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Milenković MR, Čobeljić B, Anđelković K, Turel I. Molecular Structures and Spin‐States of Pseudohalide Metal Complexes with Hydrazones of Girard's T Reagent. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201701387] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Milica R. Milenković
- Faculty of Chemistry University of Belgrade Studentski trg 12–16 11000 Belgrade Serbia
| | - Božidar Čobeljić
- Faculty of Chemistry University of Belgrade Studentski trg 12–16 11000 Belgrade Serbia
| | - Katarina Anđelković
- Faculty of Chemistry University of Belgrade Studentski trg 12–16 11000 Belgrade Serbia
| | - Iztok Turel
- Faculty of Chemistry and Chemical Technology University of Ljubljana Večna pot 113 1000 Ljubljana Slovenia
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Synthesis, characterization and crystal structures of two pentagonal-bipyramidal Fe(III) complexes with dihydrazone of 2,6-diacetylpyridine and Girard's T reagent. Anticancer properties of various metal complexes of the same ligand. J Inorg Biochem 2017; 174:137-149. [PMID: 28672143 DOI: 10.1016/j.jinorgbio.2017.06.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 05/19/2017] [Accepted: 06/22/2017] [Indexed: 12/11/2022]
Abstract
In this work synthesis, characterization and crystal structures of two isothiocyanato Fe(III) complexes with 2,2'-[2,6-pyridinediylbis(ethylidyne-1-hydrazinyl-2-ylidene)]bis[N,N,N-trimethyl-2-oxoethanaminium] dichloride (H2LCl2) ligand, with composition [FeL(NCS)2]SCN·2H2O and [FeL(NCS)2]2[Fe(H2O)(NCS)5]·4H2O, has been reported. Both iron(III) complexes possess the same pentagonal-bipyramidal complex cation, while the nature of their anions depends on mole ratio of NH4SCN and FeCl3·6H2O used in reaction. Cytotoxic activity of new Fe(III) complexes, as well as of previously synthesized isothiocyanato Co(II), Ni(II), Mn(II), Zn(II) and Cd(II) complexes with the same ligand, was tested against five human cancer cell lines (HeLa, MDA-MB-453, K562, LS174 and A549) and normal cell line MRC-5. The best activity was observed in the case of Fe(III), Co(II) and Cd(II) complexes. The investigation of potential of these complexes to induce HeLa and K562 cell cycle perturbations was also evaluated. Mechanism of cell death mode was elucidated on the basis of morphological changes of HeLa cells as well as identification of target caspases. It was established that DNA damage could be responsible for the activity of Fe(III) and Co(II) complexes. SYNOPSIS Pentagonal-bipyramidal Fe(III) complexes with dihydrazone of 2,6-diacetylpyridine and Girard's T reagent have been synthesized and characterized. Cytotoxic activity of Fe(III) complexes and Co(II), Ni(II), Mn(II), Zn(II) and Cd(II) complexes with the same ligand was tested. The best activity was observed in the case of Fe(III), Co(II) and Cd(II) complexes.
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Bulhac I, Deseatnic-Ciloci A, Bourosh P, Tiurina J, Bologa O, Bivol C, Clapco S, Verejan A, Labliuc S, Danilescu O. Structure and Some Biological Properties of Fe(III) Complexes with Nitrogen-Containing Ligands. CHEMISTRY JOURNAL OF MOLDOVA 2016. [DOI: 10.19261/cjm.2016.11(1).05] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Study of a novel hepta-coordinated FeIII bimetallic complex with an unusual 1,2,4,5-tetrazine-ring opening. Polyhedron 2016. [DOI: 10.1016/j.poly.2015.11.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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5
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Correia I, Adão P, Roy S, Wahba M, Matos C, Maurya MR, Marques F, Pavan FR, Leite CQF, Avecilla F, Costa Pessoa J. Hydroxyquinoline derived vanadium(IV and V) and copper(II) complexes as potential anti-tuberculosis and anti-tumor agents. J Inorg Biochem 2014; 141:83-93. [PMID: 25226436 DOI: 10.1016/j.jinorgbio.2014.07.019] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 07/25/2014] [Accepted: 07/29/2014] [Indexed: 12/31/2022]
Abstract
Several mixed ligand vanadium and copper complexes were synthesized containing 8-hydroxyquinoline (8HQ) and a ligand such as picolinato (pic(-)), dipicolinato (dipic(2-)) or a Schiff base. The complexes were characterized by spectroscopic techniques and by single-crystal X-ray diffraction in the case of [V(V)O(L-pheolnaph-im)(5-Cl-8HQ)] and [V(V)O(OMe)(8HQ)2], which evidenced the distorted octahedral geometry of the complexes. The electronic absorption data showed the presence of strong ligand to metal charge transfer bands, significant solvent effects, and methoxido species in methanol, which was further confirmed by (51)V-NMR spectroscopy. The structures of [Cu(II)(dipic)(8HQ)]Na and [V(IV)O(pic)(8HQ)] were confirmed by EPR spectroscopy, showing only one species in solution. The biological activity of the compounds was assessed through the minimal inhibitory concentration (MIC) of the compounds against Mycobacterium tuberculosis (Mtb) and the cytotoxic activity against the cisplatin sensitive/resistant ovarian cells A2780/A2780cisR and the non-tumorigenic HEK cells (IC50 values). Almost all tested vanadium complexes were very active against Mtb and the MICs were comparable to, or better than, the MICs of drugs, such as streptomycin. The activity of the complexes against the A2780 cell line was dependent on incubation time presenting IC50 values in the 3-14 μM (at 48 h) range. In these conditions, the complexes were significantly (*P<0.05-**P<0.001) more active than cisplatin (22 μM), in the A2780 cells and even surpassing its activity in the cisplatin-resistant cells A2780cisR (2.4-8 μM vs. 75.4; **P<0.001). In the non-tumorigenic HEK cells poor selectivity toward cancer cells for most of the complexes was observed, as well as for cisplatin.
