Synthesis, spectroscopic evaluation, molecular modelling, thermal study and biological evaluation of manganese(II) complexes derived from bidentate N,O and N,S donor Schiff base ligands (original) (raw)
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Bulletin of the Korean Chemical Society, 2013
A new series of Mn(II) and Mo(VI) complexes containing the Schiff bases hydrazinecarbothioamide and hydrazinecarboxamide of 5,6-dimethyl-1H-indol-2,3-dione have been synthesized.The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, molecular weight determinations and spectral studies viz. electronic IR, ESR, 1 H NMR and 13 C NMR and X-ray diffraction spectral studies. The magnetic moment values of the manganese(II) complexes are in the range of 5.80-6.15 B.M. suggesting a high spin state of manganese in these complexes. The spectral data are consistent with a tetrahedral geometry around Mn(II) and an octahedral geometry for Mo(VI), in which the ligands act as bidentate chelating agents, coordinated through the nitrogen and sulfur/oxygen atoms. The ligands and their metal complexes have been tested against a number of pathogenic fungi and bacteria at different concentrations and were found to possess sufficient fungicidal and bactericidal properties. Further, the complexes were also tested for their antifertility activity in male albino rats and the results were indeed positive.
RSC Adv., 2015
We have synthesized four mononuclear manganese(III) complexes (1-4) of four closely related bidentate NO donor Schiff-base ligands, out of which three (2-4) were structurally characterized. Crystal structure determination reveals that all these complexes are in octahedral geometries. Magnetic studies have been carried out on complexes 2, 3 and 4 in the temperature range 2-300 K under a magnetic field of 0.1 T which yielded negative ZFS parameters of À2.96, -3.51 and À3.72 cm À1 respectively. The catecholase activities of complexes 1-4 have been investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) with molecular oxygen in DCM at 25 C, which were found to follow the Michalis-Menton type relation giving the highest TON (K cat ) for the so far reported Mn(III) complexes.
Russian Journal of General Chemistry, 2016
Novel biologically significant manganese(II) complexes with four monobasic bidentate ligands L 1 H [2-(5-fluoro-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarboxamide], L 2 H [2-(5-fluoro-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarbothioamide], L 3 H [2-(5-bromo-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarboxamide] and L 4 H [2-(5-bromo-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarbothioamide] were synthesized by complexation of the ligands with MnCl 2 •4H 2 O in 1 : 1 and 1 : 2 molar ratios in methanol. The Schiff base ligands and complexes were characterized by elemental analyses, melting points, molecular weights, IR, 1 H and 13 C NMR, UV-Vis, EPR, and mass spectra, as well as X-ray powder diffraction patterns. Based on the spectral data, a tetrahedral geometry was proposed for all the synthesized metal complexes. The ligands and complexes were tested in vitro against bacteria (Escherichia coli and Staphylococcus aureus) and fungi (Fusarium semitectum and Aspergillus flavus) to show that they were active against all the microbial strains examined, and the metal complexes were more active in comparison with the ligands. DNA cleavage activity of the complexes was examined by gel electrophoresis.
Journal of Coordination Chemistry - J COORD CHEM, 2012
Some Mn(III) complexes of N,N′-(2-hydroxy)propylenebis(acetylacetoneimine) (abbreviated to H2L1) and N,N′-(2-hydroxy)propylenebis(2-imino-3-oximino)butane (abbreviated to H2L2), [Mn(III)(Lig)(X)] (where Lig stands for the dianion of the Schiff-base ligands and X stands for CH3COO−, Cl−, Br−, I−) were synthesized. The complexes are characterized with the help of elemental analyses, magnetic moments, spectroscopic data (UV-Vis, infrared), and molecular weight determination (measured by Rast's method). The structures of the complexes were obtained using density functional theory (DFT). DFT calculation shows that 1–4 and 8 are trigonal-bipyramidal whereas 5–7 are square-pyramidal.
