Rosita Diana

Structure Modification of an Active Azo-Compound as a Route to New Antimicrobial Compounds

Some novel (phenyl-diazenyl)phenols 3a–g were designed and synthesized to be evaluated for their antimicrobial activity. A previously synthesized molecule, active against bacteria and fungi, was used as lead for modifications and optimization of the structure, by introduction/removal or displacement of hydroxyl groups on the azobenzene rings. The aim of this work was to evaluate the consequent changes of the antimicrobial activity and to validate the hypothesis that, for these compounds, a plausible mechanism could involve an interaction with protein receptors, rather than an interaction with membrane. All newly synthesized compounds were analyzed by 1H-NMR, DSC thermal analysis and UV-Vis spectroscopy. The in vitro minimal inhibitory concentrations (MIC) of each compound was determined against Gram-positive and Gram-negative bacteria and Candida albicans. Compounds 3b and 3g showed the highest activity against S. aureus and C. albicans, with remarkable MIC values of 10 µg/mL and 3 µg/mL, respectively. Structure-activity relationship studies were capable to rationalize the effect of different substitutions on the phenyl ring of the azobenzene on antimicrobial activity.

Synthesis and Antimicrobial Studies of New Antibacterial Azo-Compounds Active against Staphylococcus aureus and Listeria monocytogenes

Some novel (phenyl-diazenyl)phenols (4a–m) were designed and synthesized to be evaluated for their antibacterial activity. Starting from an active previously-synthesized azobenzene chosen as lead compound, we introduced some modifications and optimization of the structure, in order to improve solubility and drug conveyance. Structures of all newly-synthesized compounds were confirmed by 1H nuclear magnetic resonance (NMR), mass spectrometry, and UV-Vis spectroscopy. Antibacterial activity of the new compounds was tested with the dilution method against the bacteria strains Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa PAO1. All the compounds were selectively active against Gram-positive bacteria. In particular, compounds 4d, 4h, and 4i showed the highest activity against S. aureus and Listeria monocytogenes, reaching remarkable MIC100 values of 4 μg/mL and 8 μg/mL. The relationship between antimicrobial activity and compound structure has suggested that the presence of hydroxyl groups seems to be essential for antimicrobial activity of phenolic compounds.

A real-time tripodal colorimetric/fluorescence sensor for multiple target metal ions

Abstract In this work we report on the synthesis of a pyridyl/phenolic/benzothiazole functionalized colorimetric receptor (BPAP) that can selectively recognise Fe(III) and Fe(II) ions in aqueous medium with visible, naked eye colour changes. Moreover, BPAP behaves as a ‘turn-on’ fluorescent chemosensor, showing an excellent sensitivity towards Zn2+ and Cd2+ cations in water by exhibiting fluorometric change. BPAP exhibited a visible detection limit of 5.5u202fμM and 2.5u202fμM for Fe3+ and Fe2+, respectively, and a fluorometric selectivity towards Zn2+ and Cd2+ ions with lower detection limits of 205u202fnM and 642u202fnM. To understand the mode of binding to the sensor, both the nude sensor and the Zn-complex were isolated and characterized by X-ray crystallography. In Zn-BPAP, the ligand acts as neutral tridentate through Npyridine, Namine and Namide donor atoms. The N atom of benzothiazole group and the OH group of the phenole unit are not coordinated. Computational DFT study was performed on the free ligand BPAP and complex with Zn2+ to investigate the interaction site, to calculate the energies of the frontier molecular orbitals and to corroborate some of the experimental results.

A novel fluorescent solvatochromic probe for lipid bilayers

Abstract The cell membrane is a heterogeneous system constituted mainly by lipids and proteins in which the physical state is finely regulated to guarantee the regular functions. Among the numerous analytical techniques employed in membrane investigation, a special role is the one of fluorescence microscopy. Fluorescence microscopy allows a fast and non-disruptive investigation of model membranes as well as living samples. Numerous fluorescent probes are known, but most of them are unsuitable for membrane studies, since they either alter the membrane structure or they are internalized in the cell. In this work, we report the rational design and the synthesis of a new fluorescent membrane probe and its characterization in model membranes. The probe consists of a fluorescent aromatic nucleus of 7-nitrobenz-2-oxa-1,3-diazole (NBD) that emits in the visible region of the spectrum. The fluorophore has been linked to a zwitterionic structure and a saturated chain of 18 carbon atoms, to prevent the internalization in the cell and to selectively anchor it to the outer membrane layer. It is worth to notice that the probe shows a certain degree of solvatochromism, a feature that can be exploited to evaluate the liquid-ordered and liquid-disordered composition of biological membranes.

Solid-State Highly Efficient DR Mono and Poly-dicyano-phenylenevinylene Fluorophores

An efficient deep red (DR)-emitting organic solid based on a dicyano-phenylenevinylene derivative was reported. The structural and spectroscopic properties of the solid have been described in terms of crystallographic data and time-dependent DFT analysis. A noteworthy fluorescence quantum yield of 53% was observed for the brightest emitter cast into solid films. This result can be explained in terms of the aggregation-induced emission (AIE) effect.

AIE/ACQ Effects in Two DR/NIR Emitters: A Structural and DFT Comparative Analysis

The effects of aggregation-induced emission (AIE) and of aggregation caused quenching (ACQ) were observed and discussed on two solid materials based on a phenylenevinylene (PV) and a dicyano-PV structure. The brightest emitter in solid films shows a high fluorescence quantum yield in the deep red/near IR (DR/NIR) region (75%). The spectroscopic properties of the two crystalline solids have been described and compared in terms of crystallographic data and time dependent DFT analysis. The influence of the cyano-substituents on AIE/ACQ mechanism activation was discussed.

Data on a real-time tripodal colorimetric/fluorescence sensor for multiple target metal ions

Currently considerable research both in life and in environmental sciences is dedicated to chemosensors able to detect metals of biological interest such as zinc and iron or other toxic and carcinogenic, as cadmium, mercury, chromium, lead. Recently, a new chemosensor strategy of “single chemosensor for multiple metals” has emerged. For this scope, many fluorescent sensors for Cd(II) and Zn(II) have been designed and synthetized, as ligand systems or in polymeric matrices [1], [2], [3]. The data presented in this article include experimental data on the of a pyridyl/phenolic/benzothiazole functionalized colorimetric receptor (BPAP) and its selectively recognise Fe(III) and Fe(II) ions with visible, naked eye colour changes and fluorometric selectivity towards Zn2+ and Cd2+ ions in aqueous medium. This article is submitted as a companion paper to Caruso et al. (2018) [4].