Large polarization of push–pull “Cruciforms” via coordination with lanthanide ions

“Bent” or “cruciform” shaped conjugated push–pull compounds exhibit striking differences in their supramolecular recognition of lanthanide cations, with in an outstanding supramolecular polarization.

Colour-tuneable solid-state fluorescence of crystalline powders formed from push–pull substituted 2,5-diphenyl-stilbenes

Polycrystalline powders of push–pull substituted stilbenes with various acceptors emit from blue to infrared. Exciton localization on a monomer (in J-like packing) or a stacked dimer (for H-aggregates) avoid exciton migration to the quenching sites.

Crystallization-induced room-temperature phosphorescence in fumaramides

Novel fumaramides exhibit room-temperature phosphorescence in the solid state once molecular design and positioning of the carbonyl and bromine atoms allow for the formation of strong intermolecular halogen bonding interactions.

Tuning of the Electro-Optical Properties of Tetraphenylcyclopentadienone via Substitution of Oxygen with Sterically-Hindered Electron Withdrawing Groups

In this report, the substitution of the oxygen group (=O) of Tetraphenylcyclopentadienone with =CR2 group (R = methyl ester or nitrile) was found to have tuned the electro-optical properties of the molecule. Although both groups are electrons withdrawing in nature, their absorption from UV-vis spectra analysis was observed to have been blue-shifted by methyl ester substitution and red-shifted by nitrile substitution. Interestingly, these substitutions helped to enhance the overall intensity of emission, especially in the context of methyl ester substitution whereby the emission was significantly boosted at higher concentrations due to hypothesized restrictions of intramolecular motions. These observations were explained through detailed descriptions of the electron withdrawing capability and steric properties of the substituents on the basis of density functional theory calculations.

Formation of disulphide linkages restricts intramolecular motions of a fluorophore: detection of molecular oxygen in food packaging

Reliable and easy detection of oxygen in food packaging without the aid of sophisticated instruments is highly coveted. A tetraphenylethene probe based on oxygen-mediated polymerization via the formation of disulfides causes restricted intramolecular rotation of the TPE phenyls resulting in a >100 fold enhancement of emission and thus detects O2 in food packages.

Controlled aggregation of DNA functionalized poly(phenylene-vinylene)

We show that aggregation of DNA-functionalized poly(phenylene-vinylene) can be controlled in solution through ion and DNA interactions.

Highlights from Faraday Discussion: aggregation-induced emission

Faraday Discussion 196: aggregation-induced emission brought together around 100 researchers to discuss recent progress, current challenges and potential breakthroughs in the design of new AIE luminogens, the understanding of AIE mechanisms and the exploration of advanced technological applications.

Synthesis and characterisation of push–pull flavin dyes with efficient second harmonic generation (SHG) properties

We report push–pull flavins bearing different donor groups that exhibit high hyperpolarisabilities (β = 355–9550 × 10⁻³⁰ esu) and decomposition temperatures thereby indicating their potential application as non-linear optical device materials.

Structure-activity relationship for the solid state emission of a new family of "push-pull"π-extended chromophores

We report the design, synthesis, molecular optical properties, and solid state emissive behaviour of a series of novel compounds, which, similar to the archetypal AIE luminogen tetraphenylethene, are formed of a central olefin stator and decorated with either three or four rotors. These rotors, being either electron-rich substituted benzenes, or electron-withdrawing functional groups (esters, ketones, cyano groups) confer a "push-pull" character to the overall molecular structure. Building on both new and already published contributions, a comprehensive picture of the properties and the potential of these compounds is provided.

