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

Abstract

Due to hydrogen bonding, bis(18 crown 6) stilbene forms 1 : 1, 1 : 2, and 2 : 2 complexes with H 3 N + (CH 2 ) n NH 3 + 2ClO 4 -salts (n = 2-10, 12). The length of the polymethylene chain in the diammonium ions affects the phototransformation direction of stilbene and the com position of the products. In the 2 : 2 bispseudosandwich complexes with relatively short alkanediammonium ions (n = 2-4), the stereoselective reaction of [2+2] photocycloaddition proceeds to form mainly the rctt isomer of the cyclobutane derivative. The structure of rctt cyclobutane derivative as a complex with H 3 N + (CH 2 ) 4 NH 3 + 2ClO 4 -was confirmed by X ray diffraction analysis.Stilbenes and their analogs containing the 1,2 di(aryl/ hetaryl)ethylene structural fragment are objects of numerous studies, because they possess remarkable spectral fluorescence and photochemical properties, such as the ability to reversible reactions of E-Z isomeriza tion, electrocyclization, and [2+2] photocycloaddition (PCA). 1-3 These properties were used for the creation of optoelectronic media 4 and production of multiphoton absorption materials for lasers 5 and were proposed for application in information optical recording and storage systems, 6 molecular electronic devices, switchers, and machines. 7, 8 The influence on the photochemical properties of unsaturated compounds of their self assembly to supra molecular ensembles is of considerable interest because of possibility to control the direction of photoreactions in these systems, and their stereochemical result also can often be controlled. For instance, the steroselective PCA of the stilbene derivatives can occur in cavities of cucurbit[8]uril 9 and γ cyclodextrin. 10 Stilbenes contain * Dedicated to Academician A. I. Konovalov on his 75th birthday.ing the crown ether fragment also provide a possibility of comparatively easily control of their self assembly in the presence of metal cations by complexation. 11,12Ammonium ions represent wider possibilities for fine control of the structure and photochemical properties of supramolecules, 13 including those based on crown con taining stilbenes, because the assortment of ammonium compounds is much larger than the range of inorganic substrates. For example, the formation of unusually stable donor acceptor complexes between bis(18 crown 6) stilbene ((E) 1) and diammonium derivatives of viologen analogs, which can serve as fluorescent molecular sensors to alkaline earth metal cations, was observed. 14,15 The stereospecific PCA in the dimeric complex of ammo nium containing mono(24 crown 8) stilbene was stud ied. 16 The PCA reactions of biscrown containing stilbenes can be used, for example, for the creation of new photo switchable complexing agents or systems of optical record ing of information. However, photoreactions of biscrown containing stilbenes almost have not been studied up to recently, because (to a great extent) of low availability of these compounds.

Optical Sensing of Aromatic Amino Acids and Dipeptides by a Crown‐Ether‐Functionalized Perylene Bisimide Fluorophore

“…These NMR spectroscopic observations clearly indicate the formation of PBI 1/ l ‐Trp or PBI 1 /Ala‐Trp complexes. The low‐field shift of bay‐substituent protons corroborates an interaction between ammonium group of guest and crown ether unit of PBI host …”

Controlled self-assembly of bis(crown)stilbenes into unusual bis-sandwich complexes: structure and stereoselective [2+2] photocycloaddition

“…Similar effects were observed in our study of complexation of (E)-1c with Cn. 9 When the size of the macrocycle cavity was roughly the same or larger than the metal cation diameter, the signals of aromatic and ethylene protons of stilbene also underwent monotonic downfield shifts following increase in the C M /C 1 ratio (e.g., Fig. 2), which was caused by the electronwithdrawing effect of the cation in the complex.…”

“…The latter complex is formed due to complementarity of the primary ammonium group and the 18-crown-6-ether moiety and also to relatively short distance between the two ammonium groups in C3, which probably does not prevent stacking interactions between the two planar stilbene fragments in some types of bis-pseudosandwich structures. 9 Bis (12-crown-4)stilbene (E)-1a forms 1 : 1 complexes of low stability with alkali metal cations (log K 1:1 r 2.6), the stability of these complexes decreasing following increase in the cation diameter. Therefore, only with sodium cations, was the formation of relatively weak complexes (1a) 2 Á(Na + ) 2 detected (log K 2:2 = 5.0).…”

Highly Stable Supramolecular Donor–Acceptor Complexes Involving a Bis(18-Crown-6)azobenzene as Weak Donor: Structure–Property Relationships

“…1,9-Diammoniononane diperchlorate ( 6 ) and 1,10-diammoniodecane diperchlorate ( 7 ) were prepared as described previously. 38 , 43 2-Bromoethylammonium bromide (Sigma-Aldrich) and MeCN (special purity grade, water content <0.03%, v/v, Cryochrom) were used as received.…”