Geometry molecular packing

The early Hartley model [2, 3] of a spherical micellar stmcture resulted, in later years, in some considerable debate. The self-consistency (inconsistency) of spherical symmetry witli molecular packing constraints was subsequently noted [4, 5 and 6]. There is now no serious question of tlie tenet tliat unswollen micelles may readily deviate from spherical geometry, and ellipsoidal geometries are now commonly reported. Many micelles are essentially spherical, however, as deduced from many light and neutron scattering studies. Even ellipsoidal objects will appear... 

The macrocyclic phthalocyanine ligand will form a complex Pt(phthalocyanine).1106 The crystal structure shows two polymorphs present because of molecular packing.1107 The platinum is in a square planar coordination geometry with a mean Pt—N distance of 1.98 A. The complex can be partially oxidized with iodine to give conducting mixed valence solids.1108 Eighteen fundamental and overtone combination bands are observed in the resonance Raman spectrum of platinum phthalocyanine, and from this data the symmetry of the excited singlets are found to be Dy.. Qlv or D2.1109... 

Molecular geometry Crystal packing UV light Heat... 

The crystal structure of /3-Ce(acac)4 has square antiprismatic geometry for the metal polyhedron [93] in the same isomeric form as in the case [129] of a-Ce(acac)4. The mean Ce-O distance in the /1-form is 2.32 A which is shorter than 2.40 A in the inform. The main difference between the two forms lies in molecular packing rather than stereoisomerism [130]. 

Thus, in cases when weak interactions can affect the molecular geometry, the packing of the molecules in the crystal lattice and the solvent effect acquire an important role. In solutions a structure may exist which differs from that achieved in the gaseous phase under the action of intramolecular forces only. 

Determination of the crystal structures to obtain the geometrical information— molecular geometries and packing motif—of the various polymorphs. 

In spite of the close similarity of molecular geometry and the fact that the arsenic and ruthenium compounds crystallize with the same space group symmetry, the unit cell shapes are dissimilar and, moreover, the molecular packing is quite different. In FXeFAsF, the long dimensions of the formula units are all nearly parallel to each other, while in FXeFRuF, there are two orientations nearly perpendicular to each other. The molecular volumes differ by less than 3%, reflecting the... 

To assess what can be learned from a crystal structure determination the results of a few selected structure analyses will now be analyzed in terms of the molecular geometry and packing in the crystal. 

Brock, C. P., and Morelan, G. L. Relationships between molecular geometry, crystal packing, and thermal motion temperature-dependent studies of three crystal forms of 4-hydroxybiphenyl. J. Phys. Chem. 90,5631-5640 (1986). 

The structure of the optically active (.S )-alanine consists of layers of alanine molecules, all of the same enantiomer, (Figure 5.8). The structure displayed as atom packing is not helpful, (see i.e. urea, in Chapter 1), and it is preferable to delineate molecules using the familiar ball and stick approach. This allows the molecular geometry and packing to be visualised. Even so, the structure of a molecule is not easy to see from a two-dimensional figure, but in fact, the hydrogen atom is below the central carbon atom, the NH2... 

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