Tuning solid-state emission properties of pyrene-containing chalcone derivatives

Aggregation induced emission of chalcones

There is always a need for efficient luminescent materials with simple synthesis and possible ease of hydrogen atom or functional group manipulation for use in different optoelectronic and biological applications. However, for certain real-world uses aggregation caused quenching effect of luminophores in their solid/aggregate state is undesirable, and is a cause of concern in areas, wherein the solid-state optical performance is more crucial. In this regard, chalcones have been explored for their ability to display aggregation-induced emission (AIE) or aggregation-induced enhanced emission (AIEE), which can be of practical use. This article is thus focused on an integrated evidence-based report on the AIE/AIEE-active chalcone systems for potential technological and biological applications.

Graphic abstract

Twisted intramolecular motion arrested in aggregated state emission and the nonlinear optical properties of pyrene pyrazoline derivatives

Heterocyclic pyrene pyrazoline moieties containing similar structures but with differences in thiophene (PPT), furan (PPF) and pyridine (PPP) substitutions at the terminal molecules were synthesized. Their aggregation behaviour in THF-water mixtures was investigated and results demonstrated that PPT and PPP exhibited aggregation-induced emission (AIE), whereas PPF exhibited aggregation-induced blue-shifted emission (AIBSE). PPT and PPP provided red-shifted emission, while PPF had observed blue-shifted emission at high water fractions of 70-90%, confirming that aggregation effects played a major role in the molecular structure. Two emission peaks from locally excited and twisted intramolecular charge transfer confirmed the twisted nature from the dihedral angle values of the free reorganized molecules that were completely restricted in high water fractions due to molecular aggregation. This was further confirmed from colour Commission Internationale de l'Eclairage values as well as dynamic light scattering analysis. Third-order nonlinear optical properties were studied using a Nd:Yag laser beam Z-scan technique at 532 nm. The open aperture Z-scan revealed that PPT and PPF towards the peak point endured strong saturable absorption, whereas PPP indicated a strong reverse saturable absorption process. The AIE and AIBSE mechanisms from undergoing restricted twisting intramolecular motion in the aggregated luminogens provide great insight into new developments in AIEgen materials for these optoelectronic materials.

Pyrenoimidazole-fused phenanthridine derivatives with intense red excimer fluorescence in the solid state

A new series of polycyclic aromatic hydrocarbons (PAHs), namely, various pyrene-fused phenanthridines PyFPs having different substituents were developed as fluorescent emitters for optoelectronic applications.

Synthesis, regioselective aerobic Pd(ii)-catalyzed C–H bond alkenylation and the photophysical properties of pyrenylphenylpyrazoles

Pd(ii)-catalyzed C–H alkenylation of a pyrenylphenylpyrazole afforded fluorophore exhibiting solvent-dependent dual emission, resulting from locally-excited (LE) and intramolecular charge transfer (ICT) excited states.

Aggregation-induced emission enhancement in halochalcones

Decorating the periphery of chalcones with halogen atoms increased their aggregation-induced emission enhancement properties, even if their optoelectronic properties are dominated by the other substituents.