Novel Dicyanomethylenedihydrofuran (DCDHF) Fluorophores Synthesis

by Liu, Na

This dissertation includes four different subjects: 1) Benzofuran synthesis via ?-acylcarbonium ion; 2) Synthesis of partially fluorinated aromatic compounds as organic semiconducting material; 3) Synthesis of polyimide/polyamic acids and their monomers for a study of double layered alignment film (DLAF); 4) Novel DCDHF fluorophores synthesis for single-molecule imaging application. Amongst these four topics, the last one is the main research subject. One pot benzofuran synthesis from the reaction between p,p'-dialkoxy or p,p'-diaryl and even tetra-alkoxy benzoins substituted benzoins with substituted phenols or naphthols in the presence of SOCl2 or PPh3/CCl4 has been examined in a variety of solvents to study the scope of this synthesis method. The original interest to find mesogenic properties on these newly synthesized benzofurans was not found yet, while one or more crystal-to-crystal transitions existed in some of these compounds. The partially fluorinated polynuclear compounds: 1,2,3,4-tetrafluorobenzo[e]pyrene and 1,2,3,4-tetrafluorodibenzo[fg,op]naphthacene were synthesized. Both of their crystal structures display a compact cofacial packing style, which is important for organic semiconducting material to achieve high charge mobility. This study shows the dramatic crystal packing influence of perfluorination of just one of the multiple rings of benzo[e]pyrene since the former compound crystallizes in a herringbone configuration. A novel DLAF to obtain greater control of the alignment characteristics of the liquid crystal director has been studied. The DLAF consists of a thin fluorinated polymer layer on the top of a rubbed non-fluorinated, non-branched polyimide layer. Both polyimide/polyamic acids and their monomers with variable pendant perfluorinated chains to support the DLAF study were synthesized using different chemistry methods. In order to overcome autofluorescence of typical biological systems, DCDHF fluorophores with bathochromic absorption and emission were synthesized by using bisaromatic or trisaromatic units (combination of phenyl or/and thiophene rings) as the conjugation link. DCDHF dimers using a 1,4-cyclohexane as spacer with two rigidly connected DCDHF chromophores with different conjugation cores were synthesized using different synthetic method to study the influence of orientation and spacing of fluorophores on their photophysical property changes. This is a valuable method to detect the change of environment inside of the cells. A new series of fluorogenic DCDHF molecules have also been successfully synthesized. Their fluorescence can be turned on or changed after specific photoactivation or thermoactivation reactions.