Fused Isoindigo Ribbons with Absorption Bands Reaching Near Infrared

What is it about?

Through fusing isoindigo (IID) units at 6,7;6’,7’-positions, a series of new near-infrared (NIR) absorbing and stable ribbon-like conjugated molecules, namely nIIDs in which n represents the number of IID units, have been synthesized. The optical band gaps of the molecules are lowered from 2.03 eV of 1IID to 1.12 eV of 6IID with the increase of the conjugation length. 3IID, 4IID, and 6IID have strong absorption in the NIR region and exhibit photothermal conversion efficiencies of greater than 50% under laser irradiation at l = 808 nm.

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Why is it important?

In summary, new conjugated ribbon-like molecules have been synthesized. The molecules 3IID, 4IID, and 6IID, which contain 3, 4, and 6 fused IID units, respectively, have strong absorption at l > 800 nm and show impressive stability against NIR irradiation. Photothermal conversion efficiencies of > 50% have been achieved under laser irradiation at l =808 nm. Low band gaps, good stability, and high photothermal conversion efficiencies enable them as new materials for potential bio-related applications.

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