title: Effective Tuning of Ketocyanine Derivatives through Acceptor Substitution.
abstract: A series of ketocyanine derivatives possessing bis(diarylamino)fluorenyl donors and variable acceptors installed at the bridging carbon atom were synthesized to investigate how the electronic structure of the dye can be systemically tuned through stabilization of the cyanine-like character of the donor by increasing the acceptor strength. Analysis of the (1) H NMR spectra indicates that the "charge-separated" species dominates in these dyes, given that carbons possessing a positive or negative charge in the resonance structures of this state purposefully shift downfield or upfield, respectively, depending on the strength of the acceptor moiety. In DAA-Fl-PI, the acceptor strength and the gain of acceptor aromaticity indicates a predisposition of the separated state, indicated by asymmetry in the (1) H NMR spectrum, as well as uneven distribution of the HOMO on the fluorenyl donor.
authors.affiliation: Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant St., Amherst, MA 01003 (USA).
authors.forename: Ambata
authors.initials: A
authors.lastname: Poe
authors.forename: Andrea
authors.initials: A
authors.lastname: Della Pelle
authors.forename: Sean
authors.initials: S
authors.lastname: Byrnes
authors.forename: S
authors.initials: S
authors.lastname: Thayumanavan
keywords: cyanine dyes; donor-acceptor systems; optical properties; structure-activity relationships