Photochemistry of Far Red Responsive Tetrahydroquinoxaline-Based Squaraine Dyes

Wojcik, Aleksandra and Nicolaescu, Roxana and Kamat, Prashant V and Chandrasekaran, Yogesh and Patil, Satish (2010) Photochemistry of Far Red Responsive Tetrahydroquinoxaline-Based Squaraine Dyes. In: Journal of Physical Chemistry A, 114 (8). pp. 2744-2750.

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Abstract

The photochemical and redox properties of two newly synthesized tetrahydroquinoxaline-based squaraine dyes (SQ) are investigated Using femto- and nanosecond laser flash photolysis, pulse radiolysis, and cyclic voltammetry. In acetonitrile and dichloromethane, these squaraines exist its monomers in the zwitterionic form (lambda(max) approximate to 715 nm, epsilon(max) approximate to 1.66 x 10(5) M-1 cm(-1) in acetonitrile). Their excited sin-let states ((1)SQ*) exhibit a broad absorption hand at 480 nm, with singlet lifetimes of 44 and 123 ps for the two dyes. Both squaraines exhibit poor intersystem crossing efficiency (Phi(ISC) < 0.001). Their excited triplet states ((3)SQ*), however, Ire efficiently generated by triplet-triplet energy transfer Using triplet excited 9,10-dibromoanthracene. The excited triplet states of the squaraines dyes exhibit it broad absorption hand at ca. 560 nm (epsilon(triplet) approximate to 4.2 x 10(4) M-1 cm(-1)) and undergo deactivation via triplet-triplet annihilation and ground-state quenching processes. The oxidized forms of the investigated squaraines (SQ(center dot+)) exhibit absorption maxima at 510 and 610 nm.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry A
Publisher:	American Chemical Society.
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	29 Mar 2010 10:53
Last Modified:	19 Sep 2010 05:57
URI:	http://eprints.iisc.ac.in/id/eprint/26231

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