Nurcan Karacan

Structure and vibrational spectroscopy of methanesulfonic acid hydrazide: an experimental and theoretical study

A comprehensive study of the molecule of methanesulfonic acid hydrazide (MSH) is presented. The X-ray structure shows that in the crystal two centrosymmetrically oriented MSH molecules are held together by N–H···N hydrogen bonding interactions. This feature is unprecedented for the known arylsulfonic hydrazide analogues. The energetics of the various MSH staggered conformers and the stabilisation due to dimerisation are evaluated by HF abinitio calculations. Moreover, the pathways that interconvert the conformers as well as their enantiomers are outlined. The transition states between conformers correspond to the eclipsed conformation about the S–N linkage while those between enantiomers require planarisation of the N atom bound to sulfur. Some interconversions require two steps and two barriers to be bypassed. The IR and Raman spectra of MSH have been recorded and a normal coordinate analysis (NCA) has been carried out. The assignments have been double-checked through the abinitio calculated frequencies. The latter techniques also allow evaluation of the normal modes of vibration due to interacting MSH monomers, which can be experimentally detected.

Redox characteristics of Schiff base manganese and cobalt complexes related to water-oxidizing complex of photosynthesis

In an effort to obtain synthetic analogues of water-oxidizing complex (WOC) of photosystem II (PS II) of plant photosynthesis, a Schiff base manganese and a cobalt complex, employing Niten, a SALEN type ligand, have been prepared. Cyclic and square wave voltammetric measurements have been performed to assess their redox characteristics. Both complexes undergo several reduction processes in cathodic negative potential region at more or less similar potentials. In view of these reductions being independent of the nature of the metal, they are thought to be ligand-localized. Although similar in negative region, a marked difference in the behavior of the complexes is observed in anodic region. While the cobalt complex is electrochemically inactive in the positive potentials up to +1.0 V vs. Ag/AgCl, the manganese complex displays two oxidation waves at +0.25 and +0.5 V vs. Ag/AgCl. The presence of oxidation wave in manganese complex at +0.5 V vs. Ag/AgCl or +0.7 V vs. NHE suggests that this complex can catalyze the oxidation of water and can, thus, simulate the WOC of PS II.

SYNTHESIS AND CHARACTERIZATION OF THE PRODUCTS FROM REACTION OF METAL CARBONYLS (M(CO)6 (M ¼ Cr, Mo, W), Re(CO)5Br, Mn(CO)3Cp) WITH SALICYLALDEHYDE METHANESULFONYLHYDRAZONE

Five new complexes, [M(CO)5(salmsh)] (M = Cr; 1, Mo; 2, W; 3), [Re(CO)4Br(salmsh)], 4, and [Mn(CO)3 (salmsh)], 5, have been synthesized by the photochemical reaction of metal carbonyls with salicylaldehyde methanesulfonylhydrazone (salmsh). The complexes have been characterized by elemental analyses, EI mass spectrometry, FT-IR and 1H NMR spectroscopy. The spectroscopic studies show that salmsh behaves as a monodentate ligand coordinating via the imine N donor atom in 1–4 and as a tridentate ligand in 5.

Reaction of metal carbonyls with 2-hydroxy-1-naphthaldeyde methanesulfonylhydrazone and characterization of the substitution products

Five new complexes, [M(CO)5(nafmsh)] [M = Cr, 1; Mo, 2; W, 3], [Re(CO)4Br(nafmsh)], 4 and [Mn(CO)3(nafmsh)], 5 have been synthesized by the photochemical reaction of metal carbonyls [M(CO)6] (M = Cr, Mo, W), [Re(CO)5Br], and [Mn(CO)3Cp] with 2-hydroxy-1-naphthaldehyde methanesulfonylhydrazone (nafmsh). The complexes have been characterized by elemental analysis, EI mass spectrometry, FT-IR, and 1H NMR spectroscopy. The spectroscopic studies show nafmsh is a monodentate ligand coordinating via the imine N donor atom in 1–4 and as a tridentate ligand in 5.

Reconstruction of the Water-Oxidizing Complex in Manganese-Depleted Photosystem II Preparations Using Mononuclear Manganese Complexes

Abstract— The water‐oxidizing complex of chloroplast photosystem II is composed of a cluster of four manganese atoms that can accumulate four oxidizing redox equivalents. Depletion of manganese from the water‐oxidizing complex fully inhibits oxygen evolution. However, the complex can be reconstituted in the presence of exogenous manganese in a process called photoactivation. In the present study, mononuclear manganese complexes with ligands derived from either nitrosonaphthol and ethylenediamine (Niten) or from diaminohexane and salicylaldehyde (Salhxn) are used in photoactivation experiments. Measurements of photoinduced changes of chlorophyll fluorescence yield, thermal dissipation using photoacoustic spectroscopy, photoreduction of 2,6‐dichorophenolindophenol and oxygen evolution in manganese‐depleted and in reconstituted photosystem II preparations demonstrate that photoactivation is more efficient when Niten and Salhxn complexes are used instead of MnCl2. It is inferred that the aromatic ligands facilitate the interaction of the manganese atoms with photosystem II. The addition of CaCl2 and of the extrinsic polypeptide of 33 kDa known as the manganese‐stabilizing protein during photoactivation further enhances the recovery of electron transport and oxygen evolution activities. It is proposed that mononuclear manganese complexes are able to contribute to re‐constitution of the water‐oxidizing complex by sequential addition of single ions similarly to the current model for assembly of the tetranuclear manganese cluster and that these complexes constitute suitable model systems to study the assembly of the water‐oxidizing complex.

