Unusual magnetic field responsive circularly polarized luminescence probes with highly emissive chiral europium(III) complexes

Chirality is ubiquitous within biological systems where many of the roles and functions are still undetermined. Given this, there is a clear need to design and develop sensitive chiral optical probes that can function within a biological setting. Here we report the design and synthesis of magnetically responsive Circularly Polarized Luminescence (CPL) complexes displaying exceptional photophysical properties (quantum yield up to 31 % and |glum| up to 0.240) by introducing chiral substituents onto the macrocyclic scaffolds. Magnetic CPL responses are observed in these chiral EuIII complexes, promoting an exciting development to the field of magneto-optics. The |glum| of the 5D0 → 7F1 transition increases by 20 % from 0.222 (0 T) to 0.266 (1.4 T) displaying a linear relationship between the Δglum and the magnetic field strength. These EuIII complexes with magnetic CPL responses, provides potential development to be used in CPL imaging applications due to improved sensitivity and resolution

Chiral DOTA chelators as an improved platform for biomedical imaging and therapy applications

Despite established clinical utilisation, there is an increasing need for safer, more inert gadolinium-based contrast agents, and for chelators that react rapidly with radiometals. Here we report the syntheses of a series of chiral DOTA chelators and their corresponding metal complexes and reveal properties that transcend the parent DOTA compound. We incorporated symmetrical chiral substituents around the tetraaza ring, imparting enhanced rigidity to the DOTA cavity, enabling control over the range of stereoisomers of the lanthanide complexes. The Gd chiral DOTA complexes are shown to be orders of magnitude more inert to Gd release than [GdDOTA]−. These compounds also exhibit very-fast water exchange rates in an optimal range for high field imaging. Radiolabeling studies with (Cu-64/Lu-177) also demonstrate faster labelling properties. These chiral DOTA chelators are alternative general platforms for the development of stable, high relaxivity contrast agents, and for radiometal complexes used for imaging and/or therapy

Triboluminescence of Centrosymmetric Lanthanide β-Diketonate Complexes with Aggregation-Induced Emission

Triboluminescence (TL) is a form of light emission induced upon mechanical forces on the material. However, our understanding of this phenomenon is still unclear and more examples are therefore needed in order to elucidate its mechanism. In this work, two types of TL complexes, [Eu(pp-dbm-Cl2)3phen] and [Eu(mm-dbm-Cl2)3phen], which also displays aggregation-induced emission (AIE) were synthesized and investigated for its photo-physical and crystal structural properties. These complexes were crystallized in a centro-symmetric space group P21/n, and remarkably, displayed TL upon grinding that may be due to the presence of extensive π···π, C-H···π and C-H···Cl-C interactions in the close molecular packing of its structure. This rare example deviates from the widely accepted mechanism of TL, hence widening the scope of our understanding in the area

N,N′-(Ethane-1,2-diyl)bis(methanesulfonamide)

The molecular structure of the title compound, C4H12N2O4S2, has crystallographic inversion symmetry. The central N—C—C—N moiety was refined as disordered over two sets of sites with an approximate occupancy ratio of 3:1 [0.742 (15):0.258 (15). In the crystal, N—H...O hydrogen bonds link adjacent molecules into a thick sheet structure parallel to the b-axis direction

Assembly of Lanthanide(III) Cubanes and Dimers with Single-Molecule Magnetism and Photoluminescence

Discrete lanthanide­(III) tetranuclear cubane-like clusters seldom occur throughout the Ln^III series and behave as single-molecule magnets (SMMs). Herein, a series of cubanes, [Ln₄(μ₃-OH)₄(μ-tfa)₄(hfa)₄(phen)₄] (<b>1</b>–<b>9</b>, Ln = La–Dy (except <i>Pm</i>), tfa = trifluoroacetate, hfa = hexafluoroacetylacetonate, phen = 1,10-phenanthroline), and dinuclear clusters, [Ln₂(μ-OH)₂­(hfa)₄(phen)₂] (<b>10</b>–<b>16</b>, Ln = Tb–Lu), were synthesized and characterized. Two types of clusters were formed due to the change of preferred coordination geometry for lighter and heavier Ln^III ions which favor nine-coordinated cubanes and eight-coordinated dimers, respectively. A magnetic study shows that <b>8</b>-Tb₄ and <b>9</b>-Dy₄ are ferromagnetically coupled and SMM in nature because of the larger Ln···Ln distance compared to other discrete cubanes. The anisotropic barriers, <i>U</i>_eff, of <b>9</b>-Dy₄ are determined to be 67.0 K. In addition, the photophysical properties of <b>6</b>-Eu₄, <b>8</b>-Tb₄, and <b>10</b>-Tb₂ owing to tfa, hfa, and phen sensitization and O–H quenching are discussed

