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Query: UMLS:C0847097 (acidity)
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A series of iron(III) complexes of the type [Fe(L)Cl3], where L is the variously N-alkyl-substituted bis(pyrid-2-ylmethyl)amine ligand such as bis(pyrid-2-ylmethyl)amine (L1), N,N-bis(pyrid-2-ylmethyl)methylamine (L2), N,N-bis(pyrid-2-ylmethyl)-n-propylamine (L3), N,N-bis(pyrid-2-ylmethyl)-iso-butylamine (L4), N,N-bis(pyrid-2-ylmethyl)-iso-propylamine (L5), N,N-bis(pyrid-2-ylmethyl)cyclohexylamine (L6), and N,N-bis(pyrid-2-ylmethyl)-tert-butylamine (L7), have been isolated and characterized by elemental analysis and spectral and electrochemical methods. The crystal structures of the complexes [Fe(L2)Cl3] 2, [Fe(L3)Cl3] 3, and the complex-substrate adduct [Fe(L5)(TCC)(NO3)] 5a, where TCC2- is the tetrachlorocatecholate dianion, have been determined by single-crystal X-ray crystallography. The complexes [Fe(L2)Cl3] 2 and [Fe(L3)Cl3] 3 possess a distorted octahedral geometry, in which the linear tridentate 3N ligands are cis-facially coordinated to the iron(III) center, and three chloride ions occupy the remaining coordination sites. The replacement of the N-methyl group in 2 by N-n-propyl group as in 3 leads to the formation of the Fe-Npy bonds and also the Fe-Cl bonds located trans to them of different lengths. The catecholate adduct 5a also possesses a distorted octahedral geometry, in which the ligand is cis-facially coordinated to iron(III) center, TCC2- is asymmetrically chelated trans to the two pyridyl moieties of the ligand, and one of the oxygen atoms of the nitrate ion occupies the sixth coordination site. All of the present complexes have been interacted with simple and substituted catechols. The catecholate adducts [Fe(L)(DBC)Cl] and [Fe(L)(DBC)(Sol)]+, where H2DBC is 3,5-di-tert-butylcatechol and Sol=H2O/CH3CN, have been generated in situ, and their spectral and redox properties and dioxygenase activities have been studied in dimethylformamide and dichloromethane solutions. All of the complexes catalyze the cleavage of H2DBC using molecular oxygen to afford both intra- and extradiol cleavage products. The formation of extradiol cleavage products is facilitated by cis-facial coordination of the 3N ligands and availability of vacant coordination site on iron(III) center for dioxygen binding. It is remarkable that the nature of the N-alkyl substituent in 3N ligands controls the regioselectivity of cleavage, with the n-propyl, iso-butyl, iso-propyl, and cyclohexyl groups enhancing the yield of extradiol products (46-68%) in dichloromethane. The rate of oxygenation depends upon the solvent and the Lewis acidity of iron(III) center as modified by the sterically demanding N-alkyl groups-length and degree of substitution. The plot of log (kO2) versus energy of the low-energy DBC2--to-iron(III) LMCT band is linear, demonstrating the importance of the Lewis acidity of the iron(III) center in dictating the rate of the dioxygenase reaction.
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PMID:Iron(III) complexes of tridentate 3N ligands as functional models for catechol dioxygenases: the role of ligand N-alkyl substitution and solvent on reaction rate and product selectivity. 1795 55

A series of new 1 : 1 iron(iii) complexes of the type [Fe()Cl(3)], where is a tridentate 3N donor ligand, has been isolated and studied as functional models for catechol dioxygenases. The ligands (1-methyl-1H-imidazol-2-ylmethyl)pyrid-2-ylmethyl-amine (), N,N-dimethyl-N'-(1-methyl-1H-imidazol-2-ylmethyl)ethane-1,2-diamine () and N-(1-methyl-1H-imidazol-2-ylmethyl)-N'-phenylethane-1,2-diamine () are linear while the ligands tris(1-pyrazolyl)methane (), tris(3,5-dimethyl-1-pyrazolyl)methane () and tris(3-iso-propylpyrazolyl)methane () are tripodal ones. All the complexes have been characterized by spectral and electrochemical methods. The X-ray crystal structure of the dinuclear catecholate adduct [Fe()(TCC)](2)O, where TCC(2-) is a tetrachlorocatecholate dianion, has been successfully determined. In this complex both the iron(iii) atoms are bridged by a mu-oxo group and each iron(iii) center possesses a distorted octahedral coordination geometry in which the ligand is facially coordinated and the remaining coordination sites are occupied by the TCC(2-) dianion. Spectral studies suggest that addition of a base like Et(3)N induces the mononuclear complex species [Fe()(TCC)Cl] to dimerize forming a mu-oxo-bridged complex. The spectral and electrochemical properties of the catecholate adducts of the complexes generated in situ reveal that a systematic variation in the ligand donor atom type significantly influences the Lewis acidity of the iron(iii) center and hence the interaction of the complexes with simple and substituted catechols. The 3,5-di-tert-butylcatecholate (DBC(2-)) adducts of the type [Fe()(DBC)Cl], where is a linear tridentate ligand (), undergo mainly oxidative intradiol cleavage of the catechol in the presence of dioxygen. Also, the extradiol-to-intradiol product selectivity (E : I) is enhanced upon removal of the coordinated chloride ion in these adducts to obtain [Fe()(DBC)(Sol)](+) and upon incorporating coordinated N-methylimidazolyl nitrogen in them. In contrast to the iron(iii) complexes of imidazole-based ligands, those of the tripodal pyrazole-based ligands yield major amounts of the oxidized product benzoquinone and small amounts of both intra- and extradiol products. One of the pyrazole arms coordinated in the equatorial plane of these sterically constrained complexes is substituted by a solvent molecule upon adduct formation with DBC(2-), which encourages molecular oxygen to attack this site leading to benzoquinone formation. The DBSQ/DBC(2-) redox potentials of both the imidazole- and pyrazole-based complexes fall in the narrow range of -0.186 to -0.214 V supporting this proposal.
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PMID:Synthesis, structure, spectra and reactivity of iron(III) complexes of imidazole and pyrazole containing ligands as functional models for catechol dioxygenases. 1978 84

Microgreen based functional juice blends containing fenugreek (Trigonella foenum-graecum), kinnow mandarin (Citrus reticulate) and aloe vera (Aloe brobadensis) in different ratios were blended with sorbitol and stevia. The different ratios of juice blends were analyzed for total soluble solids, sedimentation, viscosity and titrable acidity. They were also screened for total phenolic content, total carotenoid content and antioxidant properties such as DPPH, reducing power and metal chelating activity. The formulation with highest TPC, TCC and antioxidant property was selected to optimize a microgreen based functional juice. The optimized microgreen blend formulation had 20 ml 100-1 ml microgreen juice, 40 ml 100-1 ml kinnow juice, 8.5 ml 100-1 ml sorbitol, 1.78 g 100-1 ml stevia and 29.72 ml 100-1 ml aloe vera juice. It had high protein, minerals (sodium and potassium) and vitamin (vitamin C) content as well as good source beta-carotene, phenols and antioxidants. Antioxidant helps in reducing diabetic complications by reducing the oxidative stress and because of their protective action against reactive oxygen species.
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PMID:Optimization of a process for microgreen and fruit-based functional beverage. 3311 19