Effects of substituents on the enrichment of the optical limiting action of novel imidazo[2,1-b][1,3,4]thiadiazole fused thiophene-based small molecules

Abstract

Schematic of the optical limiting action of a novel imidazo[2,1-b][1,3,4]thiadiazole based small molecule (ThITD3), which blocks high irradiance and transmits low-intensity (less harmful) light.

All-Optical Diode Action through Enhanced Nonlinear Response from Polymeric Photonic Crystal Microcavity

“…The nonlinear (defect) material used in the study is a novel imidazo 2a, and the detailed synthesis is mentioned in our previous report. 18 A total of 2 mg of ThITD doped with 5 mL CA solution was spin-coated with λ/2 optical thickness (∼180 nm) and sandwiched between the 20 bilayers of the PVK/CA structure as shown in Figure 1. An additional PVK layer is coated on the top surface to prevent the absorption of moisture from the atmosphere by the hygroscopic CA layer.…”

“…The absorption spectrum (Figure 2b) of ThITD exhibits two distinct peaks: one at 254 nm, which is attributed to the π−π* electronic excitations, and the other in the range of 413 nm is attributed to the intramolecular charge transfer (ICT) from the donor (thiophene, phenyl) to the acceptor imidazo[2,1-b][1,3,4]thiadiazole (ITD) unit. 18 The sample shows negligible absorption at 532 nm, which is ideal for fabricating a nonlinear photonic crystal, since the cavity mode was designed at 532 nm.…”

“…The β ef f values are comparable or better than previously reported values of small molecule organic systems. 18 The reason behind the NLO response of ThITD is due to the enhanced π-delocalization induced as a result of charge transfer from electron-donating thiophenephenyl groups to electron withdrawing imidazo[2,1-b][1,3,4]thiadiazole moieties.…”

“…Among the studied organic molecules, the donor–acceptor (D-A) system is found to be one of the best candidates for NLO applications. The intramolecular charge transfer (ICT) between donor–acceptor pairs (D-A) in organic systems extends the delocalization of π electrons, which in turn provides high polarizability and thus strong nonlinear optical response upon interacting with laser. − One can also modify the electronic structure of the D-A system by appropriate incorporation of a donor and/or acceptor that further improve the molecular polarizability as well as electronic and optoelectronic properties. Moreover, an organic system with extended conjugation with a suitable π electron linker or suitable donor and/or acceptor enhances the NLO activity through enhanced ICT.…”

Synthesis, physicochemical properties and computational study of donor–acceptor polymer for optical limiting application

“…To overcome the drawback of insolubility in organic solvents, cyclic polyimides are generally introduced with various flexible pendant groups [12], among which alkoxy groups yield better solubility and processability of polymers. Also, the fusion of heterocycles such as oxadiazole and thiadiazole in D-A polymers greatly enhances the optoelectronic performance of the polymer [13,14].…”