Synthesis and Structure of Bis-crown-Containing Stilbenes

Abstract

An improved procedure was proposed for the synthesis of stilbenes fused to two crown ether fragments at both benzene rings. The structure of new homologous symmetric bis-crown-containing stilbenes was determined by X-ray analysis. Relations were revealed between the size of the crown ether moiety and stilbene conformation in crystal and the mode of crystal packing. Conformational analysis of the prepared stilbenes in solution and in the solid state was performed by 1 H and 13 C NMR spectroscopy and by DFT quantum-chemical calculations.In the recent years, supramolecular chemistry has become one of the most extensively developing fields of organic chemistry [1]. Components of supramolecular systems are often complex and difficultly accessible organic compounds, and their synthesis in many cases constitutes the subject of a separate study. In addition, an important problem in supramolecular chemistry is prediction of properties of compounds in supramolecular systems and development of selective procedures for their self-assembly.A promising sort of molecules for studying supramolecular organization in solution, monomolecular layers, Langmuir-Blodgett films, and polymeric matrices includes crown ether-fused azobenzenes, azomethines, styryl dyes, and related compounds [2][3][4][5] possessing double N=N, C=N, and C=C bonds. Interesting properties of these compounds are the ability to form supramolecules via host-guest-like complex formation with metal and ammonium ions, considerable variations in spectral parameters due to complex formation, and the possibility of varying their structure and properties by irradiation. The most typical photochemical processes occurring in the above selforganized systems and accompanied by considerable variation of their properties are trans-cis isomerization of the double bonds, electrocyclic reactions, and [2 + 2]-cycloaddition. Crown ether-fused stilbenes were not studied in much detail [6][7][8], though these compounds might be expected to exhibit equally interesting photochemical behavior and pronounced ability to form complexes.We recently showed that bis(18-crown-6)-stilbene Id and a number of diammonioalkyl derivatives of viologen analogs in dilute solutions give rise to unusual bi-and trimolecular complexes with effective intermolecular charge transfer due to spatial preorganization of the donor and acceptor parts of the initial molecules via hydrogen bonding [9][10][11]. Such supramolecular systems were found to be very stable; therefore, they can be regarded as convenient models for studying photoinduced intermolecular electron transfer [12] and promising species with versatile electrochemical properties [13]. However, the high potential of bis-crown-containing stilbenes as building blocks for assembly of complex supramolecular systems has not been explored to a sufficient extent. One of the main reasons is relatively difficult preparation of these compounds. Therefore, the goal of the present work was to develop a convenient procedure for the synthesis of symmetric stilbenes...

Diffusion in Protein Crystals—A Computer Simulation

“…Exocyclic (with respect to the benzene ring) bond angles at the C(17) and C(18) atoms undergo a deformation previously observed for all benzocrown–ether systems 8, 9, 18. Actually, the bond angles O(1)C(18)C(19) and O(2)C(17)C(16) are opened to ∼ 125.3(3)°, whereas the bond angles O(1)C(18)C(17) and O(2)C(17)C(18) are reduced to ∼ 114.9(3)° in compounds 2a,b and 8 .…”

Structure–Property Relationships of Dibenzylidenecyclohexanones

“…On going to solutions, fast conformational equilibrium between symmetrical syn , syn-, anti,anti -, and unsymmetrical syn , anti -conformers may be established ( Figure 3 ) by analogy with the previously studied bis-crown-containing stilbenes and distyrylbenzenes. 33 , 34 …”

Stereoselective [2+2] photocycloaddition in bispseudosandwich complexes of bis(18-crown-6) stilbene with alkanediammonium ions

“…18 [(E) 2 (2,3,5,6,8,9,11,12,14,15 Decahydro 1,4,7,10,13,16 benzohexaoxacyclooctadecin 18 yl) 1 ethenyl] 2,3,5,6,8,9,11, 12,14,15 decahydro 1,4,7,10,13,16 benzohexaoxacycloocta decine ((E) 1) 17 and salts H 3 N + (CH 2 ) n NH 3 + 2ClO 4 -(C2-С6, C10, C12) 20,22,23 were synthesized according to known procedures.…”