4026-05-5Relevant articles and documents
Dinuclear cobalt complexes with a redox active biphenyl bridging ligand [Co2(BP)(tqa)2](PF6)2(H4BP = 4,4′-bis(3-tert-butyl-1,2-catechol), tqa = tris(2-quinolylmethyl)amine): structure and magnetic properties
Kuroda-Sowa, Takayoshi,Maekawa, Masahiko,Mibu, Takuto,Okubo, Takashi,Suenaga, Yusaku,Sugimoto, Kunihisa
, p. 9833 - 9841 (2021/07/28)
The biscatechol, H4BP (4,4′-bis(3-tert-butyl-1,2-catechol)) that can directly connect two redox active catechol moieties was synthesized. Also, tris(2-pyridylmethyl)amine (tpa), bis(2-pyridylmethyl)(2-quinolylmethyl)amine (bpqa), (2-pyridylmethyl)bis(2-quinolyl methyl)amine (pbqa), and tris (2-quinolylmethyl)amine (tqa) were synthesized as terminal ligands of the tetracoordinated tripod. In total, five different dinuclear Co complexes were synthesized from H4BP with various terminal ligands as follows, [Co2(BP)(tpa)2](PF6)2(1), [Co2(BP)(tpa)2](PF6)3(2), [Co2(BP)(bpqa)2](PF6)2(3), [Co2(BP)(pbqa)2](PF6)2(4), and [Co2(BP)(tqa)2](PF6)2(5). After a one-electron oxidation reaction of complex (1), complex (2), was isolated as a mixed valence state lsCoIII-[SQ-Cat]-lsCoIII, with an absorption intensity of about 1370 nm (intervalence charge transfer (IVCT) bands) in CH3CN solution. In addition, an investigation of the magnetic properties of the dinuclear Co complex (3) with SQUID showed that theχMTvalue gradually increased as the temperature increased from 280 to 380 K. Studies in the solid and solution states using electronic spectra, cyclic voltammetry and SQUID for the above complexes provide clear evidence for three different charge distributions: complexes (1) and (3) are CoIII-[Cat-Cat]-CoIII, complex (2) is CoIII-[Sq-Cat]-CoIII, complexes (4) and (5) are CoII-[Sq-Sq]-CoII. Of the five cobalt dinuclear complexes, only complex (3) shows evidence of the temperature dependence of the charge distribution, displaying a thermally induced valence tautomeric transition from the lsCoIII-[Cat-Cat]-lsCoIIIto hsCoII-[Sq-Sq]-hsCoIIin both solid and solution states. However, this valence tautomeric step is incomplete at 380 K, with the?χMT?value of hsCoII-[Sq-Sq]-hsCoII. This suggests that the steric hindrance of the quinolyl rings around the Co ion produces a coordination atmosphere that is weaker than that observed with pyridyl rings, which facilitates a change in the CoIIIions to CoII
Syntheses, structure and properties of dinuclear Co complexes with bis(catecholate) ligands – Effect of a quinoline ring in the terminal group
Suenaga, Yusaku,Mibu, Takuto,Okubo, Takashi,Maekawa, Masahiko,Kuroda-Sowa, Takayoshi
, p. 480 - 485 (2019/08/26)
Two types of biscatechol, namely H4L1 (5,5′-(buta-1,3-diyne-1,4-diyl)bis(3-t-butylcatechol)) and H4L2 (5,5′-(ethyne-1,2-diyl)bis(3-t-butylcatechol)) were synthesized. In these ligands, two redox active catechol moieties are connected by one or two triple bonds. Also, tpa (tris(2-pyridylmethyl) amine), bpqa (bis(2-pyridylmethyl)(2-quinolylmethyl)amine) and pbqa ((2-pyridylmethyl)bis(2-quinolylmethyl)amine) were synthesized as terminal ligands of the tetracoordinated tripod type. In total, six dinuclear Co complexes were synthesized from these biscatechol and terminal ligands as follows: [Co2(L1)(tpa)2](BF4)2 (1), [Co2(L1)(bpqa)2](PF6)2 (2), [Co2(L1)(pbqa)2](PF6)2 (3), [Co2(L2)(tpa)2](BF4)2 (4), [Co2(L2)(bpqa)2](PF6)2 (5), [Co2(L2)(pbqa)2](PF6)2 (6). Of the six dinuclear Co complexes, complex 6, which was isolated as a mixed valent state CoII(HS)-[SQ-Cat]-CoIII(LS) compound, showed an absorption intensity at around 703 nm (MLCT bands) that increased with increasing temperature in acetonitrile solution. In addition, an investigation of the magnetic properties of the complex 6 with SQUID showed that the χMT value gradually increased as the temperature increased from 150 to 380 K. This suggests that a transition from CoIII(LS) (S = 0) to CoII(HS) (S = 3/2) accompanies the temperature rise. This means the steric hindrance and electronic effect of the quinolyl groups around the Co ion produce a coordination atmosphere weaker than that of pyridyl groups, with the result that the CoIII ions easily convert to CoII ions.
