Modulation of fluorescence properties of MMeAQ in micelles and cyclodextrins

Engineering the Excited-State Dynamics of 3-Aminoquinoline by Chemical Modification and Temperature Variation

“…Steady-state absorption and fluorescence spectra of 3AQ have been discussed at length in earlier publications from our group. 45,52,61 We have reproduced the results once again, so as to perform back-to-back experiments for comparison with 3PQ. Briefly, the energy of the absorption maxima of 3AQ decreases linearly with the increase in the polarity of the solvent, even though the linear correlation is not very strong.…”

“…50 The excited-state dynamics of 3-aminoquinoline (3AQ) and their derivatives at room temperature in different solvents has been studied previously in our group. 45,52 The remarkably low quantum yield in nonpolar solvents has been attributed to a nonpolar LE state, from which a facile nonradiative relaxation pathway is provided by the flip-flop motion of the amino group. The nonradiative rate constant is found to be smaller in more polar solvents and particularly so in protic solvents.…”

Photophysical and Quantum Chemical Studies on the Interactions of Oxazine-1 Dye with Cucurbituril Macrocycles

“…Host–guest complexes formed through inclusion of small guest molecules into cavities of macrocyclic molecules (hosts) has been the topic of intense research in supramolecular chemistry for a long time. − An important inquisitiveness in supramolecular host–guest studies is to understand the role of different noncovalent forces in the formation of these complexes and to explore the noteworthy modulations in the properties of the encapsulated guest molecules or the host–guest systems to find their useful applications. − Chromophoric molecules often undergo quite large and extremely useful changes in their photophysical and other properties on complexation with macrocyclic hosts. − Thus, enhancement in the fluorescence yield and lifetime, increase in the photostability, alteration in the acidic/basic characteristic, modulation in the conformational relaxation, increase in the dissolution and solubility, and so forth, are among the important changes. These changes are projected to enable potential applications in different areas like drug formalisms, drug delivery, sensors, catalysis, and so on. − With these perspectives, understanding the changes in the properties of the guest molecules on their binding with different macrocyclic hosts and thus exploring their possible applications have been the subject of long lasting research interest in supramolecular chemistry. − …”

“…Among macrocyclic hosts, the cucurbit[n]uril (CBn) derivatives have made a tremendous impact in spite of their relatively new entry into the host–guest chemistry, due to their unique chemical constitution and their versatility to form strong inclusion complexes with a variety of guest molecules. − ,− Structurally, CBn homologues are highly symmetrical pumpkin-shaped macrocyclic molecules formed by the linking of glycoluril monomer units in a cyclic manner by a pair of methylene bridges. Depending on the number of glycoluril units present, different CBn homologues of varying cavity and portal sizes are available, the most common ones being CB5, CB6, CB7, CB8, and CB10, composed of 5, 6, 7, 8, and 10 monomer units, respectively.…”

“…Besides this hydrophobic interaction, CBn can also provide additionally, a very strong ion–dipole or charge–dipole interaction for the encapsulated guest molecule when the latter possesses a cationic charge or an intramolecular charge transfer (ICT) character, respectively. The Coulombic interaction arises due to the presence of the two identical and highly polarizable carbonyl portals of the CBn cavity, and it provides an exceptionally large stability for the CBn-based inclusion complexes in comparison to those formed with other conventional hosts. − ,− This important feature of CBn homologues has been the main impetus for extensive supramolecular host–guest studies carried out involving these macrocycles, aiming to explore their potentials for various useful applications.…”