Influence of collective excitonic effects on the photophysics of flexibly- and rigidly-bridged SQ dimers targeted for DNA-based applications
In this work we synthesized three squaraine dimers featuring either a rigid or a flexible bridge. We characterized their optical properties and excited-state dynamics in chloroform and methanol via steady-state and time-resolved optical spectroscopies. Compared to the corresponding monomers, we found that both rigidly- and flexibly-bridged squaraine dimers exhibit signatures of collective excitonic effects─that is, red-shifted absorption, band narrowing, small Stokes shift, and superradiance─in both polar and nonpolar solvents. We also found that while rigidly-bridged dimers featured all of these properties, the flexibly-bridged dimers did not feature significant band narrowing and a small Stokes shift. Interestingly, the fluorescence quantum yields and singlet excited-state lifetimes of both monomers and dimers decreased in the polar solvent. As a first step toward the assembly of a functional dimer aggregate network, we covalently tethered the flexibly-bridged dimer and its corresponding monomer to single- and double-stranded DNA and characterized their photophysical properties in an aqueous buffer solution. We observed that the optical properties of the monomer served as a sensitive probe of the local polarity of the environment. In the case of the dimer, we observed a large distribution of conformations via absorption spectroscopy and sampled a subset of the distribution via fluorescence spectroscopy. Our work is an important first step toward implementing molecular aggregates preprogrammed to exhibit desired collective excitonic effects in DNA-assembled networks.
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https://pubs.acs.org/doi/10.1021/acsaom.5c00176
Some of the other SETA squaraine dye products which are readily available are listed below:
| Excitation Light Sources | Characteristics | ||||||||||||||||||||
| Product Number (Specs Sheet) |
Product Name (Product Info) |
Target Group | 380 | 405 | 436 | 488 | 532 | 594 | 635 | 650 | 680 | 700 | 750 | 780 | Medium | λ abs [nm] |
ε [M –1 cm–1] |
λ em [nm] |
QY [%] |
FLT [ns] |
Buy |
| K8-1342 | Seta-670-NHS | NH2 | • | • | • | • | PB 7.4 | 667 | 180000 | 688 | 7 | 0.42 | |||||||||
| K8-1352 | Square-660-NHS | NH2 | • | • | • | • | PB 7.4 | 657 | 182000 | 676 | 3 | 0.27 | |||||||||
| K8-1384 | Seta-700-NHS | NH2 | • | • | • | • | • | PB 7.4 | 687 | 177000 | 703 | 6 | |||||||||
| K8-1407 | Square-650-pH-NHS | NH2 | • | • | • | PB 5.6 | 653 | 135000 | 671 | 16 | 1.17 | ||||||||||
| K8-1642 | Seta-632-NHS | NH2 | • | PB 7.4 | 632 | 280000 | 641 | 6 | |||||||||||||
| K8-1663 | Seta-633-NHS | NH2 | • | • | PB 7.4 | 633 | 250000 | 644 | 7 | 0.25 | |||||||||||
| K8-1682 | Seta-660-di-NHS | NH2 | • | • | PB 7.4 | 661 | 220000 | 672 | 11 | 0.9 | |||||||||||
