Synthesis, characterization and biological activity of Zn coordination compounds with the quinolone gatifloxacin

Metal(II) Complexes of the Fluoroquinolone Fleroxacin: Synthesis, Characterization and Biological Profile

“…Of the compounds studied, complexes 3 and 15 have the highest k q values for HSA and BSA, respectively (k q(HSA), 3 = 2.26(±0.10) × 10 13 M −1 s −1 and k q(BSA), 15 = 5.12(±0.17) × 10 13 M −1 s −1 ). The k q constants of the complexes are within the range of previously reported values for metal(II)–quinolone complexes [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 52 , 56 , 57 ].…”

“…The pH values of solutions were adjusted to 6–8 by dropwise addition of a HCl solution. The spectra of all complexes remained unchanged (no shift in λ max , or appearance of new bands), which confirms the integrity of the complexes in solution [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. In particular, in the visible region of the spectra, the expected bands assigned to d–d transitions were observed for the copper(II) (one band at 645–675 nm), cobalt(II) (three bands at 610–630 nm, 515–540 nm and 430–435 nm) and Ni(II) (three bands at 995–1000 nm, 605–615 nm and 395–415 nm) complexes.…”

“…All expected sets of signals related to the existence of the respective ligands in the corresponding compounds have been observed: seven signals for fleroxacin ligands and four for the N,N ′-donor co-ligands. In the 1 H NMR spectra of the Zn(II) complexes, the absence of a signal attributed to carboxylic hydrogen of free Hflrx proves its deprotonation upon binding to zinc(II) [ 26 , 47 , 48 ]. All signals were shifted slightly upon binding to zinc(II) ion.…”

“…Albumin-binding constants (K) were calculated using the Scatchard equation ( Equation (S4) ). The K values for the complexes ( Table 5 ) are relatively high (K (HSA), 7 = 1.31(±0.05) × 10 5 M −1 and K (BSA), 15 = 2.84(±0.11) × 10 5 M −1 are the highest values for each albumin) and are in the range of values reported for metal(II) complexes with quinolones as ligands [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 56 , 57 ]. The albumin-binding constants for the compounds are high enough to support albumin binding, leading to effective transport to their potential biological targets.…”

“…Continuing the research project on the characterization and biological evaluation of metal complexes with quinolones as ligands [ 12 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ], we selected the quinolone fleroxacin and prepared a series of its coordination compounds with divalent ions of transition metals. More specifically, a series of copper(II), manganese(II), zinc(II), cobalt(II) and nickel(II) complexes were synthesized with fleroxacin as a ligand in the absence or presence of the N,N ′-donor co-ligands 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) or 2,2′-bipyridylamine (bipyam) ( Figure 1 ).…”