Cascade Fluorescence Modulation in Photochromic Microcapsules.

Certain derivatives of terarylene are able to undergo a highly efficient oxidative cycloreversion cascade effect, a ring opening reaction with quantum yields above unity, resulting in a colored-to-colorless transition in solution. In the presence of chloroform, high-energy UV and X-rays can trigger this phenomenon, potentially acting as a visual detection system for ionizing radiation. However, chloroform is sensitive to different irradiation wavelengths without distinction, making it difficult to adapt to a reusable device.

C-Symmetric Luminescent Diketone with Amido-Linkage as a Polymorphic Fluorescence Emitter.

The study introduces a novel C-symmetric β-diketone compound, BTA-D3, and its monomeric counterpart, D, with a focus on their synthetic procedure, photophysical properties and aggregation behavior. Both compounds exhibit characteristic absorption and weak fluorescence in solution, with BTA-D3 displaying higher absorption coefficients due to its larger number of diketone units. Density Functional Theory (DFT) calculations suggest increased co-planarity of diketone groups in BTA-D3.

Conglomerate, Racemate, and Achiral Crystals of Polymetallic Europium(III) Compounds of Bis- or Tris-β-diketonate Ligands and Circularly Polarized Luminescence Study.

This work reports (a) conglomerate and racemic crystal structures of [(Δ,Δ,Δ,Δ,Δ,Δ)- or/and (Λ,Λ,Λ,Λ,Λ,Λ)-Eu (TTP)(OH)Na] coordination polymers, (b) racemic crystal structures of (Δ,Δ,Δ,Δ)-/(Λ,Λ,Λ,Λ)-Eu (TTP)(bipy)(MEK)(OH) tetrahedral clusters, and (c) the achiral crystal structure of the [Eu (BTP)(OH)Na] coordination polymer (where BTP = dianionic bis-β-diketonate, TTP = trianionic tris--diketonate, and bipy = 2,2'-bipyridine). The screw coordination arrangement of the TTP ligand has led to the formation of homoconfigurational racemic Eu products. The conglomerate crystallization of [Eu (TTP)(OH)Na] appears to be caused by the presence of the sodium, Na counterions, and interactions between oxygen atoms and the trifluoromethyl unit of the TTP ligand and Na ions.

Circularly Polarized Luminescence and Circular Dichroism of Bichromophoric Difluoroboron-β-diketonates: Inversion and Enhanced Chirality Based on Spatial Arrangements and Self-Assembly.

We synthesized two bichromophoric difluoroboron-β-diketonates (DFB) connected in para and meta positions by using cyclohexane diamine as a chiral bridge (para and meta (R/S)-CyDFB). TD-DFT calculations revealed that the variation in connectivity of the DFB units leads to different spatial arrangements and a chirality inversion of the bichromophoric DFB. Higher g values were obtained in (R/S)-CyDFB connected in para as compared to meta position.

Aromatic Phosphonates: A Novel Group of Emitters Showing Blue Ultralong Room Temperature Phosphorescence.

In recent years, there has been a growing interest in purely organic materials showing ultralong room-temperature phosphorescence with lifetimes in the range of seconds. Still, the longest known phosphorescence lifetimes are only achieved with crystalline systems so far. Here, a rational design of a completely new family of halogen-free organic luminescent derivatives in amorphous matrices, displaying both conventional fluorescence and phosphorescence is reported.

Dissecting Tetra--phenylbenzidine: Biphenyl as the Origin of Room Temperature Phosphorescence.

Amorphous purely organic thin films are able to show efficient phosphorescence under ambient conditions at room temperature. This opens the perspective to a wide range of new applications, which have attracted lots of interest in the field of material science recently. Therefore, an increasing number of different molecules displaying room temperature phosphorescence (RTP) have already been reported.

Mechanofluorochromism of a Difluoroboron-β-Diketonate Derivative at the Nanoscale.

Mechanofluorochromic nanoparticles have been prepared from a difluoroboron β-diketonate complex, and their behavior has been investigated at the nanoscale using atomic force microscopy (AFM) coupled with fluorescence spectroscopy. Two types of nanoparticles were observed, associated with green and yellow emission, reflecting the crystalline polymorphism of this material. While the green-emitting nanoparticles are mechanically insensitive under our conditions, the yellow-emitting ones display a marked hypsochromic shift upon shearing with the AFM tip.

Mechano-responsive circularly polarized luminescence of organic solid-state chiral emitters.

Two difluoro-boron β-diketonate complexes bearing chiral amido groups have been synthesized. Their mechano-responsive luminescence and chiroptical properties have been investigated in the solid state. Both compounds display a bright blue-green emission and a significant circularly polarized luminescence (CPL) signal in the crystalline state, with | | values as high as 2.

Blue-Light-Absorbing Thin Films Showing Ultralong Room-Temperature Phosphorescence.

The development of organic materials displaying ultralong room-temperature phosphorescence (URTP) is a material design-rich research field with growing interest recently, as the luminescence characteristics have started to become interesting for applications. However, the development of systems performing under aerated conditions remains a formidable challenge. Furthermore, in the vast majority of molecular examples, the respective absorption bands of the compounds are in the near ultraviolet (UV) range, which makes UV excitation sources necessary.

Revealing the Origins of Mechanically Induced Fluorescence Changes in Organic Molecular Crystals.

Mechanofluorochromic molecular materials display a change in fluorescence color through mechanical stress. Complex structure-property relationships in both the crystalline and amorphous phases of these materials govern both the presence and strength of this behavior, which is usually deemed the result of a mechanically induced phase transition. However, the precise nature of the emitting species in each phase is often a matter of speculation, resulting from experimental data that are difficult to interpret, and a lack of an acceptable theoretical model capable of capturing complex environmental effects.

β-Diketone derivatives: influence of the chelating group on the photophysical and mechanofluorochromic properties.

A diphenyl-boron β-diketonate complex was synthesized. Its photophysical properties were studied in solution and in the solid-state, and compared to those of its parent diketone and the corresponding difluoro-boron complex. TD-DFT calculations show that the molecular orbitals involved in the first Franck-Condon transition are very different for the three compounds studied.

Enantioselective Light Harvesting with Perylenediimide Guests on Self-Assembled Chiral Naphthalenediimide Nanofibers.

Self-assembling molecular systems often display amplified chirality compared to the monomeric state, which makes the molecular recognition more sensitive to chiral analytes. Herein, we report the almost absolute enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI-based host nanofibers to the guest PDI molecules.