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Photophysics and nonlinear absorption of 4,4′-diethynylazobenzene derivatives terminally capped with substituted aromatic rings

Paper ID Volume ID Publish Year Pages File Format Full-Text
27129 44003 2012 8 PDF Available
Title
Photophysics and nonlinear absorption of 4,4′-diethynylazobenzene derivatives terminally capped with substituted aromatic rings
Abstract

The photophysical properties of a series of 4,4′-diethynylazobenzene derivatives terminally capped with substituted aromatic rings (1a: R = phenyl; 1b: R = 4-(diphenylamino)phenyl; 1c: R = 4-(9H-carbazol-9-yl)phenyl; 1d: R = 9H-fluoren-2-yl; 1e: R = biphenyl-4-yl; 1f: R = naphthalen-2-yl) were systematically investigated. All compounds exhibit strong 1π,π* absorption bands in the UV region; and a broad, structureless charge-transfer band/shoulder in the visible region (except for 1a), which systematically red-shifts when electron-donating substituents are introduced to the terminal phenyl rings, but blue-shifts when π-conjugation of the terminal aromatic ring increases. All compounds are emissive in solution at room temperature and at 77 K. When excited at the low-energy absorption band, the compounds emit fluorescence between 369 and 419 nm, which can be attributed to 1π,π*/1ICT (intramolecular charge transfer) state. Density functional theory (DFT) calculations on 1a–1f in gas phase were also performed to gain insight into the nature of the ground electronic state and the low-lying excited electronic states. 1d–1f exhibit strong triplet transient absorption band(s) in the visible spectral region, which are mainly attributed to the 3π,π* state. Reverse saturable absorption (RSA) of these compounds was demonstrated at 532 nm using ns laser pulses. The degree of RSA follows this trend: 1b > 1c ≈ 1a > 1e >1f > 1d, which is mainly determined by the ratio of the triplet excited-state absorption cross-section to that of the ground-state and the triplet excited-state quantum yield.

Graphical abstractThe photophysical properties, nonlinear absorption characteristics and the influence of the substituted aromatic rings on the nature of excited states of a series of 4,4′-diethynylazobenzene derivatives (1a–1f) were systematically investigated. All compounds exhibit reverse saturable absorption at 532 nm and could potentially be used as nonlinear absorbing materials.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Photophysics of 4,4′-diethynylazobenzene derivatives was systematically investigated. ► Excited state properties can be tuned by alternation of the terminal substituents. ► Compounds exhibit varied reverse saturable absorption at 532 nm for ns laser pulses.

Keywords
Azobenzene; Electronic absorption; Emission; DFT calculations; Transient difference absorption; Nonlinear absorption
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Photophysics and nonlinear absorption of 4,4′-diethynylazobenzene derivatives terminally capped with substituted aromatic rings
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 239, 1 July 2012, Pages 47–54
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
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