Fluorescence and room temperature phosphorescence of 6-bromo-2-naphthol in β-cyclodextrin solution and its selective molecular recognition for cyclohexane

Conformation-Dependent Phosphorescence of Galactose-Decorated Phosphors and Assembling-Induced Phosphorescence Enhancement

Amorphous organic room-temperature phosphorescent (RTP) materials are promising for their facile preparation and processability, while the conformation effects of phosphors at amorphous state are lack of study in comparison with the rigid effects due to the commonly irregular assembling and dispersal of phosphors in rigid systems. Herein, we report a series of phosphorescent molecules modified by polyhydroxy galactose, whose RTP emission at the amorphous state can be regulated by controlling the conformational distortion of the phosphorescent segments. Further, a strong RTP emission is facilely obtained by the co-assembling between polyhydroxy phosphors and polyhydroxy matrices (α-CD, β-CD, and chitosan). Owing to the rigid effect of the enhanced hydrogen bonding cross-linking, the highest RTP quantum yield reaches 19.4%; whereas, the RTP emissions of assemblies become conformation insensitive. The conflicting relationship between the conformation effect and rigid effect is attributed to the differences between aggregated single-component systems and dispersed assembling systems. Besides, the unique and different moisture responsiveness of the co-assembling samples is discovered and further applied in data encryption. The research expands the scope for designing amorphous pure organic RTP materials with supramolecular strategies and shows a modularized approach for assembling-enhanced phosphorescence.

Amorphous Metal-Free Room-Temperature Phosphorescent Small Molecules with Multicolor Photoluminescence via a Host-Guest and Dual-Emission Strategy

Metal-free room-temperature phosphorescence (RTP) materials offer unprecedented potentials for photoelectric and biochemical materials due to their unique advantages of long lifetime and low toxicity. However, the achievements of phosphorescence at ambient condition so far have been mainly focused on ordered crystal lattice or on embedding into rigid matrices, where the preparation process might bring out poor repeatability and limited application. In this research, a series of amorphous organic small molecular compounds were developed with efficient RTP emission through conveniently modifying phosphor moieties to β-cyclodextrin (β-CD). The hydrogen bonding between the cyclodextrin derivatives immobilizes the phosphors to suppress the nonradiative relaxation and shields phosphors from quenchers, which enables such molecules to emit efficient RTP emission with decent quantum yields. Furthermore, one such cyclodextrin derivative was utilized to construct a host-guest system incorporating a fluorescent guest molecule, exhibiting excellent RTP-fluorescence dual-emission properties and multicolor emission with a wide range from yellow to purple including white-light emission. This innovative and universal strategy opens up new research paths to construct amorphous metal-free small molecular RTP materials and to design organic white-light-emitting materials using a single supramolecular platform.

Inclusion of fluorophores in cyclodextrins: a closer look at the fluorometric determination of association constants by linear and nonlinear fitting procedures

The author discusses methods for the fluorometric determination of affinity constants by linear and nonlinear fitting methods. This is outlined in particular for the interaction between cyclodextrins and several anesthetic drugs including benzocaine. Special emphasis is given to the limitations of certain fits, and the impact of such studies on enzyme-substrate interactions are demonstrated. Both the experimental part and methods of analysis are well suited for students in an advanced lab.

INHIBIT logic operations based on light-driven β-cyclodextrin pseudo[1]rotaxane with room temperature phosphorescence addresses

INHIBIT logic gates based on light-driven β-cyclodextrin pseudo[1]rotaxane were fabricated conveniently utilizing reversible ICD and RTP as output addresses respectively.

Fluorescence enhancement of 1-napthol-5-sulfonate by forming inclusion complex with beta-cyclodextrin in aqueous solution

Fluorescence enhancement of 1-naphthol-5-sulfonate (1N5S) upon inclusion in beta-cyclodextrin is studied by spectrophotometry and spectrofluorimetery techniques. The spectral shifts were only observed in the emission spectra in different solvents and were found to be directly correlated to the solvent's hydrogen-bond donor strength (alpha). Spectral changes in the absorption spectra upon the addition of beta-cyclodextrin to 1N5S in aqueous medium were too small to allow for the determination of the binding constant. On the other hand; fluorescence measurements show that the emission of both the anionic and neutral forms of 1N5S increase upon the addition of beta-cyclodextrin with an increase in the quantum yield by about 60%. Fluorescence measurements show 1:1 inclusion of 1N5S in the beta-cyclodextrin cavity with an association constant of 88+/-10M(-1). (1)H NMR studies are used to confirm the inclusion and to provide information on the geometry of 1N5S inside the cavity of beta-cyclodextrin.

Room temperature phosphorescence of α-bromonaphthalene induced by cyclodextrin in the presence of hexahydropyridine or 1-ethylpiperidine and its application

Two novel heterocyclic third components, hexahydropyridine (HHP) and 1-ethylpiperidine (EP) were firstly found to enhance room temperature phosphorescence (RTP) of alpha-bromonaphthalene (alpha-BrN) induced by cyclodextrin. The effects of equilibrium time for formation of inclusion complex, temperature, pH values and the variation of concentrations of each component on RTP of alpha-BrN and the RTP lifetime of each ternary complex had been investigated and compared to discuss inclusion mechanism of ternary complexes. The RTP lifetimes of alpha-BrN/beta-CD/HHP, alpha-BrN/beta-CD/cyclohexane (CH) and alpha-BrN/beta-CD/EP were 6.18, 7.71 and 9.36 ms, respectively. Based on the strongest RTP of alpha-BrN induced by CD in the presence of EP, a method for determination of EP was established. Under the optimal conditions, the analytical curve of EP gave a liner dynamic range of 1.50x10(-4) to 1.50x10(-3) mol L(-1) with a detection limit of 4.8x10(-5) mol L(-1). When the established CD-RTP method was applied to determine the concentration of EP synthetic samples in distilled water, the experimental results demonstrated that the recovery was 91.4% with a relative standard deviation less than 2.85% (n=7).