VALIDATION OF HPLC METHOD FOR THE DETERMINATION OF RIVAROXABAN FOR COMPARATIVE EXTRACTION IN STUDYING THE DELIVERY OF THE DRUG VIA NASOGASTRIC TUBE IN VITRO.

Abstract

A new coordination compound of Ni(II) with cyclohexylacetoacetate and N,N-diethylnicotinamide was synthesized and characterized by IR spectroscopy and X-ray analysis. The IR spect­rum exhibits intense broad absorption bands corresponding to the stretching vibrations of the C=O and C=C bonds conjugated within the chelate ring (1625, 1502 cm⁻¹), as well as other absorption bands characteristic of β-dicarbonyl complexes, in particular a sharp band at 775 cm⁻¹ attributed to the out-of-plane bending vibration of the C–H bond in the chelate ring. In the high-frequency region of the spectrum, there are signals of stretching vibrations of the C-H bonds of alkyl groups (2855–2990 cm^–1) and weak signals of stretching vibrations of the C-H of the pyridine ring (3080–3110 cm^–1). The absorption bands of the amide group (ν_С=О 1620–1650 cm^–1) and the pyridine ring (ν_С=С, ν_С=N 1500–1600 cm^–1) of N,N‑diethylnicotinamide overlap with the vibration bands of the chelate rings and cannot be unambiguously assigned. The medium-intensity band at 1300 cm⁻¹, present in both the free ligand and the complex, is assigned to C–N stretching vibrations of the amide group. The low-intensity bands in the 600–400 cm⁻¹ region are assigned to Ni–N and Ni–O vibrations. According to X-ray data, the crystal system of NiL₂NK₂ complex is monoclinic, space group P2₁/с, a = 7.0360(15) Å, b = 13.233(4) Å, c = 23.619(5) Å, α = γ = 90º,  β = 93.301(12)º. The structure corresponds to the formula [Ni(C₁₀H₁₅O₃)₂(C₁₀H₁₄N₂O)₂] and represents a mononuclear complex located in a special position relative to the inversion center. The cent­ral Ni atom has a O₄N₂ distorted octahedral environment. The axial positions of the coordination polyhedron are occupied by the nitrogen atoms of the pyridine ring of N,N‑diethylnicotinamide. The molecules of chelating ligands, coordinated through oxygen atoms, occupy an equatorial position with a trans configuration relative to each other. In the crystal, the complex molecules are bound by weak C-H…π interactions and form layers in the (001) plane, alternating with each other. The structure of the coordination polyhedron of the described compound is similar to the structure of adducts of β-dicarbonyl complexes of d‑metals with pyridine.