What question did this study set out to answer?

The aim is to design and synthesize thieno[3,4-b]thiophene-based quinoidal oligomers with specific photophysical properties.

June 4, 2026Open Access

Effective Approach toward Selective Near-Infrared Dyes: Rational Design, Synthesis, and Characterization of Thieno3,4-bthiophene-Based Quinoidal Oligomers

Key Points

The aim is to design and synthesize thieno[3,4-b]thiophene-based quinoidal oligomers with specific photophysical properties.
Synthesized three quinoidal oligomers, measuring their photophysical and electrochemical properties.
Characterized their absorption bands and energy band gaps through experiments and density functional theory calculations.
O4TTO showed strong NIR absorption near 1200 nm while remaining transparent in the visible region.
Absorption bands were red-shifted with longer TT units, indicating modified optical properties.
Energy band gaps narrowed as TT units increased, confirming predictions from theoretical calculations.

Abstract

This paper describes syntheses, photophysical properties, and electrochemical characteristics of three thieno3,4-bthiophene (TT)-based quinoidal oligomers OnTTO. The rigid planar backbones of these oligomers give the molecules narrow absorption bands, and the main absorption bands were significantly red-shifted when the TT units were extended and demonstrated wide transparent windows. The compound O4TTO was found to possess strong absorption in the near-infrared (NIR) region approaching 1200 nm but remained transparent in the visible region. Electrochemical experiments have shown that the energy band gaps gradually narrow when the TT units are increased. Optical properties predicted by density functional theory calculations are in good agreement with the experimental optical results. These dye molecules could be promising candidates for future NIR photodetectors, filters, and bioimaging technologies.

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