Helical donor-acceptor platinum complexes displaying dual luminescence and near-infrared circularly polarized luminescence

A series of chiral platina[5]helicenes displaying dual luminescence, i.e., fluorescence between 450 and 600 nm and red/NIR phosphorescence between 700 and 900 nm, has been synthesised, characterised and studied by first-principle calculations. This unusual behavior has been attributed to limited electronic interactions between the d orbitals of the metal and the π-orbitals of the organic ligand on the excited-state. Accordingly, the electron richness of the donor group on the helical ligand does not affect the energy of the phosphorescence process but does play a role on its efficiency. Interestingly, near-infrared circularly polarized luminescence can be obtained for the three complexes with dissymmetry factors up to 3 × 10^-3 at 750 nm.

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

Chirality has become an important research subject. The research areas associated with chirality are under substantial development. Meanwhile, graphene is a rapidly growing star material and has hard-wired into diverse disciplines. Rational combination of graphene and chirality undoubtedly creates unprecedented functional materials and may also lead to great findings. This hypothesis has been clearly justified by the sizable number of studies. Unfortunately, there has not been any previous review paper summarizing the scattered studies and advancements on this topic so far. This overview paper attempts to review the progress made in chiral materials developed from graphene and their derivatives, with the hope of providing a systemic knowledge about the construction of chiral graphenes and chiral applications thereof. Recently emerging directions, existing challenges, and future perspectives are also presented. It is hoped this paper will arouse more interest and promote further faster progress in these significant research areas.

Steric and Electronic Control of Chiral Eu(III) Complexes for Effective Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) is characterized by the differential emission of right and left circularly polarized light by a chiral molecule. This mini-review describes the recent developments in chiral trivalent europium (Eu(III)) complexes with effective CPL. CPL has many potential applications in security tags, lasers, and three-dimensional organic electroluminescence devices, which is one of the most intensely investigated topics in molecular luminophores. Eu(III) complexes have attracted considerable attention as effective CPL luminophores for the above-mentioned applications. In this review, recent studies on the Eu(III) CPL, including the steric (dimer, tetramer, aggregates, and coordination polymers) and electronic control (mononuclear) of Eu(III) complexes for the construction of a luminophore with effective CPL, are discussed. The characteristic CPL applications employing the chiral mononuclear Eu(III) complexes are also described. Chiral Eu(III) complexes with well-designed organic ligands can result in the establishment of new research areas in the fields of photochemistry and materials science.

Solution structure and structural rearrangement in chiral dimeric ytterbium(iii) complexes determined by paramagnetic NMR and NIR-CD

Chiral lanthanide complexes are attracting interest in enantioselective catalysis and due to their unique optical and magnetic properties. Here, we investigate the chiral ytterbium complex [Yb((S)-THP)] ((S)-THP = ((1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane), which has found applications in catalysis and as a CEST agent in MRI, by means of near-IR circular dichroism (NIR CD), NMR, and mass spectrometry, in different solvents. The NMR analysis revealed that this complex, different from the analogues including early lanthanides, is not axially coordinated by the solvent. In non-protic solvents, and in the presence of bases, [Yb((S)-THP)]3+ dimerizes to [Yb((S)-H2THP)]22+. The careful analysis of the paramagnetic contributions in the NMR spectra allowed us to determine the structure of the dimeric species in solution, revealing a structural rearrangement of the coordination cage following the dimerization process.

Understanding the Molecular Structure of the Sialic Acid-Phenylboronic Acid Complex by using a Combined NMR Spectroscopy and DFT Study: Toward Sialic Acid Detection at Cell Membranes

The origin of the unusually high stability of the sialic acid (SA) and phenylboronic acid (PBA) complex was investigated by a combined nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) study. SA is a glycan-terminating monosaccharide, and its importance as a clinical target has long been recognized. Inspired by the fact that the binding properties of SA-PBA complexation are anomalously high relative to those of typical monosaccharides, great effort has been made to build a clinical platform with the use of PBA as a SA-selective receptor. Although a number of applications have been reported in recent years, the ability of PBA to recognize SA-terminating surface glycans selectively is still unclear, because high-affinity SA-PBA complexation might not occur in a physiological environment. In particular, different forms of SA (α- and β-pyranose) were not considered in detail. To answer this question, the combined NMR spectroscopy/DFT study revealed that the advantageous binding properties of the SA-PBA complex arise from ester bonding involving the α-carboxylate moieties (C1 and C2) of β-SA but not α-SA. Moreover, the facts that the C2 atom is blocked by a glycoside bond in a physiological environment and that α-SA basically exists on membrane-bound glycans in a physiological environment lead to the conclusion that PBA cannot selectively recognize the SA unit to discriminate specific types of cells. Our results have a significant impact on the field of SA-based cell recognition.

Monitoring of the ADP/ATP Ratio by Induced Circularly Polarised Europium Luminescence

A series of three europium complexes bearing picolyl amine moieties was found to possess differing binding affinities towards Zn²⁺ and three nucleotides: AMP, ADP, and ATP. A large increase in the total emission intensity was observed upon binding Zn²⁺ , followed by signal amplification upon the addition of nucleotides. The resulting adducts possessed strong induced circularly polarised emission, with ADP and ATP signals of opposite sign. Model DFT geometries of the adducts suggest the Δ diastereoisomer is preferred for ATP and the Λ isomer for ADP/AMP. This change in sign allows the ADP/ATP (or AMP/ATP) ratio to be assessed by monitoring changes in the emission dissymmetry factor, g_em .

A chiral lactate reporter based on total and circularly polarized Tb(iii) luminescence

Lactate anion signaling by a chiral Tb(iii) complex based on total and circularly polarized luminescence.

Specific circularly polarized luminescence of Eu(iii), Sm(iii), and Er(iii) induced by N-acetylneuraminic acid

Sialic acid chelated with the Eu, Sm and Er ions provides distinct circularly polarized luminescence (CPL) patterns that can be used for its detection. The CPL spectra were measured using the Raman optical activity (ROA) technique.

Selective signalling of glyphosate in water using europium luminescence

Selective sensing of glyphosate in the micromolar regime in water.