A Novel Approach to the Synthesis of 1,3,4-Thiadiazole-2-amine Derivatives

The main purpose of the study was the development of a new method for synthesis of 1,3,4-thiadiazol-2-amine derivatives in a one-pot manner using the reaction between a thiosemicarbazide and carboxylic acid without toxic additives such as POCl3 or SOCl2. The reaction was investigated in the presence of polyphosphate ester (PPE). It was found that, in the presence of PPE, the reaction between the thiosemicarbazide and carboxylic acid proceeds in one-pot through three steps with the formation of corresponding 2-amino-1,3,4-thiadiazole. Using the developed approach five, 2-amino-1,3,4-thiadiazoles were synthesized. The structures of all compounds were proven by mass spectrometry, IR, and NMR spectroscopies

Theoretical Modeling of the Magnetic Behavior of Thiacalix[4]arene Tetranuclear Mn^II₂Gd^III₂ and Co^II₂Eu^III₂ Complexes

In view of a wide perspective of 3d–4f complexes in single-molecule magnetism, here we propose an explanation of the magnetic behavior of the two thiacalix[4]­arene tetranuclear heterometallic complexes Mn^II₂Gd^III₂ and Co^II₂Eu^III₂. The energy pattern of the Mn^II₂Gd^III₂ complex evaluated in the framework of the isotropic exchange model exhibits a rotational band of the low-lying spin excitations within which the Landé intervals are affected by the biquadratic spin–spin interactions. The nonmonotonic temperature dependence of the χ<i>T</i> product observed for the Mn^II₂Gd^III₂ complex is attributed to the competitive influence of the ferromagnetic Mn–Gd and antiferromagnetic Mn–Mn exchange interactions, the latter being stronger (<i>J</i>(Mn, Mn) = −1.6 cm^–1, <i>J</i>_s(Mn, Gd) = 0.8 cm^–1, <i>g</i> = 1.97). The model for the Co^II₂Eu^III₂ complex includes uniaxial anisotropy of the seven-coordinate Co^II ions and an isotropic exchange interaction in the Co^II₂ pair, while the Eu^III ions are diamagnetic in their ground states. Best-fit analysis of χ<i>T</i> versus <i>T</i> showed that the anisotropic contribution (arising from a large zero-field splitting in Co^II ions) dominates (weak-exchange limit) in the Co^II₂Eu^III₂ complex (<i>D</i> = 20.5 cm^–1, <i>J</i> = −0.4 cm^–1, <i>g</i>_Co = 2.22). This complex is concluded to exhibit an easy plane of magnetization (arising from the Co^II pair). It is shown that the low-lying part of the spectrum can be described by a highly anisotropic effective spin-¹/₂ Hamiltonian that is deduced for the Co^II₂ pair in the weak-exchange limit

The Influence of Cationic Nitrosyl Iron Complex with Penicillamine Ligands on Model Membranes, Membrane-Bound Enzymes and Lipid Peroxidation

This paper shows the biological effects of cationic binuclear tetranitrosyl iron complex with penicillamine ligands (TNIC–PA). Interaction with a model membrane was assessed using a fluorescent probes technique. Antioxidant activity was studied using a thiobarbituric acid reactive species assay (TBARS) and a chemiluminescence assay. The catalytic activity of monoamine oxidase (MAO) was determined by measuring liberation of ammonia. Antiglycation activity was determined fluometrically by thermal glycation of albumine by D-glucose. The higher values of Stern–Volmer constants (KSV) obtained for the pyrene located in hydrophobic regions (3.9 × 104 M−1) compared to KSV obtained for eosin Y located in the polar headgroup region (0.9 × 104 M−1) confirms that TNIC–PA molecules prefer to be located in the hydrophobic acyl chain region, close to the glycerol group of lipid molecules. TNIC–PA effectively inhibited the process of spontaneous lipid peroxidation, due to additive contributions from releasing NO and penicillamine ligand (IC50 = 21.4 µM) and quenched luminol chemiluminescence (IC50 = 3.6 μM). High activity of TNIC–PA in both tests allows us to assume a significant role of its radical-scavenging activity in the realization of antioxidant activity. It was shown that TNIC–PA (50–1000 μM) selectively inhibits the membrane-bound enzyme MAO-A, a major source of ROS in the heart. In addition, TNIC–PA is an effective inhibitor of non-enzymatic protein glycation. Thus, the evaluated biological effects of TNIC–PA open up the possibility of its practical application in chemotherapy for socially significant diseases, especially cardiovascular diseases

