Absorption maxima substituted systems

Substitution of a phenyl residue in the 4-position of the selenazole ring causes only a minor alteration in the position of the absorption maximum. By contrast, the benzylidene compounds are markedly bathochromically shifted compared to the isopropylidene derivatives. Thus the absorption is caused by the whole of the conjugated system, which can be compared to that found in amino derivatives of... 

Behavior of metal complexes of phthalocyanines in supramolecular systems with TX-lOO (Fig. 13.8) is very different from other systems of micellar carriers. Tetra-substituted ZrL Pc, as in other supramolecular systems, has an absorption band with a wavelength of 678 nm corresponding to monomeric of molecules in the micelles. In micellar solutions of SiCl Pc absorption maximum at wavelength of 676 nm is observed only, indicating a completely isolated metal complex in this conditions. Unlike other systems, V=OPc has a well-defined absorption band at 678 mn, which corresponds to the presence of monomers in the system, the band bathochromic shifted to 830 nm, which corresponds to J-aggregates and the absorption band hypsochromic shifted to 630 nm, which corresponds to H-aggregates. Hence, V=OPc molecules interaction with TX-lOO micelles form three different type aggregation states of the molecules. 

An isomer of the molecule used in Example 5.6 is shown in Example 5.7. The calculated absorption maximum is 286 nm. This spectrum is different in several ways from Example 5.6. For example, the carbon at the 5-position has only one alkyl substitution. The double bond between the y- and 5-positions is exocyclic to a ring in this case and therefore increases the wavelength of the absorption maximum. The conjugated system is not within a ring, and therefore, contributions from ring currents are not observed. These two isomers could be distinguished from each other by their UV spectra. 

The largest well-defined oligomer of this type is currently the linear hexa-indium complex, 21 (Fig. 8), supported by a single ortho- y y substituted P-diketiminate ligand at each four-coordinate In centre and terminated by two iodide substituents to maintain charge balance [200]. Compound 21 displayed an absorption maximum in hexane at ca. 349 nm, which was interpreted as evidence for the existence of electronic delocalisation across the indium a framework analogous to that observed in isoelectronic catenated group 14 systems. 

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