1. |
- Gromov, Sergey P, et al.
(författare)
-
Novel Photoswitchable Receptors: Synthesis and Cation-Induced Self-Assembly into Dimeric Complexes Leading to Stereospecific [2+2]-Photocycloaddition of Styryl Dyes Containing a 15-Crown-5 Ether Unit
- 2003
-
Ingår i: The Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 68:16, s. 6115-25
-
Tidskriftsartikel (refereegranskat)abstract
- Styryl dyes 4a-e containing a 15-crown-5 ether unit and a quinoline residue with a sulfonatoalkyl or sulfonatobenzyl N-substituent were synthesized. The relationship between the photochemical behavior of these dyes and their aggregates derived from complexation with Mg2+ in MeCN was studied using 1H NMR and absorption spectroscopy. The E-isomers of 4a-e were shown to form highly stable dimeric (2:2) complexes with Mg2+. Upon irradiation with visible light, the dimeric complexes undergo two competing photoreactions, viz., geometric E Z isomerization, resulting in an anion-capped 1:1 complex of the Z-isomer with Mg2+ and stereospecific syn-head-to-tail [2+2]-cycloaddition, affording a single isomer of bis-crown-containing cyclobutane. The N-substituent in the dye has a dramatic effect on the photochemical behavior of the dimeric complex. Molecular dynamics and semiempirical quantum-chemical calculations were carried out to interpret the observed photocycloaddition in the dimer. Conformational equilibria for the dimer of (E)-4b were analyzed using 1H NMR spectroscopy.
|
|
2. |
- Gromov, Sergey P, et al.
(författare)
-
Synthesis, Structure, Spectroscopic Studies, and Complexation of Novel Crown Ether Butadienyl Dyes
- 2002
-
Ingår i: Helvetica Chimica Acta. ; 85:1, s. 60-81
-
Tidskriftsartikel (refereegranskat)abstract
- Butadienyl dyes of the benzothiazole series with various fragments of benzocrown ethers 1a-c were synthesized for the first time. The structures and spectral properties of crown-containing butadienyl dyes and their complexes with alkali and alkaline-earth metal cations were studied by X-ray diffraction analysis and 1H-NMR, UV/VIS, and resonance Raman spectroscopy. To interpret the experimental results, quantum-chemical calculations were performed. In the case of Sr2+ and Ba2+ ions, the formation of strong sandwich complexes [M(1b)2]2+ of an unusual structure involving stacking interactions was established; the dye molecules are arranged one above another in the complex according to the head-to-head' pattern.
|
|
3. |
- Ushakov, Evgeny N, et al.
(författare)
-
Self-Organization of Highly Stable Electron Donor-Acceptor Complexes via Host-Guest Interactions
- 2002
-
Ingår i: The Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 106:10, s. 2020-3
-
Tidskriftsartikel (refereegranskat)abstract
- Biscrown stilbene S forms complexes of 1:1 and 2:1 composition with bisammonium viologen salt V4+ in acetonitrile solution. Both of the complexes exhibit spectroscopic behavior typical of molecular electron donor-acceptor complexes. The 1:1 complex [S·V]4+ has a very high thermodynamic stability (log K = 9.08), which is due to simultaneous interaction of the two ammonium groups of V4+ with the two 18-crown-6-ether units of S. The 2:1 complex (log K = 12.28) [S·V·S]4+ likely has a sandwich-type layered structure in which the acceptor salt is located between two complexed molecules of the biscrown stilbene.
|
|