With the recent development of clinical two-photon microscopes or endoscopes, new photosensitisers for two-photon photodynamic therapy are the subject of increasing interest. Herein, we review the advances within the ten last years of molecular two-photon photosensitisers.

Magnetic resonance imaging (MRI) is a powerful non-invasive diagnostic tool that can provide important insights for medical treatment monitoring and optimization. Photodynamic therapy (PDT), a minimally invasive treatment for various types of tumors, is drawing increasing interest thanks to its temporal and spatial selectivity. The combination of MRI and PDT offers real-time monitoring of treatment and can give significant information for drug-uptake and light-delivery parameters optimization. In this review we will give an overview of molecular theranostic agents that have been designed for their potential application in MRI and PDT.

The syntheses of a porphyrin bearing four peripheral rings and of the corresponding [3]rotaxane are reported. The porphyrinic tetra-macrocycle consists of four 1,10-phenanthroline-containing rings attached to the meso positions of a central zinc porphyrinvia single C–C bonds. The [3]rotaxane is composed of one central porphyrin and of two short rigid axles that contain two bidentate coordination sites and end with bulky stoppers. The rotaxane displays a novel architecture where each axle is threaded through two adjacent rings of the porphyrin. The free-base porphyrin was synthesised in 25% yield under optimised conditions. A microwave-enhanced procedure derived from the Adler–Rothemund method was developed for this condensation. The “gathering-and-threading” effect of copper(I) and subsequent stoppering by click chemistry were used to synthesise the [3]rotaxane in a two-step, one-pot reaction.