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Affiliation(s)
- Isabel Correia
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Pedro Adão
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Somnath Roy
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Mohamed Wahba
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; Inorganic Chemistry Dep., National Research Center, El Buhouth St., Dokki, Cairo, Egypt
| | - Cristina Matos
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Mannar R Maurya
- Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247 667, India
| | - Fernanda Marques
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10,km 139.7, 2695-066 Bobadela LRS, Portugal
| | - Fernando R Pavan
- Faculdade de Ciências Farmacêuticas, UNESP, C.P. 582, Araraquara, SP 14801-902, Brazil
| | - Clarice Q F Leite
- Faculdade de Ciências Farmacêuticas, UNESP, C.P. 582, Araraquara, SP 14801-902, Brazil
| | - Fernando Avecilla
- Departamento de Química Fundamental, Universidade da Coruña, Campus de A Zapateira, 15071 A Coruña, Spain
| | - João Costa Pessoa
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
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Stepanović S, Andjelković L, Zlatar M, Andjelković K, Gruden-Pavlović M, Swart M. Role of Spin State and Ligand Charge in Coordination Patterns in Complexes of 2,6-Diacetylpyridinebis(semioxamazide) with 3d-Block Metal Ions: A Density Functional Theory Study. Inorg Chem 2013; 52:13415-23. [DOI: 10.1021/ic401752n] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
| | | | | | | | | | - Marcel Swart
- Institut de Química
Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Facultat de Ciències, 17071 Girona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís
Companys 23, 08010 Barcelona, Spain
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Aljahdali M, El-Sherif AA, Shoukry MM, Hosny WM, Abd-Elmoghny MG. Complex Formation Equilibria of Unusual Seven Coordinate Fe(III) Complexes with DNA Constituents. J SOLUTION CHEM 2013. [DOI: 10.1007/s10953-013-0055-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Gutman CT, Guzei IA, Brunold TC. Structural, spectroscopic, and computational characterization of the azide adduct of Fe(III)(2,6-diacetylpyridinebis(semioxamazide)), a functional analogue of iron superoxide dismutase. Inorg Chem 2013; 52:8909-18. [PMID: 23875582 DOI: 10.1021/ic401098x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have prepared and thoroughly characterized, using X-ray crystallographic, spectroscopic, and computational methods, the diazide adduct of [Fe(III)(dapsox)(H2O)2](+) [dapsox = 2,6-diacetylpyridinebis(semioxamazide)], (1), a low-molecular weight, functional analogue of iron superoxide dismutase (FeSOD). The X-ray crystal structure of the dimeric form of 1, (Na[Fe(III)(dapsox)(N3)2]·DMF)2 (2) shows two axially coordinated, symmetry inequivalent azides with differing Fe-N3 bond lengths and Fe-N-N2 bond angles. This inequivalence of the azide ligands likely reflects the presence of an interdimer hydrogen bonding interaction between a dapsox NH group and the coordinated nitrogen of one of the two azide ligands. Resonance Raman (rR) data obtained for frozen aqueous solution and solid-state samples of 2 indicate that the azides remain inequivalent in solution, suggesting that one of the azide ligands of 1 engages in an intermolecular hydrogen bonding interaction with a water molecule. Density functional theory (DFT) and time-dependent DFT calculations have been used to study two different computational models of 1, one using coordinates taken from the X-ray crystal structure of 2, and the other generated via DFT geometry optimization. An evaluation of these models on the basis of electronic absorption, magnetic circular dichroism, and rR data indicates that the crystal structure based model yields a more accurate electronic structure description of 1, providing further support for the proposed intermolecular hydrogen bonding of 1 in the solid state and in solution. An analysis of the experimentally validated DFT results for this model reveals that the azides have both σ- and π-bonding interactions with the Fe(III) center and that more negative charge is located on the Fe-bound, rather than on the terminal, nitrogen atom of each azide. These observations are reminiscent of the results previously reported for the azide adduct of FeSOD and provide clues regarding the origin of the high catalytic activity of Fe-dapsox for superoxide disproportionation.
