Asymmetric benzimidazolo carbo, di- and tricarbocyanines form ion pairs of the solvent-separated and contact types with different counterions in tetrahydrofuran, toluene and toluene-nitrile mixtures. The dissociation constants of the ion pairs in tetrahydrofuran, evaluated from conductivity data, do not depend on the length of the polymethine chain and show only a small decrease with decreasing counterion size. The absorption and fluorescence excitation spectra of the contact ion pairs exhibit a pronounced hypsochromic shift with respect to the solvated ions and the solvent-separated ion pairs. H-1-NMR experiments have provided information about the electronic structures of the ions of both the asymmetric dyes and the corresponding symmetric carbocyanines. They have also revealed different preferred anion locations in the contact ion pairs of the symmetric indocarbocyanine on one hand, and of the benzimidazolo carbocyanine and the asymmetric dyes on the other. This structural difference is suggested to be a cause of the observed opposite effects of ion pairing on the isomerization kinetics of the two groups of dyes. (C) 1998 Elsevier Science B.V. All rights reserved.

Ion pairs of indobenzimidazolo cyanines: a structural study based on conductivity, absorption, fluorescence and H-1-NMR / Tatikolov, As; Ishchenko, Aa; Ghelli, S; Ponterini, Glauco. - In: JOURNAL OF MOLECULAR STRUCTURE. - ISSN 0022-2860. - STAMPA. - 471:(1998), pp. 145-159.

Ion pairs of indobenzimidazolo cyanines: a structural study based on conductivity, absorption, fluorescence and H-1-NMR

PONTERINI, Glauco
1998

Abstract

Asymmetric benzimidazolo carbo, di- and tricarbocyanines form ion pairs of the solvent-separated and contact types with different counterions in tetrahydrofuran, toluene and toluene-nitrile mixtures. The dissociation constants of the ion pairs in tetrahydrofuran, evaluated from conductivity data, do not depend on the length of the polymethine chain and show only a small decrease with decreasing counterion size. The absorption and fluorescence excitation spectra of the contact ion pairs exhibit a pronounced hypsochromic shift with respect to the solvated ions and the solvent-separated ion pairs. H-1-NMR experiments have provided information about the electronic structures of the ions of both the asymmetric dyes and the corresponding symmetric carbocyanines. They have also revealed different preferred anion locations in the contact ion pairs of the symmetric indocarbocyanine on one hand, and of the benzimidazolo carbocyanine and the asymmetric dyes on the other. This structural difference is suggested to be a cause of the observed opposite effects of ion pairing on the isomerization kinetics of the two groups of dyes. (C) 1998 Elsevier Science B.V. All rights reserved.
1998
471
145
159
Ion pairs of indobenzimidazolo cyanines: a structural study based on conductivity, absorption, fluorescence and H-1-NMR / Tatikolov, As; Ishchenko, Aa; Ghelli, S; Ponterini, Glauco. - In: JOURNAL OF MOLECULAR STRUCTURE. - ISSN 0022-2860. - STAMPA. - 471:(1998), pp. 145-159.
Tatikolov, As; Ishchenko, Aa; Ghelli, S; Ponterini, Glauco
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

Licenza Creative Commons
I metadati presenti in IRIS UNIMORE sono rilasciati con licenza Creative Commons CC0 1.0 Universal, mentre i file delle pubblicazioni sono rilasciati con licenza Attribuzione 4.0 Internazionale (CC BY 4.0), salvo diversa indicazione.
In caso di violazione di copyright, contattare Supporto Iris

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/8109
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 5
  • ???jsp.display-item.citation.isi??? 5
social impact