CCVJ is not a simple rotor probe

Christopher Rumble, Kacie Rich, Gang He, Mark Maroncelli

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

The photochemistry of the rotor probe 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ) was studied to elucidate a curious effect of fluid flow previously reported. The apparent sensitivity to fluid motion observed in CCVJ but not in the closely related molecule 9-(dicyanovinyl)julolidine (DCVJ) is found to be an indirect effect of a photoisomerization reaction. The results presented here demonstrate that it is this isomerization, rather than the commonly assumed TICT process, that confers viscosity-sensing ability on these fluorophores. In micromolar solutions in hydroxylic solvents CCVJ exists primarily in the carboxylate form. Only the E isomer of this anion is initially present in solutions prepared from the solid, but in room light such solutions rapidly achieve a photostationary state in which the E isomer and an essentially nonfluorescent Z isomer exist in comparable concentrations. The Z isomer is metastable in S0 such that in the absence of light the solution reverts slowly to pure E. Unlike DCVJ where only a single isomer is possible, the production of long-lived photoproducts in CCVJ and other asymmetrically substituted styryenyl probes complicates their fluorescence response. Considerable care is needed when such fluorphores are used as steady-state sensors of environmental fluidity are used.

Original languageEnglish (US)
Pages (from-to)10786-10792
Number of pages7
JournalJournal of Physical Chemistry A
Volume116
Issue number44
DOIs
StatePublished - Nov 8 2012

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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