Elena N. Gulakova

Cucurbit[7]uril Complexes of Crown-Ether Derived Styryl and (Bis)styryl Dyes

In this paper, we report the interaction of the CB[7] molecular container with crown ether styryl and (bis)styryl dyes 1-6. The interaction of monostyryl dyes (1 and 2) with CB[7] results in the formation of 1:1 complexes where the CB[7] molecule is located on the region of the guest encompassing the pyridinium ring, C=C double bond, and a portion of the aryl ring of benzocrown ethers 1 and 2. For (bis)styryl dyes (3-5), the formation of two types of complexes with composition dye.CB[7].dye and CB[7].dye.CB[7] was confirmed by a combination of optical and electrospray ionization mass spectroscopy (ESI-MS) methods. In the case of (bis)styryl dye (6), both 2:1 and 1:1 compositions 6.CB[7].6 and CB[7].6 were formed. Complex formation is accompanied by substantial changes in the optical characteristics of the dyes and formation of long-lived excimer species. We tested the stimuli responsiveness of this system in response to metal ions. We find that the metal ions prefer to bind to the electrostatically negative ureidyl C=O portals of the CB[7] rather than with the crown ether moiety of the styryl dyes.

Regiospecific C–N Photocyclization of 2-Styrylquinolines

Regiospecific C-N photocyclization of 2-styrylquinolines resulting in formation of potentially biologically active quino[1,2-a]quinolizinium derivatives was investigated. The presence of strong electron-donating groups in the phenyl ring reveals to be a crucial factor managing photocyclization effectiveness. Introduction of a crown ether moiety allows changing the photoreaction parameters by means of complexation with Mg(ClO4)2.

Metal Ions Drive Thermodynamics and Photochemistry of the Bis(styryl) Macrocyclic Tweezer

UV/Vis and NMR spectroscopy were used for the structural elucidation and thermodynamic and photochemical studies of the metal-coordinated crown-containing macrocyclic tweezer (E,E)-1. The bis(styryl) tweezer (E,E)-1 formed two types of complexes with magnesium(II): a 1:1 intramolecular asymmetric sandwich complex [(E,E)-1].Mg(2+) and a 1:2 complex [(E,E)-1].(Mg(2+))(2). In the former case, there is direct cation intramolecular exchange (0.299 s(-1), DeltaG(++)=69.4 kJ mol(-1)) between two parts of the bis(styryl) tweezer (E,E)-1. Addition of barium(II) to the bis(styryl) tweezer (E,E)-1 led to an intramolecular centrosymmetric sandwich 1:1 complex [(E,E)-1].Ba(2+). Irradiation of [(E,E)-1]Ba(2+) afforded reversible intramolecular [2pi+2pi] photocyclization with excellent stereoselectivity and quantitative yield. In contrast, irradiation of [(E,E)-1].(Mg(2+))(2) resulted in reversible stepwise E,Z-isomerization.