Ayşe Erçağ

Photochemical reactions of metal carbonyls [M(CO)6 (M = Cr, Mo, W), Re(CO)5Br, Mn(CO)3Cp] with 3,5-dimethyl-tetrahydro-2H-1,3,5-thiadiazine-2-thione (DTTT) and the crystal structure of [W(CO)5(DTTT)]

Abstract Five new complexes, [M(CO)5(DTTT)] [M=Cr; 1, Mo; 2, W; 3], [Re(CO)4Br(DTTT)] (4) and [Mn(CO)2Cp(DTTT)] (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 3,5-dimethyl-tetrahydro-2H-1,3,5-thiadiazine-2-thione (DTTT). The complexes have been characterized by elemental analysis, mass spectrometry, FTIR, 1H and 13C{1H} NMR spectroscopy. The spectroscopic studies show that DTTT behaves as a monodentate ligand coordinating via the sulfur (CS) donor atom in 1–5. An X-ray diffraction study of [W(CO)5(DTTT)] (3) confirms that the tungsten adopts a distorted octahedral geometry with local C4v symmetry.

Synthesis, characterization, EPR, electrochemical, and in situ spectroelectrochemical studies of salen-type oxovanadium(IV) and copper(II) complexes derived from 3,4-diaminobenzophenone

A new half unit and some new symmetrical or asymmetrical VO(IV) and Cu(II) complexes of tetradentate ONNO Schiff base ligands were synthesized. The probable structures of the complexes have been proposed on the basis of elemental analyses and spectral (IR, UV–Vis, electron paramagnetic resonance, ESI-MS) data. VO(IV) and Cu(II) complexes exhibit square pyramidal and square-planar geometries, respectively. The complexes are non-electrolytes in dimethylformamide (DMF) and dimethylsulfoxide. Electrochemical behaviors of the complexes were studied using cyclic voltammetry and square wave voltammetry. Half-wave potentials (E 1/2) are significantly influenced by the central metal and slightly influenced by the nature of substituents on salen. While VO(IV) complexes give VOIV/VOV redox couples and a ligand-based reduction process, Cu(II) complexes give only a ligand-based reduction. In situ spectroelectrochemical studies were employed to determine the spectra of electrogenerated species of the complexes and to assign the redox processes. The g-values were calculated for all these complexes in polycrystalline state at 298 K and in frozen DMF (113 K). The evaluated metal–ligand bonding parameters showed strong in-plane σ-bonding for some Cu(II) complexes.

Photochemical Complexation Reactions of M(CO)6 (M=Cr, Mo, W) and Re(CO)5Br with Rhodanine (4‐Thiazolidinone‐2‐thioxo) and 5‐Substituted Rhodanines

The new complexes [M(CO)5‐DABRd] [M=Cr; 1, Mo; 2, W; 3], [cis‐Re(CO)4Br‐DABRd] (4), [M(CO)5‐BRd] [M=Cr; 5, Mo; 6, W; 7] and [Mo(CO)5‐L] [L=Rd, 8; 2CBRd, 9; 2HNARd, 10; IBRd, 11] have been synthesized by the photochemical reactions of VIB and VIIB group metal carbonyls [M(CO)6] [M=Cr, Mo, W] and [Re(CO)5Br] with 5‐(4‐dimethylaminobenzylidene)rhodanine (DABRd), 5‐benzylidenerhodanine (BRd), rhodanine (Rd), 5‐(2‐chlorobenzylidene)rhodanine (2CBRd), 5‐(2‐hydroxynaphtylidene)rhodanine (2HNARd), 5‐(4‐isopropylbenzylidene)rhodanine (IBRd) and characterized by elemental analysis, FT‐IR, 1H and 13C‐{1H}‐NMR spectroscopy and by Mass spectrometry. The spectroscopic studies show that all rhodanine ligands act as monodentate ligands coordinating via the sulfur (C˭S) donor atom in (1–11).