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Affiliation(s)
- Craig T Gutman
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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Gutman CT, Brunold TC. Spectroscopic and computational studies of a small-molecule functional mimic of iron superoxide dismutase, iron 2,6-diacetylpyridinebis(semioxamazide). Inorg Chem 2012; 51:12729-37. [PMID: 23140435 DOI: 10.1021/ic301547z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron 2,6-diacetylpyridinebis(semioxamazide) (Fe(dapsox)) is a heptacoordinate pentagonal bipyramidal, functional mimic of iron-dependent superoxide dismutase that has been well-characterized on the basis of kinetics and mechanistic studies; however, prior to our studies, its electronic structure had yet to be examined. This paper details our initial characterization of Fe(dapsox) in both its reduced and oxidized states, by electronic absorption (Abs) and low-temperature magnetic circular dichroism spectroscopies. Density functional theory (DFT) geometry optimizations have yielded models in good agreement with the published crystal structures. Time-dependent DFT and INDO/S-CI calculations performed on these models successfully reproduce the experimental Abs spectra and identify intense, low-energy transitions in the reduced complex (Fe(II)(H(2)dapsox)) as metal-to-ligand charge transfer transitions, suggesting the presence of π-backbonding in this complex. This backbonding, along, with the proton uptake accompanying metal ion reduction, provides a compelling mechanism by which the metal-centered redox potential is correctly tuned for catalytic superoxide disproportionation.
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Affiliation(s)
- Craig T Gutman
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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Schmidt H, Asztalos A, Bok F, Voigt W. New iron(III) nitrate hydrates: Fe(NO3)3·xH2O with x = 4, 5 and 6. Acta Crystallogr C 2012; 68:i29-33. [PMID: 22669180 DOI: 10.1107/s0108270112015855] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 04/11/2012] [Indexed: 11/11/2022] Open
Abstract
Crystals of the title compounds were grown from their hydrous melts or solutions. The crystal structure of iron(III) trinitrate hexahydrate {hexaaquairon(III) trinitrate, [Fe(H(2)O)(6)](NO(3))(3)} is built up from [Fe(H(2)O)(6)](2+) octahedra and nitrate anions connected via hydrogen bonds. In iron(III) trinitrate pentahydrate {pentaaquanitratoiron(III) dinitrate, [Fe(NO(3))(H(2)O)(5)](NO(3))(2)}, one water molecule in the coordination octahedron of the Fe(III) atom is substituted by an O atom of a nitrate group. Iron(III) trinitrate tetrahydrate {triaquadinitratoiron(III) nitrate monohydrate, [Fe(NO(3))(2)(H(2)O)(3)]NO(3)·H(2)O} represents the first example of a simple iron(III) nitrate with pentagonal-bipyramidal coordination geometry, where two bidentate nitrate anions and one water molecule form a pentagonal plane.
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Affiliation(s)
- Horst Schmidt
- TU Bergakademie Freiberg, Institute of Inorganic Chemistry, Leipziger Strasse 29, D-09596 Freiberg, Germany.
