Ligand centered radical pathway in catechol oxidase activity with a trinuclear zinc-based model: Synthesis, structural characterization and luminescence properties

Pal, Sukanta; Chowdhury, Biswajit; Patra, Moumita; Maji, Milan; Biswas, Bhaskar

doi:10.1016/j.saa.2015.02.046

Cited by 43 publications

(13 citation statements)

References 44 publications

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“…In both the 5 and 75 m m samples, new red‐shifted absorption bands appear over time. These bands are assigned to o ‐quinones, the fully oxidized form of catechol . This assignment is supported by mass spectrometry measurements made with the 5 m m sample (Figure in Appendix ).…”

Section: Discussionsupporting

confidence: 53%

Intermolecular Hydrogen Bonding Modulates O‐H Photodissociation in Molecular Aggregates of a Catechol Derivative

Grieco

Kohl

Zhang

et al. 2018

Photochem & Photobiology

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The catechol functional group plays a major role in the chemistry of a wide variety of molecules important in biology and technology. In eumelanin, intermolecular hydrogen bonding between these functional groups is thought to contribute to UV photoprotective and radical buffering properties, but the mechanisms are poorly understood. Here, aggregates of 4‐t‐butylcatechol are used as model systems to study how intermolecular hydrogen bonding influences photochemical pathways that may occur in eumelanin. Ultrafast UV‐visible and mid‐IR transient absorption measurements are used to identify the photochemical processes of 4‐t‐butylcatechol monomers and their hydrogen‐bonded aggregates in cyclohexane solution. Monomer photoexcitation results in hydrogen atom ejection to the solvent via homolytic O‐H bond dissociation with a time constant of 12 ps, producing a neutral semiquinone radical with a lifetime greater than 1 ns. In contrast, intermolecular hydrogen bonding interactions within aggregates retard O‐H bond photodissociation by over an order of magnitude in time. Excited state structural relaxation is proposed to slow O‐H dissociation, allowing internal conversion to the ground state to occur in hundreds of picoseconds in competition with this channel. The semiquinone radicals formed in the aggregates exhibit spectral broadening of both their electronic and vibrational transitions.

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Section: Discussionsupporting

confidence: 53%

Intermolecular Hydrogen Bonding Modulates O‐H Photodissociation in Molecular Aggregates of a Catechol Derivative

Grieco

Kohl

Zhang

et al. 2018

Photochem & Photobiology

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“…In order to investigate the efficiency of catecholase activity of complex 1 , 3,5‐DTBC with two bulky t ‐butyl substituents on the ring and low quinone–catechol reduction potential has been chosen as substrate. These properties of the substrate help it to undergo easy oxidation (Scheme ) to the corresponding o ‐quinone, 3,5‐DTBQ, which is highly stable and shows a maximum absorption in the wavelength range 380–420 nm …”

Section: Resultsmentioning

confidence: 99%

Catalytic promiscuity of an iron(II)–phenanthroline complex

De¹,

Garai²,

Yadav

et al. 2016

Applied Organom Chemis

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A mononuclear iron(II) complex, [Fe(phen) 3 ]Cl 2 (1) (phen =1,10-phenanthroline), has been synthesized in crystalline phase and characterized using various spectroscopic techniques including single crystal X-ray diffraction. Crystal structure analysis revealed that 1 crystallizes in a monoclinic system with C2/m space group. Complex 1 acts as a functional model for a biomimetic catalyst promoting the aerobic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) through radical pathways with a significant turnover number (k cat =3.55 × 10 3 h À1 ) and exhibits catechol dioxygenase activity towards the same 3,5-DTBC substrate at room temperature in oxygen-saturated ethanol medium. The existence of an isobestic point at 610 nm from spectrophotometric data indicates the presence of Fe 3+ À3,5-DTBC adduct favouring an enzyme-substrate binding phenomenon. Upon stoichiometric addition of 3,5-DTBC pretreated with two equivalents of triethylamine to the iron complex, two catecholate-to-iron(III) ligand-to-metal charge transfer bands (575 and 721 nm) are observed and the in situ generated catecholate intermediate reacts with dioxygen (k obs =9.89 × 10 À4 min À1 ) in ethanol medium to afford exclusively intradiol cleavage products along with a small amount of benzoquinone, and a small amount of extradiol cleavage products, which provide substantial evidence for a substrate activation mechanism.

