Ultraviolet‐visible (UV‐vis) absorption, flash photolysis, and 1H and 13C NMR spectroscopy were used to investigate the mechanism of formation and structure of complexes in the ...1',3',3'‐trimethylspiro2H‐1‐benzopyran‐2,2'‐indoline (SP, also well known as BIPS) with Al3+ (inorganic salts) in ethanol (EtOH), methanol (MeOH), and in aqueous MeOH solutions. A labile (equilibrium constants ≤ 5000 M−1) complex of SP and Al3+ with broad absorption band in the UV‐vis with λmax = 380 nm appeared promptly in the presence of an excess of Al3+. The slow formation of a stable complex (SC) between Al3+ and two merocyanine (MC) forms of SP with an intensive absorption band at λmax = 430 nm is observed with a yield of 1.0 upon keeping the solutions of these two compounds at constant concentration ratio Al3+ ≥SP/2 in the dark. The rate constants of such SC formation were close to the corresponding rate constant of the transformation of SP into MC in the dark (5.0×10−5‐1×10‐3 s‐1, depending upon the solvent). The photolysis of the SC with visible light (λ > 400 nm) results in the total conversion of the SC into SP. The SC forms promptly after the addition of Al3+ at concentrations of the same order as those of MC. This method allows detection of Al3+ to concentrations as low as 50 nM. The kinetics and thermodynamic parameters of the SP and MC reactions and of their complex formation with Al3+ are discussed.
A new stable colored complex of a merocyanine form of 1',3',3'‐trimethylspiro2H‐1‐benzopyran‐2,2'‐indoline with Al3+ was observed. Spectroscopic, kinetic, and thermodynamic properties of the study systems are presented. The developed method allows detection of Al3+ at concentrations as low as 50nM.
Methods for preparation of 5′-substituted spiropyrans, their chemical properties, and the effects of various factors on the relative stabilities of the spiropyrans and their isomeric merocyanine ...forms are examined, reviewed, and discussed.
Two new photochromic labels of spirochromene-2,2’-indole series supplied with 5-positioned maleimide moieties suitable for labelling macromolecules with sulfhydryl groups were synthesized.
Abstract
Ultraviolet‐visible (UV‐vis) absorption, flash photolysis, and
1
H and
13
C NMR spectroscopy were used to investigate the mechanism of formation and structure of complexes in the ...1',3',3'‐trimethylspiro2
H
‐1‐benzopyran‐2,2'‐indoline (SP, also well known as BIPS) with Al
3+
(inorganic salts) in ethanol (EtOH), methanol (MeOH), and in aqueous MeOH solutions. A labile (equilibrium constants ≤ 5000 M
−1
) complex of SP and Al
3+
with broad absorption band in the UV‐vis with λ
max
= 380 nm appeared promptly in the presence of an excess of Al
3+
. The slow formation of a stable complex (SC) between Al
3+
and two merocyanine (MC) forms of SP with an intensive absorption band at λ
max
= 430 nm is observed with a yield of 1.0 upon keeping the solutions of these two compounds at constant concentration ratio Al
3+
≥SP/2 in the dark. The rate constants of such SC formation were close to the corresponding rate constant of the transformation of SP into MC in the dark (5.0×10
−5
‐1×10
‐3
s
‐1
, depending upon the solvent). The photolysis of the SC with visible light (λ > 400 nm) results in the total conversion of the SC into SP. The SC forms promptly after the addition of Al
3+
at concentrations of the same order as those of MC. This method allows detection of Al
3+
to concentrations as low as 50 nM. The kinetics and thermodynamic parameters of the SP and MC reactions and of their complex formation with Al
3+
are discussed.
Properties of nanoparticles are significantly different from their bulk counterparts, including their biological and toxic activity. The properties of silver nanoparticles governing their ...toxicological effects are summarized. These basic characteristics can be used as descriptors for modelling the toxic properties of nanoparticles.
