Antibacterial activity assays of a new cadmium complex with o-phenanthroline and cyanoguanidine: crystal structure, fluorescence properties, and chemical speciation studies

Abstract

A new coordination complex, aqua bis(o-phenanthroline) cadmium(II) sulfate cyanoguanidine pentahydrate, [Cd(o-phen) 2 (SO 4 )(H 2 O)](cnge) Á 5H 2 O, was synthesized and characterized. The crystal structure was solved by X-ray diffraction methods. It crystallizes in the monoclinic space group P2 1 /n with a ¼ 13.7650(2) A ˚, b ¼ 10.2796(2) A ˚, c ¼ 21.4418(3) A ˚, ¼ 90.106(2) , and Z ¼ 4 molecules per cell unit. The cadmium(II) is in a distorted octahedral environment coordinated to two nearly planar and mutually perpendicular o-phenanthrolines, one oxygen atom of sulfate, and a water molecule. Non-bonded and planar cyanoguanidine and five crystallization water molecules complete the asymmetric unit. Vibrational (FT-IR and FT-Raman) spectroscopies and thermogravimetric determinations support this structure. Intensity enhancement of the fluorescence spectrum may be a demonstration of the interaction of the metal with phenanthroline. In solution the coordination behavior is rather different, and the speciation studies point to coordination of both cnge and phenanthroline to cadmium. The improvement of the antibacterial activity of cadmium upon complexation has been determined.

Structural, spectral and potentiometric characterization, and antimicrobial activity studies of [Zn(phen)2(cnge)(H2O)](NO3)2 · H2O

“…The log K values are in agreement with those measured by us under identical conditions [7,8]. The experimental log 0101 value of 5.0 for o-phenH þ was recalculated and found in agreement with the reported value [28,29].…”

“…The complex exhibited more intense blue fluorescent emission bands at 365, 377 (sh), and 405 (sh) nm upon photoexcitation at 334 nm (figures 4 and 5). Similar effects were also observed in the Cd, o-phen, cnge complex [8].…”

“…Vibration bands and corresponding assignments for cnge, phen, and [Zn(cnge)(phen) 2 (H 2 O)](NO 3 ) 2 Á H 2 O are given in table 3. The tentative assignments were based on the reported ones [24][25][26] and our previous work [7,8]. The characteristic phen strong bands at 850 and 721 cm À1 are observed in the complex with small shifts and different intensities due to coordination.…”

“…cnge is the dimeric form of cyanamide, the latter being recently recognized as a substrate for nitrogenase containing cyano and guanidine that can coordinate with various metals [4][5][6]. Similar studies concerning the preparation, characterization, and in vitro biological activity determinations using copper(II) and cadmium(II) coordination compounds were reported previously [7,8].…”

“…The stability constants of complexes and the protonation constants of the ligands were determined at 298 K, 0.150 mol L À1 ionic strength (NaCl) and under nitrogen, as previously described [7,8]. A Schott Gerate TS165 pH meter was used for EMF measurements and the added volumes were measured using a Techware (Sigma) Digitrate (25 mL).…”