Zero-Field Slow Magnetic Relaxation in Binuclear Dy Acetylacetonate Complex with Pyridine-N-Oxide

A new complex [Dy(C5H7O2)3(C5H5NO)]2·2CHCl3 (1) has been synthesized by the reaction of pyridine-N-oxide with dysprosium (III) acetylacetonate in an n-heptane/chloroform mixture (1/20). X-ray data show that each dysprosium atom is chelate-like coordinated by three acetylacetonate ligands and the oxygen atom from two bridging molecules of pyridine-N-oxide, which unite the dysprosium atoms into a binuclear complex. Static (constant current) and dynamic (alternating current) investigations and ab initio calculations of the magnetic properties of complex 1 were performed. The complex was shown to exhibit a frequency maximum under alternating current. At temperatures above 10 K, the maximum shifts to a higher frequency, which is characteristic of SMM behavior. It is established that the dependence of ln(τ) on 1/T for the relaxation process is nonlinear, which indicates the presence of Raman relaxation mechanisms, along with the Orbach mechanism

Novel Type of Tetranitrosyl Iron Salt: Synthesis, Structure and Antibacterial Activity of Complex [FeL’₂(NO)₂][FeL’L”(NO)₂] with L’-thiobenzamide and L”-thiosulfate

In this work a new donor of nitric oxide (NO) with antibacterial properties, namely nitrosyl iron complex of [Fe(C6H5C-SNH2)2(NO)2][Fe(C6H5C-SNH2)(S2O3)(NO)2] composition (complex I), has been synthesized and studied. Complex I was produced by the reduction of the aqueous solution of [Fe2(S2O3)2(NO)2]2− dianion by the thiosulfate, with the further treatment of the mixture by the acidified alcohol solution of thiobenzamide. Based on the structural study of I (X-ray analysis, quantum chemical calculations by NBO and QTAIM methods in the frame of DFT), the data were obtained on the presence of the NO…NO interactions, which stabilize the DNIC dimer in the solid phase. The conformation properties, electronic structure and free energies of complex I hydration were studied using B3LYP functional and the set of 6–31 + G(d,p) basis functions. The effect of an aquatic surrounding was taken into account in the frame of a polarized continuous model (PCM). The NO-donating activity of complex I was studied by the amperometry method using an “amiNO-700” sensor electrode of the “inNO Nitric Oxide Measuring System”. The antibacterial activity of I was studied on gram-negative (Escherichia coli) and gram-positive (Micrococcus luteus) bacteria. Cytotoxicity was studied using Vero cells. Complex I was found to exhibit antibacterial activity comparable to that of antibiotics, and moderate toxicity to Vero cells

A new member of the cationic dinitrosyl iron complexes family incorporating N-ethylthiourea is effective against human HeLa and MCF-7 tumor cell lines

<p>A new analog of the active site of mononuclear dinitrosyl [1Fe–2S] proteins, [C₃N₂H₈SFe(NO)₂Cl][Fe(NO)₂(C₃N₂H₈S)₂]⁺Cl⁻ (<b>I</b>), has been synthesized by reacting NO with an aqueous mixture of iron(II) sulfate and N-ethylthiourea in acidic medium. The structure and properties of the complex were studied by X-ray diffraction, IR, Mössbauer, and EPR spectroscopy, in addition to quantum chemical calculations. Complex <b>I</b> spontaneously generates NO in protic media. The cytotoxicity of <b>I</b> was investigated against human cervical carcinoma (HeLa), breast cancer (MCF7), and non-immortalized (FetMCS) cell lines. The cytotoxicity of <b>I</b> against HeLa is similar to that of anticancer agents currently used clinically (platinum complexes), but <b>I</b> is 10 times less toxic in normal cells. The cytotoxicity of MCF7 cells to <b>I</b> is low.</p