•New 6-nitro-substituted spiropyrans have been synthesized.•We studied spectral-kinetic properties of intermediates of spiropyran vinylogs.•Nanosecond laser flash photolysis techniques were used for ...investigation.•Relative quantum yields of different intermediates formation have been measured.
The absorption spectra and decay kinetics of the ground and triplet states of merocyanine (MC) form of spiropyran vinylogs have been investigated by nanosecond laser flash photolysis techniques in toluene and ethanol. The 3MC decays to the ground state MC either by quenching with O2 or due to the intersystem crossing. Relative quantum yield of both 3MC and MC drastically decreases when the terminal polar group is separated from the indoline moiety by the CC-linker. In the presence of the CC-linker the replacement of terminal CN by CHO has no effect. The yield of 3MC and corresponding MC in ethanol is 5 times smaller than that in toluene solution.
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The effects of chromophoric group structures on the functional properties of bacteriorhodopsin (BR) and proteorhodopsin from E. sibiricum (ESRh) were compared. ESRh retinal binding ...site was found as preserving the similar stereo- and spatial restrictions on the chromophore structure during the retinal protein reconstitution process (except for C25-analog AR8). It was revealed that the structure peculiarities of the chromophore analog molecules affect the optical parameters of ESRh and BR pigment families in similar ways.
► We studied spectral-kinetic properties of intermediates of spiropyran retinal analogs. ► Nanosecond laser flash photolysis techniques were used for investigation. ► Relative quantum yields of ...different intermediates formation have been measured. ► Formation of merocyanine form upon photolysis depends on polyenic chain length.
Spectral-kinetic properties of intermediates of spiropyran retinal analogs (SRA), which molecules contain spiropyran and retinoid (with different polyenic chain length and aldehyde terminal group) fragments, have been investigated by nanosecond laser flash photolysis techniques using excitation wavelengths 337 and 380–450nm in toluene. Relative quantum yields of different SRA intermediates formation relative to those of model compounds, namely triplet excited state and merocyanine form generated upon pyran cycle cleavage have been measured. It has been found that merocyanine form does not form upon photolysis of SRA with polyenic chain length of 5 and 9 using excitation wavelengths of 380–450nm, the triplet state of retinoid fragment is observed exclusively. The yield of merocyanine (MC) form is the largest one upon SRA photolysis with excitation wavelength of 337nm for 6′-formylsubstituted spiropyran (it exceeds that of unsubstituted analog in 8 times and forms mainly from the triplet state). The yields of MC for SRA with polyenic chain length of 3, 5 and 9 carbon atoms are 5–10 times smaller than that for unsubstituted spiropyran.
A new 5,10,15,20-tetrasubstituted porphyrin containing four 6’-nitro-1,3,3-trimethylspiro(indolino-2,2’-2H-chromene) substituents and its complexes with Zn2+ and Cu2+ ions were prepared and ...characterized by physicochemical methods of analysis.
5,6-Epoxy-, 4-methoxy-, 4-hydroxy-, and 3,4-dehydrobacteriorhodopsins can generate delta psi coupled to a photochemical cycle with intermediate M. The kinetics of delta psi comprises three main ...electrogenic phases: the fast small negative, the microsecond, and the millisecond positive phases. The photocycle efficiency is lower in all the analogs. The photocycle is modified insignificantly only in 3,4-dehydrobacteriorhodopsin. In the other pigments the decay of the flash-induced bleaching in the chromophore main absorption band is slower than the decay of M or long-wave intermediates, especially in the 4-hydroxy analog. In the latter analog, such distinctions, according to delta pH measurements, are partly due to deceleration of the decay of the novel intermediate (P). In 5,6-epoxybacteriorhodopsin, at all wavelengths, the decay of the intermediates takes seconds upon M formation. According to our and literature data, no bacteriorhodopsin analogs are known to have a cycle which preserves the M-intermediate and does not transport a proton.
