Molecular Motion and Performance Enhancement of BORAZAN Fluorescent Dyes

Authors

Tyler James Morin, Marquette UniversityFollow
Sergey Lindeman, Marquette UniversityFollow
James R. Gardinier, Marquette UniversityFollow

Document Type

Article

Language

eng

Publication Date

1-2009

Publisher

Wiley

Source Publication

European Journal of Inorganic Chemistry

Source ISSN

1434-1948

Abstract

The preparation of three 2,6-dipyrazolyl-4-X-anilines, H(pz₂An^X) (X = p-CF₃, Cl, tBu) using CuI-catalyzed amination is described. Subsequent reactions of H(pz₂An^X) with triphenylboron proceeds with benzene elimination to give the corresponding Ph₂B(pz₂An^X) compounds in high yields. The Ph₂B(pz₂An^X) are more highly emissive in the solid state than the previously reported BORAZAN fluorophores, Ph₂B(pzAn^X), their monopyrazolyl counterparts. As with the Ph₂B(pzAn^X), the color of emission in Ph₂B(pz₂An^X) can be tuned simply by varying the para-aniline substituent where the emission of Ph₂B(pz₂An^X) is red-shifted relative to the corresponding Ph₂B(pzAn^X) derivatives. The electronic properties were studied by cyclic voltammetry and electronic absorption/emission spectroscopy as well as by density functional calculations (B3LYP/6-31G*). The di-pyrazolyl derivatives exhibit greater stability toward solvolysis and higher photoluminescent quantum yields (despite the red-shift in emission) compared to their monopyrazolyl counterparts presumably due to kinetic stabilization of the chromophore imparted by the second pyrazolyl ligand. For Ph₂B(pz₂An^X), evidence for intramolecular motion of the diphenylboryl moiety traversing both pyrazolyl groups was detected by variable temperature ¹H NMR spectroscopy. The rate increases with increasing electron-donor abilities of the para-aniline substituent.

Comments

Accepted version. European Journal of Inorganic Chemistry, Vol. 2009, No. 1, (January 2009): 104-110. DOI. © Wiley-VCH Verlag. Used with permission.

Recommended Citation

Morin, Tyler James; Lindeman, Sergey; and Gardinier, James R., "Molecular Motion and Performance Enhancement of BORAZAN Fluorescent Dyes" (2009). Chemistry Faculty Research and Publications. 579.
https://epublications.marquette.edu/chem_fac/579