Synthesis and use of ortho-(branched alkoxy)-tert-butoxybenzenes
Rast, Slavko,Stephan, Michel,Mohar, Barbara
supporting information, p. 6815 - 6818 (2013/01/15)
A series of sterically hindered o-(branched alkoxy)-tert-butoxybenzenes was efficiently prepared in good yields owing to a new practical and simple preparation of o-tert-butoxyphenol starting from catechol and isobutene. Use of DMF di-tert-butyl acetal reagent instead of isobutene/H2SO 4 (cat.) for O-tert-butylation was very convenient in case of ortho bulky phenols affording the corresponding tert-butyl ethers in high yield and purity. This general route proved to be useful since no reliable access was available to o-di-t-BuO-substituted arenes. Application to the synthesis of congested phosphorus-based compounds is presented.
Alkylation of pyrocatechol in tert-butyl alcohol-sulfuric acid-benzene
Vol'eva,Prokof'eva,Belostotskaya,Komissarova,Gorbunov,Kurkovskaya
, p. 1310 - 1312 (2011/12/05)
Alkylation of pyrocatechol with tert-butyl alcohol in benzene in the presence of sulfuric acid gave 3,5-di-tert-butylbenzene-1,2-diol in a higher yield than in analogous reaction with tert-butyl alcohol. This result was rationalized by reduction of inhibitory effect of liberated water, formation of heterogeneous system, and occurrence of the alkylation process in nonpolar organic phase. Intermediate products were identified and found to undergo intra- and intermolecular tert-butyl group transfer with formation of more stable 3,5-di-tert-butylbenzene-1,2-diol. The formation of p-di-tert-butylbenzene indicated participation of benzene in crossalkylation processes. Pleiades Publishing, Ltd., 2011.
Nitronyl nitroxide radicals as organic memory elements with both n- and p-type properties
Lee, Junghyun,Lee, Eunkyo,Kim, Sangkwan,Bang, Gyeong Sook,Shultz, David A.,Schmidt, Robert D.,Forbes, Malcolm D. E.,Lee, Hyoyoung
, p. 4414 - 4418 (2011/06/22)
Can't fight the SEEPR: Simultaneous electrochemical electron paramagnetic resonance reveals that a molecule containing the nitronyl nitroxide (NN) radical (structure and red layer) is redox-active, with switchability between oxidized and reduced states. An organic NN radical device utilizes the dual p- and n-type properties in a memory device. Copyright
A comparative study of the synthesis of 3-substituted catechols using an enzymatic and a chemoenzymatic method
Berberian,Allen,Sharma,Boyd,Hardacre
, p. 727 - 739 (2008/02/09)
A series of cis-dihydrodiol metabolites, available from the bacterial dioxygenase-catalysed oxidation of monosubstituted benzene substrates using Pseudomonas putida UV4 , have been converted to the corresponding catechols using both a heterogeneous catalyst (Pd/c) and a naphthalene cis-diol dehydrogenase enzyme present in whole cells of the recombinant strain Escherichia coli DH5α(pUC129: nar B). A comparative study of the merits of both routes to 3-substituted catechols has been carried out and the two methods have been found to be complementary. A similarity in mechanism for catechol formation under both enzymatic and chemoenzymatic conditions, involving regioselective oxidation of the hydroxyl group at C-1, has been found using deuterium labelled toluene cis-dihydrodiols. The potential, of combining a biocatalytic step (dioxygenase-catalysed cis-dihydroxylation) with a chemocatalytic step (Pd/C-catalysed dehydrogenation), into a one-pot route to catechols, from the parent substituted benzene substrates, has been realised.
