Synthesis and Characterization of Mono-, Bis-, and Trissubstituted Pyridinium and Pyrylium Dyes

Abstract

A series of mono-, bis-, and trissubstituted pyridinium and pyrylium dyes have been synthesized by the condensation of methylpyridinium and methylpyrylium salts with aldehydes or nitroso compound. Large bathochromic shifts were observed in the following order, both in substituted azomethine pyridinium and pyrylium dyes, mono < bis < tris. The magnitude of the shift appeared in the order of multiple bonds, –CH=CH– < –CH=CH–CH=CH– < –CH=N–.

trans-4-[(4-Dimethylaminophenyl)iminomethyl]-N-methylpyridiniumpara-toluenesulfonate

“…trans-4-[(4-Dimethylaminophenyl)iminomethyl]-N-methylpyridinium iodide was synthesized as described previously (Matsui et al, 1992) and metathesized to (I) by precipitation from water/aqueous sodium para-toluenesulfonate (Acros). Crystals suitable for single-crystal X-ray diffraction measurements were obtained by slow diffusion of diethyl ether (BDH) vapour into a methanol (BDH) solution of (I) at room temperature; note that the same method is used to produce SHG-active crystals of DAST (Marder et al, 1994).…”

Star-Shaped Conjugated Systems

“…In the series with dimethylaminophenylbutadienyl groups, the sequence for λ max is mono-α: λ max = 508 nm; mono-γ: λ max = 525 nm; di-α,α´: λ max = 552 nm, di-α,γ: λ max = 557 nm and the tri(phenylbutadienyl) dye 81b shows λ max = 559 nm [250]. These dyes are negative solvatochromic, the absorption maxima are shifted about 36 and 30 nm resp.…”

“…Trisstyrylpyrylium analogues of 81 were prepared by condensation of trimethylpyrylium perchlorate with dimethylaminobenzaldehyde (97%) or dimethylaminocinnamic aldehyde (5%) [250]. Compared to the pyridinium salts, the absorption maxima are severely shifted to lower energies ( λ max = 685 nm and λ max = 781 nm resp.…”

Interaction of Carbocyanine Dyes with DNA: Synthesis and Spectroscopic Studies

“…14 The potential utility of cyanine dyes in nucleic acid detection has been improved by enhancing the fluorescence intensity of nucleic acid bound dye relative to unbound (free) dye 15 or by chemical modifications that increase light sensitivity of cyanine dyes to photobleaching. 16,17 In this paper, we present the results of a study on the photobleaching of cyanine dyes. To study the role of oxygen in the photodegradation process, the experiments were performed in solutions deaereated with Ar gas or saturated with O 2 .…”