Tailoring Photoisomerization Pathways in Donor-Acceptor Stenhouse Adducts: The Role of the Hydroxy Group

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989592%3A15310%2F18%3A73591232" target="_blank" >RIV/61989592:15310/18:73591232 - isvavai.cz</a>

Result on the web

<a href="https://pubs.acs.org/doi/10.1021/acs.jpca.7b10255" target="_blank" >https://pubs.acs.org/doi/10.1021/acs.jpca.7b10255</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1021/acs.jpca.7b10255" target="_blank" >10.1021/acs.jpca.7b10255</a>

Result language

angličtina

Original language name

Tailoring Photoisomerization Pathways in Donor-Acceptor Stenhouse Adducts: The Role of the Hydroxy Group

Original language description

Donor-acceptor Stenhouse adducts (DASAs) arc a rapidly emerging class of visible light-activatable negative photochromes. They are closely related to (mero)cyanine dyes with the sole difference being a hydroxy group in the polyene chain. The presence or absence of the hydroxy group has far-reaching consequences for the photochemistry of the compound: cyanine dyes are widely used as fluorescent probes, whereas DASAs hold great promise for visible light-triggered photoswitching. Here we analyze the photophysical properties of a DASA lacking the hydroxy group. Ultrafast time-resolved pump-probe spectroscopy in both the visible and IR region show the occurrence of E-Z photoisomerization on a 20 ps time scale, similar to the photochemical behavior of DASAs, but on a slower time scale. In contrast to the parent DASA compounds, where the initial photoisomerization is constrained to a single position (next to the hydroxy group), H-1 NMR in situ-irradiation studies at 213 K reveal that for nonhydroxy DASAs E-Z photoisomerization can take place at two different bonds, yielding two distinct isomers. These observations arc supported by TD-DFT calculations, showing that in the excited state the hydroxy group (pre)selects the neighboring C2-C3 bond for isomerization. The TD-DFT analysis also explains the larger solvatochromic shift observed for the parent DASAs as compared to the nonhydroxy analogue, in terms of the dipole moment changes evoked upon excitation. Furthermore, computations provide helpful insights into the photoswitching energetics, indicating that without the hydroxy group the 4 pi-electrogclization step is energetically forbidden. Our results establish the central role of the hydroxy group for DASA photoswitching and suggest that its introduction allows for tailoring photoisomerization pathways, presumably both through (steric) fixation via a hydrogen bond with the adjacent carbonyl group of the acceptor moiety, as well as through electronic effects on the polyene backbone. These insights are essential for the rational design of novel, improved DASA photoswitches and for a better understanding of the properties of both DASAs and cyanine dyes.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10403 - Physical chemistry

Project

<a href="/en/project/LO1305" target="_blank" >LO1305: Development of the center of advanced technologies and materials</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

JOURNAL OF PHYSICAL CHEMISTRY A

ISSN

1089-5639

e-ISSN

—

Volume of the periodical

122

Issue of the periodical within the volume

4

Country of publishing house

US - UNITED STATES

Number of pages

10

Pages from-to

955-964

UT code for WoS article

000424316400012

EID of the result in the Scopus database

2-s2.0-85041435667