An expedient one-pot entry to catecholestrogens and other catechol compounds via IBX-mediated phenolic oxygenation
Pezzella, Alessandro,Lista, Liliana,Napolitano, Alessandra,D'Ischia, Marco
, p. 3541 - 3544 (2007/10/03)
A one-pot procedure for the preparation of catecholestrogens in over 90% yield is reported, involving oxygenation of 17β-estradiol or estrone with o-iodoxybenzoic acid (IBX) followed by reduction with methanolic NaBH 4. The procedure, which was extended to the o-hydroxylation of a number of representative phenols in good-to-high yields, expands significantly the scope of phenolic oxidation mediated by IBX.
Substituent effects on the benzene ring. Determination of the intramolecular interactions of substituents in tert-alkyl-substituted catechols from thermochemical measurements
Verevkin, Sergey P.,Schick, Christoph
, p. 946 - 952 (2007/10/03)
Chemical equilibria of reactions of transalkylation among tert-butylphenols and tert-butylcatechols in the liquid phase were investigated in the temperature range 373-483 K. The molar enthalpies of fusion ΔcrlH°m of the catechol, 4-tert-butylcatechol, and 3,5-di-tert-butylcatechol were measured by DSC. The standard (p° = 0.1 MPa) molar enthalpies of formation ΔfH°m (cr) at the temperature T = 298.15 K were measured by means of combustion calorimetry for 4-tert-butylcatechol and 3,5-di-tert-butylcatechol. The standard molar enthalpies of sublimation of these compounds, and also the enthalpy of vaporization of 3-tert-butylcatechol, were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The measured reaction enthalpies were utilized for reconciliation of calorimetrically derived standard molar enthalpies of formation of tert-butyl-substituted phenols and catechols, as a stringent test of thermodynamic consistency of results derived from the diverse techniques employed in this work. Resulting values of ΔfH°m(g) of tert-butylcatechols were obtained at the temperature T = 298.15 K and used to derive their strain enthalpies. The intramolecular interactions of the substituents were discussed in terms of deviations of ΔfH°m(g) from the group additivity rules. No peculiarities in the interaction energy among alkyl groups and the hydroxyl groups in the ortho-, para-, and meta-positions of alkylcatechols in comparison with those of alkyl-substituted phenols were detected. Thus, no new parameters are needed for the prediction of the ΔfH°m(g) values of alkylcatechols by using the group-additive procedure.
Elucidation of the catalytic mechanisms of the non-haem iron-dependent catechol dioxygenases: Synthesis of carba-analogues for hydroperoxide reaction intermediates
Winfield, Christopher J.,Al-Mahrizy, Zeyana,Gravestock, Michael,Bugg, Timothy D.H.
, p. 3277 - 3289 (2007/10/03)
The catalytic mechanisms of the non-haem iron-dependent intradiol and extradiol catechol dioxygenases are thought to involve transient hydroperoxide reaction intermediates, formed by reaction of a catechol substrate with dioxygen. The synthesis of carba-analogues of these intermediates is described in which the hydroperoxide functional group (-OOH) is replaced by a hydroxymethyl group (-CH2OH), and the cyclohexadienone skeleton simplified to a cyclohexanone. Analogues of the "proximal" hydroperoxide in which the hydroxymethyl group was positioned axially with respect to the ring were found to act as reversible competitive inhibitors (Ki 0.7-7.6 mM) for the extradiol enzyme 2,3-dihydroxyphenylpropionate 1,2-dioxygenase (MhpB) from Escherichia coli, whereas analogues in which the hydroxymethyl group was positioned equatorially showed no inhibition. In contrast, assays versus the intradiol-cleaving protocatechuate 3,4-dioxygenase from Pseudomonas sp. showed inhibition only by an analogue containing an equatorial hydroxymethyl group (IC50 9.5 mM). These data support the existence of a proximal hydroperoxide intermediate in the extradiol catechol dioxygenase mechanism, and suggest that the conformation adopted by the hydroperoxide reaction intermediate may be an important determinant in the reaction specificity of the extradiol and intradiol dioxygenases. The Royal Society of Chemistry 2000.
