Porphyrazines have recently emerged as a useful class of tetrapyrroles suitable for photodynamic therapy of cancer (PDT) with excellent uptake and retention properties in vivo. Here we demonstrate that the photophysical properties of cyano-aryl porphyrazine pz1 are strongly viscosity dependent, i.e. the fluorescence lifetime and the quantum yield of pz1 increase as a function of solution viscosity. We have calibrated pz1 as a red-emitting fluorescent ‘molecular rotor’ in a large range of viscosities from 80 to ca. 5500 cP, in solutions of various solvent compositions and temperatures. On the other hand, pz1 works as an efficient PDT sensitiser, i.e. it induces apoptosis and necrosis in cells upon irradiation with red light through formation of singlet oxygen. We demonstrate that PDT in cells using pz1 is accompanied by a significant viscosity increase by monitoring the fluorescence lifetime of the rotor. We suggest that this increase could be used as a completely new type of diagnostic and dosimetry tool in a PDT treatment.

Tumor cells are well adapted to grow in conditions of variable oxygen supply and hypoxia by switching between different metabolic pathways. However, the regulatory effect of oxygen on metabolism and its contribution to the metabolic heterogeneity of tumors have not been fully explored. In this study, we develop a methodology for the simultaneous analysis of cellular metabolic status, using the fluorescence lifetime imaging microscopy (FLIM) of metabolic cofactor NAD(P)H, and oxygen level, using the phosphorescence lifetime imaging (PLIM) of a new polymeric Ir(III)-based sensor (PIr3) in tumors in vivo. The sensor, derived from a polynorbornene and cyclometalated iridium(III) complex, exhibits the oxygen-dependent quenching of phosphorescence with a 40% longer lifetime in degassed compared to aerated solutions. In vitro, hypoxia resulted in a correlative increase in PIr3 phosphorescence lifetime and free (glycolytic) NAD(P)H fraction in cells. In vivo, mouse tumors demonstrated a high degree of cellular-level heterogeneity of both metabolic and oxygen states, and a lower dependence of metabolism on oxygen than cells in vitro. The small tumors were hypoxic, while the advanced tumors contained areas of normoxia and hypoxia, which was consistent with the pimonidazole assay and angiographic imaging. Dual FLIM/PLIM metabolic/oxygen imaging will be valuable in preclinical investigations into the effects of hypoxia on metabolic aspects of tumor progression and treatment response.

New tetraaryltetracyanoporphyrazines have been obtained in the form of metal complexes and free bases via template assembly of a variety of aryltricyanoethylenes as structural units of the macrocycle, and photophysical properties of the products have been studied. The unique high sensitivity of the fluorescent properties to viscosity has been demonstrated. This property opens the possibility of application of the said compounds as sensors of local viscosity. The prepared macrocycles exhibit significant photocytotoxicity, and can be thus used as sensitizers of photodynamic therapy.

The preparation and properties are described of two types of novel PEG-organized nanoparticles including silica-modified uniform disk-shaped nanoparticles doped with a fluorescent ytterbium cyanoporphyrazine complex; a large enhancement of red emission for both types of nanoparticles is observed in physiological liquids owing to their binding to biomolecules.

A novel facile synthetic route to the metal-template assembly of a tetrapyrrollic framework from tetracyanoethylene (TCNE) and tricyanovinylbenzene (TCNVB) structural units through reaction of TCNE and TCNVB with metal π-sandwich complexes has been developed. The reactions occur under extremely mild conditions, the porphyrazine macrocycles being assembled in high yield from TCNE and TCNVB building-blocks by VO²⁺ or Yb³⁺-template synthesis. The redox behaviour of the novel complexes has been investigated. The vanadyl octacyanoporphyrazine complex was found to be a rare example of a highly-absorbing dye combining significant electron-acceptor properties with a band gap unusually narrow for an organic semiconductor (ca. 1.1 eV). The preparation is described of a novel highly emissive ytterbium complex with a proposed unusual structure obtained by reaction of TCNVB with bis(indenyl)ytterbium(II) in THF. The analytical, spectral and electrochemical investigations of the obtained ytterbium complex indicate it to be a binuclear adduct with Yb(TCNVB)₃ species in which a single doubly-reduced TCNVB molecule bridges two Yb³⁺ cations. The formation of a disordered polynuclear coordination polymer network including a macrocyclic structure and metal cations bridged through the nitrile nitrogen atoms is proposed. The complex is readily soluble and is compatible with a variety of polymeric matrices giving doped polymeric glasses and films which are highly luminescent in the biologically relevant optical window covering the visible and near-infrared (NIR) range (640–1000 nm). In addition, doped polymeric glasses and films highly emissive at the telecommunication wavelength (1540 nm), including a composition consisting of the novel ytterbium complex and an equimolar ratio of the novel ytterbium complex and a per se non-luminescent erbium chelate, have been obtained. The complex is found to be an extraordinarily strong sensitizer of NIR Er³⁺ emission.