Synthesis And Study Of Functional D-π-A Molecules With Thienylenevinylene

A series of D-Ï€-A molecules, containing pyrrolidine group as electron donor and cyano acetic acid, formacyl, diethyl cyanomethyl phosphonate groups as electron acceptor covalently attached to thienylenevinylene Ï€-conjugated bridges, are synthesized and their photophysical and electrochemical properties are studied. Pyrrolidine group is induced according to the literature based on 2-bromothiophene and p-bromobenzoaldehyde. Then by Horner-Emmons-Witting condition, Vilsmeier reaction and Knoevenagel condensation, ten target compounds are obtained which have been characterized by ¹H-NMR and MS, Some by the element analysis.PPTCA and PTTCA are used in dye sensitized nanocrystalline solar cell. A solar energy-to-electricity conversion efficiency of 1.54% is obtained based on PPTCA under simulated AM 1.5 irradiation with a short-circuit photocurrent density (J_sc) of 4.72 mA cm^-2, an open-circuit voltage (V_oc) of 0.51 V and a fill factor (FF) of 0.64, which is close to 50% of N3 measured in the same condition. While for PTTCA, it is unstable and easy to decompose when used for DSSCs, which lead to low conversion efficiency.By comparing the influence of the solvent polarity, in the fluorescence experiment, for PTCP and PPCP, the bathochromic shifts are attributed to the locally excited process. While with the extension of the Ï€-conjugated bridges, the intramolecular charge transfer happenes and the fluorescence is attributed to the ICT state. This point could be confirmed by the calculation of the dipole moments later. In addition the ICT does not occur immediately when the compound is excitated but undergoes a process from the FC state to the equilibrium state.In the electrochemical experiment, with the extension of the Ï€-conjugated bridges, the donor is easy to be oxidized and the acceptor is easy to be reduced. With the external voltage, electrogenerated chemiluminescence can be observed for PTCP, PTTC, PPCP and PPTC. After the discussion of the mechanism of ECL, the processes of PTCP and PPCP are accord with the T-route and PTTC, PPTC are seem to go through the S-route. While for PTTCP and PPTCP, this phenomena is unconspicuous.