Photoresponsive crown ethers. 2. Photocontrol of ion extraction and ion transport by a bis(crown ether) with a butterfly-like motion

Molecular machines operated by light

“…These are ideal processes to obtain light-driven operation of molecular machines because they bring about evident structural changes that can be exploited to cause large amplitude motions in suitably designed molecular and supramolecular systems. As a matter of fact, molecular tweezers based on the azobenzene unit were the first examples of light-driven molecular machines reported in the literature [9,64]. The photoisomerization about a -C=C-bond is at the basis of a very interesting class of molecular rotary motors based on sterically hindered alkenes [19,65,66].…”

“…In the last few years the development of powerful synthetic methodologies, combined with a device-driven ingenuity evolved from the attention to functions and reactivity, have led to remarkable achievements in this field. Among the systems reported are molecular tweezers [9], propellers [10], rotors [11], turnstiles [12], gyroscopes [13,14], gears [15], brakes [16], a molecular pedal [17], ratchets [18], rotary motors [19], shuttles [20], elevators [21], muscles [22], valves [23], processive artificial enzymes [24], walkers [25][26][27], vehicles [28], and catalytic self-propelled micro-and nano-objects [29,30]. Several excellent reviews [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] and a monograph [47] dealing with artificial molecular machines and motors are available.…”

Enhanced photocontrolled binding of Ag+ by thioindigo derivative containing oxyethylene chains with OH groups at the terminal positions

“…When photoinduced, Fatah-ur-Rahman and Fukunishi (1992), Shinkai et al (1980Shinkai et al ( , 1981, noted that structural changes of many substances occurred, the results of which are of interest in converting light energy to chemical function. Since the time of Pedersen, extensive studies of the nature of the complexes formed by the macro-cyclic polyethers and also by acyclic crown ether-like macromolecules, mentioned in a number of papers, with many salts have been done in a number of techniques such as, isolation of the solid crystalline complexes (Pedersen , 1970, solubilization of salts in organic solvents (Hiratani et al 1980), extraction studies (Pedersen 1970) and proton magnetic resonance studies (Prestegard and Sunny 1969).…”

Supramolecular effects in dendritic systems containing photoactive groups

“…In this class of systems, in general, a photocontrolled host-guest behavior is observed as in functionalized crown-ether (Shinkai et al 1981) or cyclodextrin (Ueno et al 1979) molecules. In the second one there is a significant electronic interaction between the assembled components or, alternatively, nuclear constraints that change the photophysical properties of the individual components are introduced, as in the case of many polynuclear (Bignozzi & Scandola 1984) and caged (Pina et al 1985) metal complexes.…”