Thermal, spectroscopic (IR, Raman, NMR) and theoretical (DFT) studies of alkali metal complexes with pyrazinecarboxylate and 2,3-pyrazinedicarboxylate ligands

Abstract

Pyrazinecarboxylic acid and its derivatives show biological properties (inter alia antimicrobial and antifungal). In the frame of this work, the salts of 2-pyrazinecarboxylic and 2,3-pyrazinedicarboxylic acids with alkali metal cations were synthesized as well as the spectroscopic (IR, Raman, NMR), theoretical [density functional theory (DFT)] and thermogravimetric studies of obtained compounds were done. The FT-IR and FT-Raman spectra of alkali metal 2-pyrazinecarboxylates and 2,3-pyrazinedicarboxylates were recorded and analyzed in the region of 4000-400 cm -1 . 1 H NMR and 13 C NMR spectra of analyzed compounds have been registered and assigned. The electronic charge distribution for the studied acids and their salts with lithium, sodium and potassium was calculated. All the calculations were done in the frame of p) basis set. The thermal decomposition of the analyzed compounds was done.

Spectroscopic (IR, Raman, UV–Vis) study and thermal analysis of 3d-metal complexes with 4-imidazolecarboxylic acid

“…This means that sodium destabilizes the electronic charge distribution in the aromatic ring of 4-imidazolecarboxylic acid, while the 3d metals can have a stabilizing effect on the distribution of this charge. Analogous observations have been made for other ligands (aromatic and heteroaromatic acids)-the alkali metals disturb the aromatic system of ligands, while the 3d metals stabilize the system [22,23,30,31].…”

“…Spectroscopic (IR, Raman, UV-Vis) study and thermal analysis of 3d-metal complexes with… 519 matter and the gaseous products that arise during thermal decomposition [22,23]. If the thermal decomposition is conducted in an inert gas atmosphere (argon), other end products are created.…”

“…In our earlier work, we studied the structure and thermal properties of metal complexes with nitrogen-containing heteroaromatic acids, i.e., pyridinecarboxylic and pyrazinecarboxylic acids [22,23]. In this work, the thermal properties of 4-imidazolecarboxylic acid complexes have been investigated.…”

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes (sodium, manganese, copper, nickel, cobalt and zinc) with pyrimidine-5-carboxylic and pyrimidine-2-carboxylic acids

“…In complexes of heteroaromatic acids, the metal may be attached via a carboxyl anion and heteroatoms of the aromatic ring. These types of binding are formed inter alia in the pyridine-2-carboxylic, pyrazine-2-carboxylic or pyrimidine-2-carboxylic acid complexes [15][16][17][18]. The pyrimidine-5-carboxylic acid may form complexes by attaching a metal via a ring nitrogen atom without the participation of a carboxylic group [19].…”

Reinvestigations of the Li2O–WO3 system

“…The pure phases obtained in this work were examined additionally by the DTA-TG, UV-Vis-IR/DRS and IR methods. These measuring methods were selected because they allow determination of phase composition of samples, establishing their melting temperatures as well as melting behaviour [23][24][25][26][27][28][29][30]. X-ray phase analysis (XRD) of the samples was performed using an Empyrean II diffractometer (PANalytical, The Nederlands, copper radiation filtered with a graphite monochromator) with the help of Highscore ?…”