Complexes of Some Pyrido[1,2-a]pyrimidinium Perchlorates with Scandium,Yttrium, and Lanthanum. Crystal and Molecular Structure of 3-Chloro-9-Hydroxy-2,4-Dimethylpyrido[1,2-a]pyrimidinium Perchlorate

Complexes of scandium, yttrium, and lanthanum nitrates with 3-chloro-9-hydroxy-2,4-dimethylpyrido[1,2-a]pyrimidinium perchlorate (HL¹ClO₄) and 9-hydroxy-2,4-dimethylpyrido[1,2-a]pyrimidinium perchlorate (HL²ClO₄) were obtained. Their composition was formulated as Sc(LClO₄)₂(NO₃) and M(LClO₄)₂(NO₃)₂ (L = L¹ or L²; M = Y or La); structures for the complexes obtained were proposed. The crystal and molecular structure of HL¹ClO₄ was determined. Dissociation and complexation of HL¹ClO₄ and HL²ClO₄ in aqueous ethanol were studied using the spectroscopic method. Ligand dissociation and complexation constants were calculated. It was shown that a chlorine-containing organic ligand only slightly changes the composition and stability of the metal complexes.     

Synthesis,electronic structure,and absorption spectra of 9-hydroxypyrido[1,2-a]-pyrimidinium derivatives

Pyrido[1,2-a]pyrimidinium salt derivatives have been prepared by condensation of 2-aminopyridinium salts with -dicarbonyl compounds. The acid-base equilibrium dissociation constants for 2,4-dimethyl-9-hydroxypyrido[1,2-a]pyrimidinium perchlorate have been measured, and the spectroscopic characteristics of its neutral, anionic, and cationic forms have been determined; the electronic absorption spectra of the neutral and anionic forms of 2,4-dimethyl-9-hydroxypyrido[1,2-a]-pyrimidinium perchlorate have been interpreted based on this experimental and calculated data.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1381–1387, October, 1991.     

Synthesis and Physicochemical Properties of Some Transition Metal Complexes with 3-Hydroxypyridine

The complexes ML₂ · 2H₂O and CrL₃ · 8H₂O were synthesized by the reaction of Cu(II), Ni(II), Co(II), Cd(II), and Cr(III) nitrates with 3-hydroxypyridine (HL) and identified. The spectroscopic characteristics of neutral, anionic, and cationic forms of the ligand were determined. It was shown that 3-hydroxypyridine enters the complex as an anion to give polymeric chains due to the ligand coordination through the N and O atoms. Complexation of copper, cobalt, and chromium nitrates with 3-hydroxypyridine in ethanol solutions was studied, and the formation constant of the copper complex was calculated. It was found that Cu(II) and Cr(III) complexes are formed in the solid state and in solutions (M : L = 1 : 2 and 1 : 3, respectively; in the case of Cu(II), the M : L ratio is 1 : 3).     

X-ray diffraction studies of 6-methyl-5-acetyl-4-α-furyl-2-keto-1,2,3,6-tetrahydropyrimidine and 6-methyl-5-acetyl-4-γ-bromophenyl-2-thio-1,2,3,6-tetrahydropyrimidine

6-Methyl-5-acetyl-4-α-furyl-2-keto-1,2,3,6-tetrahydropyrimidine (I) and 6-methyl-5-acetyl-4-γ-bromophenyl-2-thio-1,2,3,6-tetrahydropyrimidine (II) are prepared by the modified Biginelli reaction, and their crystal and molecular structures are studied. It is shown that, in crystals I and II, the pyrimidine ring has an amide tautomeric form and adopts a sofa conformation. The IR absorption spectra are analyzed, and the stability of the tautomers of the pyrimidine fragments is evaluated using quantum-chemical calculations.     

Synthesis,Crystal Structure,and IR Absorption Spectra of the Adduct of Copper(II) Acetate Monohydrate with 1-Amino-4-aza-9-fluorenone Cu2(CH3COO)4(H2O)2· C12H8N2O

The crystal structure of the adduct of copper(II) acetate monohydrate and 1-amino-4-aza-9-fluorenone Cu₂(CH₃COO)₄(H₂O)₂· C₁₂H₈N₂O was determined. The structure is layered; the layers are formed by alternating columns of copper(II) acetate monohydrate complexes and columns of dimers of 1-amino-4-aza-9-fluorenone. The layered structure of the adduct is stabilized by a hydrogen bonding system. Changes in the IR absorption spectra due to the formation of the adduct were discussed.     

Spectral characteristics,structure, and properties of phenanthridone derivatives

On the basis of IR and electronic spectra and quantum-chemical calculations, a conclusion has been drawn regarding the structure of phenanthridone and its derivatives: It has been confirmed that in the crystalline state and in solutions, phenanthridones exist primarily in the lactam form. An interpretation is given for the longwave bands in the electronic absorption spectra. Certain spectral criteria are proposed for determining the positions of substituents in the phenyl rings of phenanthridones, and the direction of aromatic substitution of the lactim and cationic forms of phenanthridone have been evaluated. Acid association constants of phenanthridone and its derivatives have been determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1361–1368, October, 1992.     

Spectral characteristics and acid-base equilibria of 4,9-dihydroxy-5,10-dioxo-4,5,9,10-tetrahydro-4,9-diazapyrene and its 2,7-derivatives

The IR and electronic spectra of 2,7-disubstituted 4,9-dihydroxy-5,10-dioxo-4,5,9,10-tetrahydro-4,9-diazapyrene (R = H, I, NH₂, NO₂, OH) are studied. Analysis of the IR bands shows that, in crystalline form and in neutral and basic solutions, the compounds exist predominantly in the hydroxamic form. It is established that in sulfuric acid solutions the oxygen atoms of the C=O groups are protonated. The spectral characteristics of the neutral and ionized forms of the compounds are determined. The acid ionization constants are measured by potentiometric titration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 94–99, January, 1993.