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• 67-56-1 methanol 
• 3383-21-9 3,5-di-tert-butyl-o-benzoquinone 
• 1020-31-1 3,5-Di-tert-butylcatechol 
• 96-76-4 2,4-di-tert-Butylphenol 

Relevant academic research and scientific papers

Catalytic promiscuity of an iron(II)–phenanthroline complex

A mononuclear iron(II) complex, [Fe(phen)3]Cl2 (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 (kcat =3.55?×?103?h?1) 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 Fe3+??3,5-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 (kobs =9.89?×?10?4?min?1) 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. Copyright

Iron and cobalt complexes of 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11- dione dioxime ligand: Synthesis, characterization and reactivity studies

Two oximate bridged dinuclear complexes [CoII2 (HL)2](ClO2)2 (1) and [FeII 2 (HL)2](ClO2)2 (2), and a biomimetic iron(III)-catecholate complex [FeIII(HL)(DBC)] (3) of a dioxime ligand (H2L = 4,4,9,9- tetramethyl-5,8-diazadodecane-2,11- dione dioxime and DBCH2 = 3,5-di-tert-butylcatechol) were synthesized and characterized. X-ray single-crystal structures of both the dinuclear complexes exhibit an out-of-plane oximate bridge where the six-membered M 2(NO)2 ring adopt a boat conformation with the metal ions in a fivecoordinate distorted trigonal bipyramidal geometry. Complexes 1 and 2 react with dioxygen at ambient condition to form the corresponding hydroxo- or oxo-bridged dinuclear cobalt(III) or iron(III) complexes. On the other hand, the iron(III)-catecholate complex (3) activate dioxygen to undergo oxidative C-C bond cleavage of catechol. The selective formation of extradiol catechol cleavage products in the reaction of 3 with dioxygen mimics the functional aspect of extradiol-cleaving catechol dioxygenases. The flexibility of ligand backbone is proposed to control the dioxygen reactivity of metal complexes. Indian Academy of Sciences.

Oxidative Ring Cleavage of o-Benzoquinone by Potassium Peroxomonosulphate

Oxidation of 3,5-di-t-butyl-1,2-benzoquinone by potassium peroxomonosulphate gave both extra- and intra-diol cleavage products.

Oxidation of 3,5-di-tert-butylcatechol in the presence of V-polyoxometalate

The oxidase and dioxygenase reactions of 3,5-di-tert-butylcatechol (DTBC, I ) in the presence of V-polyoxometalate were studied. It was found that the addition of a Lewis base quenched the V-polyoxometalate-catalysed catechol dioxygenase reaction and catalysed the oxidase reaction selectively. The existence of V-polyoxometalate accelerates the autoxidation rate of I as demonstrated by the rate measurements. ESR and UV-VIS spectra showed that the Lewis base destroyed the dioxygenation reaction catalyst as formed and restrained its regeneration by suppressing the coordination of catechol radical to vanadium. The by-products of the dioxygenation and oxidation reactions are H2O and H2O2, respectively.

Biomimetic intradiol-cleavage of catechols with incorporation of both atoms of O2: The role of the vacant coordination site on the iron center

This is the first example of model system for the active site of protocatechuate 3,4-dioxygenase to display intradiol-cleavage of catechols with incorporation of two oxygen atoms of O2 promoted by iron complexes.

Catalytic aspects of a copper(II) complex: biological oxidase to oxygenase activity

Abstract: A coper(II) complex, [Cu(dpa) 2(OAc)](ClO 4) (1) [dpa =2 , 2 ′-dipyridylamine; OAc = acetate], has been synthesized and crystallographically characterized. X-ray structure analysis revealed that this mononuclear Cu(II) complex crystallizes as a rare class of hexa coordination geometry named bicapped square pyramidal geometry with P2 1/ c space group. This copper complex displays excellent catalytic efficiency, k cat/ K M(h - 1) = 6.17 × 10 5 towards the oxidative coupling of 2-aminophenol (2-AP) to aminophenoxazin-3-one. Further, upon stoichiometric addition of copper(II) complex to 3,5-DTBC in presence of molecular oxygen in ethanol medium, the copper complex affords predominantly extradiol cleavage products along with a small amount of benzoquinone and a trace amount of intradiol cleavage products at a rate, k obs= 1.09 × 10 - 3min - 1, which provide substantial evidence for the oxygen activation mechanism. This paper presents a novel addition of a copper(II) complex having the potential to mimic the active site of phenoxazinone synthase and catechol dioxygenase enzymes with significant catalytic efficiency. Graphical Abstract : SYNOPSIS The mononuclear copper complex having unusual hexa coordination geometry exhibits significant catalytic efficiency, k cat/ K M(h - 1) = 6.17 × 10 5 towards oxidation of 2-aminophenol which predominantly produced extradiol cleavage products at a rate, k obs= 1.09 × 10 - 3min - 1 upon addition of 3,5-DTBC in presence of molecular oxygen. [Figure not available: see fulltext.].

