Structure effect on absorption

While other structural effects on absorption frequencies are known, the above factors are the ones most commonly encountered in routine organic structure determination. 

Armand B. Christophe Ghent University Hospital, Ghent, Belgium, Structural Effects on Absorption, Metabolism, and Health Effects of Lipids. 

Some other polymers of the same type with valence (I) were also prepared (Fig. 17). They exhibit almost the same structure, except that halides are replaced by diphosphine ligands (diphos) such as bis(diphenylphosphino) butane (dppb), bis(diphenylphosphino)pentane (dpppen), and bis(diphenyl-phosphino)hexane (dpph).36,40 Again a model complex, compound 25, was studied as reference (Fig. 17). The electronic spectra exhibit an absorption band near 480 nm. These coordination materials are not luminescent at room temperature but are luminescent in solution in butyronitrile at low temperature (i.e., 77 K). Density functional theory (DFT) calculations showed that luminescence arises from a da-da triplet excited state. In these polymers, the nature of the phosphine ligand has a crucial effect on absorption and emission bands. Such behavior is explained by the increase in electronic density on the... 

It is worth pointing out, as do Capon and Wu69, Hickmott6/ and many others, that structural effects on the reactivity of enamines toward electrophiles are anticipated by a variety of physical properties of the enamines, including UV absorption frequencies, IR stretching frequencies, NMR chemical shifts and first ionization potentials. These properties in turn are influenced by the ability of the formal lone pair on the nitrogen to conjugate with the formal double bond, an ability which is modulated by both steric and electronic effects. 

Distinct polarity effects on absorption were encountered for guest molecules exhibiting polarity-dependent vibronic fine structure in their spectra, as for instance naphthalene [21], whicdi showed a marked enhancement of fine structure in the presence of 0.05-M a-CyD but not in that of 0.01-M fi-CyD (Fig. 10.3.1). In such favorable cases, the stoichiometry of inclusion could be probed using a suitably modified Benesi-HUdebrand treatment based on the absorption of a vibronic subband whose intensity is specifically enhanced by CyD inclusion. This is the case for the 290-nm transition of the La band of naphthalene which is threefold more intense in the presence of a high a-CD concentration than in neat aqueous solution... 

In a similar study, we have investigated the solvent effect on absorption and fluorescence spectra for some photochromic copolymathacrylates with azo sulfonamide chromophores in side chains [10]. The structure of the polymers are shown in Table 2. In this study, behavior of these polymeric azo compounds... 

In Sec. 2 the effective mass equation is introduced and the band structure is discussed with a special emphasis on an Aharonov-Bohm effect. Optical absorption spectra are discussed in Sec. 3. A lattice instability, in particular induced by a magnetic field perpendicular to the tube axis, is discussed in Sec. 4 and magnetic properties of ensembles of CNTs are discussed in Sec. 5. 

Therefore a continued interest exists in the role of in oral absorption, which often is related to its effect on lipophilicity and solubility. Medicinal chemists can modulate these properties through structural modifications [47]. Various methods to measure pK values have been developed [47-50] and considerable databases are now available. 

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