@article {6689, title = {Modulation of the ligational properties of a new cylindrical macrotricycle by coupling of photochemical- and pH-switching properties}, journal = {Journal of the Chemical Society-Perkin Transactions 2}, year = {1998}, note = {

ISI Document Delivery No.: YY098Times Cited: 14
Cited Reference Count: 24
Bencini, A Bernardo, MA Bianchi, A Ciampolini, M Fusi, V Nardi, N Parola, AJ Pina, F Valtancoli, B
Pina, Fernando/C-8161-2011; Fusi, Vieri/H-1006-2012; Parola, A. Jorge/F-4048-2010
Parola, A. Jorge/0000-0002-1333-9076
Royal soc chemistry
Cambridge

}, month = {1998}, pages = {413-418}, abstract = {

The new cylindrical molecule L containing two tetraazamacrocyclic rings linked by two azobenzene pillars displays photoelastic properties, Light absorption at 366 nm gives rise to trans --\> cis isomerization of the azobenzene moieties producing two isomers containing one or two cis-azobenzenes, respectively, The three trans-trans (E-E), trans-cis (E-Z) and cis-cis (Z-Z) isomers have been identified and characterized by H-1 NMR spectroscopy, allowing the dependence of their formation percentages with irradiation time to be determined, The sequence of photochemical reactions E-E --\> E-Z --\> Z-Z allows almost complete conversion of the E-E into the Z-Z isomer at 366 nm and 298 K, Both thermal (k = 1.75 x 10(-5) s(-1) at 313 K) and photo-induced (at 436 and 313 nm) back-isomerization reactions have been studied, The protonation constants of the three isomers in equimolar solutions of water-DMSO indicate a decreasing basicity in the order E-E \> E-Z \> Z-Z, in agreement with increasing electrostatic repulsion between the positive charges caused by a reduction in the separation between the protonation sites occurring upon Z --\> E isomerization.

}, isbn = {0300-9580}, url = {://WOS:000072112500033}, author = {Bencini, A and Bernardo, M. A. and Bianchi, A and Ciampolini, M. and Fusi, V. and Nardi, N. and A. J. Parola and Pina, F and Valtancoli, B} }