Crystal structure and spectral characteristics of 2-methyl-3-chloro-9- hydroxypyrido[1,2-a]pyrimidin-4-one and bis(2-methyl-3-chloro-9-hydroxypyrido[1, 2-a]pyrimidin-4-onium) perchlorate

- 2-Methyl-3-chloro-9-hydroxypyrido[1,2-a]pyrimidin-4-one (I) and bis(2-methyl-3-chloro-9-hydroxypyrido[1,2-a]pyrimidin-4-onium) perchlorate (Ia) are synthesized and studied by X-ray diffraction and IR spectroscopy. It is shown that compound I exists in the molecular form in crystals and in the zwitterion form in solutions. The structural units of compound Ia are partially protonated centrosymmetric dimeric cations and perchlorate anions. The dimeric cation involves two molecules I in the zwitterion form. These molecules are linked together by a strong symmetric hydrogen bond formed with the participation of a proton located at the inversion center. The structures of a series of pyrido[1,2-a]pyrimidines are investigated and compared. It is demonstrated that the tautomeric equilibrium revealed in solutions of compounds of this class depends on the solvent type and pH of the medium. © 2004 MAIK "Nauka/Interperiodica"

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 ((HLClO4)-Cl-1) and 9-hydroxy-2,4-dimethylpyrido[1,2-a]pyrimidinium perchlorate ((HLClO4)-Cl-2) were obtained. Their composition was formulated as Sc(LClO4)(2)(NO3) and M(LClO4)(2)(NO3)(2) (L = L-1 or L-2; M =Y or La); structures for the complexes obtained were proposed. The crystal and molecular structure of (HLClO4)-Cl-1 was determined. Dissociation and complexation of (HLClO4)-Cl-1 and (HLClO4)-Cl-2 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 and Structure of the 2-Amino-3-Hydroxypyridine Complexes with Trivalent Praseodymium, Neodymium, Samarium, and Europium Nitrates: Crystal Structure of Tris(2-Amino-3-Hydroxypyridine)trinitratosamarium(III) Monohydrate

The complexes of the composition LnL3(NO3)3 · nH2O (Ln = Pr, Nd, Sm, Eu; n = 0-3) are prepared by the reaction of Ln(NO3)3 with 2-amino-3-hydroxypyridine (L) in acetone at pH 2. The crystal structure of SmL3(NO3)3 · H2O is determined. The ligand is involved in the complex as a neutral species of the bipolar ion coordinated through the oxygen atom. The IR and UV spectral parameters of the complexes are discussed

Crystal structure and spectral characteristics of 2-methyl-3-chloro-9- hydroxypyrido[1,2-a]pyrimidin-4-one and bis(2-methyl-3-chloro-9-hydroxypyrido[1, 2-a]pyrimidin-4-onium) perchlorate

- 2-Methyl-3-chloro-9-hydroxypyrido[1,2-a]pyrimidin-4-one (I) and bis(2-methyl-3-chloro-9-hydroxypyrido[1,2-a]pyrimidin-4-onium) perchlorate (Ia) are synthesized and studied by X-ray diffraction and IR spectroscopy. It is shown that compound I exists in the molecular form in crystals and in the zwitterion form in solutions. The structural units of compound Ia are partially protonated centrosymmetric dimeric cations and perchlorate anions. The dimeric cation involves two molecules I in the zwitterion form. These molecules are linked together by a strong symmetric hydrogen bond formed with the participation of a proton located at the inversion center. The structures of a series of pyrido[1,2-a]pyrimidines are investigated and compared. It is demonstrated that the tautomeric equilibrium revealed in solutions of compounds of this class depends on the solvent type and pH of the medium. © 2004 MAIK "Nauka/Interperiodica"

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 ((HLClO4)-Cl-1) and 9-hydroxy-2,4-dimethylpyrido[1,2-a]pyrimidinium perchlorate ((HLClO4)-Cl-2) were obtained. Their composition was formulated as Sc(LClO4)(2)(NO3) and M(LClO4)(2)(NO3)(2) (L = L-1 or L-2; M =Y or La); structures for the complexes obtained were proposed. The crystal and molecular structure of (HLClO4)-Cl-1 was determined. Dissociation and complexation of (HLClO4)-Cl-1 and (HLClO4)-Cl-2 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 and Structure of the 2-Amino-3-Hydroxypyridine Complexes with Trivalent Praseodymium, Neodymium, Samarium, and Europium Nitrates: Crystal Structure of Tris(2-Amino-3-Hydroxypyridine)trinitratosamarium(III) Monohydrate

The complexes of the composition LnL3(NO3)3 · nH2O (Ln = Pr, Nd, Sm, Eu; n = 0-3) are prepared by the reaction of Ln(NO3)3 with 2-amino-3-hydroxypyridine (L) in acetone at pH 2. The crystal structure of SmL3(NO3)3 · H2O is determined. The ligand is involved in the complex as a neutral species of the bipolar ion coordinated through the oxygen atom. The IR and UV spectral parameters of the complexes are discussed