Near Infrared Polyene Radical‐Cation Derived from 7,8‐Dihydrobenzo[c,d]Furo[2,3‐f]Indole: Synthesis, Spectra and Nature of Electron Transitions

Abstract

The stable polyene cation‐radical containing the 7,8‐dihydrobenzo[cd]furo[2,3–f]indol terminal groups was synthesized and the features of its lowest electron transitions were studied, in detail. The electronic structure and absorption spectra of the polyene cation‐radical obtained, was compared with the electronic and spectral properties of the corresponding neutral poleynes, dications and related polymethine dye having the same terminal groups. While polyene and its dication absorb in the relative short wavelength spectral region, the polymethine‐cation absorbs in the long wavelength region; it is shown that two splitting bands appear in the spectra of the polyenic cation‐radical: the low‐ intensive long wavelength band (≈ 1200 nm) and of the high‐ intensive short wavelength band (≈800 nm); they take correctly into consideration splitting of excited states, generated by α‐ and β‐electrons.

Nature of Lowest Electron Transitions in Anionic Polymethine Dyes with Keto-Containing Terminal Groups

“…They form a basis for the design of new effective materials connected with the light conversion [1][2][3][4]. In addition, PMDs were found to be convenient objects for new theoretical conceptions and quantum-chemical models to develop [5][6][7][8][9][10]. Both cationic and anionic PMDs have been established to distinguish, first at all, by a specific distribution of the total positive or negative charge within the chromophore in the ground and excited states; it is not completely and uniformly delocalized along the conjugated chain of p-electrons, but it generates the wave of the alternated partial charges [11], independently on the sign of the total charge [5,7,9,11,13].…”

Nature of Lowest Electron Transitions in Anionic Polymethine Dyes With Keto-Containing Terminal Groups

“…The wide-known ionic (cationic and anionic) polymethine dyes (PMD) continue to be applied in numerous fields due to their exceptional spectral properties; they form a basis for the design of new effective materials connected with the light conversion [1][2][3][4]. Also, PMDs were found to be convenient objects for new theoretical conceptions and quantum-chemical models to develop [5][6][7][8][9][10]. Both cationic and anionic polymethine dyes have been established to distinguish, first at all, by a specific distribution of the total positive or negative charge within chromophore in the ground and excited state: it is not completely and uniformly delocalized along the conjugated chain of p-electrons, but it generates the wave of the alternated partial charges [11], independently on the sign of the total charge [5,7,9,11,13].…”