Title

Structure And Linear Spectroscopic Properties Of Near Ir Polymethine Dyes

Keywords

Absorption; Charge delocalization; Chromophore; Cyanine; Excited states; Fluorescence; Near infrared; Organic dyes; Polymethine; Quantumchemical analysis; Red shift; Solvatochromism; Solvent-dependent; Squaraine; Structure-property relations; Symmetry breaking; Terminal groups; Tetraone; Visible; Weak fluorescence

Abstract

We performed a detailed experimental investigation and quantum-chemical analysis of a new series of near IR polymethine dyes with 5-butyl-7,8-dihydrobenzo[cd]furo[2,3-f]indolium terminal groups. We also synthesized and studied two neutral dyes, squaraine and tetraone, with the same terminal groups and performed a comparison of the spectroscopic properties of this set of "near IR" dyes (polymethine, squaraine, and tetraone) with an analogous set of "visible" dyes with simpler benzo[e]indolium terminal groups. From these measurements, we find that the dyes with dihydrobenzo[cd]furo[2,3-f]indolium terminal groups are characterized by a remarkably large shift ≈300 nm (≈200 nm for tetraone) of their absorption bands towards the red region. We discuss the difference in electronic structure for these molecules and show that the "near IR" dyes are characterized by an additional weak fluorescence band from the higher lying excited states connected with the terminal groups. Absorption spectra for the longest polymethines are solvent-dependent and are characterized by a broadening of the main band in polar solvents, which is explained by ground state symmetry breaking and reduced charge delocalization within the polymethine chromophore. The results of these experiments combined with the agreement of quantum chemical calculations moves us closer to a predictive capability for structure-property relations in cyanine-like molecules. © 2008 Elsevier B.V. All rights reserved.

Publication Date

12-1-2008

Publication Title

Journal of Luminescence

Volume

128

Issue

12

Number of Pages

1927-1936

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.jlumin.2008.06.002

Socpus ID

51249102142 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/51249102142

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