Jt-n interaction

The crystal structure of [CiCiIm][Tf2N] bears little resemblance to the liquid [38] in contrast to those for [CiCiIm]Cl and [CiCiIm][PFJ. Stacks of cations resulting from jt-n interactions are clearly seen in the solid state, yet in the liquid the relevant positions above and below the imidazolium ring are occupied solely by anions. Also, the conformation of the [TfjN] in the crystal is almost exclusively cis, but in the liquid a mixture of trans and cis conformers is observed in the ratio of 4 1. Even aspects as subtle as this are picked up by the complementary forcefield simulations that predict a similar ratio. 

The Schiff base complex (123) forms a 1 1 complex with p-chloranil, which has been intensively investigated. There is evidence for both a jt-n interaction of the aromatic rings with the complex, and a local donor-acceptor interaction of the metal with the chloro substituent. 

Carbon nanotubes (CNTs) have been added to a polymeric matrix to improve their mechanical and other properties [69]. The use of CNTs in PEM must be carried out with caution because the well-known high electrical conductivity may cause short circuiting in proton exchange membrane fuel cells. The jt-n interaction between PBI and the side walls of CNT makes these two different materials compatible. Despite CNT-PBI composite membranes have shown enhancement in mechanical strength, the proton conductivity resulted in some cases compromised [70, 71]. Hence, different authors functionalized the CNTS in order to increase both the proton conductivity and the mechanical properties for hydrogen fed PBI-based HT-PEMFC [72, 73]. In this context,... 

On the other hand, when n lies close to Jt-HOMO, the interaction between 7t-HOMO and n is strong. Both orbitals contribute considerably to FMO. The combined orbital, Jt-HOMO - n is a component of FMO. The Jt orbital interacts with the n more strongly than with the jt-HOMO dne to the spatial proximity. The phase of is determined by the relation with n rather than jt-HOMO so as to be out-of-phase with n (viz. in phase with Jt-HOMO). As a result, is the opposite... 

X-Ray diffraction studies of l-(4,6-dimethylethylsulfanyl-l-//-pyrazolo[3,4-r/ pyrimidinyl)-3-(5-methyl-6-methyl-sulfanyl-4-oxo-l,5-dihydropyrazolo[3,4-, pyrimidin-l-ylpropane 69, the Leonard trimethylene linker, showed unusual U-moieties formed due to intramolecular 7t—Jt stacking interactions, CH- -N, CH- -S, and S- -S interactions <2006JST106>. 

Stepnowski, R, Nichthauser, Mrozik, W., and Buszewski, B., Usefulness of jt- -n aromatic interactions in the selective separation and analysis of imidazolium and pyridinium ionic liquid cations. Anal. Bioanal. Chem., 385, 1483-1491,2006. 

This type of dinuclear unit has been reported elsewhere and has been characterized with bis-2-pyridyl-pyrazine or quinoxaline both in Cu [31] and in Ag [32] compounds. However, until now such units have not been used as building blocks (loops) in the construction of coordination polymers, an aspect that is discussed below. Each ligand acts in a bidentate manner with one metal center and as a monodentate system with the other. The two rings that are coordinated to the same metal center are nearly coplanar but the other deviates clearly from this plane. In this way, the structure if this dinuclear unit is very well adapted to the preferred conformation of the free ligand. The relative disposition of the ligands allows the existence of face-to-face n-jt-stacking interactions between the quinoxaline and... 

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