Abstract:The bis(ethene) complex [Tp*Ir-(C2H4)J (1*) (Tp* = tris(3,Sdimethyl-1 -pyrazol-1

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Bridging the gap: The dinuclear ferric enterobactin mimic [{Fe(mecam)}2]6− (H6‐mecam=1,3,5‐N,N′,N′′‐tris(2,3‐dihydroxybenzoyl)triaminomethylbenzene) is recognized by two periplasmic binding protein molecules (yellow and blue; see structure). The assembly is stabilized through hydrophobic interactions between the ligand backbones of the dinuclear iron complex.

The global pandemic caused by infections of the new coronavirus (COVID-19) makes it necessary to find possible less toxic and easily accessible therapeutic agents. In this study, we used strategies docking and molecular dynamics to analyze phytochemical compounds against FDA-approved antimalarial drugs recommended for the treatment of COVID-19. The evaluation was performed with the docking scores MolDock Score and Rerank Score calculated by Molegro Molecular. The DockThor server was used to generate the complexes and myPresto for the dynamic studies. Preliminary results suggested that piperine, capsaicin, and curcumin have the best docking scores and that they are capable of promoting structural changes in the viral protease by inducing folding of the enzyme. Curcumin and capsaicin bring the enzyme to a more compact conformational state compared to the native state, compared to chloroquine. Even though, it is unknown if these induced changes in protease are related to any inhibitory effect observed both in vitro and in vivo for any of these compounds. Further studies on the mechanisms of action of these compounds of interest are required, as well as experimental demonstrations. However, these results are interesting because they can serve as a starting point for subsequent experimental or/and in silico studies based on chemical structure-activity relationships taking these small molecules and their possible derivatives.

The concept of atom-based quadratic indices is extended to a series of molecular descriptors (MDs) (both total and local) based on adjacency between edges. The kth edge-adjacency matrix (E ( k )) denotes the matrix of bond-based quadratic indices (non-stochastic) with respect to the canonical basis set. The kth "stochastic" edge-adjacency matrix, ES ( k ), is here proposed as a new molecular representation easily calculated from E ( k ). Then, the kth stochastic bond-based quadratic indices are calculated using ES ( k ) as operators of quadratic transformations. The study of six representative physicochemical properties of octane isomers was used to compare the ability of both series of MDs to produce significant quantitative structure-property relationship (QSPR) models. Moreover, the general performance of the new MDs in this QSPR study has been evaluated with respect to other 2D/3D well-known sets of indices and the obtained results shown a quite satisfactory behavior of the present method. The novel bond-level MDs were also used for the description and prediction of the boiling point of 28 alkyl-alcohols and to the modeling of the specific rate constant (log k) of 34 derivatives of 2-furylethylenes. These models were statistically significant and showed very good stability to data variation in leave-one-out (LOO) cross-validation experiment. The comparison with other approaches (edge- and vertices-based connectivity indices, total and local spectral moments, and quantum chemical descriptors as well as E-state/biomolecular encounter parameters) expose a good behavior of our method in this QSPR studies. The approach described in this report appears to be a very promising structural invariant, useful for QSPR/QSAR studies, similarity/diversity analysis, and computer-aided "rational" molecular (drug) design.

A kinetic study of the regioselective homogeneous hydrogenation of quinoline (Q) to 1,2,3,4-tetrahydroquinoline (THQ) was carried out using the cationic complex I-RuH-(CO)(NCMe)2(PPh3)2]BF4 (1) as the precatalyst. The experimentally determined rate law was r = {k2Kj(1 + K 1 [H2] )} [Ruo] [H2] 2, which becomes r = kzK 1 [Ruo]-[H2] 2 at low hydrogen concentrations (kzK 1 = 28.5 M -2 s-1 at 398 K). The corresponding activation parameters were found to be AH~=42+6kJmo1-1, ASS= -ll5___2JK-lmo1-1 and AG~=92+8kJmo1-1 Complex (1) was found to react with Q in CHC13 under reflux to yield [RuH(CO)(NCMe)(N--Q)(PPh3)2]BF4 (2) which was also isolated from the hydrogenation runs. These experimental findings, together with the results of ab initio self-consistent-field molecular orbital calculations on the free organic molecules involved, are consistent with a mechanism involving a rapid and reversible partial hydrogenation of (2) to yield the corresponding dihydroquinoline (DHQ) species [RuH-(CO)(NCMe)(DHQ)(PPh3)z]BF 4 (4), followed by a ratedetermining second hydrogenation of DHQ to yield [RuH(CO)(NCMe)(THQ)(PPh 3)2]BF4 (3).

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