Circularly Polarized Lanthanide Luminescence from Langmuir-Blodgett Films Formed from Optically Active and Amphiphilic EuIII-Based Self-Assembly Complexes

Interfacial self-assembly of a chiral pyrene exciplex into a superhelix with enhanced circularly polarized luminescence

We found that the interfacially confined self-assembly of pyrene and phenanthrene glutamides can form strong exciplexes and amorphous superhelices, which show intensity-enhanced and sign-inverted CPL activity with improved quantum yield compared to a pyrene excimer. This work unveils the predominant role of supramolecular nanostructures over molecular configurations on CPL performance.

Boost the Circularly Polarized Phosphorescence of Chiral Organometallic Platinum Complexes by Hierarchical Assembly into Fibrillar Networks

Circularly polarized luminescence (CPL)-active molecular materials have drawn increasing attention due to their promising applications for next-generation display and optoelectronic technologies. Currently, it is challenging to obtain CPL materials with both large luminescence dissymmetry factor (glum) and high quantum yield (Φ). A pair of enantiomeric N N C-type Pt(II) complexes (L/D)-1 modified with chiral Leucine methyl ester are presented herein. Though the solutions of these complexes are CPL-inactive, the spin-coated thin films of (L/D)-1 exhibit giantly-amplified circularly polarized phosphorescences with |glum| of 0.53 at 560 nm and Φair of ~50 %, as well as appealing circular dichroism (CD) signals with the maximum absorption dissymmetry factor |gabs| of 0.37-0.43 at 480 nm. This superior CPL performance benefits from the hierarchical formation of crystalline fibrillar networks upon spin coating. Comparative studies of another pair of chiral Pt(II) complexes (L/D)-2 with a symmetric N C N coordination mode suggest that the asymmetric N N C coordination of (L/D)-1 are favorable for the efficient exciton delocalization to amplify the CPL performance. Optical applications of the thin films of (L/D)-1 in CPL-contrast imaging and inducing CP light generation from achiral emitters and common light-emitting diode lamps have been successfully realized.

Ligand Chirality Transfer from Solution State to the Crystalline Self-Assemblies in Circularly Polarized Luminescence (CPL) Active Lanthanide Systems

The synthesis of a family of chiral and enantiomerically pure pyridyl-diamide (pda) ligands that upon complexation with europium [Eu(CF3SO3)3] result in chiral complexes with metal centered luminescence is reported; the sets of enantiomers giving rise to both circular dichroism (CD) and circularly polarized luminescence (CPL) signatures. The solid-state structures of these chiral metallosupramolecular systems are determined using X-ray diffraction showing that the ligand chirality is transferred from solution to the solid state. This optically favorable helical packing arrangement is confirmed by recording the CPL spectra from the crystalline assembly by using steady state and enantioselective differential chiral contrast (EDCC) CPL Laser Scanning Confocal Microscopy (CPL-LSCM) where the two enantiomers can be clearly distinguished.

Enhancing the Circularly Polarized Luminescence of Europium Coordination Polymers by Doping a Chromophore Ligand into Superhelices

Lanthanide-based molecular materials showing efficient circularly polarized luminescence (CPL) activity with a high quantum yield are attractive due to their potential applications in data storage, optical sensors, and 3D displays. Herein we present an innovative method to achieve enhanced CPL activity and a high quantum yield by doping a chromophore ligand into a coordination polymer superhelix. A series of homochiral europium(III) phosphonates with a helical morphology were prepared with the molecular formula S-, R-[Eu(cyampH)3-3n(nempH)3n]·3H2O (S/R-Eu-n, n = 0-5%). The doping of chromophore ligand S- or R-nempH2 into superhelices of S/R-Eu-0% not only turned on the CPL activity with the dissymmetry factor |glum| on the order of 10-3 but also increased the quantum yield by about 14-fold. This work may shed light on the development of efficient CPL-active lanthanide-based coordination polymers for applications.

