192819-69-5Relevant academic research and scientific papers
Dinuclear zinc(II) complexes with hydrogen bond donors as structural and functional phosphatase models
Bosch, Simone,Comba, Peter,Gahan, Lawrence R.,Schenk, Gerhard
, p. 9036 - 9051 (2014)
It is becoming increasingly apparent that the secondary coordination sphere can have a crucial role in determining the functional properties of biomimetic metal complexes. We have therefore designed and prepared a variety of ligands as metallo-hydrolase mimics, where hydrogen bonding in the second coordination sphere is able to influence the structure of the primary coordination sphere and the substrate binding. The assessment of a structure-function relationship is based on derivates of 2,6-bis{[bis(pyridin-2-ylmethyl)amino]methyl}-4- methylphenol (HBPMP = HL1) and 2-{[bis(pyridin-2-ylmethyl)amino] methyl}-6-{[(2-hydroxybenzyl)(pyridin-2-ylmethyl)amino]methyl}-4-methylphenol (H2BPBPMP = H2L5), well-known phenolate-based ligands for metallo-hydrolase mimics. The model systems provide similar primary coordination spheres but site-specific modifications in the secondary coordination sphere. Pivaloylamide and amine moieties were chosen to mimic the secondary coordination sphere of the phosphatase models, and the four new ligands H3L2, H3L3, HL4, and H4L6 vary in the type and geometric position of the H-bond donors and acceptors, responsible for the positioning of the substrate and release of the product molecules. Five dinuclear ZnII complexes were prepared and structurally characterized in the solid, and four also in solution. The investigation of the phosphatase activity of four model complexes illustrates the impact of the H-bonding network: the Michaelis-Menten constants (catalyst-substrate binding) for all complexes that support hydrogen bonding are smaller than for the reference complex, and this generally leads to higher catalytic efficiency and higher turnover numbers.
SpiroZin1: A reversible and pH-insensitive, reaction-based, red-fluorescent probe for imaging biological mobile zinc
Rivera-Fuentes, Pablo,Lippard, Stephen J.
, p. 1238 - 1243 (2014)
A reversible, reaction-based sensor for biological mobile zinc was designed, prepared, and characterized. The sensing mechanism of this probe is based on the zinc-induced, ring-opening reaction of spirobenzopyran to give a cyanine fluorophore that emits i
Synthesis, Crystal Structures, and Magnetic and Catalytic Studies on a Linear Trinuclear MnII3 Complex
Dutta, Arpan,Biswas, Surajit,Escuer, Albert,Dolai, Malay,Ghosh, Subhadip,Ali, Mahammad
, p. 1440 - 1447 (2015)
An almost linear (3(L)(N3)4]·2 H2O (1) of a decacoordinating N8O2 donor ligand, H2L, was synthesized and structurally characterized by means of single-crystal X-ray crystallography and mass spectrometry. All the MnII centers are in pseudo-octahedral geometry and wrapped by a single decacoordinating N8O2 donor ligand. The central manganese atom (Mn2) is connected to two terminal manganese (Mn1 and Mn3) atoms by two bridging phenolate O atoms and two bridging azide N atoms. Compound 1 is the first example of a linear trinuclear model to show pronounced epoxidation of olefins by tert-butylhydroperoxide (TBHP) with a turnover number (TON) greater than 950. Though epoxidation of olefins by m-chloroperbenzoic acid (m-CPBA) was found to be complete within 20 minutes of mixing, the conversion was not more than 40 % and corresponding alcohols were found to be major products, whereas with H2O2 as oxidant there was no visible catalytic epoxidation of olefins. Furthermore, the compound was characterized by temperature-dependent magnetic susceptibility measurements and a total spin ground state of St=15/2 was found.
A geometrically asymmetric dinuclear copper(II) complex derived from a new unsymmetric 'end-off' compartmental ligand
Uozumi, Syunsuke,Ohba, Masaaki,Okawa, Hisashi,Fenton, David E.