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Pavan FR, Maia PIS, Leite SR, Deflon VM, Batista AA, Sato DN, Franzblau SG, Leite CQ. Thiosemicarbazones, semicarbazones, dithiocarbazates and hydrazide/hydrazones: Anti – Mycobacterium tuberculosis activity and cytotoxicity. Eur J Med Chem 2010; 45:1898-905. [DOI: 10.1016/j.ejmech.2010.01.028] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 01/11/2010] [Accepted: 01/14/2010] [Indexed: 10/19/2022]
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Guisado-Barrios G, Li Y, Slawin AMZ, Richens DT, Gass IA, Murray PR, Yellowlees LJ, Brechin EK. High spin d5 complexes of tris(6-hydroxymethyl-2-pyridylmethyl)amine (H3L): hepta-coordinated [Mn(H3L)]Cl2and linear trinuclear [Fe3L2](ClO4)3. Dalton Trans 2008:551-8. [DOI: 10.1039/b712188a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ivanović-Burmazović I. Catalytic dismutation vs. reversible binding of superoxide. ADVANCES IN INORGANIC CHEMISTRY 2008. [DOI: 10.1016/s0898-8838(08)00003-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Liu GF, Filipović M, Heinemann FW, Ivanović-Burmazović I. Seven-Coordinate Iron and Manganese Complexes with Acyclic and Rigid Pentadentate Chelates and Their Superoxide Dismutase Activity. Inorg Chem 2007; 46:8825-35. [PMID: 17880209 DOI: 10.1021/ic7012039] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reactions of seven-coordinate [Fe(III)(dapsox)(H(2)O)(2)]ClO(4).H(2)O (1), [Fe(II)(H(2)dapsox)(H(2)O)(2)](NO(3))(2).H(2)O (2), and [Mn(II)(H(2)dapsox)(CH(3)OH)(H(2)O)](ClO4)2(H2O) (3) complexes of the acyclic and rigid pentadentate H(2)dapsox ligand [H2dapsox = 2,6-diacetylpyridinebis(semioxamazide)] with superoxide have been studied spectrophotometrically, electrochemically, and by a submillisecond mixing UV/vis stopped-flow in dimethyl sulfoxide (DMSO). The same studies were performed on the seven-coordinate [Mn(II)(Me(2)[15]pyridinaneN(5))(H(2)O)(2)]Cl(2).H(2)O (4) complex with the flexible macrocyclic Me(2)[15]pyridinaneN(5) ligand (Me(2)[15]pyridinaneN(5) = trans-2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),14,16-triene), which belongs to the class of proven superoxide dismutase (SOD) mimetics. The X-ray crystal structures of 2-4 were determined. All complexes possess pentagonal-bipyramidal geometry with the pentadentate ligand in the equatorial plane and solvent molecules in the axial positions. The stopped-flow experiments in DMSO (0.06% of water) reveal that all four metal complexes catalyze the fast disproportionation of superoxide under the applied experimental conditions, and the catalytic rate constants are found to be (3.7 +/- 0.5) x 10(6), (3.9 +/- 0.5) x 10(6), (1.2 +/- 0.3) x 10(7), and (5.3 +/- 0.8) x 10(6) M(-1) s(-1) for 1-4, respectively. The cytochrome c McCord-Fridovich (McCF) assay in an aqueous solution at pH = 7.8 resulted in the IC(50) values (and corresponding kMcCF constants) for 3 and 4, 0.013 +/- 0.001 microM (1.9 +/- 0.2 x 10(8) M(-1) s(-1)) and 0.024 +/- 0.001 microM (1.1 +/- 0.3 x 10(8) M(-1) s(-1)), respectively. IC(50) values from a nitroblue tetrazolium assay are found to be 6.45 +/- 0.02 and 1.36 +/- 0.03 microM for 1 and 4, respectively. The data have been compared with those obtained by direct stopped-flow measurements and discussed in terms of the side reactions that occur under the conditions of indirect assays.