Journal of the Chemical Society, Dalton Transactions, 1997
A number of manganese() complexes of tetradentate N 2 O 2 Schiff-base ligands have been prepared with various additional carboxylate anions. Five of these compounds have been crystallographically characterised revealing that a remarkable array of structural chemistry is available. A polymeric species is observed for [{Mn(saltn)(O 2 CEt)} n ] 1, whereas a monomeric species is found in [Mn(saltn)(O 2 CBu t )] 2 [H 2 saltn = N,NЈbis(salicylidene)trimethylenediamine]. The anti-anti bridging of the manganese centres in 1 is in contrast to that in [{Mn(bsaltn)(O 2 CCH 2 Ph)} 2n ] 3 (H 2 bsaltn = 5-bromo derivative of H 2 saltn), which exhibits rare syn-anti bridging; 3 also contains a dimeric repeat unit due to an alternate 180Њ twist in the polymeric chain necessitated by steric constraints. In contrast, the complexes containing the dianion of N,NЈ-bis(3-methoxysalicylidene)ethane-1,2diamine (H 2 msalen) appear to be isostructural, [{Mn(msalen)(O 2 CEt)} 2 ]ؒEtOH 4 and [{Mn(msalen)(O 2 CBu n )} 2 ] 5 being structurally characterised as essentially identical phenoxy-bridged dimers. An insoluble material of stoichiometry Mn 4 (O 2 CR) 3 (saltn) 3 (H 2 O) n (n = 0-3) was isolated from all reactions involving the saltn ligand; attempts to characterise these compounds by X-ray diffraction have been unsuccessful. However, the previously characterised manganese() dimer [{Mn(saltn)O} 2 ]ؒ2dmf 6 (dmf = dimethylformamide) and the monomeric species [Mn(saltn)(O 2 CEt)] 7 were isolated in attempts to crystallise these materials.
2011
A series of carboxylate-bridged manganese(III) complexes derived from Schiff bases obtained by the condensation of salicylaldehyde or 5-bromo-salicylaldehyde and different types of diamine have been synthesized and characterized and, in the case of [Mn 2 (L1) 2 (l-ClCH 2 COO)](ClO 4) (1), the structure has been obtained by X-ray crystallography. The structure of 1 consists of two manganese atoms separated by 5.487(3) Å and bridged by a carboxylate anion. This dinuclear structural unit is linked by bridging phenoxy oxygens to adjacent dinuclear units to produce a one-dimensional chain. Cyclic voltammograms of all the compounds exhibit grossly similar features consisting of a reversible or quasi-reversible Mn III /Mn II reduction and a Mn III /Mn IV oxidation. It has been observed that bromo-substitution stabilizes the lower oxidation state in the Mn III /Mn II couple and destabilizes the higher oxidation state in the Mn III /Mn IV couple. Variable temperature magnetic susceptibility measurements of 1 show a weak antiferromagnetic interaction. The magnetic behavior is satisfactorily modeled by inclusion of zero-field splitting and an intermolecular interaction component.
