Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data

Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data

Quantum-chemical and correlation study of deprotonation and complexation of 1-amino-4-hydroxyanthraquinone

Existing views on the deprotonation and complexation of 1-amino-4-hydroxyanthraquinone are wrong. This compound, its anions, and complexes with metals are not individual substances, but they form a dynamic equilibrium mixture of keto-enol (keto-oxide) and amino-imine tautomers. Different samples of the same compound differ by the tautomeric composition, the respective information is contained in their electron absorption spectra. In weak alkaline solutions the deprotonation occurs exclusively at the hydroxy group. Most typical structure of 1-amino-4-hydroxyanthraquinone anions is 1,10-quinoid, its metal complexes have 9,10-and 1,10-quinoid structures. The ground states of molecules are more responsible for the tautomeric transformations than the excited states. Quantum-chemical calculations of tautomeric anthraquinones by semiempirical PPP methods are more reliable than modern ab initio calculations. © 2010 Pleiades Publishing, Ltd

Refinement of the Molecular Structure of Ammonium Pentachloroaquaferrate (NH4)2[FeCl5(H2O)]

Abstract: The crystal structure of ammonium pentachloroaquaferrate (NH4)2[FeCl5(H2O)] is refined (CIF file CCDC no. 1831198). Compounds (А)х[FeCl5(H2O)], where A is an organic or inorganic anion (х = 1, 2), crystallize in the orthorhombic crystal system. The geometry and structural parameters of the [FeCl5(H2O)]2– anion are nearly independent of the counterion nature. © 2019, Pleiades Publishing, Ltd

Quantum-chemical and correlation study of deprotonation and complexation of 1-amino-4-hydroxyanthraquinone

Existing views on the deprotonation and complexation of 1-amino-4-hydroxyanthraquinone are wrong. This compound, its anions, and complexes with metals are not individual substances, but they form a dynamic equilibrium mixture of keto-enol (keto-oxide) and amino-imine tautomers. Different samples of the same compound differ by the tautomeric composition, the respective information is contained in their electron absorption spectra. In weak alkaline solutions the deprotonation occurs exclusively at the hydroxy group. Most typical structure of 1-amino-4-hydroxyanthraquinone anions is 1,10-quinoid, its metal complexes have 9,10-and 1,10-quinoid structures. The ground states of molecules are more responsible for the tautomeric transformations than the excited states. Quantum-chemical calculations of tautomeric anthraquinones by semiempirical PPP methods are more reliable than modern ab initio calculations. © 2010 Pleiades Publishing, Ltd

Refinement of the Molecular Structure of Ammonium Pentachloroaquaferrate (NH₄)₂[FeCl₅(H₂O)]

The crystal structure of ammonium pentachloroaquaferrate (NH4)2[FeCl5(H2O)] is refined (CIF file CCDC no. 1831198). Compounds (А)х[FeCl5(H2O)], where A is an organic or inorganic anion (х = 1, 2), crystallize in the orthorhombic crystal system. The geometry and structural parameters of the [FeCl5(H2O)]2– anion are nearly independent of the counterion nature

Tautomeric transformations and electronic structures of azopyrazolone dyes and their metal complexes

The features of molecular and electronic structures of complex compounds derived from azopyrazolone derivatives are reviewed. Despite the wide use of metal-containing azopyrazolone dyes for more than 1.5 centuries, little information on their molecular structure is found. Our recent researches allowed the introduction of new coordination modes of azopyrazolone derivatives at complexation with metals. Together with traditional bi- and tridentate coordination, the possibility of an N pyrazolone atom to be involved in coordination was also found. As a result, polymeric or polynuclear complexes were isolated and described by X-ray analysis, NMR, EPR, IR, and UV spectroscopy. The analysis of the interatomic distances in the organic anions indicated that azopyrazolone derivatives do not undergo significant azo-hydrazo tautomeric transformations at ionization and complexation despite strong shifts of the absorption bands in their IR and UV-VIS spectra. © 2018 Walter de Gruyter GmbH, Berlin/Boston

Complexation of chalocogenadiazoles with 3d metals: Crystal and molecular structure of naphtho[1,2-c][1,2,5]thiazol-9-ol

Nine complexes of copper(II), cobalt(II), Ni(II), and Zn(II) chlorides with naphtho[1,2,-c][1,2,5]oxadiazol-9-ol (HL1), naphtho[1,2-c][1,2,5] thiadiazol-9-ol (HL2), and naphtho[1,2-c][1,2,5]sel-enadiazol-9-ol (HL3) have been synthesized, isolated in the crystalline state, and studied by physicochemical methods. The composition of the complexes in solutions as been determined and their stability constants have been calculated from spectrophotometric data. The electronic structures of the ligands and complexes have been calculated by quantum-chemical methods. The crystal and molecular structure of HL2 has been determined by X-ray crystallography. © Pleiades Publishing, Ltd., 2011