Transition Metal Complexes of 4-Aminoantipyrine Derivatives and Their Antimicrobial Applications

Transition metal complexes of 4-aminoantipyrine derivatives have been gaining great interest due to their rich coordination chemistry and potential applications in the field of pharmaceutical science. The presence of a free amine and a cyclic ketone functionality makes 4-aminoantipyrine an attractive amphoteric substrate for Schiff base formation. Varieties of aldehydes/ketones or amines of versatile steric, electronic and functional nature could be condensed with the 4-aminoantipyrine motif to obtain the ligand systems of multi-denticity and diverse coordination behaviour. The transition metal complexes obtained from these ligand systems exhibit unique structural and functional properties. This review compiles the important transition metal complexes developed from the Schiff base derivatives of 4-aminoantipyrine, and their utility as antibacterial and antifungal agents. Rationale of the strategies involved in the development of highly potential antimicrobial agents is discussed.

Insights into the Antimicrobial Potential of Dithiocarbamate Anions and Metal-Based Species

Bacterial infection remains a worldwide problem that requires urgent addressing. Overuse and poor disposal of antibacterial agents abet the emergence of bacterial resistance mechanisms. There is a clear need for new approaches for the development of antibacterial therapeutics. Herein, the antibacterial potential of molecules based on dithiocarbamate anions, of general formula R(R’)NCS2(−), and metal salts of transition metals and main group elements, is summarized. Preclinical studies show a broad range of antibacterial potential, and these investigations are supported by appraisals of possible biological targets and mechanisms of action to guide chemical syntheses. This bibliographic review of the literature points to the exciting potential of dithiocarbamate-based therapeutics in the crucial battle against bacteria. Additionally, included in this overview, for the sake of completeness, is mention of the far fewer studies on the antifungal potential of dithiocarbamates and even less work conducted on antiparasitic behavior.

Synthesis, electrochemical, fluorescence and antimicrobial studies of 2-chloro-3-amino-1,4-naphthoquinone bearing mononuclear transition metal dithiocarbamate complexes [M{κ2S,S-S2C–piperazine–C2H4N(H)ClNQ}n]

A new series of transition metal dithiocarbamate complexes displayed medium to very strong fluorescence bands, redox and interesting antimicrobial properties.

In vitro studies of the activity of dithiocarbamate organoruthenium complexes against clinically relevant fungal pathogens

The in vitro antifungal activity of nine dirutheniumpentadithiocarbamate complexes C1-C9 was investigated and assessed for its activity against four different fungal species with clinical interest and related to invasive fungal infections (IFIs), such as Candida spp. [C. albicans (two clinical isolates), C. glabrata, C. krusei, C. parapsolisis, C. tropicalis, C.dubliniensis (six clinical isolates)], Paracoccidioides brasiliensis (seven clinical isolates), Cryptococcus neoformans and Sporothrix schenckii. All synthesized complexes C1-C9 and also the free ligands L1-L9 were submitted to in vitro tests against those fungi and the results are very promising, since some of the obtained MIC (minimal inhibitory concentration) values were very low (from 10-6 mol mL-1 to 10-8 mol mL-1) against all investigated clinically relevant fungal pathogens, except for C. glabrata, that the MIC values are close to the ones obtained for fluconazole, the standard antifungal agent tested. Preliminary structure-activity relations (SAR) might be suggested and a strong influence from steric and lipophilic parameters in the antifungal activity can be noticed. Cytotoxicity assays (IC50) showed that the complexes are not as toxic (IC50 values are much higher-30 to 200 fold-than MIC values). These ruthenium complexes are very promising lead compounds for novel antifungal drug development, especially in IFIs, one of most harmful emerging infection diseases (EIDs).

Theoretical investigations of the structures and electronic spectra of Zn(II) and Ni(II) complexes with cyclohexylamine-N-dithiocarbamate

The ground-state structures of two ligands cyclohexylamine-N-dithiocarbamate (L) and PPh3 and four complexes [Zn(L)2] (A), [Ni(L)2] (B), [Zn(L)2PPh3] (C), and [Ni(L)2PPh3] (D) are optimized by M06, B3LYP, and B3PW91 methods with the same mixed basis set. As compared with the experimental data of other complexes containing the Ni-P bond, the result obtained by M06/6-31+G(d)-LANL2DZ method is finally regarded as accurate and reliable for this project. Based on the optimized geometries, the compositions of molecular orbitals are analyzed and the absorption spectra are simulated. When one more ligand PPh3 is coordinated, the lowest-lying transition energy presents red-shift; while it shows blue-shift when the metal coordination center change from Ni to Zn with the same ligands. The detailed transition characters related with the absorption spectrum are assigned. In all the key transitions, it is hard to find the contribution from Zn atom. On the contrary, the d orbital of Ni atom contributes a lot for the HOMO and LUMO of complexes B and D. Consequently, the transition characters of Zn(II) and Ni(II) complexes are different.