Two-Photon Circularly Polarized Luminescence of Chiral Eu Complexes

We report the synthesis of chiral lanthanide complexes with extended π conjugation for efficient circularly polarized luminescence (CPL) via two-photon excitation (2PE). The pyridine bis-oxazoline (PyBox) core provides the chiral Ln3+ environment, while the extension of the conjugated backbone through the pyridine 4-position with a phenylacetylene unit increases the two-photon absorption cross section. This work presents an important step toward the development of chiral systems displaying enhanced nonlinear optical properties, with potential applications in imaging and sensing, as well as in photodynamic therapy due to the selective excitation of molecules within a specific focal volume.

Long aliphatic chain derivatives of trigonal lanthanide complexes

The trigonal lanthanide complexes LnL (H₃L = tris(((3-formyl-5-methylsalicylidene)amino)ethyl)amine) contain three pendant aldehyde groups and are known to react with primary amines. Reacting LnL (Ln = Yb, Lu) with 1-octadecylamine yields the novel aliphatic lanthanide complexes LnL¹⁸ (H₃L¹⁸ = tris(((3-(1-octadecylimine)-5-methylsalicylidene)amino)ethyl)amine) where the three aldehyde groups are transformed to 1-octadecylimine groups. Herein the syntheses, structural characterisation and magnetic properties of LnL¹⁸ are presented. The crystal structure of YbL¹⁸ shows that the reaction of YbL with 1-octadecylamine leads to only very subtle perturbations in the first coordination sphere of Yb(III), with the Yb(III) ion retaining its heptacoordination and similar bond lengths and angles to the ligand. The three octadecyl chains in each complex were found to direct crystal packing into lipophilic arrays of van der Waals interaction-driven hydrocarbon stacking. The static magnetic properties of YbL¹⁸ were compared to those of the non-derivatised complex YbL. The energy level splitting of the ²F_7/2 ground multiplet was found, by emission spectroscopy, to be very similar between the derivatised and non-derivatised complexes. A.c. magnetic susceptibility measurements on YbL¹⁸ and YbL diluted at 4.8% and 4.2% into the diamagnetic hosts LuL¹⁸ and LuL, respectively, revealed that the spin-lattice relaxation of both complexes is governed by a low temperature direct process and a high temperature Raman process. In the high temperature regime, the derivatised complex was also found to have faster spin-lattice relaxation, which is likely due to the increased number of phonons in the octadecyl chains.

Highlights of the development and application of luminescent lanthanide based coordination polymers, MOFs and functional nanomaterials

The development of lanthanide based coordination polymer and metal-organic framework (CPs and MOFs) nanomaterials as novel functional (e.g. luminescent and magnetic) materials has attracted significant attention in recent times. This is in part due to the wide, but yet unique coordination requirements that the f-metal ions possess, as well as their attractive physical properties, which are often transferred to the bulk material. Hence, there is no surprise, that the design, synthesis and characterisation of lanthanide based CP/MOF materials (featuring either 'pure' lanthanides, or a mixture of both f- and d-metal ions) for applications in gas and small molecule absorption, storage, conversion/catalysis, chemical sensing, bio-imaging, drug delivery, etc. has been a prominent feature in the scientific literature. In this review, we give a selected overview of some of the recent developments in the area of Ln CP/MOF based nanomaterials for sensing, optical materials and bio-medicine research, as well as making reference to some more established examples, with the view of introducing, particularly to new researchers to the field, the powerful and attractive features of lanthanide based materials.

Circularly polarized luminescence of nanoassemblies via multi-dimensional chiral architecture control

Circularly polarized luminescence (CPL) materials are currently an important class of chiroptical materials that are attracting increasing interest. Nanoassemblies constructed from chiral or achiral building blocks show great potential for achieving CPL-active nanomaterials with high quantum yields and dissymmetry factors, which is crucial for further applications. In nanoassemblies, the dimensional morphology affects the chiroptical properties significantly since the microscopic packing modes will affect the luminescence processes and chirality transfer processes. In this review, we will show some examples for illustrating the relationship between multi-dimensional morphology and chiroptical properties. Furthermore, with dimensional morphology tuning, higher dissymmetry factors would be obtained. We hope to provide a useful and powerful insight into the design and control of CPL-active nanoassemblies via morphology control.

