Bis squaraine

A Ca2+-ion selective rigid -flexible - rigid type bichromophoric sensors based on the conformation liable bis-squaraine dyes 27 works on the principle of Cation-steered folding, which leads to dramatic perturbations in the optical properties as a result of exciton interactions [87],... 

Some bis-squaraine derivatives 2.211 have been prepared as near-infrared emissive fluorophores, where two squaraine units were linked by oligothiophene spacers (Chart 1.43) [300], These dyes showed absorption bands at 780 and 700 nm with high molar absorptivities. Additionally, by increasing the number of thiophene units, blue shifts in the absorption bands were observed. The noncovalent interactions with human serum albumin (HAS) and BSA have been studied in trizma buffer and showed the formation of 1 1 complexes concomitant with a fluorescence enhancement. 

H. Nakazumi, T. Ohta, H. Etoh, T. Uno, C. L. Colyer, Y. Hyodo and S. Yagi, Near-infrared luminescent bis-squaraine dyes linked by a thiophene or p5Tene spacer for noncovalent protein labeling, Synth. Met., 153, 33-36 (2005). 

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