: Ian A
authors.initials: IA
authors.lastname: Fallis
authors.forename: Athanasia
authors.initials: A
authors.lastname: Dervisi
mesh_terms: D000890:Anti-Infective Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D002176:Candida albicans / Q000187:drug effects; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006046:Gold / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D008024:Ligands; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D012834:Silver / Q000737:chemistry*; D014227:Triazines / Q000737:chemistry*
chemical_list: D000890:Anti-Infective Agents; D056831:Coordination Complexes; D006571:Heterocyclic Compounds; D007093:Imidazoles; D008024:Ligands; D014227:Triazines; C030011:carbene; D012834:Silver; C019309:cyanuric chloride; D006046:Gold; C029899:imidazole; D008697:Methane