The understanding of the role played by cyanine dyes in various fields of application calls for a thorough knowledge of the excited state properties of their parent chromophores, i.e. cationic streptopolymethyne cyanines. For this aim we performed a detailed CS INDO CI investigation on the electronic spectra oftri-, penta- and heptamethine cyanines, both unsubstituted (TC, PC, HC) and terminally substituted by methyl groups (BMTC, BMPC, BMHC). The study comprised 5,-S, and S,-T, transitions of the truns and all mono-& isomers. CI expansions involved solely n orbitals of the polymethine chains and pseudo-n orbitals ofthe substituents and included all singly-excited and the most important doubly- and triply-excited configurations.The spectroscopic effects of methyl substitution are fairly well described and are shown to be especially important in the upper excited states. The identification of the photochemically formed stereoisomers is attempted in terms of mono-cir isomers. For BMPC, in particular, we report the absorption spectrum of thephototropic form and show that the photoisomer is identifiable as the 3-4 cb form.

ELECTRONIC-SPECTRA AND TRANS-CIS ISOMERISM OF STREPTOPOLYMETHINE CYANINES - A CS INDO CI STUDY / Momicchioli, Fabio; Baraldi, Ivan; Ponterini, Glauco; G., Berthier. - In: SPECTROCHIMICA ACTA. PART A, MOLECULAR SPECTROSCOPY. - ISSN 0584-8539. - STAMPA. - 46:(1990), pp. 775-791.

ELECTRONIC-SPECTRA AND TRANS-CIS ISOMERISM OF STREPTOPOLYMETHINE CYANINES - A CS INDO CI STUDY

MOMICCHIOLI, Fabio;BARALDI, Ivan;PONTERINI, Glauco;
1990

Abstract

The understanding of the role played by cyanine dyes in various fields of application calls for a thorough knowledge of the excited state properties of their parent chromophores, i.e. cationic streptopolymethyne cyanines. For this aim we performed a detailed CS INDO CI investigation on the electronic spectra oftri-, penta- and heptamethine cyanines, both unsubstituted (TC, PC, HC) and terminally substituted by methyl groups (BMTC, BMPC, BMHC). The study comprised 5,-S, and S,-T, transitions of the truns and all mono-& isomers. CI expansions involved solely n orbitals of the polymethine chains and pseudo-n orbitals ofthe substituents and included all singly-excited and the most important doubly- and triply-excited configurations.The spectroscopic effects of methyl substitution are fairly well described and are shown to be especially important in the upper excited states. The identification of the photochemically formed stereoisomers is attempted in terms of mono-cir isomers. For BMPC, in particular, we report the absorption spectrum of thephototropic form and show that the photoisomer is identifiable as the 3-4 cb form.
46
775
791
ELECTRONIC-SPECTRA AND TRANS-CIS ISOMERISM OF STREPTOPOLYMETHINE CYANINES - A CS INDO CI STUDY / Momicchioli, Fabio; Baraldi, Ivan; Ponterini, Glauco; G., Berthier. - In: SPECTROCHIMICA ACTA. PART A, MOLECULAR SPECTROSCOPY. - ISSN 0584-8539. - STAMPA. - 46:(1990), pp. 775-791.
Momicchioli, Fabio; Baraldi, Ivan; Ponterini, Glauco; G., Berthier
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11380/622944
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