Forms, structural properties, intermolecular interaction

Dithiolene complexes with the maleonitriledithiolate (mnt) ligand form highly delocalized systems and are widespread in studies of conducting and magnetic materials. The electronic properties have been extensively studied with various computational methods including Hiickel and extended Hiickel approaches to identify the nature of the orbitals involved in intramolecular and intermolecular interactions. These structural properties allow the complexes to interact in the solid state via short stacking S, S and short interstack S---S contacts.10 4-1048... 

Another important lesson that we can leam from the data presented in Table 6.1 is that the activity coefficient of an organic compound in an organic solvent depends strongly on the prospective involvements of both the partitioning compound and the solvent for dispersive, dipolar, H-donor, and H-acceptor intermolecular interactions. This implies that we may need to represent the properties of both the solute and the solvent when we seek to correlate air-liquid partition constants of structurally diverse substances. Thus, if the types of intermolecular interactions of a variety of solutes interacting with two chemically distinct solvents 1 and 2 are very different, a one-parameter LFER for all compounds, i, of the form ... 

The above properties (a and b) are interpreted by Cohen and Schmidt (21) on the basis of a detailed crystallographic study of photochromic and thermochromic anils. They conclude that photochromic crystals involve structures in which the central portion of adjacent molecules are essentially isolated from one another, so that, to a first approximation the energetics are that of an isolated molecule. On the other hand, when the alignment of the molecular dipoles is such as to give strong intermolecular interactions then the transition to the quinoid form requires much less energy and can occur thermally. For crystals in which thermochromism occurs, the photochemical isomerization is still possible but the reverse reaction is so rapid that no buildup of color is observed. In fact, fluorescence measurements on the thermochromic 5 -chlorosalicylidene-aniline (Fig. 5) indicate that photochemical isomerization precedes the luminescence process via the photochromic route ... 

A hydrogen bond is formed through intermolecular interaction between an electron-deficient hydrogen and a region of high electron density. Its fundamental role in the structure of DNA and the secondary and tertiary structures of proteins is known. The specific properties and structures of water are also caused by hydrogen bonds. 

Substituted cyclopentadienyl with the pentamethyl group results in (i) increased covalent character of the metal-cyclopentadienyl bond, (ii) strong n donor and weak n acceptor properties, (iii) kinetic stabilization due to steric shielding of the metal ion, and (iv) increased thermal stability of the metal complexes, (v) decrease in tendency to form polymeric structures due to increase in intermolecular interactions, (vi) increased solubility in organic solvents, and (vii) increase in vapour pressure. 

Ceo forms complexes with a variety of molecules. In the solid state the intermolecular interactions in these materials stabilize lattice structures which, because they are novel, are of potentially great interest. This is particularly the case if the resulting systems exhibit the properties associated with partial or complete electron transfer (Section 6.1.1). 

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