On the conformational geometry for "almost" self-avoidance polymers chains.

We deduce the efective ordinary non linear differential equations satisfied by the moments associated to the end to end probability distribution of a polymer chain in the presence of a potential simulating phenomenologically the self avoidance of the chain with the coordinate z axis

Qualitative and quantitative analysis of intermolecular interactions in xanthenedione derivatives

The existence of intermolecular interactions and the conformational geometry adopted by molecules are related to biological activity. Xanthenedione molecules are promising and emerging antioxidants and acetylcholinesterase inhibitors. To examine the role of different functional groups involved in the intermolecular interactions and conformational geometries adopted in xanthenediones, a series of three substituted xanthenediones have been crystallized [9-(3-hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione, C23H26O4, 9-(5-bromo-2-methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione, C24H27BrO4, and 3,3,6,6-tetramethyl-9-(pyridin-2-yl)-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione, C22H25NO3] and their intermolecular interactions analyzedviaHirshfeld analysis. The results show that all the derivatives adopt the same structural conformation, where the central ring has a shallow boat conformation and the outer rings have a twisted boat conformation. The intermolecular interactions in the molecules are predominantly O—H...O, C—H...O and π–π interactions. The optimized structures of the derivatives from theoretical B3LYP/6-311G** calculations show a good correlation with the experimental structures. The lattice energy involved in the intermolecular interactions has been explored usingPIXELC.

Crystal Structures of [H4L](ClO4)4.6H2O And [Zn(H2L)(S2O6)2].4H2O (L = 6,13-Dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine)

The substituted macrocycle 6,13-dimethyl-1,4,8,11- tetraazacyclotetradecane-6,13-diamine (L) can be crystallized as the perchlorate salt or the zinc dithionate complex. The crystal structures of [H4L](ClO4)4.6H2O (1) and [Zn(H2L)(S2O6)2].4H2O (2) have been determined by X-ray diffraction methods and refined to a residual of 0.058 for 1926 independent observed reflections for (1) and 0.022 for 2122 independent reflections for (2). The crystals of (1) are monoclinic, P21/c, a 10.657(2), b 12.466(7), c 12.216(3)Ǻ, β 96.73(2)° and those of (2) are monoclinic, P21/c, a 8.521(1), b 12.990(1), c 12.731(1)Ǻ,β 105.45(1)°. The pendant primary amines in the zinc(II) complex of L are protonated and not coordinated, with conformational geometry very similar in both structures.

A quantum-chemical study of pesticidal activity of phenylurea derivatives. The equilibrium geometries

Quantum-chemical methods have been used to study geometry of 13 phenylurea derivatives with respect to their herbicidal activity. From energy hypersurfaces of the equilibrium geometries it was possible to determine the shape and evaluate the flexibility of the molecules. An interdependence is observed between space arrangement and herbicidal activity of some derivatives. However, the exception found indicate that conformational geometry of the molecules studied does not represent a sufficient condition for their herbicidal activity.