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Vanadium in Technical Applications and Pharmaceutical Issues
Published in Jörg Rinklebe, Vanadium in Soils and Plants, 2023
High work function of mixed metal oxides, for example, by combining V2O5 with MoO3 or Co3O4 via hydrothermal synthesis and subsequent calcination, leads to the incorporation of vanadium into the host oxides, namely the formation of V6MoxO40 (x = 6, 9) and biphasic V2O5-Co3O4, respectively. These phases provide selective materials in energy devices that can basically be employed as metallic (semi)conductors, as light-harvesting devices and light absorbers (Feste et al. 2021). Compound 2 in Figure 12.7 is an example of a catalyst that promotes the oxidative bromination of aromatic aldehydes (and thus mimics the bromoperoxidase activity of the halo-peroxidase in marine algae; vide supra). Compound 2 also exhibits catechol oxidase activity. Along with these catalytic features, an intercalating interaction with circulating tumor DNA in the peripheral blood has been noted (Majunder and Rajak 2020). Vanadium-based photoredox catalysts have been shown to be active in the environmentally relevant conversion of plastics to fuels. An example – the oxidative light-induced conversion of a polyalcohol – is provided in Equation 12.2; for the catalyst, see compound 3 in Figure 12.7 (Gazi et al. 2019). Highly active and stable vanadium catalysts based on naphthalinesufonato complexes (4 in Figure 12.7) effectively catalyze the co-polymerization of ethylene and propylene (Hao et al. 2017). Homogenous recyclable vanadium-based catalysts, obtained through covalent binding – and thus immobilization – of vanadium coordination compounds to polystyrene have been employed in the oxidation of phenols, olefins, benzoin, cumene and organic sulfides (Maurya 2018). For an example, see compound 5 in Figure 12.7.
Mn(IV), Co(II) and Ni(II) complexes of the Schiff bases of 2-hydroxy-naphthaldehyde with amino alcohols: synthesis, characterization and electrochemical study; DFT study and Catecholase activity of Mn(IV) complex
Published in Journal of Coordination Chemistry, 2020
Shipra Sagar, Arfa Parween, Tarun K. Mandal, William Lewis, Subhendu Naskar
Manganese is one of the most abundant transition elements present in biological system. In the human body, deficiency of this essential element causes weak bones (osteoporosis), one type of “tired blood” (anemia) and premenstrual syndrome (PMS). Manganese-containing complexes exist in nature both as the mononuclear species (catalases) [7], superoxide dismutase [8], arginase [9], and as polynuclear species in water oxidation catalyst-WOC [10]. The enzyme catechol oxidase (CO) found in bacteria, fungi, and plants is a type-3 copper protein, which oxidized catechol to the corresponding o-quinones [11–15]. The highly reactive o-quinone undergoes auto polymerization and form brown pigment—melanin that protects damage tissue against a pathogen and insects [16–18]. In the case of manganese, mononuclear complexes have come out to be the best candidates for the catechol oxidation among all the metal ions, even better than the binuclear copper mimics [19]. So far, researchers have highlighted a number of manganese complexes which showed catecholase activity [20–24]. Both mononuclear [25] and binuclear [26, 27] Mn(II)/Mn(III) complexes have been established to show catecholase activity. However, there are limited examples of Mn(IV) complexes with potential catecholase activity as revealed from the literature till date [21].
Development of multi-metallic complexes using metal-salen complexes as building blocks
Published in Journal of Coordination Chemistry, 2019
Ipsita Mondal, Shouvik Chattopadhyay
Many multi-metallic complexes have been found to mimic metalloenzymes, e.g. catechol oxidase, phenoxazinone synthase, etc. Catechol oxidase is a type-III copper protein which catalyzes the oxidation of catechols to the corresponding o-quinones without acting on monophenols [127]. It consists of binuclear copper, where each copper is coordinated by three histidine nitrogens. Catechol oxidase mimicking activities of several multi-metallic complexes have been reported [102, 127, 214]. Phenoxazinone synthase, on the other hand, is a type-II copper protein and is found in Streptomyces antibioticus bacterium [216]. It catalyzes oxidative dimerization of two molecules of substituted ortho-aminophenol to the phenoxazinone chromophore in the final step in the biosynthesis of actinomycin D, which is used to destroy different tumors [217].
Mn(III) and Cu(II) complexes of 1-((3-(dimethylamino)propylimino)methyl) naphthalen-2-ol): Synthesis, characterization, catecholase and phenoxazinone synthase activity and DFT-TDDFT study
Published in Journal of Coordination Chemistry, 2018
Swaraj Sengupta, Binitendra Naath Mongal, Suman Das, Tarun K. Panda, Tarun K. Mandal, Michel Fleck, Shyamal K. Chattopadhyay, Subhendu Naskar
Catechol oxidase (CO) is a type-III copper protein which catalyzes the oxidation of o-diphenol to corresponding quinone (Scheme 1). Highly reactive quinone then undergoes auto-polymerization forming melanin. In this way, CO protects damaged tissues of plants against pathogens or insects.