Coupling exitonic

Baldeck and Andraud provide a chapter entitled Exitonic Coupled Oligomers and Dendrimers for Two-Photon Absorption, wherein the concepts of exci-tonic coupling are developed and their relevance to multi-photon absorption processes are described. 

An interesting feature of system 3.123 is the finding that the two porphycene rings are well separated. As a result, there is no apparent barrier to rotation about the piperazine bridge. Further, the visible absorption spectrum of 3.123 ( max = 380 nm and 618 nm in CH2CI2) is rather unperturbed relative to the monomer 3.119 and displays no evidence of appreciable exitonic coupling between the rings." ... 

Circular Dichroic Spectroscopy - Exiton Coupling in Organic Chemistry, University Press Oxford, 1983. 

Nakanishl and co-workers have continued to develop the exiton chirality method. The remarkable additivity relationship in the coupled c.d. of pyranose p-methoxycarbonylbenzyl ethers has permitted the identification of constituent sugars and their glycoside... 

K. Nakanishi and N. Harada, Circular Dichroism Spectroscopy Exiton Coupling in Organic Stereochemistry, University Science Books, Mill Valley, California, 1983 D. N. Kirk, Tetrahedron 42, 111 (1986). 

Diphenyl-3,3 -diboronic acid 41 forms T.l complexes with cellobiose, maltose and lactose (but not sucrose), giving exiton coupling in c.d. spectroscopy owing to the immobilisation of the two phenyl rings of 41 in a chiral form. " 2... 

CIRCULAR DICHROISM SPECTRA The CD spectriun of the natural high pH form shows a complex pattern at the 1020 (limited in our machine to 1010 nm) and the 800/830 nm bands (fig 2), which is indicative of exiton coupling between more than two chromophores The spectrum of the low pH form is less complex, with only a doublet in the region of the 960 nm band, and a strongly decreased optical activity in the 8OO/83O nm band region ... 

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