RESUMEN
In the present work, the two-dimensional (2D) polymer poly[[µ4-2-(4-nitrobenzenesulfonamido)benzoato-κ4O1:O1:O1':N6]silver(I)] (AgL), [Ag(C13H9N2O6S)]n, was obtained from 2-(4-nitrobenzenesulfonamido)benzoic acid (HL), C13H10N2O6S. FT-IR, 1H and 13C{1H} NMR spectroscopic analyses were used to characterize both compounds. The crystal structures of HL and AgL were determined by single-crystal X-ray diffraction. In the structure of HL, O-H...O hydrogen bonds between neighbouring molecules result in the formation of dimers, while the silver(I) complex shows polymerization associated with the O atoms of three distinct deprotonated ligands (L-). Thus, the structure of the Ag complex can be considered as a coordination polymer consisting of a one-dimensional linear chain, constructed by carboxylate bridging groups, running parallel to the b axis. Neighbouring polymeric chains are further bridged by Ag-C monohapto contacts, resulting in a 2D framework. Fingerprint analysis of the Hirshfeld surfaces show that O...H/H...O hydrogen bonds are responsible for the most significant contacts in the crystal packing of HL and AgL, followed by the H...H and O...C/C...O interactions. The Ag...Ag, Ag...O/O...Ag and Ag...C/C...Ag interactions in the Hirshfeld surface represent 12.1% of the total interactions in the crystal packing. Studies of the interactions of the compounds with human serum albumin (HSA) indicated that both HL and AgL interact with HSA.
RESUMEN
The interaction of the antimicrobial drug norfloxacin (NFX) with anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) micelles was studied using the intrinsic spectroscopic properties of NFX to obtain association constants and molecular modifications. Nonionic Tween(®) 20 micelles were also investigated, but the spectroscopic properties of NFX did not detect interactions with these micelles, and quenching by iodide suggested a weak association constant around 47 M(-1). For SDS and CTAB, UV-Vis absorption spectroscopy, steady-state and time-resolved fluorometry were monitored as a function of surfactant concentration ranging from the premicellar to micellar region. It was found that cationic (pH 4.0) and zwitterionic NFX (pH 7.4) associate with SDS micelles, with binding constants equal to 5.4 × 10(3) and 1.7 × 10(3) M(-1), respectively. Premicellar interaction slightly decreases the critical micelle concentration of SDS. Association of anionic NFX (pH 10.6) is very weak. The fluorescence spectrum and lifetime showed that SDS-associated NFX is cationic and that the heterocycle penetrates the interfacial environment of decreased polarity. Cationic CTAB micelles do not bind cationic NFX, and the association constant with zwitterionic NFX is two orders of magnitude lower than that of SDS micelles. From a pharmacological point of view, it is important that at neutral pH, NFX presented a two orders of magnitude higher affinity for anionic than for cationic sites, and did not interact significantly with nonionic or zwitterionic micelle interfaces.
