Congested Cyclometalated Platinum(II) Ditopic Frameworks and Their Phosphorescent Responses to S-Containing Amino Acids

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

Synthetic molecular probes, chemosensors, and nanosensors used in combination with innovative assay protocols hold great potential for the development of robust, low-cost, and fast-responding sensors that are applicable in biofluids (urine, blood, and saliva). Particularly, the development of sensors for metabolites, neurotransmitters, drugs, and inorganic ions is highly desirable due to a lack of suitable biosensors. In addition, the monitoring and analysis of metabolic and signaling networks in cells and organisms by optical probes and chemosensors is becoming increasingly important in molecular biology and medicine. Thus, new perspectives for personalized diagnostics, theranostics, and biochemical/medical research will be unlocked when standing limitations of artificial binders and receptors are overcome. In this review, we survey synthetic sensing systems that have promising (future) application potential for the detection of small molecules, cations, and anions in aqueous media and biofluids. Special attention was given to sensing systems that provide a readily measurable optical signal through dynamic covalent chemistry, supramolecular host-guest interactions, or nanoparticles featuring plasmonic effects. This review shall also enable the reader to evaluate the current performance of molecular probes, chemosensors, and nanosensors in terms of sensitivity and selectivity with respect to practical requirement, and thereby inspiring new ideas for the development of further advanced systems.

Saccharide-Functionalized Poly(Zn-salphen)-alt-(m- and p-phenyleneethynylene)s as Dynamic Helical Metallopolymers

The study of metallopolymers with controllable helical sense remains in its infancy. We report arabinose-functionalized (Zn-salphen)-based conjugated polymers that display mirror-image circular dichroism spectra for L- and D-sugar sidechains respectively, signifying ordered (helical) coiling of the polymer backbone with opposite screw-sense preferences. The observation of different spectroscopic behavior and Cotton effects for a variety of solvents (in a reversible manner) and temperatures, ascribed to changes in the extent of intrachain (Zn⋅⋅⋅O(salphen) and π-stacking) interactions between Zn-salphen moieties, thus indicate the flexible, responsive and dynamic nature of the folded helical conformation in these systems. An application study signifying that activity can be governed by the structure and helical sense of the polymer is described.

A family of readily synthesised phosphorescent platinum(ii) complexes based on tridentate N^N^O-coordinating Schiff-base ligands

Tridentate ligands, easily synthesised by condensation reactions of simple starting materials, can be used to prepare Pt(ii) complexes that are luminescent in solution, emitting in the red or deep-red spectral region, according to the substituents.

Controlling the emission in flexibly-linked (N^C^N)platinum dyads

Comparative luminescence studies of the mononuclear complex Pt-1 and the differently linked dinuclear complexes Pt-2 and Pt-3 reveal distinctive luminescent properties. The emission of Pt-2 can be readily modulated over a wide range of the visible part of the spectrum.

Pincer-Type Platinum(II) Complexes Containing N-Heterocyclic Carbene (NHC) Ligand: Structures, Photophysical and Anion-Binding Properties, and Anticancer Activities

Two classes of pincer-type Pt(II) complexes containing tridentate N-donor ligands (1-8) or C-deprotonated N^C^N ligands derived from 1,3-di(2-pyridyl)benzene (10-13) and auxiliary N-heterocyclic carbene (NHC) ligand were synthesized. [Pt(trpy)(NHC)](2+) complexes 1-5 display green phosphorescence in CH2 Cl2 (Φ: 1.1-5.3 %; τ: 0.3-1.0 μs) at room temperature. Moderate-to-intense emissions are observed for 1-7 in glassy solutions at 77 K and for 1-6 in the solid state. The [Pt(N^C^N)(NHC)](+) complexes 10-13 display strong green phosphorescence with quantum yields up to 65 % in CHCl3 . The reactions of 1 with a wide variety of anions were examined in various solvents. The tridentate N-donor ligand of 1 undergoes displacement reaction with CN(-) in protic solvents. Similar displacement of the N^C^N ligand by CN(-) has been observed for 10, leading to a luminescence "switch-off" response. The water-soluble 7 containing anthracenyl-functionalized NHC ligand acts as a light "switch-on" sensor for the detection of CN(-) ion with high selectivity. The in vitro cytotoxicity of the Pt(II) complexes towards HeLa cells has been evaluated. Complex 12 showed high cytotoxicity with IC50 value of 0.46 μM, whereas 1-4 and 6-8 are less cytotoxic. The cellular localization of the strongly luminescent complex 12 traced by using emission microscopy revealed that it mainly localizes in the cytoplasmic structures rather than in the nucleus. This complex can induce mitochondria dysfunction and subsequent cell death.

Luminescent oligo(ethylene glycol)-functionalized cyclometalated platinum(II) complexes: cellular characterization and mitochondria-specific localization

A readily tunable series of non-planar oligo(ethylene glycol)-substituted phosphorescent Pt(II) complexes has been investigated as live cell imaging agents; suitable structural modifications can give good cellular uptake, traceable mitochondria-specific localization and potent cytotoxic characteristics towards HeLa cells.