Design, synthesis and evaluation of enzyme-responsive fluorogenic probes based on pyridine-flanked diketopyrrolopyrrole dyes

The ever-growing demand for fluorogenic dyes usable in the rapid construction of analyte-responsive fluorescent probes, has recently contributed to a revival of interest in the chemistry of diketopyrrolopyrrole (DPP) pigments. In this context, we have explored the potential of symmetrical and unsymmetrical DPP derivatives bearing two or one 4-pyridyl substituents acting as optically tunable group(s). The unique fluorogenic behavior of these molecules, closely linked to N-substitution/charge state of their pyridine unit (i.e., neutral pyridine or cationic pyridinium), has been used to design DPP-based fluorescent probes for detection of hypoxia-related redox enzymes and penicillin G acylase (PGA). In this paper, we describe synthesis, spectral characterization and bioanalytical validations of these probes. Dramatic differences in terms of aqueous stability and enzymatic fluorescence activation were observed. This systematic study enables to delineate the scope of application of pyridine-flanked DPP fluorophores in the field of enzyme biosensing.

Phenothiazin-N-yl-capped 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole exhibiting strong two-photon absorption and aggregation-enhanced one- and two-photon excitation red fluorescence

A phenothiazin-capped simple DPP dye exhibits a large two-photon absorption cross section and aggregation-enhanced one- and two-photon excitation red fluorescence.

Design of Diketopyrrolopyrrole (DPP)-Based Small Molecules for Organic-Solar-Cell Applications

After the first report in 2008, diketopyrrolopyrrole (DPP)-based small-molecule photovoltaic materials have been intensively explored. The power conversion efficiencies (PCEs) for the DPP-based small-molecule donors have been improved up to 8%. Furthermore, through judicious structure modification, DPP-based small molecules can also be converted into electron-acceptor materials, and, recently, some exciting progress has been achieved. The development of DPP-based photovoltaic small molecules is summarized here, and the photovoltaic performance is discussed in relation to structural modifications, such as the variations of donor-acceptor building blocks, alkyl substitutions, and the type of conjugated bridges, as well as end-capped groups. It is expected that the discussion will provide a guideline in the exploration of novel and promising DPP-containing photovoltaic small molecules.

Triplet state formation in homo- and heterometallic diketopyrrolopyrrole chromophores

The synthesis, structural characterization, and excited-state dynamics of series of diketopyrrolopyrrole (DPP) bridged homodinuclear Ir(III) and heterodinuclear Ir(III)/Pt(II) complexes is described. Steady-state and time-resolved photoluminescence along with transient absorption measurements were used to probe the nature of the emissive and long-lived excited states. Upon excitation into the (1)DPP ligand-localized excited state in the presence of coordinated Ir(III) or Pt(II) metal centers, the intersystem crossing is enhanced, leading to a quenching of the (1)DPP fluorescence and the formation of the long-lived (τ ≈ 30-40 μs) (3)DPP excited state in all instances.