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Affiliation(s)
- Gao-Feng Liu
- Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstrasse 1, 91058 Erlangen, Germany
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Sarauli D, Popova V, Zahl A, Puchta R, Ivanović-Burmazović I. Seven-Coordinate Iron Complex as a Ditopic Receptor for Lithium Salts: Study of Host−Guest Interactions and Substitution Behavior. Inorg Chem 2007; 46:7848-60. [PMID: 17715913 DOI: 10.1021/ic7005056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Interactions between the seven-coordinate tweezerlike [Fe(dapsox)(H2O)2]ClO4 complex (H2dapsox = 2,6-diacetylpyridine-bis(semioxamazide)) with different lithium salts (LiOTf, LiClO4, LiBF4, and LiPF6) in CH3CN have been investigated by electrochemical, spectrophotometric, 7Li and 19F NMR, kinetic, and DFT methods. It has been demonstrated that this complex acts as ditopic receptor, showing spectral and electrochemical ion-pair-sensing capability for different lithium salts. In general, the apparent binding constants for lithium salts increase in the order LiOTf < LiClO4 < LiBF4. From the electrochemical measurements, the apparent lithium salt binding constants for the Fe(III) and Fe(II) forms of the complex have been obtained, suggesting a stronger host-guest interaction with the reduced form of the complex. In the presence of LiPF6, the solution chemistry is more complex because of the hydrolysis of PF6-. The kinetics of the complexation of [Fe(dapsox)(CH3CN)2]+ by thiocyanate at -15 degrees C in acetonitrile in the presence of 0.2 M NBu4OTf shows two steps with the following rate constants and activation parameters: k(1) = 411 +/- 14 M(-1) s(-1); DeltaH(1) not equal = 9 +/- 2 kJ mol(-1); DeltaS1 not equal = -159 +/- 6 J K(-1) mol(-1); k(2) = 52 +/- 1 M(-1) s(-1); DeltaH(2) not equal = 4 +/- 1 kJ mol(-1); DeltaS(2) not equal = -195 +/- 3 J K(-1) mol(-1). The very negative DeltaS not equal values are consistent with an associative (A) mechanism. Under the same conditions but with 0.2 M LiOTf, k1Li and k2Li are 1605 +/- 51 and 106 +/- 2 M(-1) s(-1), respectively. The increased rate constants for the {[Fe(dapsox)(CH3CN)2] x LiOTf}+ adduct are in agreement with an associative mechanism. Kinetic and spectrophotometric titration measurements show stronger interaction between the lithium salt and the anion-substituted forms, [Fe(dapsox)(CH3CN)(NCS)] and [Fe(dapsox)(NCS)2]-, of the complex. These experiments demonstrate that in nonaqueous media lithium salts cannot be simply used as supporting electrolytes, since they can affect the kinetic behavior of the studied complex. DFT calculations revealed that the negatively charged alpha-oxyazine oxygen atoms are responsible for cation binding (electrostatic interactions), whereas the two terminal amide groups bind the anion via hydrogen bonding.
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Affiliation(s)
- David Sarauli
- Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstrasse 1, D-91058 Erlangen, Germany
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Sarauli D, Meier R, Liu GF, Ivanović-Burmazović I, van Eldik R. Effect of pressure on proton-coupled electron transfer reactions of seven-coordinate iron complexes in aqueous solutions. Inorg Chem 2006; 44:7624-33. [PMID: 16212389 DOI: 10.1021/ic0507767] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For the first time, the effect of pressure on proton-coupled electron-transfer reactions of two selected seven-coordinate FeIII/II(H2L)(H2O)2 systems [where H2L = 2,6-diacetylpyridine-bis(semicarbazone) and 2,6-diacetylpyridine-bis(semioxamazide), respectively] was examined. The acid-base equilibria of the different Fe(III/II) systems were investigated by spectrophotometric, potentiometric, and electrochemical titrations. On the basis of the obtained species distributions, the pH intervals in which the different protonated forms of the two studied systems exist were defined. In different pH ranges, a different number of protons (from 0 to 3 protons per electron) can be transferred during the redox process, which affects the change in the overall charge on the complexes. For all the different protonation forms of the studied complexes, the change in the redox potentials with pressure was measured and the redox reaction volume was obtained by high-pressure cyclic voltammetry. The results show that in the case of proton-coupled electron transfer, the reaction volume for the neutralization of protons contributes to the overall reaction volume. A linear correlation between Deltaz2 (change in the square of the charge) and the overall reaction volume of the complexes upon reduction, DeltaVcomplex0, was found. The average value of the intrinsic volume change for the selected seven-coordinate iron complexes was estimated from the intercept of the plot of DeltaVcomplex0 versus Deltaz2 to be 9.2 +/- 0.7 cm3 mol(-1). For the combined redox and protonation processes, the data are discussed in terms of linear correlations between Deltaz2 and the redox and neutralization reaction volumes reported in the literature.
