About the origin of the large Stokes shift in aminoalkyl substituted heptamethine cyanine dyes
| Autor: | Cristina Sissa, Massimo Trotta, Anna Painelli, Roberta Ragni, Francesca Terenziani |
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| Rok vydání: | 2020 |
| Předmět: |
Substituent
General Physics and Astronomy artificial antennas 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Photochemistry 01 natural sciences Fluorescence 0104 chemical sciences Photoexcitation Polymethine dyes chemistry.chemical_compound symbols.namesake chemistry Stokes shift Excited state symbols Molecule chromophores Physical and Theoretical Chemistry Cyanine 0210 nano-technology Ground state Dyes |
| Zdroj: | Physical Chemistry Chemical Physics PCCP. Physical chemistry chemical physics 22 (2020): 129–135. doi:10.1039/c9cp05473a info:cnr-pdr/source/autori:Sissa, Cristina; Painelli, Anna; Terenziani, Francesca; Trotta, Massimo; Ragni, Roberta/titolo:About the origin of the large Stokes shift in aminoalkyl substituted heptamethine cyanine dyes/doi:10.1039%2Fc9cp05473a/rivista:PCCP. Physical chemistry chemical physics (Print)/anno:2020/pagina_da:129/pagina_a:135/intervallo_pagine:129–135/volume:22 |
| ISSN: | 1463-9076 |
| DOI: | 10.1039/c9cp05473a |
| Popis: | Aminoalkyl-substituted heptamethine cyanine dyes are characterized by a large Stokes shift, an uncommon feature for cyanine molecules yet very promising for their application as fluorescent probes in bioimaging and as light harvesting antennas in biohybrid systems for solar energy conversion. The origin of this photophysical feature has not been adequately explored so far, and a combined experimental and theoretical work is herein provided to shed light on the role played by the central aminoalkyl substituent bound to the heptamethine cyanine backbone in defining the unusual properties of the dye. The spectra recorded in solvents of different polarities point to a marginal role of the medium in the definition of the Stokes shift, which conversely can be ascribed to the relaxation of the molecular geometry upon photoexcitation. This hypothesis is supported by an extensive theoretical investigation of the ground and excited states of the dye. TD-DFT results on the aminoalkyl-substituted dye and its unsubstituted precursor demonstrate a very similar cyanine-like structure for both molecules in the relaxed excited state. Conversely, in the ground state the amino substitution disrupts the conjugation in the polymethine chain, leading to a broken-symmetry, non-planar structure. |
| Databáze: | OpenAIRE |
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