Biomimetic iron(iii) complexes of facially and meridionally coordinating tridentate 3N ligands: Tuning of regioselective extradiol dioxygenase activity in organized assemblies

Four mononuclear iron(iii) complexes of the type [Fe(L)Cl3] 1-4, where L is a tridentate 3N ligand such as (2-pyridin-2-ylethyl)(pyridin-2- ylmethyl)amine (L1), (methyl)(2-pyridin-2-ylethyl)(pyridin-2-ylmethyl)amine (L2), bis(pyridin-2-ylethyl)amine (L3), and (1-methyl-1H-imidazol-2-ylmethyl) (pyridin-2-ylethyl)amine (L4), have been isolated and studied as functional models for catechol dioxygenase enzymes. In [Fe(L2)Cl3] 2, the ligand L2 is coordinated facially to iron(iii) whereas in [Fe(L1)Cl3] 1 and [Fe(L4)Cl3] 4 the ligands L1 and L4 are coordinated meridionally. In DCM, CH3CN and aqueous SDS, CTAB and TX-100 micellar media, the positions of both the low and high energy catecholate-to-iron(iii) LMCT bands (465-530, 690-860 nm) observed for the 3,4-di-tert-butylcatecholate (DBC 2-) adducts of the iron(iii) complexes vary in the order 2 > 1 > 3 > 4, which reflects the influence of the stereoelectronic factors, mode of coordination and the chelate ring size formed by the tridentate ligands. Spectral and electrochemical studies disclose the formation and location of the cationic adducts as solvated [Fe(L)(DBC)(H2O)]+ species mostly in the aqueous micellar pseudophases of SDS and TX-100 and in the aqueous phase of CTAB micellar solution. The [Fe(L)(DBC)Cl] adducts of 1, 3 and 4, generated in situ, afford major amounts of intradiol cleavage products (17.0-70.0%) and smaller amounts of extradiol (1.2-4.2%) products with varying extradiol to intradiol cleavage product selectivity (E/I: 1, 0.08:1; 3, 0.02:1; 4, 0.3:1). On the other hand, interestingly, the adduct [Fe(L2)(DBC)Cl] of 2 generated in DCM yields a major amount of extradiol (54.0%) and a lower amount (18.3%) of the intradiol cleavage products (E/I, 3:1). Remarkably, in aqueous SDS micellar media, it shows exclusive extradiol cleavage products (79.4%) while all the other complexes show very low selectivity (E/I: 1, 0.03:1; 2, 79.4:0, 3, 0.06:1, 4, 0.06:1), suggesting the suitability of SDS medium for 2 to elicit exclusive extradiol cleavage. The TX-100 micellar medium also provides a suitable hydrophobic environment for 2 to elicit extradiol cleavage. However, in CTAB micellar medium, 2 shows cleavage selectivity lower than others. Also, the rate of dioxygenation is higher in SDS micellar medium than in DCM, and is dependent upon the chelate ring size. This journal is the Partner Organisations 2014.

Iron(iii) complexes of tripodal tetradentate 4N ligands as functional models for catechol dioxygenases: The electronic vs. steric effect on extradiol cleavage

