Synthesis of imidazole schiff base ligands, their silver (I) complexes and their activities against candida albicans

The work described in this thesis concerns the synthesis of ca. 50 new imidazole-containing Schiff base ligands, the formation of their Ag(I) complexes and their evaluation as agents for inhibiting the growth of the fungal pathogen, Candida albicans. The synthesis of some Schiff base ligands proved problematic and the products were characterized using standard IR and NMR spectroscopic methods, micro-analysis and, in two instances, by X-ray crystallography. Compared to the synthesis of the ligands the preparation of the Ag(I) complexes was relatively simple and pure products were isolated in moderate to good yields. The Ag(I) complexes were also characterized using standard IR and NMR spectroscopic methods, micro-analysis and, in two cases, by mass spectrometry. All of the Schiff base ligands and their corresponding Ag(I) complexes were tested for their anti-Candida activity. While the metal-free Schiff base ligands were essentially inactive, the corresponding Ag(I) complexes showed excellent activity. The set of Ag(I) complexes based on the Apim (Apim = 1-(3-aminopropyl)imidazole) Schiff base ligands were the most potent. A progressive improvement in activity of the Ag(I) complexes was seen on going from Schiff base ligands derived from 1H-imidazole-2-amine to histamine to Apim, corresponding to the increase in spacer chain length of the respective ligand sets. A notable reduction in activity was observed in the Ag(I) complexes of di-Schiff base ligands derived from 1,2-diaminoethane, 1,3-diaminopropane and 1,4-diaminobutane. The extra imine group in the spacer chain may have had a negative impact on activity and negate any positive effect due to the progressive increase in spacer chain length. The set of Ag(I) complexes containing di-Schiff base ligands derived from 1,2-, 1,3- and 1,4-phenylenediamine had similar activity to those complexes with ligands derived from 1,2-diaminoethane, 1,3-diaminopropane and 1,4-diaminobutane. In this instance, the resulting increase in the level of aromaticity does not appear to affect the anti-Candida activity.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

National University of Ireland Maynooth

Year dc:date.issued

2010

Author dc:creator

• Tallon, Theresa M.

• Chemistry

Language dc:language

en