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“…Since dicopper(II) units are the centers of activity in catechol oxidase, the preferred choice to several research groups is dinuclear Cu(II) systems as catalysts for catechol oxidation reaction . In contrast with various dinuclear Cu(II) systems, a few mononuclear Cu(II) complexes and Zn(II) based compounds bearing diversified ligands with N/O donors were reported in the literature . Thus, there is an excellent scope of exploitation of such mononuclear Cu (II) units and hexanuclear Zn (II) compound as catalysts towards the conversion of 3,5‐di‐ tert ‐butylcatechol (3,5‐DTBC) to 3,5‐di‐ tert ‐butylquinone (3,5‐DTBQ).…”

Section: Resultsmentioning

confidence: 99%

“…The interest has been manifested due to their ease of preparation and formation of stable coordination complexes with most of the transition metals. In these complexes, variable coordination number, oxidation states of metal ion, type of the attached ligand, kinetic and thermodynamic prospects do offer the active impetus to exploit a wide range of pharmaceutical and biological domains . They also have enormous potential to create versatile platforms for rational strategies of drug design.…”

Section: Introductionmentioning

confidence: 99%

Hexanuclear Zn(II) and Mononuclear Cu(II) Complexes containing imino phenol ligands: Exploitation of their Catalytic and Biological Perspectives

Mondal

Chatterjee

Tiwari

et al. 2019

Applied Organom Chemis

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A unique hexanuclear zinc(II) (1) and two mononuclear copper(II) (2 and 3) complexes anchored with imino phenol ligand HL 1 and HL 2 were synthesized with good yield and purity (where HL 1 = 4-tert-butyl-2,6-bis((mesitylimino) methylphenol and HL 2 = 5-tert-butyl-2-hydroxy-3-((mesitylimino)methyl) benzaldehyde). These complexes were characterized by utilizing various spectroscopic protocols like NMR, FTIR, UV as well as ESI-Mass spectrometry, elemental analysis and single crystal X-ray diffraction studies. Their potential to bind calf thymus DNA (CT-DNA) was tested utilizing different techniques such as UV-visible and fluorescence spectroscopy. The experiment implies that they interact with CT-DNA via non-intercalative mode with moderate capabilities (K b~1 0 4 M −1 ). On the other hand, these complexes have high capabilities to quench the fluorescence of bovine serum albumin (BSA) following the static pathway. In addition, they are active catalysts for the oxidation reaction of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) under aerobic condition. From the recorded EPR signals of all complexes, it has been concluded that the oxidation reaction proceeds via ligand oriented radical pathway instead of metal based redox participation. Kinetic studies using 1-3 indicate that it follows Michaelis-Menten type of equation with moderate to high turnover number (k cat ). Apart from these aspects, complexes 1-3 were screened for their cytotoxic behavior towards HeLa cells (human cervical carcinoma) and found quite active with comparable IC 50 values to cisplatin.

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Ligand centered radical pathway in catechol oxidase activity with a trinuclear zinc-based model: Synthesis, structural characterization and luminescence properties

Cited by 43 publications

References 44 publications

Intermolecular Hydrogen Bonding Modulates O‐H Photodissociation in Molecular Aggregates of a Catechol Derivative

Intermolecular Hydrogen Bonding Modulates O‐H Photodissociation in Molecular Aggregates of a Catechol Derivative

Catalytic promiscuity of an iron(II)–phenanthroline complex

Hexanuclear Zn(II) and Mononuclear Cu(II) Complexes containing imino phenol ligands: Exploitation of their Catalytic and Biological Perspectives

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