Photochemical reactions of group VIB metal carbonyls with heterocyclic Schiff bases derived from 4-amino -3-hydrazino-5-mercapto-1,2,4-triazole

The new complexes, M(CO)5(Schiff base) [M = Cr; 1, Mo; 2, W; 3, Schiff base = 4-salicylidenamino-3-hydrazino-5-mercapto-1,2,4-triazole, SAHMT, a; 4-(2-hydroxynaphthylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 2HNAHMT, b; 4-(3-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 3HBAHMT, c; 4-(4-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 4HBAHMT, d; 4-(5-bromosalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 5BrSAHMT, e; were synthesized by photochemical reaction of metal carbonyls M(CO)6 (M = Cr, Mo, W) with new heterocyclic Schiff bases derived from 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, a–e. The ligands and complexes have been characterized by elemental analysis, EI-mass spectrometry, FT-IR, 1H and 13C-{1H}-NMR spectroscopy. The spectroscopic studies show that Schiff bases, a–e, are monodentate and coordinate via azomethine N donor to the central metal atom in M(CO)5(Schiff base) (M = Cr, Mo, W).

Synthesis and Characterization of Oligo-Salicylidene-3-Amino-1, 2, 4-Triazole and Oligo-2-Hydroxy Naphthalidene-3-Amino-1, 2, 4-Triazole

Abstract: In this study, the oxidative polycondensation reaction conditions of oligo-salicylidene-3-amino-1, 2, 4-triazole (OSAT) and oligo-2-hydroxy naphthalidene-3-amino-1, 2, 4-triazole (OHNAT) with air O2, H2O2, and NaOCl were studied in an aqueous alkaline medium at 80°C. The oligo-salicylidene-3-amino-1, 2, 4-triazole and oligo-2-hydroxy naphthalidene-3-amino-1, 2, 4-triazole were characterized by 1H-nuclear magnetic resonance (NMR), Fourier transform-infrared (FT-IR), ultraviolet-visible spectrometry (UV-Vis), size exclusion chromatography (SEC), and elemental analysis techniques. According to the SEC analysis, the number average–molecular weight (Mn), weight average–molecular weight (Mw), and polydispersity index (PDI) values of OSAT and OHNAT were found to be 1980 g mol−1, 5115 g mol−1, and 2.58 and 1752 g mol−1, 4300 g mol−1, and 2.45, respectively. Also, thermogravimetric (TG) analyses were shown to be unstable for oligo-salicylidene-3-amino-1, 2, 4-triazole and oligo-2-hydroxy naphthalidene-3-amino-1, 2, 4-triazole against thermo-oxidative decomposition. The weight losses of OSAT and OHNAT were found to be 97.30% and 98.48% at 900°C, respectively.

Synthesis, characterization and antioxidant activities of dioxomolybdenum(VI) complexes of new Schiff bases derived from substituted benzophenones

Abstract Five novel ONS donor Schiff base ligands were synthesized by the reaction of 2-hydroxybenzophenone (L1), 2-hydroxy-4-methoxybenzophenone (L2), 2-hydroxy-4-octyloxybenzophenone (L3), 2-hydroxy-4-methoxy-4′-methylbenzophenone (L4), and 2-hydroxy-4-allyloxybenzophenone (L5) with thiocarbohydrazide. Neutral solvate dioxomolybdenum(VI) complexes with the general formula [MoO2L(ROH)], [C1–C5] (L = L1, L2, L3, L4, L5 and R = CH3, C2H5, or C4H9), were prepared from these Schiff bases. Characterization of all compounds was carried out by means of elemental analysis, conductivity measurements, 1H-NMR, FT-IR, UV-Vis spectroscopy and mass spectrometry (for L1, C2, and C4) techniques. The crystal structures of ligand (L5) and complex (C1) were determined by single-crystal X-ray crystallography. Spectroscopic data and X-ray diffraction studies confirmed that the ligand is coordinated to the cis-MoO22+ core through ONS, while the sixth coordination site is occupied by solvent (ROH). The ligands and complexes were tested for in vitro antioxidant capacities. The TEAC coefficients of the ligands and complexes were found higher than reference compound. DPPH radical scavenging activities of these compounds were also investigated. Graphical Abstract