Dithiafulvalene functionalized diketopyrrolopyrrole based sensitizers for efficient hydrogen production

Abstract

We have designed and synthesized two new diketopyrrolopyrrole (DPP) based organic sensitizers (DPPCA and DPPCN) with the dithiafulvalene (DTF) unit as donor and cyanoacrylic acid/malononitrile as acceptor moieties. These dyes showed excellent efficiency of photocatalytic hydrogen production over a Pt-TiO2 composite via solar-induced water splitting. The sensitizers showed broad absorptions over the wide visible regime (500-800 nm). In DPPCN, the malononitrile moiety led to strong intra-molecular charge transfer, as evidenced by red shifted (∼24 nm) absorption maxima with highly enhanced molar absorptivity (108 190 M(-1) cm(-1)). The electrochemical characterization of as-prepared sensitizers confirmed the feasible electron injection from the dye to the TiO2 conduction band (CB) which has been further validated by theoretical studies. In this study, the rate of the photocatalytic activity was found to be dependent on the acceptor part of the dye molecule as DPPCN sensitized Pt-TiO2 (DNPT) exhibited remarkable (1208 μmol) hydrogen evolution yield in comparison to DPPCA sensitized Pt-TiO2 (DAPT) (840 μmol). The rigid DPP core made the sensitizers significantly photo-stable as affirmed by their high hydrogen production efficiency over 80 h of prolonged irradiation. As predicted from density functional theory (DFT) calculations, ground state geometry of the dyes was almost planar, facilitating continuous conjugation throughout the molecule. Time-dependent DFT (TD-DFT) calculations were also carried out to make clear the understanding of charge transfer transition of the dye molecules.

Towards Sustainable H2 Production: Rational Design of Hydrophobic Triphenylamine‐based Dyes for Sensitized Ethanol Photoreforming

“…Some studies concerning the use of dyes endowed with hydrophobic substituents have already been published, and in a few cases it was actually shown that elongation of the alkyl chains had a positive influence on hydrogen generation . Nevertheless, a specific investigation on the effect that different positioning of the lipophilic side chains could have on dye properties, and therefore on photocatalytic activity, was not reported so far.…”

“…Some studies concerningt he use of dyes endowed with hydrophobic substituents have already been published, [20][21][22][23] and in af ew cases it was actually shown that elongation of the alkyl chains had ap ositive influence on hydrogen generation. [24,25] Nevertheless,as pecific investigation on the effect that different positioning of the lipophilic side chains could have on dye properties, and therefore on photocatalytic activity,w as not reported so far.I nt his work, we decided to test a series of D-p-A dyes with hydrophobic side chains in different positions of their molecular scaffold, presuming that such designc ould influence both the reduction of dyed esorption and the anti-aggregation/recombination effect, and, at the same time, still allow SED molecules dissolved in the aqueous environment to interactwitht he oxidized dye.…”

An Organic Dyad Composed of Diathiafulvalene‐Functionalized Diketopyrrolopyrrole–Fullerene for Single‐Component High‐Efficiency Organic Solar Cells

“…[8,11] In this context, we have designed and synthesized DPP-Ful by covalent linkage of dithiafulvalene (DTF)-functionalized DPP containing oligothiophene and N-methyl fulleropyrrolidine to achieve ab road spectral response,a nd it achieved the highest PCE of 2.2 %a mong reported singlecomponent organic dyads.D PP-Ful displayed red-shifted absorption in the solid state when compared to reported fullerene-based dyads owing to strong intermolecular interactions and aggregate formation. [15,16] DPP-Ful is synthesized (Scheme 1) by refluxing C 60 -fullerene, N-methyl glycene,a nd DPP-ald [17] in toluene solvent and yields ab lue solid. [15] Thei ncorporation of DTF improves donating strength and charge transporting property,w hich is crucial to obtain high PCE.…”

“…[15,17] Thep eak in the higher-energy region at 330 nm arises from the fullerene unit, and the peak at 380 nm arises from the oligothiophene-containing DPP unit. 330, 380, and 653 nm; absorption spectra of fullerene and DPP-ald were also recorded for comparison.…”

“…Thealkyl chains at 2,5 positions of DPP and 4,5 positions of dithiafulvalene increases solubility for as olution-processable device and enhanced the PCE of the solar cell devices. [15,16] DPP-Ful is synthesized (Scheme 1) by refluxing C 60 -fullerene, N-methyl glycene,a nd DPP-ald [17] in toluene solvent and yields ab lue solid. It was thoroughly characterized by NMR and MALDI-TOF-MS;s ynthetic details and spectroscopic data are given in the Supporting Information.…”