Synthesis and nonlinear optical properties of novel conjugated small molecules based on indole donor

Synthesis and Study of the Optical Properties of a Conjugated Polymer with Configurational Isomerism for Optoelectronics

A π-conjugated polymer (PBQT) containing bis-(2-ethylhexyloxy)-benzo [1,2-b'] bithiophene (BDT) units alternated with a quinoline-vinylene trimer was obtained by the Stille reaction. The chemical structure of the polymer was verified by nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR), and mass spectroscopy (MALDI-TOF). The intrinsic photophysical properties of the solution were evaluated by absorption and (static and dynamic) fluorescence. The polymer PBQT exhibits photochromism with a change in absorption from blue (449 nm) to burgundy (545 nm) and a change in fluorescence emission from green (513 nm) to orange (605 nm) due to conformational photoisomerization from the trans to the cis isomer, which was supported by theoretical calculations DFT and TD-DFT. This optical response can be used in optical sensors, security elements, or optical switches. Furthermore, the polymer forms spin-coated films with absorption properties that cover the entire visible range, with a maximum near the solar emission maximum. The frontier molecular orbitals, HOMO and LUMO, were calculated by cyclic voltammetry, and values of -5.29 eV and -3.69, respectively, and a bandgap of 1.6 eV were obtained, making this material a semiconductor with a good energetic match. These properties could suggest its use in photovoltaic applications.

Preparation of Polyphenylene Ring Derivative Dyes with Wide Wave Absorption Properties and Their Performance Study

Some conjugated benzene ring molecules were prepared using the Sonogashira reaction, and the molecules were post-functionally modified using click chemistry. The optical and electrical band gaps were measured using UV-VIS absorption spectroscopy and the three-electrode method, and the results of both were verified against each other to prove the accuracy of the characterization. In addition, the optical performances of the material were studied by z-scan; almost all materials exhibited good nonlinear optical properties and interconversion between saturable and anti-saturable absorption due to the invocation of click reagents.

A novel domino protocol for three-component synthesis of new dibenzo[e,g]indoles: flexible intramolecular charge transfers

New and electronically interesting 2-aryl-3-nitrodibenzo[e,g]indoles were synthesized effectively via a hitherto unreported three-component domino reaction under catalysis of a superparamagnetic nano-composite.

Optical properties of 3-substituted indoles

The optical properties of various donor or acceptor p-phenyl substituted ethenyl indoles were studied in solvents of varying polarity using absorption, fluorescence and TDDFT methods. Ethenyl indole exhibits non-linear optical properties (NLO) in a substituent dependent manner. Compound with a strong electron-attracting substituent, shows large NLO properties with charge transfer behavior, whereas ethenyls with moderate electron withdrawing or electron donating substituent exhibit lower NLO properties with non polar excited state. A highly dipolar excited state for p-nitro phenyl substituted ethenyl indoles (μ _e: 18.2-27.1 debye; Δμ: 9.4-17.8 debye) is observed as compared to other ethenyls (μ _e: 6.6-9.5 debye; Δμ: 4.2-6.2 debye). From TDDFT study, it is shown that the HOMO-LUMO energy of ethenyl is increased with increasing the electron donating ability of the p-phenyl substitution. The optical band gap of ethenyl 3 without substitution, is decreased upon p-phenyl substitution either with an electron withdrawing (Cl, NO₂) or an electron donating (OCH₃, OH, NH₂) substituent. The compound with a strong electron accepting, p-nitrophenyl ethenyl indole 1 shows 12 times better NLO response as compared to the reference ethenyl indole 3 (β: 1: 115 × 10^-30 esu^-1 cm⁵, 3: 9 × 10^-30 esu^-1 cm⁵). Ethenyls 2-6 bearing a weak or moderately electron withdrawing or electron accepting substituent, exhibit lower NLO response. The β of ethenyl is increased with increasing the order of electron withdrawing nature of phenyl ring. Overall, a correlation of β with the optical band gap, ground state dipole moment, % of charge transfer in the ground and excited state is found.