Electrostatic Control of Intramolecular Electron Transfer in Calix[4]diquinones Bearing an Appended Chromophore

Abstract

Binding of K or Ba ions attenuates intramolecular electron transfer between a chromophore and an electron-affinic macrocyclic receptor (see schematic representation), and simultaneously amplifies luminescence. In the complexed state, photons absorbed by the dicationic chromophore are emitted as luminescence, whereas illumination of the uncomplexed superstructure causes rapid reduction of the receptor.

Tris(rhenium fac-tricarbonyl) Polypyridine Functionalized Cyclotriguaiacylene Ligands with Rich and Varied Emission

“…While there are no previous examples of Re­(CO) 3 X moieties being appended to CTV-type host molecules, there are a number of reports of other classes of macrocyclic host molecules being decorated in this fashion. For example, decorations of calixarenes with [Re­(CO) 3 X­(bpy)] (bpy = 2,2′-bipyridyl) groups at the upper , or lower calixarene rim , have been reported and include cases of complexes showing luminescence sensing behavior for fullerenes or anions . The Re­(CO) 3 Br unit has also been employed as a building tecton to link pyridyl-appended cavitands into ditopic cavitand assemblies and as a metallobridge to stabilize the extended cavity of an expanded calix[4]­arene .…”

Controlling electron exchange in molecular assemblies

“…1b), but many other pairs of light-induced reactions are possible. The goal now is to direct the chemistry along one particular direction by careful balancing of the entire system, by perturbation of one small part of the spacer unit [19][20][21] or by changing the experimental conditions. Perhaps the most elegant way to achieve such possibilities is to use different input photon frequencies such that dissimilar excited states are populated by excitation.…”

Isocyanate-, Isothiocyanate-, Urea-, and Thiourea-Substituted Boron Dipyrromethene Dyes as Fluorescent Probes

“…Mapping of both the spatial and temporal distribution of calcium within biological systems is a typical challenge . We and others have previously argued the case that rational modification of known molecules is a field that still retains great promise. , Binding of the target analyte to a synthetic fluorophore (sensor) can result in either amplification or quenching of the fluorescence but a common instance is that in which photoinduced electron transfer (PET) quenches the luminescence in the absence of the analyte. Analyte binding may then lead to the “switching on” of the emission by inhibition of PET, either because of a direct interaction of the analyte with redox active centers of the sensor or because the binding induces a conformational change which places these centers remote from the emissive site. , Aromatic amines are good reductants and for this reason have been widely used to provide PET quenching by covalent binding to various fluorophores such as acridine, acridinium, anthracene, phenanthrene, pyrene, and Bodipy dyes. , These are fluorophores where, in some cases, charge transfer (CT) occurs upon excitation of the fluorophore, leading to emission from a highly polarized CT state in the weak energy domain .…”