Search Results (6)

New cyclotriphosphazene derivatives featuring amide–Schiff base linkages with a hydrazine bridge and different terminal ends, such as decyl alkyl chains and hydroxy groups, were successfully synthesized and characterized. Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and CHN elemental analysis were used to characterize the structures of these compounds. The formation of hydrazine-bridged cyclotriphosphazene derivatives with amide–Schiff base linkages was confirmed by the FTIR spectra, showing a primary amine band for the amide linkage around ~3300 cm⁻¹ and a band for the Schiff base linkage near ~1595 cm⁻¹. This was further supported by NMR analysis, which displayed an amide proton (H-N-C=O) at ~δ 10.00 ppm and an azomethine proton (H-C=N) within the δ 8.40–8.70 ppm range. The ³¹P NMR spectra of cyclotriphosphazene compounds display a singlet at ~δ 8.20 ppm, indicating an upfield shift that suggests the complete substitution of all phosphorus atoms with identical side chains. Furthermore, CHN analysis verified the purity of the synthesized compounds, with a percentage error below 2%. The introduction of hydrazine bridges and amide–Schiff base linkages into the cyclotriphosphazene core significantly enriches the molecular structure with diverse functional groups. These modifications not only improve the compound’s stability and reactivity, but also expand its potential for a wide range of applications. Full article

A new Ag(I)-azine complex of the formula [Ag(L^a)]₂(ClO₄)₂.1/2(L^b) was synthesized and characterized using elemental analysis, FTIR, XPS and single-crystal X-ray diffraction. The [Ag(L^a)]₂(ClO₄)₂.1/2(L^b) complex was obtained via Ag(I)-mediated hydrolysis of 2-(((1-(pyridin-2-yl)ethylidene)hydrazineylidene)methyl)phenol (L) with AgClO₄ leading to the formation of the azines (1E,2E)-1,2-bis(1-(pyridin-2-yl)ethylidene)hydrazine (L^a) and 2,2’-((1E,1’E)-hydrazine-1,2-diylidene bis(methanylylidene)) diphenol (L^b). The former underwent complexation with AgClO₄, while the latter was co-crystallized with the resulting Ag(I) complex, leading to the complex formula [Ag(L^a)]₂(ClO₄)₂.1/2(L^b). In this complex, the azine L^a is acting as a bridged bidentate chelate connecting the two Ag(I) sites, leading to a tetra-coordinated Ag(I) with a distorted square planar coordination environment. Hirshfeld analysis indicated the importance of the H…H (38.4%), O…H (17.9%), H…C (13.2%), C…C (9.0%) and N…H (8.9%) interactions in the molecular packing. The antimicrobial, antioxidant and cytotoxic activities of the [Ag(L^a)]₂(ClO₄)₂.1/2(L^b) complex were examined and compared with those of [Ag(L^a)]₂(ClO₄)₂. The former was found to have lower bioactivity than the latter, which shed light on the lowering of biological actions as a consequence of the incorporation of the azine L^b within the Ag(I) complex. In other words, lowering the %Ag decreases the biological actions. The [Ag(L^a)]₂(ClO₄)₂.1/2(L^b) complex (ΜIC = 39 μg/mL) has higher activity against the fungus A. fumigatus than the control Ketoconazole (ΜIC =156 μg/mL). This complex also has good cytotoxic activity against colon carcinoma and weak antioxidant activity. Full article

Elaboration of a convenient route towards donor-substituted pyrazoles from heteropropargyl precursors is challenging due to a number of thermodynamically favorable side reactions (e.g., acetylene–allene isomerization and Glaser homocoupling). In this work, Sonogashira cross-coupling conditions of 4-tert-butylphenyl propargyl ether with benzoyl chloride followed by tandem Michael addition/cyclocondensation with hydrazine into 3,5-disubstituted pyrazole (kinetic control), as well as cycloisomerization conditions of ketoacetylene intermediate into 2,5-disubstituted furan (thermodynamic control), were established through a variation of the catalyst loading, solvent polarity, excess of triethylamine, and time of reaction. During the optimization of process parameters, a number of by-products represented by a monophosphine binuclear complex (PPh₃PdI₂)₂ with two bridging iodine atoms and diyne were identified and isolated in the pure form. The quantum-chemical calculations and solution-state ¹H/¹³C NMR spectroscopy suggested that the 5(3)-(4-tert-butylphenyloxy)methoxy-3(5)-phenyl-1H-pyrazole exists in the tautomeric equilibrium in a polar methanol solvent and that individual tautomers could be characterized in case aprotic solvents employed. The pyrazole features a unique tetramer motif in the crystal phase formed by alternating 3(5)-phenyl-1H-pyrazole tautomers, which was stabilized by N–H···N bonds and stacking interactions of pyrazole rings, whereas pyrazole dimers were identified in the gas phase. Full article

The facile preparation of a racemic hydrazine bridged diphosphonium compound possessing a ring system analogous to bicyclo[3.3.2]decane is reported. Although the reaction yield is low, the structure of the compound, which possesses an eight-membered ring, two phosphonium cationic centers, a biimino bridge, molecular chirality and two fused aromatic rings locked into roughly perpendicular planes is unusual. The compound displays substantial biological activity in the brine shrimp test and cleaves plasmid DNA. Full article

A series of chiral linear and macrocyclic bridged pyridines has been prepared starting from pyridine-2,6-dicarbonyl dichloride (2). The coupling of 1 with D-alanyl methyl ester gave 2,6-bis-D-alanyl pyridine methyl ester (3). Hydrazinolysis of 3 with hydrazine hydrate afforded bis-hydrazide 4. The latter was reacted with thiophene-2-carbaldehyde, phthalic anhydride or cyclohexanone to afford bis-carboxamide pyridine derivatives 5-7, respectively. Compound 4 was coupled with p-methoxy- or p-nitroaceto-phenone to yield compounds 8 and 9. In addition, 4 was reacted with 1,2,4,5-benzenetetra-carboxylic acid dianhydride or 1,4,5,8-naphthalenetetracarboxylic acid dianhydride to afford the macrocyclic octacarboxaamide pyridines 10 and 11. The detailed synthesis, spectroscopic data and antimicrobial screening for the synthesized compounds are reported. Full article

A series of pyridine-bridged 2,6-bis-carboxamide Schiff's bases has been prepared starting from 2,6-pyridinedicarbonyl dichloride (1) and L-alanine or 2-methyl-alanine methyl ester.The coupling of acid chloride 1 with L-alanine methyl ester hydrochloride -or 2-methylalanine methyl ester hydrochloride gave the corresponding 2,6-bis-carboxamide pyridine methyl esters 2a,b.Hydrazonolysis of 2 with hydrazine hydrate afforded the corresponding bis-hydrazides 3a,b. Treatment of 3a,b with appropriate aromatic or heterocyclic aldehydes afforded the corresponding pyridine- bridged 2,6-bis-carboxamide Schiff's bases 4a-f and 5a-f, respectively. The newly synthesized compounds 2-5 were screened for their bactericidal and fungicidal activities. Many of the obtained compounds exhibited significant antimicrobial activity, comparable to streptomycin and fusidic acid, which were used as reference antibiotic drugs. Full article