Title

Fluorescent pseudorotaxanes of a quinodicarbocyanine dye with gamma cyclodextrin

School/Department

School of Science Technology and Health

Publication Date

8-2017

Abstract

Spectrophotometric titration of buffered solutions of gamma cyclodextrin (γCD) and 1,1’-diethyl,2,2’-dicarbocyanine (DDI) demonstrates extension of the known 1:2 host:guest complex to form a previously unreported 2:2 complex near the γCD solubility limit. Though DDI is predominantly hosted as a non-fluorescent H-aggregate, both complexes exist in respective equilibria with two secondary complexes hosting unaggregated DDI as 1:1 and 2:1 complexes. The 2:1 complex exhibits significant fluorescence emission, with a quantum yield six times that of DDI in organic solvents, but ten times lower than that of an analogous indodicarbocyanine. Fragment Molecular Orbital calculations suggest that the 2:1 complex has the tail-to-tail conformation, and that solvent access to the dye strongly favors photoisomerization. In the host-guest complex, γCD limits solvent access to the dye and hinders rotation of the quinolyl terminal groups, but nevertheless pairwise rotation of methine carbons within the γCD cavity likely remains as a significant nonradiative relaxation pathway for the excited state.

Keywords

Quinodicarbocyanine; Gamma cyclodextrin;Soliton; Pseudorotaxane

Publication Title

Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy

Volume

189

DOI of Published Version

10.1016/j.saa.2017.07.060

Link to Full Text

Share

COinS