ABSTRACT
In the title compound, C11H17N5O4, the bond distances show evidence of a highly polarized molecular-electronic structure. The molecules are linked into a three-dimensional framework by a combination of O-H...O and N-H...O hydrogen bonds, including a very short O-H...O hydrogen bond [H...O=1.67 A, O...O=2.494 (2) A and O-H...O=166 degrees].
ABSTRACT
The results presented in this work are related to the design of a guideline to develop specific properties at the surface of an activated carbon (AC). For this, two model aromatic compounds have been synthesized and their electrolytic behavior in aqueous solutions was studied by a potentiometric method. The textural characteristics of the activated carbon were determined by porosimetry methods. The nature of oxygen-carrying functions and the acid-base behavior of the AC surface were characterized by TPD and potentiometric titration methods, respectively. The adsorption and desorption equilibria of the aromatic compounds on activated carbon were measured in aqueous solutions, and the hysteresis between adsorption and desorption, which reveals irreversible adsorption, was discussed on the basis of the frontier orbital theory. HOMO and LUMO orbitals of the adsorbent and adsorbates were calculated, and irreversible adsorption was attributed to the small energy difference between HOMO and LUMO of the aromatic adsorbates and the adsorbent. Adsorption equilibria of K2CrO4 in aqueous solution on the AC alone and on the AC-aromatic ligand adsorbents, respectively, prove the efficient development of specific chemical functions at the carbon surface provided by the adsorbed aromatic compounds.
ABSTRACT
Molecules of the title compound, C(9)H(9)N(5)O(3), are linked into sheets by a combination of one O-H...N hydrogen bond and one N-H...O hydrogen bond.
Subject(s)
Glycine/analogs & derivatives , Glycine/chemistry , Pteridines/chemistry , Crystallography, X-Ray , Hydrogen Bonding , Models, Molecular , Molecular ConformationABSTRACT
Nine hydrated complexes of Group 2 (alkaline earth) cations with organic ligands which are N-substituted amino acids containing the 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl group have been structurally characterized. The octahydrated calcium glycinate complex, where the six-coordinate Ca cation lies on an inversion centre in the space group P(-)1, forms a finite (zero-dimensional) complex. The hexahydrated barium glycinate complex contains eight-coordinate Ba and it is isostructural with the known Sr analogue, and its one-dimensional coordination polymer takes the form of a simple chain. The octahydrated calcium and strontium threonine complexes are isostructural, with eight-coordinate cations lying on twofold rotation axes in the space group C2: the one-dimensional coordination polymers take the form of a chain of spiro-fused rings and a similar chain of spiro-fused rings is found in the heptahydrated barium serine complex, although here the ten-coordinate cation lies in a general position. In the tetrahydrated strontium and barium glycylglycinate complexes, the eight-coordinate cations lie on twofold rotation axes in the space group C2/c, but in the Sr complex the coordination polymer is a chain of spiro-fused rings, while in the Ba complex the coordination polymer forms deeply puckered sheets. There are two types of Ca site in the hexahydrated calcium valine complex: one is eight coordinate and gives rise to a two-dimensional coordination polymer, while the other is seven coordinate forming a finite, zero-dimensional coordination complex. In the heptahydrated barium methionine complex, the coordination polymer is three dimensional. In all of the complexes, the coordination aggregates are further linked by an extensive series of hydrogen bonds.
Subject(s)
Amino Acids/chemistry , Cations, Divalent/chemistry , Nitroso Compounds/chemistry , Pyrimidinones/chemistry , Barium/chemistry , Calcium/chemistry , Crystallography, X-Ray , Glycine/analogs & derivatives , Glycine/chemistry , Glycylglycine/analogs & derivatives , Glycylglycine/chemistry , Hydrogen Bonding , Ligands , Methionine/analogs & derivatives , Methionine/chemistry , Molecular Conformation , Molecular Structure , Molecular Weight , Polymers/chemistry , Serine/analogs & derivatives , Serine/chemistry , Strontium/chemistry , Threonine/analogs & derivatives , Threonine/chemistry , Valine/analogs & derivatives , Valine/chemistry , Water/chemistryABSTRACT
Molecules of the title compound, C(5)H(6)N(4)O(3), are linked into a single three-dimensional framework by a two-centre N-H.O hydrogen bond [H.O = 1.92 A, N.O = 2.785 (2) A and N-H.O = 168 degrees ], a two-centre N-H.H hydrogen bond [H.N = 2.19 A, N.N = 3.017 (2) A and N-H.N = 157 degrees ] and the intermolecular component of an effectively planar three-centre N-H.(O)(2) hydrogen bond [H.O = 2.03 and 2.31 A, N.O = 2.645 (2) and 2.957 (2) A, N-H.O = 126 and 130 degrees, and O.H.O = 101 degrees ].
ABSTRACT
The title compound, C(10)H(13)N(5)O(6), exhibits a highly polarized molecular-electronic structure and the conformation is influenced by two intramolecular N-H.O hydrogen bonds. The molecules are linked into a single framework by hydrogen bonds of types O-H.O [O-H = 1.22, H.O = 1.38, O.O = 2.558 (6) A and O-H.O = 160 degrees ], N-H.O [H.O = 2.26, N.O = 2.866 (6) A and N-H.O = 126 degrees ] and O-H.N [O-H = 1.26, H.N = 1.56, O.N = 2.811 (6) A and O-H.N = 170 degrees ]. The substructure generated by the O-H.O and N-H.O hydrogen bonds takes the form of a double helix.
Subject(s)
Glutamic Acid/analogs & derivatives , Glutamic Acid/chemistry , Pyrimidines/chemistry , Crystallography, X-Ray , Hydrogen Bonding , Models, Molecular , Molecular Conformation , Molecular StructureABSTRACT
In the title compound, [Sr(C7H8N5O4)2(H2O)5]*H2O, one of the anionic (C7H8N5O4)- ligands acts as a simple monodentate ligand coordinated via a carboxyl O atom, while the other acts as a bridging ligand between pairs of Sr atoms, utilizing one carboxyl O and the nitroso O atom, so generating a one-dimensional coordination polymer. Five water molecules are coordinated to Sr, resulting in eight-coordination in the form of a distorted square antiprism, while the sixth water molecule is hydrogen bonded to a coordinated water. The coordination polymer chains are reinforced by O-H.N and O-H...O hydrogen bonds and are linked into a three-dimensional framework by an extensive series of N-H...O and O-H...O hydrogen bonds.