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

New chiral atropisomeric biphenyl diols 3, 4 and 6 containing additional peripheral chiral centers with different steric bulkiness and/or electronic properties were synthesized. The X-ray crystal structure of 3 shows the formation of a supramolecular structure whereas that of 6, containing additional CF3 substituents, shows the formation of a monomeric structure. Diols 1–6 were found to be active organocatalysts in oxo-Diels–Alder reactions in which 2 recorded a 72% ee with trimethylacetaldehyde as a substrate

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

New chiral atropisomeric biphenyl diols 3, 4 and 6 containing additional peripheral chiral centers with different steric bulkiness and/or electronic properties were synthesized. The X-ray crystal structure of 3 shows the formation of a supramolecular structure whereas that of 6, containing additional CF3 substituents, shows the formation of a monomeric structure. Diols 1–6 were found to be active organocatalysts in oxo-Diels–Alder reactions in which 2 recorded a 72% ee with trimethylacetaldehyde as a substrate

Synthesis of a Conformationally Stable Atropisomeric Pair of Biphenyl Scaffold Containing Additional Stereogenic Centers

The synthesis of a new CF3-containing stereogenic atropisomeric pair of ortho-disubstituted biphenyl scaffold is presented. The atropisomers are surprisingly conformationally stable for isolation. X-ray structures show that their stability comes from an intramolecular hydrogen bond formation from their two hydroxyl groups and renders the spatial arrangement of their peripheral CF3 and CH3 groups very different. The synthesized stereogenic scaffold proved to be effective in catalyzing the asymmetric N-nitroso aldol reaction of enamine and nitrosobenzene. Compared to similar scaffolds without CF3 groups, one of our atropisomer exhibits an increase in enantioselectivity in this reaction

Unusual Magnetic Field Responsive Circularly Polarized Luminescence Probes with Highly Emissive Chiral Eu(III) Complexes

Chirality is ubiquitous within biological systems where many of the roles and functions are still undetermined. Given this, there is a clear need to design and develop sensitive chiral optical probes that can function within a biological setting. Here we report the design and synthesis of magnetically responsive Circularly Polarized Luminescence (CPL) complexes displaying exceptional photophysical properties (quantum yield up to 31% and |g lum | up to 0.240) by introducing chiral substituents onto the macrocyclic scaffolds. Magnetic CPL responses are observed in these chiral Eu(III) complexes, promoting an exciting development to the field of magneto‐optics. The |g lum | of the 5 D 0 à 7 F 1 transition increases by 20% from 0.222 (0 T) to 0.266 (1.4 T) displaying a linear relationship between the Δg lum and the magnetic field strength. These Eu(III) complexes with magnetic CPL responses, provides potential development to be used in CPL imaging applications due to improved sensitivity and resolution

Mechanistic Investigation of Inducing Triboluminescence in Lanthanide(III) β‑Diketonate Complexes

In this work, we synthesized a series of lanthanide­(III) β-diketonate complexes to investigate the induction of triboluminescence. Triboluminescence (TL) spectra, solid-state emission spectra, and luminescence lifetimes of the complexes were obtained to prove consistent emitting species for steady-state and triboluminescence measurements. Detailed analyses of the crystal lattice packing were conducted in an attempt to correlate crystal symmetry, gas discharge, and structural arrangements with “triboexcitation”, and it is found that either noncentrosymmetric or centrosymmetic compounds can be TL-active. Furthermore, an intensely TL compound, Eu­(dbm)₄TMP, was achieved, and its light emission can be seen under daylight upon mechanical stress