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Bicyclic molecule
About: Bicyclic molecule is a research topic. Over the lifetime, 29587 publications have been published within this topic receiving 451252 citations. The topic is also known as: bicyclic molecule.
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TL;DR: In this paper, the pK[sub a] values of the mixed-valence dinuclear complexes are quite close to those of each M(II) and M(III) component, which suggests that the bridging ligand can be used to serve as a trigger signal for switching the metal-metal interaction.
Abstract: New dinuclear complexes [M(L)[sub 2](bpbimH[sub 2])M(L)[sub 2]][sup 4+] (M = Ru, Os; L = bpy, phen; bpbimH[sub 2] = 2,2[prime]-bis(2-pyridyl)bibenzimidazole) act as dibasic acids. Both the absorption spectra and oxidation potentials are strongly dependent on the solution pH, which is responsible for the deprotonation of the N-H group on the coordinated bridging ligand. The pK[sub a] values reflect the metal oxidation states, M(II) and M(III). The pK[sub a] values of the mixed-valence dinuclear complexes are quite close to those of each M(II) and M(III) component, which suggests that mixed-valence complexes bridged by the protonated ligand bpbimH[sub 2] exhibit the intervalence (IT) band at 7300 cm[sup [minus]1] for M = Ru and at 9100 cm[sup [minus]1] for M = Os, respectively. When the bridging ligand is deprotonated, this IT band is shifted to lower energy at 5880 cm[sup [minus]1] for M = Ru and 7700 cm[sup [minus]1] for M = Os and intensified. The degree of metal-metal interaction of the deprotonated dinuclear complexes becomes 4-6 times larger than that of the protonated complexes. This proton-induced change of metal-metal interaction can be rationalized by change of HOMO energy levels on deprotonation or protonation in the bridging ligands. Thus, proton transfer in themore » bpbimH[sub 2] bridging dinuclear complexes can be utilized to serve as a trigger signal for switching the metal-metal interaction.« less
135 citations
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TL;DR: L'influence du rayonnement proche UV and l'effet d'inhibiteurs impliquent un mecanisme radicalaire en chaine as mentioned in this paper.
Abstract: L'influence du rayonnement proche UV et l'effet d'inhibiteurs impliquent un mecanisme radicalaire en chaine
135 citations
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134 citations
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134 citations
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TL;DR: The synthesis of a series of N-phosphonalkyl dipeptides 6 is described, devised that allowed the preparation of single diastereoisomers and the assignment of stereochemistry and potency was enhanced by introducing bicyclic aromatic P2' substituents.
Abstract: The synthesis of a series of N-phosphonalkyl dipeptides 6 is described. Syntheses were devised that allowed the preparation of single diastereoisomers and the assignment of stereochemistry. The compounds were evaluated in vitro for their ability to inhibit the degradation of radiolabeled collagen by purified human lung fibroblast collagenase. Several of the compounds were potent collagenase inhibitors and were at least 10-fold more potent than their corresponding N-carboxyalkyl analogues. Activity was lost when the phosphonic acid group P(O)(OH)2 was replaced by the phosphinic acid groups P(O)(H)(OH) and P(O)(Me)(OH). At the P1 position, (R)- or (S)-alkyl groups, especially ethyl and methyl (e.g., 12a,b, 52a,b, and 53a,b), or an (R)-phenethyl moiety (55a) conferred high potency (IC50 values in the range 0.23-0.47 microM). (S)-Stereochemistry was preferred for the P1' isobutyl side chain. Structure-activity relationships were also investigated at the P2' site, and interestingly, compounds with basic side chains, such as the guanidine 57a, were equipotent with more lipophilic compounds, such as 52a. As with other series of collagenase inhibitors, potency was enhanced by introducing bicyclic aromatic P2' substituents. The most potent phosphonic acid of the series was the bicyclic aromatic P2' tryptophan analogue 59a (IC50 0.05 microM).
133 citations