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Affiliation(s)
- David Sarauli
- Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstrasse 1, D-91058 Erlangen, Germany
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Abstract
Cytotoxic activity of four series of coordinated complexes of Zn(II) and Fe(II) with hydrazone/hydrazide ligands against HeLa and B16 cells was evaluated. The ligands N’,N'2- bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide (H2L1) and N’,N'2-bis[(1E)-1-(2-pyridyl) ethylidene]propanedihydrazide (H2L2) and their Zn(II) complexes showed IC50 values in the low micromolar range, while the other ligands and complexes were less active or inactive.
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Ivanović-Burmazović I, Hamza MSA, van Eldik R. Solvent Tuning of the Substitution Behavior of a Seven-Coordinate Iron(III) Complex. Inorg Chem 2006; 45:1575-84. [PMID: 16471968 DOI: 10.1021/ic0514694] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A detailed kinetic study of the substitution behavior of the seven-coordinate [Fe(dapsox)(L)2]ClO4 complex (H(2)dapsox = 2,6-diacetylpyridine-bis(semioxamazide), L = solvent or its deprotonated form) with thiocyanate as a function of the thiocyanate concentration, temperature, and pressure was undertaken in protic (EtOH and acidified EtOH and MeOH) and aprotic (DMSO) organic solvents. The lability and substitution mechanism depend strongly on the selected solvent (i.e., on solvolytic and protolytic processes). In the case of alcoholic solutions, substitution of both solvent molecules by thiocyanate could be observed, whereas in DMSO only one substitution step occurred. For both substitution steps, [Fe(dapsox)(L)2]ClO4 shows similar mechanistic behavior in methanol and ethanol, which is best reflected by the values of the activation volumes (MeOH DeltaV(I) = +15.0 +/- 0.3 cm(3) mol(-1), DeltaV(II) = +12.0 +/- 0.2 cm(3) mol(-1); EtOH DeltaV(I) = +15.8 +/- 0.7 cm(3) mol(-1), DeltaV(II) = +11.1 +/- 0.5 cm(3) mol(-1)). On the basis of the reported activation parameters, a dissociative (D) mechanism for the first substitution step and a D or dissociative interchange (I(d)) mechanism for the second substitution step are suggested for the reaction in MeOH and EtOH. This is consistent with the predominant existence of alcoxo [Fe(dapsox)(ROH)(OR)] species in alcoholic solutions. In comparison, the activation parameters for the substitution of the aqua-hydroxo [Fe(dapsox)(H2O)(OH)] complex by thiocyanate at pH 5.1 in MES were determined to be DeltaH = 72 +/- 3 kJ mol(-1), DeltaS = +38 +/- 11 J K(-1) mol(-1), and DeltaV = -3.0 +/- 0.1 cm(3) mol(-1), and the operation of a dissociative interchange mechanism was suggested, taking the effect of pressure on the employed buffer into account. The addition of triflic acid to the alcoholic solutions ([HOTf] = 10(-3) and 10(-2) M to MeOH and EtOH, respectively) resulted in a drastic changeover in mechanism for the first substitution step, for which an associative interchange (Ia) mechanism is suggested, on the basis of the activation parameters obtained for both the forward and reverse reactions and the corresponding volume profile. The second substitution step remained to proceed through an I(d) or D mechanism (acidified MeOH DeltaV(II) = +9.2 +/- 0.2 cm(3) mol(-1); acidified EtOH DeltaV(II) = +10.2 +/- 0.2 cm(3) mol(-1)). The first substitution reaction in DMSO was found to be slowed by several orders of magnitude and to follow an associative interchange mechanism (DeltaS = -50 +/- 9 J K(-1) mol(-1), DeltaV(I) = -1.0 +/- 0.5 cm(3) mol(-1)), making DMSO a suitable solvent for monitoring substitution processes that are extremely fast in aqueous solution.
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IVANOVIĆ-BURMAZOVIĆ IVANA, JELKOVIĆ KATARINA. TRANSITION METAL COMPLEXES WITH BIS(HYDRAZONE) LIGANDS OF 2,6-DIACETYLPYRIDINE. HEPTA-COORDINATION OF 3d METALS. ADVANCES IN INORGANIC CHEMISTRY 2004. [DOI: 10.1016/s0898-8838(03)55006-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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