Synthesis and spectroscopic characterization of some lanthanide(III) nitrate complexes of 3-[3-carboxyethyl-4,5- dimethylthiophene-2-yl)azo]pent-2,4-dione

Abstract

Ethyl 2-[2-(1-acetyl-2-oxopropyl)azo]-4,5-dimethyl-3-thiophenecarboxyate was synthesized by coupling diazotized ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate with acetylacetone. Based on various spectral studies and elemental analysis, an intramolecularly hydrogen-bonded azo-enol structural form was assigned for the ligand. This ligand is versatile in forming a series of lanthanide(III) complexes, viz., lanthanum(III), cerium(III), praseodymium(III), neodymium(III), samarium(III) and gadolinium(III), which were characterized through various spectral studies, elemental analysis, magnetic susceptibility measurements, molar conductance and thermal analysis. The spectral data revealed that the ligand acted as a neutral tridentate, coordinating to the metal ion through one of the azo nitrogen atoms, the ester carbonyl and the enolic oxygen of the acetylacetone moiety, without deprotonation. Molar conductance values adequately supported their non-electrolytic nature. The ligand and lanthanum(III) complex were subjected to X-ray diffraction studies. In addition, the lanthanum(III) complex underwent a facile transesterification reaction on refluxing with methanol for a long period. The thermal behaviour of the lanthanum(III) complex was also examined.

Synthesis, structural characterization and biological studies of neodymium(III) and samarium(III) complexes with mercaptotriazole Schiff bases

“…Powder X‐ray diffraction is a rapid analytical technique. This technique is based on constructive interference of monochromatic X‐rays and a crystalline sample . These X‐rays are generated by a cathode ray tube, filtered to produce monochromatic radiation to concentrate and directed towards the sample.…”

Synthesis, characterization, fluorescence imaging, and cytotoxicity studies of a uracil‐based azo derivative and its metal complexes

“…The ligand is soluble in organic solvents like methanol, ethanol, benzene, toluene etc. [21] The IR spectra of the ligand showed a broad band centered at 3,469 cm −1 for the OH stretching vibration. The elemental analyses are consistent with 1:2 metal-ligand stoichiometry for manganese(II) and cobalt(II) complexes and 1:1 metal-ligand stoichiometry for nickel(II), copper(II), and zinc(II) complexes.…”

“…This band is shifted to a lower frequency by 15-20 cm −1 indicating the involvement of the azo nitrogen in coordination to the metal ion. [21] The IR spectra of the ligand showed a broad band centered at 3,469 cm −1 for the OH stretching vibration. A band due to the intramolecular O HÁ Á ÁN hydrogen bond was observed at 2,844 cm −1 .…”

Synthesis and Characterization of Unique Nickel(II) Carboxylates and Their Coordination Complexes

“…It is reported in the literature [3,22,27,28] that the vibrational band due to the free >C=O group of carboxylic moiety appears in the region of 1725-1700 cm -1 and in metal carboxylate ν(COO -) asymmetric and symmetric stretching vibrations appeared in the region of 1610-1520 and 1460-1300 cm -1 . Also ν(M-O) vibrational bands appeared in the region of 400-600 cm -1 have been reported [23,[29][30][31][32][33] in the literature. The vibrational bands in the region of 3000-2800 cm -1 have been reported [3] in literature due to asymmetric and symmetric vibrations of methylene group.…”