Sorption-luminescence determination of gold,silver, and platinum with the use of silica gel chemically modified with <Emphasis Type="Italic">N</Emphasis>-(1,3,4-thiodiazole-2-thiol)-<Emphasis Type="Italic">N</Emphasis>′-propylurea groups

Silica gel chemically modified with N-(1,3,4-thiodiazole-2-thiol)-N′-propylurea extracted gold(III) from solutions in the range of 6 M HCl-pH 8 and silver(I) from nitric acid solutions in the range of 6 M HNO₃-pH 8 and 1–2 M HCl at 20°C with 99.0–99.9% recovery and a sorption equilibration time of 5 min. Platinum(II) was quantitatively extracted at room temperature from solutions in the range of 4 M HCl-pH 8; the sorption equilibration time was 20 min. For the quantitative extraction of platinum(IV), it should be reduced to platinum(II). The intense yellowish orange luminescence (λ_max (Au) = 575 nm, λ_max (Ag) = 550 nm, and λ_max(Pt) = 620 nm) of surface complexes at 77 K under UV irradiation was used in the development of procedures for the low-temperature sorption-luminescence determination of gold, silver, and platinum. The detection limits were 0.15 (Au), 0.1 (Ag), and 0.05 μg (Pt) per 0.1 g sorbent. The calibration function was linear to 50 (Au, Ag) or 80 μg (Pt) per 0.1 g sorbent. The relative standard deviation in the determination of more than 5 μg of a metal was no higher than 6%. The sorption-luminescence determination procedures were tested in the determination of gold in gold-containing concentrates and their processing products and platinum in alumina-platinum catalysts.     

Synthesis and photochromic properties of spiropyrans containing a fused benzopyranone fragment

New spiro compounds of the indole, phthalazine, isobenzofuran, and benzopyran series, containing a fused benzopyranone fragment in the chromene moiety, were synthesized. Indole derivatives were found to exhibit photochromic properties under stationary conditions at 293 K. The thermal stability of merocyanine isomers sharply decreases upon introduction of electron-withdrawing nitro group into the indole fragment and fusion of a benzene ring to the chromene fragment.     

Synthesis and photochromic properties of novel nonsymmetric dihetarylethenes based on benzindole and thiophene

Novel nonsymmetric dihetarylethenes 3-(5-methoxy-1,2-dimethyl-1H-benzo[g]indol-3-yl)-4-(3-thienyl)-furan-2,5-dione and 1-alkyl- and 1-aryl-3-(5-methoxy-1,2-dimethyl-1H-benzo[g]indol-3-yl-4-(3-thienyl)-1(H)-pyrrole-2,5-diones were synthesized. The substitution of the furandione moiety for pyrroledione gives rise to the radiation and photochemical channels of deactivation of the electron excitation energy of dihetarylethenes. The products of photolysis of pyrrolediones undergo recyclization in both the ground and excited states.     

Electrochemical and chemical synthesis of new luminescent schiff base complexes

Bis-chelate complexes of zinc, cadmium, lead, and mercury with o-N-tosylbenzylidene imines containing the C₇H₁₅ and C₁₈H₃₇ substituents at the C=N group nitrogen atom were prepared by the methods of electrochemical and chemical syntheses. The structure of the azomethines and their complexes was established by the methods of heteronuclear ¹H, ¹³C NMR spectroscopy (multidimensional and multinuclear COSY, HETCOR and HETCOR_LONG techniques). The complexes, as demonstrated by the X-ray analysis for the zinc chelate, have strongly distorted octahedral structure formed by the four azomethine nitrogen atoms and two oxygen atoms of the tosyl fragments. The coordination compounds show fluorescence in the blue part of the spectrum in high quantum yields for the zinc chelates.     

Photo- and thermochromic spirans. 35.* Synthesis and photochromic properties of spiro[indoline-2,3′-pyrano[3,2-f]quinolines] and their cationic derivatives

New photochromic spiropyranoquinolines and their cationic derivatives have been synthesized. Quaternization of the quinoline fragment leads to significant enhancement of the thermal stability of the merocyanine isomers of these cationic spiropyrans.     

Spiropyrans and spirooxazines 7. Novel spirobipyrans and their cationic derivatives

Novel photochromic spirobipyrans containing the dimethylamino group in position 7 of the benzopyran moiety and their cationic derivatives with the trimethylammonium substituent exhibiting no photochromic properties were synthesized.     

The structural transformations and photo-induced processes in salicylidene alkylimines

The detailed comparative investigations of the mechanism of the fluorescent properties, formation and photochromic reaction in the salicylidene alkylimine (SALK) molecules with various N-Alk substituents and in corresponding more rigid model structures without C–Ph ring (A) twist have been carried out by the experimental and quantum-chemical methods.

The crucial role of the A ring twist and the importance of the N-Alk substituent structure in the light-induced processes including the ESIPT, TICT formation, fluorescence with anomalous Stokes shift (ASS) and the formation of the metastable coloured so-called “post-TICT” structures has been shown. The mechanism of these processes is similar to that of the salicylidene aniline (SA) molecule but there are some important distinctions caused mainly by the lack of the l_N–π_Ph electrons interactions and also by the steric ones. In general the decrease of the photochromic efficiency and the increase of the ASS in comparison to the SA molecule are provoked by the SALK structures’ peculiarities.     

Structures of spiropyrans exhibiting photochromic properties in the solid state

Russian Chemical Bulletin - Solid-state photochromic indoline spiropyrans bearing a formyl group at the 6′ and 8′ positions of the 2H-chromene moiety of the molecules were...