Synthesis and Photoelectrochemical Performance of Chalcogenopyrylium Monomethine Dyes Bearing Phosphonate/Phosphonic Acid Substituents

Abstract

Chalcogenopyrylium monomethine dyes were prepared via condensation of a 4-methylchalcogenopyrylium compound with a chalcogenopyran-4-one bearing a 4-(diethoxyphosphoryl)phenyl substituent (or the phosphonic acid derivative). The dyes have absorbance maxima of 603-697 nm in the window where the solar spectrum is most intense. The dyes formed H-aggregates on TiO2, increasing the light-harvesting efficiency of the dyes. Shortcircuit photocurrent action spectra were acquired to evaluate the influence of dye structure on the photoelectrochemical performance.

Panchromatic Donor–Acceptor–Donor Conjugated Oligomers for Dye-Sensitized Solar Cell Applications

“…Importantly, our molecular design diverges from the commonly employed D-π-A structure since we are not using strongly electron-withdrawing groups such as cyanoacrylic acid at the binding end of the molecule. Although the carboxylic acid functionality is most commonly employed as anchoring group in DSSCs, the use of phosphonic acid has also been studied as an alternative, first reported for efficient DSSCs by Péchy and coworkers for a Ru-based system, followed by several other examples of metal-based molecules − and D-π-A molecules. − Compared to carboxylic acids, phosphonic acids have been reported to enhance the strength and chemical stability of dye adsorption onto TiO 2 surfaces. − Specifically, we have designed and synthesized three thiophene-based discrete-length oligomers unsymmetrically functionalized with one phosphonic acid group. The conjugated systems were varied from an all-thiophene seximer (T6-A) to D-A-D structures incorporating benzothiadiazole (BTD) and 6,6′-isoindigo (iI) as electron-deficient (acceptor) cores flanked with two bithiophene (donor) units (T4BTD-A and T4iI-A, respectively).…”

Excited State Torsional Processes in Chalcogenopyrylium Monomethine Dyes

“…After the structure of the dyes was optimized, time-dependent density functional theory (TD-DFT) was employed at the same level. From the TD-DFT results, transition energies and oscillator strengths were determined and can be compared to the previously determined experimental values …”

“…From the TD-DFT results, transition energies and oscillator strengths were determined and can be compared to the previously determined experimental values. 1 RR spectra were calculated in the independent mode displaced harmonic oscillator (IMDHO) model using the orca_asa package. 25,26 At the same level of theory as described above, the potential energy gradient was calculated in the Franck−Condon (FC) region of S 1 .…”

“…Chalcogenopyrylium monomethine (CGPM) dyes (Figure ) have been utilized in a broad range of applications including dye-sensitized solar cells (DSSCs), photodynamic therapy, − (PDT) and photoassisted chemotherapy (PACT), and recently as a biocompatible surface enhanced resonance Raman scattering (SERRS) nanoprobe . CGPM dyes have very small fluorescence and singlet-oxygen quantum yields in solution (Φ F < 0.001, Φ­( 1 O 2 ) < 0.01) but, upon binding to DNA, exhibit an increase in both quantities (Φ F < 0.12, Φ­( 1 O 2 ) < 0.35) .…”

“…Dyes were synthesized according to an existing literature procedure. 1 For transient absorption experiments, each of the CGPM dye samples was prepared in 100% methanol (MeOH), 33% (v/v) glycerol, 66% glycerol, and 100% glycerol. Each of the samples was vigorously stirred to break up any aggregates.…”