Imidazoline density

Along these lines, imidazoline [68, 69] rather than oxazoline coordination sites better fitted into a modular concept in order to understand how the electronic properties should ideally be, since electron density can be readily adjusted by the choice of the N substituent [70]. The Cp ligand C5R5 in 47 permits steric and electronic tuning. With the electron-withdrawing effect of five Ph groups R, the... 

From a comparative analysis of H NMR spectra of structurally similar pairs of nitroxyl radicals of 3-imidazoline and 3-imidazoline-3-oxide, it was concluded that the nitrone group contributes to a more efficient long-range spin density delocalization in the conjugated n -system of functional groups bonded with atom C-4 (404). 

The electron density induced at the metal center increases in the order C(OR)R < C(NHR)R < C(NHR)2 imidazolidin-2-ylidene imidazolin-2-ylidene. According to these data the difference between diamino-substituted carbenes whether cyclic or acyclic, aromatic or nonaromatic, seems to be quite small. 

NH4 over K". Our initial calculations indicated that a benzene-based tripodal system with imidazoline arms (Fig. 34.7a) possessed vacant sites for the interaction with only one solvent molecule, while the K" " ion has three vacant sites for three solvent molecules. In order to maximize the affinity and selectivity of these receptors for NH4, it becomes important to maximize the ir-electron density of the receptor. Indeed, receptors with enhanced ir-electron density by trimethylated phenyl ring with the strong proton-withdrawing subunits exhibit much higher affinities and selectivities [129]. 

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