Silver(i) complexes of 9-anthracenecarboxylic acid and imidazoles: synthesis, structure and antimicrobial activity

Abstract

Ag 2 (9-aca) 2 ] (1) (9-acaH = 9-anthracenecarboxylic acid) reacts with a series of imidazoles to give [Ag(imidH) The mononuclear complex 3, hexanuclear 4-6, and polymeric 7, were all characterised using X-ray crystallography. While many of the complexes possess excellent in vitro antifungal and antibacterial activities they are, unanimously, more effective against fungal cells. The insect, Galleria mellonella, can survive high doses of the Ag(I) complexes administered in vivo, and a number of the complexes offer significant protection to larvae infected with a lethal dose of pathogenic Candida albicans cells. † Electronic supplementary information (ESI) available. CCDC reference numbers 782886-782890 (X-ray supplementary data for [Ag-(imidH) 2.3 (CH 3 CN) 0.7 ](9-aca) (3), [Ag 6 (imidH) 4 (9-aca) 6 (MeOH) 2 ] (4), {[Ag(1-Me-imid) 2 ] 2 [Ag 4 (9-aca) 6 ]} (5), {[Ag(1-Bu-imid) 2 ] 2 [Ag 4 (9aca) 6 ]} (6) and [Ag(apim)](9-aca)•H 2 O (7)). For ESI and crystallographic data in CIF or other electronic format see

Imidazole Schiff base ligands: Synthesis, coordination complexes and biological activities

“…[Ag(6)]ClO 4 was the least active across all of the microbial species, and the activities of the other water-insolubl e Ag(I) complexes were similar to that observed for water-soluble AgNO 3 . In these cases, activity against the fungal pathogen , C. albicans , was greater than that for bacterial pathogens, which is a trend similar to that previously reported for other Ag(I) complexes [5,6,16]. Although there was no clear discriminatory trends observed in activities between Gram-positive (S. aureus and MRSA) and Gram-negati ve (E. coli and P. aeruginosa ) bacteria, most of the complexes, and especially [Ag(4)]ClO 4 ÁMeOH, were more cytotoxic against P. aeruginosa .…”

“…Although there was no clear discriminatory trends observed in activities between Gram-positive (S. aureus and MRSA) and Gram-negati ve (E. coli and P. aeruginosa ) bacteria, most of the complexes, and especially [Ag(4)]ClO 4 ÁMeOH, were more cytotoxic against P. aeruginosa . The growth inhibitory effects of the present Ag(I) imidazole Schiff base complexes against MRSA and E. coli are similar to those recently documented for a series of Ag(I) complexes of 9-anthracen ecarboxylic acid containing non-Schiff base imidazole ligands and also the clinically used compound, silver sulphadiazi ne [6]. However, some of the latter complexes displayed significantly greater anti-Candida activity compare d to the present complexes.…”

“…1650 cm À1 ) due to the complexity of the bands in the region. Several major differences were observed between the 1 H NMR spectra of the free ligands in d 6 -DMSO and those of the Ag(I) and Zn(II) complexes of the same ligands. In all cases, the H-C@N proton signal corresponding to the imine of the chain was significantly shifted in the metal complexes, suggesting that binding of the metal ion at this N atom was occurring.…”

“…Commercially available 1-(3-aminopropyl)imidazole (Apim) (Fig. 1) has recently been complexed to the Ag(I) ion and the structurally characterised complexes, [Ag(Apim)]ClO 4 [5] and [Ag(Apim)](9-aca)ÁH 2 O (9-acaH = 9-anthracen ecarboxylic acid) [6], exhibit high antimicro bia l act ivi ties , in vit ro . In add iti on , me tal com ple xes com pri sin g Schiff base ligands derived from Apim have also attracted attention.…”

“…H and 13 C NMR (d ppm; J Hz) spectra were recorded on a BrukerAvan ce 300 MHz NMR spectromete r using saturated d 6 -DMSO solutions with Me 4 Si reference, unless indicated otherwise, with resolutions of 0.18 Hz and 0.01 ppm, respectively . Infrared spectra (cm À1 ) were recorded as KBr discs using a Perkin Elmer System2000 FT-IR spectromete r. UV-vis spectra were run on a Unicam UV 540 spectromete r. Melting point analyses were carried out using a Stewart Scientific SMP 1 melting point apparatus and are uncorrected.…”