Beyond Chiral Organic (p-Block) Chromophores for Circularly Polarized Luminescence: The Success of d-Block and f-Block Chiral Complexes

Chiral molecules are essential for the development of advanced technological applications in spintronic and photonic. The best systems should produce large circularly polarized luminescence (CPL) as estimated by their dissymmetry factor (g _lum), which can reach the maximum values of -2 ≤ g _lum ≤ 2 when either pure right- or left-handed polarized light is emitted after standard excitation. For matching this requirement, theoretical considerations indicate that optical transitions with large magnetic and weak electric transition dipole moments represent the holy grail of CPL. Because of their detrimental strong and allowed electric dipole transitions, popular chiral emissive organic molecules display generally moderate dissymmetry factors (10^-5 ≤ g _lum ≤ 10^-3). However, recent efforts in this field show that g _lum can be significantly enhanced when the chiral organic activators are part of chiral supramolecular assemblies or of liquid crystalline materials. At the other extreme, chiral Eu^III- and Sm^III-based complexes, which possess intra-shell parity-forbidden electric but allowed magnetic dipole transitions, have yielded the largest dissymmetry factor reported so far with g _lum ~ 1.38. Consequently, 4f-based metal complexes with strong CPL are currently the best candidates for potential technological applications. They however suffer from the need for highly pure samples and from considerable production costs. In this context, chiral earth-abundant and cheap d-block metal complexes benefit from a renewed interest according that their CPL signal can be optimized despite the larger covalency displayed by d-block cations compared with 4f-block analogs. This essay thus aims at providing a minimum overview of the theoretical aspects rationalizing circularly polarized luminescence and their exploitation for the design of chiral emissive metal complexes with strong CPL. Beyond the corroboration that f-f transitions are ideal candidates for generating large dissymmetry factors, a special attention is focused on the recent attempts to use chiral Cr^III-based complexes that reach values of g _lum up to 0.2. This could pave the way for replacing high-cost rare earths with cheap transition metals for CPL applications.

Dimension-Tunable Circularly Polarized Luminescent Nanoassemblies with Emerging Selective Chirality and Energy Transfer

The selective interplay between dimensional morphology transition and signal transfer is an important feature for both nanomaterials and biosystems. While most of those reported examples considered either dimensional transition or signal transfer, the integrated interplay or selectivity for these two aspects in single self-assembled system has been rarely studied. Here, we report that a positively charged chiral π-building block could self-assemble into multidimensional nanostructures, which showed tunable circularly polarized luminescence (CPL). Impressively, when these CPL-active multidimensional structures interacted with two achiral dyes (positively charged ThT and negatively charged CNA), 3D nanocubes and 0D nanospheres showed neither chirality transfer nor energy transfer, while 2D nanoplates could successfully trigger a selective chirality or energy transfer depending on the charge type of acceptor dyes, which then emitted an enhanced CPL signal. This work demonstrated rational design of charged π-building block for the construction of dimension controllable and selective signal transfer self-assembly system, which might deepen the understanding the interplay of dimensional structures and signal transfer functions in natural and nano systems.

Strong CPL of achiral liquid crystal fluorescent polymer via the regulation of AIE-active chiral dopant

Strong CPL induced by ternary polymer dispersed cholesteric liquid crystals (PD-CLCs) can deliver a new strategy for designing excellent CPL materials.

