“…Two close relatives of 30 , and a more distant one,226a also show similar cation responses. The use of benzodiazinone in 31 and 32 instead of benzoxazinone moieties permits the attachment of extra functionalities on the new nitrogen atom. …”
Section: Charge-transfer (Ct) Excited States and
Relativesmentioning
“…Two close relatives of 30 , and a more distant one,226a also show similar cation responses. The use of benzodiazinone in 31 and 32 instead of benzoxazinone moieties permits the attachment of extra functionalities on the new nitrogen atom. …”
Section: Charge-transfer (Ct) Excited States and
Relativesmentioning
“…Most of the known macrocyclic chromo- and fluoroionophores with a styryl moiety ,− were designed by using a common principle, namely, by combining a macrocycle (usually, N- phenylaza- or benzocrown ether) with a chromophore so that both functional units share some critical atoms. The chromophore unit with an internal charge-transfer (ICT) excited state is used to produce a strong optical response to the cation−macrocycle interaction .…”
Section: Introductionmentioning
confidence: 99%
“…Crowned styryl compounds may show significant cation-induced changes in the absorption and/or fluorescence spectra. − However, most of them have rather low cation-binding ability and poor selectivity within the series of alkali or alkaline-earth metal cations. The introduction of the sulfo group into the N- alkyl substituent of 1 results in a considerable increase in the ability of the dye to bind alkaline-earth metal cations and photochemical control of the complex formation, but the cation-binding selectivity remains poor.…”
Section: Introductionmentioning
confidence: 99%
“…[6][7][8][9] Combination of a crown ether with a styryl compound yields molecular systems where the styryl moiety can provide the chromo-and fluorogenic properties as well as the switching function, 7 the latter being related to either trans-cis isomerization or [2+2]cycloaddition photoreactions, which are typical of styryl compounds. 10 Most of the known macrocyclic chromo-and fluoroionophores with a styryl moiety 1,[11][12][13][14][15][16][17][18][19][20] were designed by using a common principle, namely, by combining a macrocycle (usually, N-phenylaza-or benzocrown ether) with a chromophore so that both functional units share some critical atoms. The chromophore unit with an internal charge-transfer (ICT) excited state is used to produce a strong optical response to the cationmacrocycle interaction.…”
The formation of complexes between a bisstyryl dye containing two benzo-15-crown-5 ether groups, 2, and
Mg2+, Ca2+, Sr2+, and Ba2+ ions was studied in acetonitrile solution by using a spectrophotometric approach.
In contrast to its monostyryl analogue 1, which shows a rather low cation-binding selectivity, the bisstyryl
dye 2 selectively binds the Sr2+ and Ba2+ ions because of formation of intramolecular sandwich complexes.
Alkaline-earth metal cations induce substantial blue shifts of the absorption maximum of 1 and 2, particularly
in the case of sandwich complex formation. The emission behavior of 1 and 2 and their Ba2+ complexes in
acetonitrile solution has also been studied. In both cases, complex formation leads to a blue shift of the
fluorescence maximum and a decrease in the emission quantum yield. The fluorescence decay is
monoexponential for the complex of 1 and biexponential for that of 2. The longer-lived fluorescence component,
which corresponds to the lower-energy band in the steady-state spectrum, is assigned to an intramolecular
excimer state.
“…In addition, photochromic compounds containing ionophoric fragments are able to react with metal cations; in some cases this can also change the spectral characteristics of the photochromic ligands. [4][5][6][7][8] Compounds of this type provide the possibility of monitoring the presence of metal ions in solutions; they are of considerable interest in developing efficient ionophores for selective determination of metal ions.…”
Spironaphthoxazines conjugated with aza-15(18)-crown-5(6)-ether moieties at the 6 0 -position of the naphthalene fragment (crown-containing spironaphthoxazine, CSN) were synthesised and studied for the first time. The addition of Li þ and alkaline earth (Mg 2þ , Ca 2þ , Sr 2þ and Ba 2þ ) metal cations to CSN solutions results in a hypsochromic shift of the UV absorption band of the spiro form and a bathochromic shift of the absorption band of the merocyanine form in the visible region. In addition, the equilibrium shifts to the merocyanine form, and the lifetime of the photoinduced merocyanine form increases. Analysis of the spectral and kinetic data allows a complexation scheme to be proposed and the stability constants of the resulting complexes to be calculated. According to the results obtained, the complexation with Li þ and alkaline earth metal cations in acetonitrile initially involves the crown ether moiety; the participation of the merocyanine oxygen atom in the complexation process occurs at a high metal cation concentration. The UV-induced isomerisation of CSN into the merocyanine form causes a decrease of the cation binding ability.
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