One-Pot Click Access to a Cyclodextrin Dimer-Based Novel Aggregation Induced Emission Sensor and Monomer-Based Chiral Stationary Phase

A 'two birds, one stone' strategy was developed via a one-pot click reaction to simultaneously prepare a novel cyclodextrin (CD) dimer based aggregation induced emission (AIE) sensor (AIE-DCD) and a monomer based chiral stationary phase (CSP-MCD) for chiral high performance liquid chromatography (CHPLC). AIE-DCD was found to afford satisfactory AIE response for specific detection of Zn²⁺ with a detection limit of 50 nM. CSP-MCD exhibits excellent enantioseparation ability toward dansyl amino acids, where the resolution of dansyl amino leucine reaches 5.43.

Long-living optical gain induced by solvent viscosity in a push–pull molecule

The combination of continuum and ultrafast pump–probe spectroscopy, in viscous and non-viscous environments, with DFT and TDDFT calculations, is effective in unraveling important features of the twisted intramolecular charge transfer mechanism in a new push–pull molecule that possesses aggregation induced emission properties.

Synthesis of Binaphthyl-Based Push-Pull Chromophores with Supramolecularly Polarizable Acceptor Ends

We report on the design and synthesis of new enantiopure binaphthyl derivatives in which electron-donating and electron-withdrawing substituents are placed in direct conjugation, to create push-pull dyes potentially active for NLO applications. The dyes, unprecedentedly, extend theirπ-bridge from the 3,3′ positions of the binaphthyl units and incorporate as acceptors 1,3-dicarbonyl and tetrafluorobenzene units, useful for further supramolecular polarization of the chiral dyes.

Synthesis, chiroptical and SHG properties of polarizable push–pull dyes built on π-extended binaphthyls

Novel binaphthyl push–pull dyes extend their π-bridge and incorporate as acceptors pyridine units, useful for further supramolecular polarization.

Synthesis and luminescent properties of Lewis base-appended borafluorenes

A series of Lewis base adducts of 9-bromo-9-borafluorene (BrBFl-LB, LB = IPr, IPrCH2, PPh3, and PCy3), parent borafluorenes (HBFl-IPr and HBFl-IPrCH2), and the bisadduct [(DMAP)2BFl]Br were prepared and structurally characterized (IPr = [(HCNDipp)2C:], IPrCH2 = [(HCNDipp)2C═CH2], Dipp = 2,6-i-Pr2C6H3, and DMAP = N,N-dimethylaminopyridine). The adducts BrBFl-IPr, BrBFl-PPh3, BrBFl-PCy3, [(DMAP)2BFl]Br, BrBFl-IPrCH2, and HBFl-IPrCH2 were found to exhibit bright blue luminescence with low to moderately high quantum efficiencies (19 to 63%). Selective irradiation at different excitation wavelengths revealed the presence of two distinct emission processes in the adducts BrBFl-LB, leading to a ligand-independent, presumably borafluorene-based, blue light emission at 435 nm and another less intense emission band in the ultraviolet region (315-324 nm); [(DMAP)2BFl]Br exhibits an emission profile that tails into the visible region. Time-dependent density functional theory studies are also included for representative borafluorene adducts. With a judicious choice of functional groups at boron, one can envisage the future generation of a whole library of 4-coordinate borafluorene-based luminogens that complement the efficient light-emitting behavior known for the widely studied boron-dipyrromethene analogues.

Novel electro-optic chromophores based on substituted benzo[1,2-b:4,5-b′]dithiophene π-conjugated bridges

The electro-optic coefficient of benzo[1,2-b:4,5-b′]dithiophene unit (BDT)-based chromophores was improved to 102 pm V⁻¹ with suitable isolation groups and electron donors.

Synergy between twisted conformation and effective intermolecular interactions: strategy for efficient mechanochromic luminogens with high contrast

A strategy towards efficient mechanochromic luminogens with high contrast is developed. The twisted propeller-like conformations and effective intermolecular interactions not only endow the luminogens with AIE characteristics and high efficiency in the crystalline state, but also render them to undergo conformational planarization and disruption in intermolecular interactions upon mechanical stimuli, resulting in remarkable changes in emission wavelength and efficiency.