, p. 673 - 674 (1997)
An unsymmetrical 'end-off' compartmentai lignd, 2-[N,N-di(2-pyridylmethyl)aminomethyl]-6-{N-[2-(dimethylamino)-ethyl] iminomethyl}-4-methylphenol, forms a μ-phenoxo-μ-hydroxodicopper(II) core complex which has a geometric asymmetry being comprised of squa
The dicopper(II) complex of the novel asymmetric dinucleating ligand Hpy3asym as a structural model of catechol oxidase
Koval, Iryna A.,Pursche, Daniel,Stassen, Arno F.,Gamez, Patrick,Krebs, Bernt,Reedijk, Jan
, p. 1669 - 1674 (2003)
The new asymmetric dinucleating ligand 2-{[bis(2- pyridinylmethyl)amino]methyl}-4-methyl-6-{[(2-pyridinyl- methyl)amino]methyl}phenol (Hpy3asym) has been designed in order to model the type-3 active site of the copper proteins. This phenol-based "end-off" compartmental ligand has one tridentate and one didentate arm attached to the 2- and 6- positions of the phenolic ring, respectively. A dinuclear copper(II) nitrate complex with this ligand [Cu2(py3asym)- (H2O)1.5(NO3)2]NO3 has been obtained and structurally characterized. In this complex both copper ions have a distorted octahedral geometry and are endogenously bridged by the phenolic oxygen atom of the deprotonated ligand. The complex shows a donor-atom asymmetry that consists of an N3O3 donor set for the Cu1 ion and an N2O4 donor set for the Cu2 ion. The electrochemical, magnetic behavior and spectral properties of the complex are discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
2-{[Bis(2-pyridylmethyl)amino]-methyl}-6-[(2-hydroxy-anilino)-methyl] -4-methyl-phenol: A novel binucleating asymmetric ligand as a precursor to synthetic models for metalloenzymes
Bortoluzzi, Adailton J.,Neves, Ademir,Rey, Nicolas A.
, p. o84-o86 (2007)
The title compound (H2 L), C27H28N4O2, is an asymmetric binucleating ligand with well defined soft (N3O-donor) and hard (NO2-donor) sides. H2 L was designed as a ligand for the preparation of heterodinuclear mixed-valence M III/M′II
Deprotonation in Mixed-Valent Diiron(II,III) Complexes with Aniline or Benzimidazole Ligands
Gouré, Eric,Carboni, Michae¨l,Troussier, Angélique,Dubourdeaux, Patrick,Clémancey, Martin,Gon, Nathalie,Balasubramanian, Ramachandran,Lebrun, Colette,Pécaut, Jacques,Blondin, Geneviève,Latour, Jean-Marc
, p. 6257 - 6266 (2015/07/15)
We have previously investigated cis/trans isomerization processes in phenoxido-bridged mixed-valent FeIIFeIII complexes that contain either one aniline or one anilide ligand. In this work, we compare the properties of similar complexes bearing one terminal protic ligand, either aniline or 1H-benzimidazole. Whatever the ligand, 1H NMR spectroscopy clearly evidences that the complexes are present in CH3CN as a mixture of cis- and trans-isomers in a close to 1:1 ratio. We show here that addition of NEt3 indeed allows the deprotonation of these ligands, the resulting complexes bearing either anilide or benzimidazolide that are coordinated to the ferric site. The latter are singular examples of a high-spin ferric ion coordinated to a benzimidazolide ligand. Whereas the trans-isomer of the anilide complex is the overwhelming species, benzimidazolide species are mixtures of cis- and trans-isomers in equal proportions. Moreover, cyclic voltammametry studies show that FeIIIFeIII complexes with 1H-benzimidazole are more stable than their aniline counterparts, whereas the reverse is observed for the deprotonated species. (Graph Presented).
Novel CuII-MII-CuII (M = Cu or Ni) trinuclear and [Na i 2 Cu II 6] hexanuclear complexes assembled by bi-compartmental ligands: Syntheses, structures, magnetic and catalytic studies
Biswas, Surajit,Dutta, Arpan,Dolai, Malay,Bhowmick, Indrani,Rouzières, Mathieu,Clérac, Rodolphe,Panja, Anangamohan,Ali, Mahammad
, p. 9426 - 9438 (2015/06/16)
In the present work, two compartmental ligands H2L1 and H2L2 were in situ generated during the syntheses of new trinuclear complexes, [Cu2Ni(L1)(2,2′-bpy)2(NO3)2][ClO4]2 (5), [Cu3(L2)(NO3)2][ClO4]2 (6), and [Cu3(L2)(NCS)2(NO3)]+ that co-crystallize in 7 with a [Cu6(L2)2Na2(NO3)6(NCS)4] unit to give the final molecular formula [Cu6(L2)2Na2(NO3)6(NCS)4][Cu3(L2)(NCS)2(NO3)]2(NO3)2·5H2O (7). The magnetic property studies of 5-7 revealed weak CuII-CuII ferromagnetic interactions in compound 6 (JCu-Cu/kB = +1.4(1) K) and 7 (JCu-Cu/kB = +1.6) while in intranuclear CuII-NiII-CuII compound 5, the magnetic coupling between two CuII ions is switched off by the diamagnetic square planar NiII bridge. The catalytic epoxidation of two olefins, namely styrene and cyclooctene, by tert-BuOOH (TBHP) was also explored in the presence of a catalytic amount of 5, 6 or 7 in MeCN. For styrene oxidation, 5 exhibited ～57% styrene epoxide selectively (conversion ～37%) with a TON of about 925 along with benzaldehyde (～43%), whereas 6 exhibited conversion up to ～63% (TON ～ 1575) with a good selectivity towards epoxide (～71%). For compound 7, this conversion is more important (TON ～ 8108) probably due to the presence of more active sites involved in the epoxidation. The concerted path was found to be operative for styrene oxidation while a radical path was suggested for the oxidation of cyclooctene.
