Binding of Carbonated Anions to Cationic Hexaureachromium(III): Synthesis, Characterization and Antimicrobial Activity of [Cr(CO(NH2 )2 )6 ](HCO3 )3 and [Cr(CO(NH2 )2 )6 ]2 (CO3 )3

Abstract

Aim: The aim of the study is to synthesize two new hexaureachromium complexes: [Cr(CO(NH2
)
2
)
6
](HCO3
)
3 (1),

[Cr(CO(NH2
)
2
)
6
]
2
(CO3
)
3 (2) followed by the analysis of binding ability of hexaureachromium(III) cation towards

carbonated anions ( 2 HCO and CO 3 3

− − ) and their antimicrobial activities against Escherichia coli, Staphylococcus
aureus S. aurses (for anti-bacterial), and Aspergillus niger (for anti-fungal). Materials and Methods: The synthesized
compounds 1 and 2 were characterized by spectroscopic studies (fourier-transform infrared and ultraviolet [UV]-
visible). The binding properties of [Cr(CO(NH2
)
2
)
6
]
3+ ([HuCr]3+) with carbonated anions ( 2 HCO and CO 3 3
− − ) in
aqueous medium have been determined with standard UV–visible spectrophotometerthrough titration method.
Further, the stoichiometric ratios for complexes 1 and 2 were found through Job’s plot. All compounds were also
tested for antimicrobial activity against selected strains. Results and Discussion: The cation, [HuCr]3+, contains
ligand urea bearing H-bond donors which are capable of forming hydrogen bonds. The binding constant values
obtained are found to be 10.5334 for and 15.7377 for . Further, the stoichiometric ratios for complexes 1 and 2 have
been found to be 1:3 and 2:3, respectively. [HuCr]Cl3

, 1 and 2 show the maximum zone of inhibition at 200 μg/mL
but the starting material [HuCr]Cl3 and compound 1 does not show any activity against A. niger at 50 and 100 μg/mL
concentration. Conclusion: The ionic reactions between anion receptor [HuCr]3+ and carbonated anions in aqueous
solution have been investigated and characterized by spectroscopic (infrared and UV–visible) techniques. The results
obtained indicate that the binding ability of the cation [HuCr]3+ towards carbonated anions is in the order 2 CO3
−
>

HCO3
−
. Thus, the selectivity of receptors for particular anion can be chosen. The results predict that the octahedral
geometry of [HuCr]3+ is capable enough to target both the carbonated anions. [HuCr]Cl3 and compound 1 do not
show any activity against A. niger at 50 and 100 μg/mL concentration while compound 2 is found to be potent against
all the tested organisms (E. coli, S. aurses, and A. niger).