cis–trans Isomerization of the Azobenzenes Included as Guests in Langmuir–Blodgett Films of Amphiphilic β-Cyclodextrin

Abstract

Azobenzenes in the host–guest Langmuir–Blodgett films prepared with amphiphilic β-cyclodextrin and azobenzene derivatives showed a photochromic behavior with complete reversibility owing to the free volume of cyclodextrin cavity, whereas the trans-to-cis isomerization was restricted in the case of the pure LB film prepared with long-chain azobenzene derivative alone. Thermal cis-to-trans isomerizations in the LB films were also studied.

Light-responsive aggregation of β-cyclodextrin covered silica nanoparticles

“…Also the inclusion of azobenzene as a guest into a cyclodextrin (CD) host is photoresponsive: the rodlike and apolar trans-isomer forms a stable inclusion complex with a-CD as well as with b-CD, while the bent and polar cisisomer does not t in either CD. The photocontrolled molecular recognition of CDs with azobenzenes has been used to develop photoresponsive host molecules and molecular shuttles, [20][21][22] hydrogels, [23][24][25][26][27][28][29][30][31][32] micelles and vesicles, [33][34][35][36][37][38][39] surfaces, 40,41 and drug delivery vehicles. 42,43 A powerful strategy to direct the self-organization of functionalized NPs is therefore to introduce CDs on the surface of NPs.…”

Photoresponsive Molecular Recognition and Adhesion of Vesicles in a Competitive Ternary Supramolecular System

“…Also, the inclusion of azobenzene as a guest into a cyclodextrin (CD) host is photoresponsive: the rod-like and apolar trans isomer forms a stable inclusion complex with a-(a-CD) and b-cyclodextrin (b-CD), whereas the bent and polar cis isomer does not fit into either CD. The photocontrolled molecular recognition of CDs with azobenzenes has been used to develop photoresponsive host molecules, [31,32] hydrogels, [33][34][35][36][37][38][39][40] molecular shuttles, [41,42] micelles and vesicles, [43][44][45][46] ion channels, [47] surfaces, [48,49] and drug-delivery vehicles. [50] In recent years we have explored the formation of vesicles of amphiphilic CDs and the molecular recognition of guest molecules at the surface of such host vesicles.…”

Effect of packing on orientation and cis–trans isomerization of azobenzene chromophore in Langmuir–Blodgett film

“…Reversible photochromism based on cis-trans isomerization has been extensively studied for azo dyes in solutions [1][2][3], liquid crystals [4], polymer matrixes [5][6][7], and organized molecular assemblies [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Among the available azo dyes, long-chain azobenzene derivatives have received much interest as functional film-forming materials because of their potential applications to photoresponsive systems such as optical data recording and storage media, light switching devices and nonlinear devices.…”

“…For example, stacking of azobenzene chromophores markedly inhibits reversible cistrans photoisomerization [10,11], while incorporation of chromophores in polymer side chains [6,12], cyclodextrin cavities [13], and polyion-complex LB films [14,15] is advantageous for photoisomerization. However, the microenvironment favorable for photoisomerization induces thermal relaxation of azobenzene chromophores from the generally unstable cis isomer to the more stable trans isomer even at ambient temperature.…”