Polar tagging in the synthesis of monodisperse oligo(p-phenyleneethynylene)s and an update on the synthesis of oligoPPEs.

One important access to monodisperse (functionalized) oligoPPEs is based on the orthogonality of the alkyne protecting groups triisopropylsilyl and hydroxymethyl (HOM) and on the polar tagging with the hydroxymethyl moiety for an easy chromatographic separation of the products. This paper provides an update of this synthetic route. For the deprotection of HOM protected alkynes, γ-MnO2 proved to be better than (highly) activated MnO2. The use of HOM as an alkyne protecting group is accompanied by carbometalation as a side reaction in the alkynyl-aryl coupling. The extent of carbometalation can be distinctly reduced through substitution of HOM for 1-hydroxyethyl. The strategy of polar tagging is extended by embedding ether linkages within the solubilising side chains. With building blocks such as 1,4-diiodo-2,5-bis(6-methoxyhexyl) less steps are needed to assemble oligoPPEs with functional end groups and the isolation of pure compounds becomes simple. For the preparation of 1,4-dialkyl-2,5-diiodobenzene a better procedure is presented together with the finding that 1,4-dialkyl-2,3-diiodobenzene, a constitutional isomer of 1,4-dialkyl-2,5-diiodobenzene, is one of the byproducts.

Synthesis and photovoltaic application of NIR-emitting perylene-monoimide dyes with large Stokes-shift.

An efficient Sonogashira coupling protocol is developed for tetra-alkynylation at the bay and peri-positions of the perylene-monoimide (PMI) dye in its PMI(Br)4 form. The absorption band for these PMI dyes covered from the visible to Near-infrared (NIR) region and PMI(NMe2)4 is found to exhibit a record-breaking Stokes-shifted NIR emission with good photovoltaic properties.

Linear and Kinked Oligo(phenyleneethynylene)s as Ideal Molecular Calibrants for Förster Resonance Energy Transfer.

We show that oligo(phenyleneethynylene)s (oligoPEs) are ideal spacers for calibrating dye pairs used for Förster resonance energy transfer (FRET). Ensemble FRET measurements on linear and kinked diads with such spacers show the expected distance and orientation dependence of FRET. Measured FRET efficiencies match excellently with those predicted using a harmonic segmented chain model, which was validated by end-to-end distance distributions obtained from pulsed electron paramagnetic resonance measurements on spin-labeled oligoPEs with comparable label distances.

Synthesis of highly-soluble push-pull perylenemonoimide derivatives by regioselective peri-functionalization for switchable memory applications.

A regioselective synthetic protocol is developed via tetrabromination of perylenemonoimide (PMI) which leads to a series of PMI derivatives. The push-pull characteristics of these derivatives are established by spectroscopic and theoretical investigations. Finally, the semiconducting properties of the PMI dyes are utilized for the development of a switchable memory device.

Large Stokes-shifted NIR-emission from nanospace-induced aggregation of perylenemonoimide-doped polymer nanoparticles: imaging of folate receptor expression.

The development of a water-soluble, perylenemonoimide (PMI) dye-doped polymer nanoparticle (PNP) with NIR emission for live-cell imaging is demonstrated. The large Stokes-shifted NIR emission is due to confined nanospace-induced aggregation offered by the polymer matrix. Later, folic acid functionalised PNP (PNP-FA) is successfully employed to differentiate folate receptor positive and negative cancer cells.

A facile microwave-assisted protocol for rapid synthesis of N-acetylneuraminic acid congeners.

We developed a simple, rapid and efficient microwave irradiation-assisted protocol that is 1- to 2-orders of magnitude faster than conventional techniques, providing an expedient access to the sialic acid congeners Neu5Ac1Me (1), Neu5Acß1,2Me2 (2), Neu5Ac1Me O-peracetate (3) and 4,5-oxazoline of Neu5Ac2en1Me O-peracetate (4).