Four manganese(II) complexes Mn 2 (paa) 2 (N 3 ) (1), [Mn(paa) 2 (NCS) 2 ]Á 3 / 2 H 2 O (2), Mn(papea) 2 (NCS) 2 (3), [Mn(dpka) 2 (NCS) 2 ]Á 1 / 2 H 2 O (4) of three neutral N,N donor bidentate Schiff bases were synthesized and physico-chemically characterized by means of partial elemental analyses, electronic, infrared and EPR spectral studies. Compounds 3 and 4 were obtained as single crystals suitable for X-ray diffraction. Compound 4 recrystallized as Mn(dpka) 2 (NCS) 2 . Both the compounds crystallized in the monoclinic space groups P2 1 for 3 and C2/c for 4. Manganese(II) is found to be in a distorted octahedral geometry in both the monomeric complexes with thiocyanate anion as a terminal ligand coordinating through the nitrogen atom. EPR spectra in DMF solutions at 77 K show hyperfine sextets with low intensity forbidden lines lying between each of the two main hyperfine lines and the zero field splitting parameters (D and E) were calculated.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright a b s t r a c t A family of four new phenoxo-bridged binuclear manganese(III) complexes of the general formula, [Mn(L)(X)] 2 where L = [N,N 0-bis(salicylidene)]propane-1,2-diamine and X = salicylaldehyde anion (sal À) (1); NCS À (2); NCO À (3) and [Mn(L 0)(N 3)] 2 Á2C 2 H 5 OH (4) where L 0 = [N,N 0-bis(2-hydroxyacetophenylid-ene)]propane-1,2-diamine has been prepared. The syntheses have been achieved by reacting manganese perchlorate with 1,2-diaminopropane and salicylaldehyde (or 2-hydroxyacetophenone for 4) or along with the respective pseudohalides so that the tetradentate Schiff base H 2 L or H 2 L 0 is obtained in situ to bind the Mn(III) ion. The complexes have been characterized by IR spectroscopy, elemental analysis, crystal structure analysis and variable-temperature magnetic susceptibility measurements. The single crystal X-ray diffraction studies show that the compounds are isostructural containing dimeric Mn(III) units with bridging phenolate oxygen atoms. Low temperature magnetic studies indicate that the complexes 1–3 exhibit intradimer ferromagnetic exchange as well as single-molecule magnet (SMM) behavior while complex 4 is found to undergo an intradimer antiferromagnetic coupling.
Mononuclear manganese(IV) complexes of hydroxyl-rich Schiff base ligands
Inorganic Chemistry, 1987
Hydroxyl-rich Schiff base ligands react with Mn(I1) and Mn(I1I) salts in basic methanolic solution, generating monomeric Mn(IV) complexes. The general stoichiometry is MnL2, where L represents a dianionic, tridentate Schiff base ligand that uses one imine nitrogen, one phenolate oxygen, and one alkoxide oxygen atom to form a neutral octahedral complex. The molecular structure of Mn(SALADHP)2 (where H2SALADHP = 1,3-dihydroxy-2-methy1-2-(salicylideneamino)propane) has been determined by X-ray crystallography. The compound cr stallizes from DMF/ether in the monoclinic space group P 2 , / a (2 = 4, a = 10.676 (5) A, least-squares methods to a final R = 0.076, R, = 0.072 with 2186 data greater than 340. Those complexes that form one fiveand one six-membered ring (where L can be H,SALAHE = 2-(salicylideneamino)-l-ethanol, H2SALAPDH = 1,3-dihydroxy-3-phenyl-2-(salicylideneamino)propane, H2SALATHM = tris(hydroxymethyl) (salicylideneamino)methane, and H2N02SALAPDH = 1,3-dihydroxy-3-(4-nitrophenyl)-2-(salicylideneamino)propane) are believed to be isostructural to Mn(SALADHP),. The X-band EPR spectra, obtained a t 90 K in DMF/methanol, show low-field features ranging between g = 4.32 and g = 5.45. The EPR spectrum for Mn(SALADHP)2 arises from a rhombically distorted S = 3 / 2 spin system with E / D = 0.22. The SALAHP ligand also forms mononuclear Mn(IV) complexes; however, it contains two six-membered chelate rings. All complexes exhibit roomtemperature solid-state and solution magnetic moments in the range 3.80-4.3 pB, further substantiating the Mn(IV) formulation. The E , values for the complexes in Me2S0 range between-320 and-480 mV vs. Ag/AgCI. The stabilization of the Mn(IV) oxidation state by alkoxide oxygen ligation is demonstrated by the nearly 1 V more negative reduction potential of these compounds compared to that of another compound, bis(salicylato)(bipyridine)manganese(IV), with an N 2 0 4 coordination environment. b = 16.473 (10) A, c = 17.541 (7) K , fl = 102.82 (4)O, V = 3008 (3) A3), and the structure has been refined by using full-matrix