The antibacterial activity of some sulfonamides and sulfonyl hydrazones, and 2D-QSAR study of a series of sulfonyl hydrazones.

Benzenesulfonicacid-1-methylhydrazide (1) and its four aromatic sulfonyl hydrazone derivatives (1a-1d), N-(3-amino-2-hydroxypropyl)benzene sulfonamide (2) and N-(2-hydroxyethyl)benzenesulfonamide (3) were synthesized and their structures were determined by IR, (1)H NMR, (13)C NMR, and LCMS techniques. Antibacterial activities of new synthesized compounds were evaluated against various bacteria strains by microdilution and disk diffusion methods. The experimental results show that presence of OH group on sulfonamides reduces the antimicrobial activity, and antimicrobial activities of the sulfonyl hydrazones (1a-1d) are smaller than that of the parent sulfonamide (1), except Candida albicans. In addition, 2D-QSAR analysis was performed on 28 aromatic sulfonyl hydrazones as antimicrobial agents against Escherichia coli and Staphylococcus aureus. In the QSAR models, the most important descriptor is total point-charge component of the molecular dipole for E. coli, and partial negative surface area (PNSA-1) for S. aureus.

Synthesis, characterization, antimicrobial activity and structure–activity relationships of new aryldisulfonamides

A series of aromatic disulfonamide (1-8) derivatives and 4-methylbenzenesulfonyl hydrazide (9) were synthesized and characterized. All compounds were evaluated in vitro for their antimicrobial activity against Staphylococcus aureus ATCC 25953, Bacillus cereus ATCC 6633, Bacillus magaterium RSKK 5117, Escherichia coli ATCC 11230, Salmonella enterititis ATCC 13076 by microdilution and disc diffusion methods. Antimicrobial activity of the aromatic disulfonamides decreased as the length of the carbon chain increased. An analysis of the structure- activity relationship (SAR) along with computational studies showed that the most active compound (9) possessed low lipophilicity (AlogP=0.59) and high solubility (logS = -1.33).

Photochemical reactions of metal carbonyls [M(CO)6 (M=Cr, Mo, W), Re(CO)5Br, Mn(CO)3Cp] with salicylaldehyde ethanesulfonylhydrazone (Hsalesh)

The new complexes, M(CO)5(Hsalesh) (M = Cr (1), Mo (2), W (3)), Re(CO)4Br(Hsalesh) (4) and Mn(CO)3(Hsalesh) (5) have been synthesized by the photochemical reaction of metal carbonyls M(CO)6 (M = Cr, Mo, W), Re(CO)5Br, and Mn(CO)3Cp with salicylaldehyde ethanesulfonyl hydrazone (Hsalesh). The complexes have been characterized by elemental analysis, EI mass spectrometry, FT-IR and 1H NMR spectroscopy. The spectroscopic studies show that Hsalesh behaves as a monodentate ligand coordinating via imine N donor atom in M(CO)5(Hsalesh) (M = Cr, Mo, W) and Re(CO)4Br(Hsalesh) and as a tridentate ligand in Mn(CO)3(salesh).

Schiff Bases of Methanesulfonylhydrazine. Synthesis, Spectroscopic Characterization, Conformational Analysis, and Biological Activity

Three novel Schiff bases: salicylaldehyde methanesulfonylhydrazone (1), 2-hydroxyacetophenone methanesulfonylhydrazone (2) and 2-hydroxy-1-naphthaldehyde methanesulfonylhydrazone (3) have been synthesized. Compounds 1-3, as well as acetone methanesulfonylhydrazone (4) have been characterized by TLC, 1H NMR and IR spectra. The spectroscopic results for 1-3 have revealed the presence of an intramolecular hydrogen bond between the hydroxyl group and the imine N atom. The conformational isomerism of 1-4 with respect to the rotations around the SN and NN bonds have been studied by the method of molecular mechanics. Compounds 1-4 and methanesulfonylhydrazine exhibit antibacterial and cytotoxic effects.

Photochemical reactions of metal carbonyls [M(CO)6 (M = Cr, Mo and W), Re(CO)5Br, Mn(CO)3Cp] with 2-hydroxyacetophenone methanesulfonylhydrazone (apmsh)

Five new complexes, [M(CO)5(apmsh)] [M = Cr; (1), Mo; (2), W; (3)], [Re(CO)4Br(apmsh)] (4) and [Mn(CO)3(apmsh)] (5) have been synthesized by the photochemical reaction of metal carbonyls [M(CO)6] (M = Cr, Mo and W), [Re(CO)5Br], and [Mn(CO)3Cp] with 2-hydroxyacetophenone methanesulfonylhydrazone (apmsh). The complexes have been characterized by elemental analysis, mass spectrometry, f.t.-i.r. and 1H spectroscopy. Spectroscopic studies show that apmsh behaves as a monodentate ligand coordinating via the imine N donor atom in [M(CO)5(apmsh)] (1–4) and as a tridentate ligand in (5).