A few mononuclear iron(iii) complexes of the type [Fe(L)Cl2]Cl 1-6, where L is a tetradentate tripodal 4N ligand such as N,N-dimethyl-N′,N′-bis(pyrid-2-ylmethyl)ethane-1,2-diamine (L1), N,N-diethyl-N′,N′-bis(pyrid-2-ylmethyl)ethane-1,2-diamine (L2), N,N-dimethyl-N′,N′-bis-(6-methylpyrid-2-ylmethyl)ethane-1,2-diamine (L3), N,N-dimethyl-N′-(pyrid-2-ylmethyl)-N′-(1-methyl-1H-imidazol-2-ylmethyl)ethane-1,2-diamine (L4), N,N-dimethyl-N′,N′-bis(1-methyl-1H-imidazol-2-ylmethyl)ethane-1,2-diamine (L5) and N,N-dimethyl-N′,N′-bis(quinolin-2-ylmethyl)ethane-1,2-diamine (L6), have been isolated and characterized by CHN analysis, UV-Visible spectroscopy and electrochemical methods. The complex cation [Fe(HL1)Cl3]+1a possesses a distorted octahedral geometry in which iron is coordinated by the monoprotonated 4N ligand in a tridentate fashion and the remaining three sites of the octahedron are occupied by chloride ions. The DFT optimized octahedral geometries of 1, 5 and 6 contain iron(iii) with a high-spin (S = 5/2) ground state. The catecholate adducts [Fe(L)(DBC)]+, where H2DBC is 3,5-di-tert-butylcatechol, of all the complexes have been generated in situ in acetonitrile solution and their spectral and redox properties and dioxygenase activities have been studied. The DFT optimized geometries of the catecholate adducts [Fe(L1)(DBC)]+, [Fe(L5)(DBC)]+ and [Fe(L6)(DBC)]+ have also been generated to illustrate the ability of the complexes to cleave H2DBC in the presence of molecular oxygen to afford varying amounts of intra- (I) and extradiol (E) cleavage products. The extradiol to intradiol product selectivity (E/I, 0.1-2.0) depends upon the asymmetry in bidentate coordination of catecholate, as determined by the stereoelectronic properties of the ligand donor functionalities. While the higher E/I value obtained for [Fe(L6)(DBC)]+ is on account of the steric hindrance of the quinolyl moiety to coordination the lower value observed for [Fe(L4)(DBC)]+ and [Fe(L6)(DBC)]+ is on account of the electron-releasing effect of the N-methylimidazolyl moiety. Based on the data obtained it is proposed that the detachment of the -NMe2 group from the coordination sphere in the semiquinone intermediate is followed for dioxygen binding and activation to yield the extradiol cleavage product. This journal is

A novel pentadentate redox-active ligand and its iron(III) complexes: Electronic structures and O2 reactivity

A novel redox-active ligand, H4Ph2SLAP (1) which was designed to be potentially pentadentate with an O,N,S,N,O donor set is described. Treatment of 1 with two equivalents of potassium hydride gave access to octametallic precursor complex [H2Ph2SL APK2(thf)]4 (2), which reacted with FeCl 3 to yield iron(III) complex [H2Ph2SL APFeCl] (3). Employing Fe[N(SiMe3)2] 3 for a direct reaction with 1 led to ligand rearrangement through C-S bond cleavage and thiolate formation, finally yielding [HLAPFe] (5). Upon exposure to O2, 3 and 5 are oxidized through formal hydrogen-atom abstraction from the ligand NH units to form [ Ph2SLSQFeCl] (4) and [LSQFe] (6) featuring two or one coordinated iminosemiquinone moieties, respectively. Moessbauer measurements demonstrated that the iron centers remain in their +III oxidation states. Compounds 3 and 5 were tested with respect to their potential as models for the catechol dioxygenase. Thus, they were treated with 3,5-di-tert-butyl- catechol, triethylamine and O2. It turned out that the iron-catecholate complexes react with O2 in dichloromethane at ambient conditions through C-C bond cleavage mainly forming extradiol cleavage products. Intradiol products are only side products and quinone formation becomes negligible. This observation has been rationalized by a dissociation of two donor functions upon coordination of the catecholate. A radical convention: A novel pentadentate O,N,S,N,O ligand system, LH4, which is redox active, has been developed, so that its iron(III) complex (H2LFeCl) reacts with O2. H atoms are abstracted from the NH units present so that the ligand is converted into a diradical, featuring two iminosemiquinonato moieties that clamp a high-spin iron(III) center. The complex proved capable of mimicking catechol dioxygenase reactivity, and mediates extradiol cleavage with remarkable selectivity.

Oxidation of 3,5-di-tert-butylcatechol in the presence of V-polyoxometalate

The oxidase and dioxygenase reactions of 3,5-di-tert-butylcatechol (DTBC, I) in the presence of V-polyoxometalate were studied. It was found that the addition of a Lewis base quenched the V-polyoxometalate-catalysed catechol dioxygenase reaction and catal