Synthesis, structural, magnetic, and redox properties of asymmetric diiron complexes with a single terminally bound phenolate ligand. Relevance to the purple acid phosphatase enzymes
Lambert, Elisabeth,Chabut, Barbara,Chardon-Noblat, Sylvie,Deronzier, Alain,Chottard, Geneviève,Bousseksou, Azzedine,Tuchagues, Jean-Pierre,Laugier, Jean,Bardet, Michel,Latour, Jean-Marc
, p. 9424 - 9437 (2007/10/03)
New asymmetrical ligands (H2L) have been synthesized to provide both a bridging and a terminal phenolate to a pair of iron ions in order to mimic the binding of a single terminal tyrosinate at the diiron center of the purple acid phosphatases. H2L1 is 2-(bis(2-pyridylmethyl) amino)methyl]-6-[((2-pyridylmethyl)(2-phenol)amino)methyl] 4-methylphenol and H2L'1 and H2L2 are obtained by replacing the 2-phenol group by the 5-nitro-2-phenol and the 6-methyl-2-phenol residues, respectively. A series of mixed valence diiron complexes [Fe(II)Fe(III)L(X)2](Y) have been obtained where (X)2 is the dianion of m-phenylenedipropionate or (H2PO4)2 and Y = BPh4 or PF6 (L = L1, 1a (X)2 = mpdp, Y = BPh4, 1b: (X)2 = (OAc)2, Y = BPh4, 1c: (X)2 = (OBz)2, Y = BPh4, 1d: (X)2 = (H2PO4)2 Y = PF6; L = L'1: 1'a(X)2 mpdp, Y = BPh4; L = L2: 2c: (X)2 = (OBz)2, Y = BPh4, 2d: (X)2 (H2PO4)2, Y = PF6. Diferric complexes have been obtained also either by direct synthesis or by iodine oxidation of the mixed valence precursor (L = L1, 3a (X)2 = mpdp, Y = BPh4, 3d: (X)2 = (H2PO4)2, Y = PF6; L = L2, 4d: (X)2 = (H2PO4)2, Y = PF6. Complex 1a [Fe(II)Fe(III)L(mpdp)](BPh4)) has been characterized by X-ray diffraction techniques. 1a crystallizes in the monoclinic space group P21/a with the following unit cell parameters: a = 22.038 (9) ?, b = 16.195 (8) ?, c = 16.536 (7) ?, β = 97.26 (1)°, Z = 4. The significant differences in the Fe-O bond lengths indicate that the metal centers are ordered. The complexes have been studied by electronic spectral, resonance Raman, magnetic susceptibility, Mossbauer, NMR, and electrochemical techniques. Mossbauer and NMR spectroscopies concur to probe that the valences of the mixed valence compounds are trapped in solution as well as in the solid state at room temperature. The electronic spectrum of the mixed-valence compounds are dominated by a charge transfer transition in the 400-600 nm domain which moves to the 550-660 nm range upon oxidation to the diferric state. In addition they exhibit a weak and broad intervalence transition close to 1100 nm. Electrochemical studies show that the systems exist in the three redox states Fe(II)Fe(II)/Fe(II)Fe(III)/Fe(III)Fe(III). Moreover they show that the introduction of the terminal phenol group results in a thermodynamic destabilization of the diferrous state higher than the stabilization of the diferric state. An expanded stability domain of the mixed valence state is therefore observed which is probably due mostly to the asymmetry of the compounds. In addition a chemical destabilization of the reduced state of 1a, 1c, and 1'a is observed. Comparison of the carboxylate and phosphate derivatives leads to attribute it to the partial dissociation in solution of the carboxylate oxygen trans to the phenolate. The latter feature bears an intrinsic resemblance with the dissociation of iron which is observed when purple acid phosphatases are reduced by dithionite. These studies clearly show the importance of tyrosine binding on the redox properties of the PAP enzymes. This questions the relationship of such a redox specificity with a hydrolytic function and raises the possibility that the latter may be redox regulated or that another (redox based) function is actually involved, possibly in line with the ability of the enzymes to react with peroxides.
