Intramolecular CT and Ultrafast NR Decay in DNA-Tethered Asymmetric Squaraines

In this work, the electronic structure and excited-state dynamics of a series of indolenine-based squaraine dyes incorporating dimethylamino (electron donating) and/or nitro (electron-withdrawing) substituents, so-called asymmetric dyes, were characterized. These dyes were covalently linked to DNA Holliday junctions to suppress aggregation and permit characterization of their monomer photophysics. A combination of density functional theory and steady-state absorption spectroscopy shows that the difference static dipole moment (Δd) successively increases with the addition of these substituents while simultaneously maintaining a large transition dipole moment (μ). Steady-state fluorescence and time-resolved absorption and fluorescence spectroscopies uncover a significant nonradiative decay pathway in the asymmetrically substituted dyes that drastically reduces their excited-state lifetime (τ).

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https://pubs.acs.org/doi/full/10.1021/acs.jpca.2c06442

Some of the other SETA squaraine dyes 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 K8-1342	Seta-670-NHS Seta-670-NHS	NH2	•	•					•	•					PB 7.4	667	180000	688	7	0.42
K8-1352 K8-1352	Square-660-NHS Square-660-NHS	NH2	•	•					•	•					PB 7.4	657	182000	676	3	0.27
K8-1384 K8-1384	Seta-700-NHS Seta-700-NHS	NH2	•	•						•	•	•			PB 7.4	687	177000	703	6
K8-1407 K8-1407	Square-650-pH-NHS Square-650-pH-NHS	NH2						•	•	•					PB 5.6	653	135000	671	16	1.17
K8-1642 K8-1642	Seta-632-NHS Seta-632-NHS	NH2							•						PB 7.4	632	280000	641	6
K8-1649 K8-1649	SQ-740-NHS SQ-740-NHS	NH2								•	•	•	•		PB 7.4	740	44000		0	0
K8-1663 K8-1663	Seta-633-NHS Seta-633-NHS	NH2						•	•						PB 7.4	633	250000	644	7	0.25
K8-1672 K8-1672	Seta-646-NHS Seta-646-NHS	NH2							•						PB 7.4	646	207000	656	10	0.38
K8-1682 K8-1682	Seta-660-di-NHS Seta-660-di-NHS	NH2							•	•					PB 7.4	661	220000	672	11	0.9