Search

The article reports the synthesis, crystal structure and spectroscopic properties of the trans-anti [CR(Me,2tn)2(OH)(H2O)]-CIO4)2 to elucidate the influence of O-donor ligands occupying the axial positions and counter anion. It shows that chromium atom is in a distorted octahedral environment coordinated by 2 biidetate, 2,2-dimethyl-1,3-propanediamine ligands and 2 O atoms of hydroxy group and water molecule in trans position.

The aim of the present study is to explore the possibility of utilizing loess for the adsorption of total phosphorous (T-P) and total nitrogen (T-N) in water. Batch adsorption studies were performed to evaluate the influences of various factors like initial concentration, contact time and temperature on the adsorption of T-P and T-N. The adsorption data showed that loess is not effective for the adsorption of T-N. However, loess exhibited much higher adsorption capacity for T-P. At concentration of 1.0 mg L-1, approximately 97% of T-P adsorption was achieved by loess. The equilibrium data were fitted well to the Langmuir isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher R² compared with the pseudo-first-order and intra-particle kinetic model. The theoretical adsorption equilibrium qe,cal from pseudo-second-order kinetic model was relatively similar to the experimental adsorption equilibrium qe,exp. The thermodynamic parameters such as free energy ρG, the enthalpy ρH and the entropy ρS were also calculated. [ABSTRACT FROM AUTHOR]

Two diastereoisomers of cyclo(Pro-Tyr) have been synthesized simultaneously. The crystal structures and conformations of both cyclo(L-Pro-L-Tyr) and a racemic mixture of cyclo(D-Pro-L-Tyr) and cyclo(L-Pro-DTyr), abbreviated as rac-cyclo(D-Pro-L-Tyr/L-Pro-D-Tyr), have been determined by a single-crystal X-ray diffraction study at low temperature. The crystals of rac-cyclo(D-Pro-L-Tyr/L-Pro-D-Tyr) belong to orthorhombic space group Pna21 with a = 10.755 (1), b = 12.699 (1), c = 9.600 (1) Å and Z = 4. The tyrosine side chain is folded towards the diketopiperazine (DKP) ring. The DKP ring adopts a twist boat conformation with pseudo symmetry C2v. The pyrrolidine ring has an envelope conformation with the N5, C4, C7 and C8 atoms in a plane. The crystal of rac-cyclo(D-Pro-L-Tyr/L-Pro-D-Tyr) is stabilized by hydrogen bonds between amide N2-H2 and carbonyl oxygen O2 in the neighbor. The hydroxyl group of tyrosine residue is also hydrogen bonded to the oxygen of the carbonyl group of the DKP ring in the next molecule. The spectroscopic properties of both isomers are also described. [ABSTRACT FROM AUTHOR]

Photodegradation of several thiols and thiones including 2-pyrimidinethiol, thiazolidine-2-thione, imidazolidine-2-thione, 1,2,4-triazole 3-thiol and 2,5-dimercapto-1,3,4-thiadiazole have been studied in aerated aqueous solution using zinc oxide under irradiation with 400W high pressure mercury lamp. Rate constants span the range from 2.44 × 102 min-1 to 1.76 × 10-1 mind. The slower degradation rate of 2-imidazoline 2- thione could be related to oxidation potential of the corresponding ring. The Langmuir-Hinshelwood (L-H) rate constant kr and adsorption constant, (KA) for all five thiols and thiones are reported. [ABSTRACT FROM AUTHOR]

In the title compound, [Cu(NO3)2(C20H40N4)]·3H2O, the Cu atom lies on a crystallographic inversion centre and has a distorted octahedral geometry, with four N atoms of the macrocyclic ligand in the equatorial positions and two O atoms of the axial nitrate ligands. The long axial Cu—O bond of 2.746 (2) Å may result from the Jahn-Teller effect. The macrocyclic ligand adopts the most stable trans-III configuration with the two six-membered rings in chair form and two five-membered rings in a gauche form. [ABSTRACT FROM AUTHOR]

In the title compound, [Cr(ONO)2(cyclam)]NO2 (cyclam is 1,4,8,11-tetraazacyclotetradecane, C10H24N2), the complex cation is located on a twofold symmetry axis. The central Cr atom has a distorted octahedral coordination, involving two Cr-O bonds, with the monodentate nitrite O atoms adopting a cis configuration, and four Cr-N bonds. The mean Cr-N and Cr-O distances are 2.0895 (14) and 1.9698 (14) Å. [ABSTRACT FROM AUTHOR]

Studies the geometrical structures of chromium complexes. Evidence of two crystallographically independent chromium complex moieties; Existence of a strong hydrogen-bonding interaction between the atoms.; Conformational isomers of the chromium complex cation.

In the title compound, [Cu(ClO4)2(C20H40N4)], the CuII ion has a tetragonally distorted octahedral environment, with the four N atoms of the macrocyclic ligand in equatorial positions and the O atoms of two perchlorate groups in axial positions. The CuII ion is situated on an inversion centre. The macrocyclic ligand adopts its most stable trans-III conformation. The long axial Cu—O bond is the result of the Jahn–Teller effect. The crystal structure is stabilized by intramolecular hydrogen bonds between secondary N—H and the O atoms of the perchlorate groups. [ABSTRACT FROM AUTHOR]

The mol­ecule of the title compound, 2,13-dibenzyl-5,16-dimethyl-2,6,13,17-tetra­azatricyclo­[16.4.01,18.07,12]docosane, C34H52N4, is centrosymmetric. The 14-membered macrocycle adopts the stable trans-III ( RRSS) configuration, with one benzyl group above and the other below the macrocycle mean plane. The crystal structure is stabilized by N—H⋯N hydrogen bonds. There is no inter­molecular π–π inter­action between benzyl planes, which are almost 6Å apart. [ABSTRACT FROM AUTHOR]