Linkage between Fluorescence and Electrochemical Properties of Imidazolium Compounds in Acetonitrile Solution.

The fluorescence properties of some imidazolium derivatives are relevant in photosensing and therefore, the structural analysis of them is a key point for its rational design, which would be useful to prepare new systems with novel applications. Herein we report a multidisciplinary study of the fluorescence and voltammetric properties of three imidazolium compounds {1,3-bis[(R,R)-1'-chloro-1'-phenylpropan-2'-yl]-imidazolium chloride (1), 1,3-bis[(Z)-1'-phenylprop-1'-en-2'-yl]imidazolium chloride (2) 1,3-bis[(R)-1'-chlorobutan-2'-yl]-imidazolium chloride (3)}. Electronic structure calculations and Bader analyses were used to correlate both fluorescence and the capability of the molecules to be reduced through a heterogeneous electron transfer process. Both properties are strongly dependent on the proton in position two of the imidazolium ring, where the electron transfer as well as the excitation of the electrons are carried out. The reactivity in this position is controlled by the N-substituents on the imidazolium ring and is due to single contacts H⋅⋅⋅Cl- , tricentric contacts Cl⋅⋅⋅Cl- ⋅⋅⋅Cl, π-electronic delocalization and π-stacking interactions.

Binding of Pb-Melatonin and Pb-(Melatonin-metabolites) complexes with DMT1 and ZIP8: implications for lead detoxification.

We have applied the docking methodology to characterize the binding modes of the divalent metal transporter 1 (DMT1) and the zinc transporter 8 (ZIP8) protein channels with: melatonin, some melatonin metabolites, and a few lead complexes of melatonin and its metabolites, in three different coordination modes (mono-coordinated, bi-coordinated and tri-coordinated). Our results show that bi-coordinated and tri-coordinated lead complexes prefer to bind inside the central region of ZIP8. Moreover, the interaction strength is larger compared with that of the free melatonin and melatonin metabolites. On the other hand, the binding modes with DMT1 of such complexes display lower binding energies, compared with the free melatonin and melatonin metabolites. Our results suggest that ZIP8 plays a major role in the translocation of Pb, bi or tri coordinated, when melatonin metabolites are present. Finally, we have characterized the binding modes responsible for the ZIP8 large affinities, found in bi-coordinated and tri-coordinated lead complexes. Our results show that such interactions are greater, because of an increase of the number of hydrogen bonds, the number and intensity of electrostatic interactions, and the interaction overlay degree in each binding mode. Our results give insight into the importance of the ZIP8 channel on lead transport and a possible elimination mechanism in lead detoxification processes. Graphical abstract .

Computational study of metal complexes formed with EDTA, melatonin, and its main metabolites: implications in lead intoxication and clues to a plausible alternative treatment.

Melatonin has been proposed as an alternative treatment to the usage of EDTA for lead intoxication. In this computational paper, since previous work has not systematically studied the complexes that may be formed in the existing and proposed treatments, we study 45 possible complexes that we suggest may be formed between Pb and some essential metals with melatonin, melatonin metabolites, and EDTA, analyzing the stability and viability of these through the Gibbs free energy of complexation (ΔΔG), molecular orbitals, and energy decomposition analysis at the DFT level of theory PBE/TZ2P. Our findings show that most complexes present exergonic energies of reaction, and thus spontaneous complex formation. In addition, we show that the AMK and 3OHM melatonin metabolites possess electronic and thermodynamic properties adequate to act as lead trapping molecules due to the lower Pauli repulsion energies involved in the complexes they form and their large negative values of ΔΔG. Therefore, it is shown that both melatonin and some of its metabolites may be employed in a viable treatment for lead intoxication through formation of stable Pb-complexes. Graphical abstract Metal complexes formed with EDTA, melatonin, and its main metabolites.

Synthesis of azepino[4,5-b]indol-4-ones via MCR/free radical cyclization and in vitro-in silico studies as 5-Ht6R ligands.

A series of nine new 3-acetamide-azepino[4,5-b]indol-4-ones were synthesized in two steps: (i) multicomponent reaction (Ugi-4CR/SN2) and (ii) free radical-mediated cyclization. These compounds, along with their tetrazole-based analogs, were studied in vitro to assess their binding with the 5-hydroxytryptamine type 6 receptor (5-Ht6R). The 3-acetamide-azepino[4,5-b]indol-4-ones displayed moderate affinity, whereas the 3-tetrazolylmethyl-azepino[4,5-b]indol-4-ones affinity values are lower. However, one of the 3-acetamide-azepino[4,5-b]indol-4-ones exhibited a hit value of Ki (211.2nM) to the 5-Ht6R. Minimal-energy structures of one cis-amide and its tetrazole-based analog (calculated by means of the Density Functional Theory) were analyzed to assess some interesting bioisosterism aspects. Interactions and binding energies between all products and the 5-Ht6R were calculated through in silico molecular couplings. Finally, a QSAR model was proposed using the results of the in vitro assays.