T.I. Sergeeva

Supramolecular assemblies of photochromic benzodithia-18-crown-6 ethers in crystals, solutions, and monolayersElectronic supplementary information (ESI) available: crystal data, data collection, and structure solution and refinement parameters. See http://www.rsc.org/suppdata/nj/b1/b110630a/

We studied the assembly of dithiacrown ether styryl dye (CSD) molecules in crystals, solutions, and films in the presence of metal cations. X-Ray diffraction data allowed us to conclude that the anion affects the supramolecular architecture of CSDs in the crystal, specifically, the type of stacking of the dye molecules. In solution, in the presence of Pb2+, CSD molecules with the betaine structure spontaneously form dimeric complexes consisting of two dye molecules and two metal cations, with a fixed mutual arrangement of the double bonds. The dimer complex is stable due to coordination between the anion substituent of one molecule and the metal cation located in the crown ether cavity of the other molecule. Irradiation of the dimer complexes leads to regio- and stereoselective [2 + 2]-cycloaddition, giving only one cyclobutane derivative of the eleven theoretically possible products. The other photoreaction studied for CSDs is reversible Z–E isomerization. Due to its specific structure, the betaine-type CSD is able to form the ‘anion-capped’ Z-isomer. Intramolecular coordination in the ‘anion-capped’ isomer enhances its stability and causes a sharp deceleration of its dark Z–E isomerization. The amphiphilic CSD forms relatively stable monolayers on distilled water and various aqueous salt subphases. The results obtained indicate that it is possible to distinguish between two types of the dye monolayer structures based on the presence of alkali or heavy metal cations in the aqueous subphase.

Monolayers of a novel ionoselective butadienyl dye

The novel amphiphilic benzodithia-18-crown-6 butadienyl dye (1) forms relatively stable insoluble monolayers on distilled water (collapse pressure of 41 mN/m) and on aqueous subphases containing alkali metal or heavy metal salts (collapse pressures in the range of 27-38 mN/m, respectively). The dye 1 monolayer organization depends on chromophore association and interactions (especially complex formation) with heavy and alkali metal ions as deduced from surface pressure-area and surface potential-area isotherms as well as reflection spectra and Brewster angle microscopy observations. Dye 1 undergoes specific interactions with Hg(2+) and Ag(+), respectively (formation of different complexes). Nonspecific interactions have been observed with other salts, such as KClO(4) or Pb(ClO(4))(2). Further, dye 1 monolayers on 1 mM Hg(ClO(4))(2) solution undergo reversible photoisomerization, in contrast to monolayers on water and other aqueous salt subphases.

Langmuir films of the novel anion-capped amphiphilic benzodithia-15-crown-5 dye.

Abstract The novel anion-capped amphiphilic benzodithia-15-crown-5 styryl dye forms relatively stable insoluble monolayers on distilled water (collapse pressure is approx. 35 mN/m) and on the aqueous subphases containing alkali metal cations (38 mN/m) or heavy metal cations (33 or 31 mN/m for Ag + or Hg 2+ ), respectively. Two types of the dye-cation complexes, depending on the nature of a particular cation in the aqueous subphase, have been distinguished by measuring surface pressure–molecular area and surface potential–molecular area isotherms, as well as observed by Brewster angle microscopy. The surface-active and spectroscopic properties of the amphiphilic dye in monolayers in the presence of K + , Na + , Ca 2+ , Mg 2+ , Ag + or Hg 2+ cations in the aqueous subphases have been studied.

Organization of butadienyl dyes containing benzodithiacrown-ether or dimethoxybenzene in monolayers at the air/aqueous salt solution interface.

Two amphiphilic butadienyl dyes 1 and 2 form stable monolayers at the air/water interface in the presence of various salts. Dye 1 consists of the basic amphiphilic butadienyl chromophore. In dye 2, the dimethoxybenzene part of dye 1 is substituted by benzodithia-15-crown-5. The monolayers have been characterized by surface pressure-area and surface potential-area isotherms as well as Brewster angle microscopy and reflection spectroscopy. In contrast to dye 1, dye 2 interacts specifically with Hg(2+) and Ag(+) cations forming complexes. No complex formation was observed with alkali and earth alkali metal ions. The nature of the anion (Cl(-) or ClO(4)(-)) influences the monolayer behaviour of both dyes. At the air/water interface, besides monomers of the dyes, two types of associates are coexisting in the pure dye monolayers on aqueous salt solutions, attributed to dimers and aggregates, respectively. Their equilibria depend on the nature of both cations and anions in the subphase, as in the case of dye 2, or only anions, as in the case of dye 1. The dimers may be organized as head-to-tail dimers with the intermolecular distances 0.38 and 0.45nm for dye 1 and dye 2, respectively. According to the extended dipole model, we propose formation of aggregates in which the chromophores are parallel to each other with the same intermolecular distances as in the dimers, and the centers of their transition moments shifted by 0.95nm (dye 1) and 1.2nm (dye 2).