A Highly Luminescent Chiral Tetrahedral Eu4L4(L')4 Cage: Chirality Induction, Chirality Memory, and Circularly Polarized Luminescence

Chiral lanthanide cages with circularly polarized luminescence (CPL) properties have found potential application in enantioselective guest recognition and sensing. However, it still remains a big challenge to develop a simple and robust method for the diastereoselective assembly of homochiral lanthanide cages in view of the large lability of the Ln(III) ions. Herein, we report the first example of the formation of a enantiopure lanthanide tetrahedral cage via a chiral ancillary ligand induction strategy. One such cage, (Eu₄L₄)(R/S-BINAPO)₄, is assembled by four achiral C₃-symmeric tris(β-diketones) (4,4',4″-tris(4,4,4-trifluoro-1,3-dioxobutyl)triphenylamine, L) as faces, four Eu(III) ions as vertices and four chiral R-/S-bis(diphenylphosphoryl)-1,1'-binaphthyl (R/S-BINAPO) as ancillary ligands. X-ray crystallography and NMR and CD spectra confirm the formation of a pair of enantiopure chiral topological tetrahedral cages, (Eu₄L₄)(R-BINAPO)₄ and (Eu₄L₄)(S-BINAPO)₄ (ΔΔΔΔ-1 and ΛΛΛΛ-1). As expected, the tetrahedral cages present strong CPL with |g_lum| values up to 0.20, while they unexpectedly give ultrahigh luminescent quantum yields (QYs) of up to 81%, the highest value reported in chiral Ln(III) complexes. More impressively, the chiral memory effect for a lanthanide-based assembly is observed for the first time. The chirality of the original cage 1 framework is retained after R/S-BINAPO is replaced by the achiral bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO), and thus another pair of enantiopure Eu(III) tetrahedral cages, ΔΔΔΔ- and ΛΛΛΛ-[(Eu₄L₄)(DPEPO)₄] (ΔΔΔΔ-2 and ΛΛΛΛ-2), have been isolated. Encouragingly, cage 2 also presents an impressive luminescence quantum yield (QY = 68%) and intense CPL (|g_lum| = 0.11). This study offers a simple and low-cost synthesis strategy for the preparation of lanthanide cages with CPL properties.

Microscopic Imaging of Chiral Amino Acids in Agar Gel through Circularly Polarized Luminescence of EuIII Complex

We recently found that [Eu(pda)₂ ]^- (pda: 1,10-phenanthroline-2,9-dicarboxylic acid), which has an achiral structure in crystals, exhibits circularly polarized luminescence (CPL) in aqueous solutions containing chiral amino acids such as arginine and histidine. CPL measurements were performed for agar gel, which includes an aqueous solution of [Eu(pda)₂ ]^- and chiral arginine or histidine. The spectral shape, concentration, and pH dependences on CPL intensity in the agar gels were very close to those in aqueous solutions, indicating that the CPL of the Eu^III complex in the agar gels was induced by mechanism similar to that in aqueous solutions. We performed spatially resolved CPL measurements using a laboratory-built microscopic CPL spectroscopic system for agar-gel samples, where d- and l- amino acids were separately dispersed. We successfully recorded CPL imaging maps showing spatial dispersions of d- and l-amino acid in the agar gels.

Chiral luminescent lanthanide complexes possessing strong (samarium, SmIII) circularly polarised luminescence (CPL), and their self-assembly into Langmuir-Blodgett films

The lanthanide directed self-assembly of chiral amphiphilic 2,6-pyridinedicarboxylic acid based ligands 1 and 2 with various Ln(CF₃SO₃)₃ (Ln = Tb^III, Sm^III, Lu^III, Dy^III) salts was studied in CH₃CN and evaluated with the expected 1 : 3 and 1 : 1 Ln : Ligand species forming in solution. Ligand chirality was retained and transferred, as depicted by circular dichroism (CD) and circularly polarised luminescence (CPL) measurements (for Tb^III and Sm^III), to the lanthanide centre upon complexation with high dissymmetry factor values for the Sm^III complexes obtained (g_lum = -0.44 and 0.29 and 0.45 and -0.23 for the ⁴G_5/2→⁶H_5/2 and the ⁴G_5/2→⁶H_7/2 transitions of Sm·1₃ and Sm·2₃, respectively). The ability of the complexes to form stable Langmuir monolayers at the air-water interface was also established while Langmuir-Blodgett films of Tb·L₃ and Sm·L₃ exhibited lanthanide luminescent emission.

Europium amphiphilic naphthalene based complex for the enhancement of linearly polarized luminescence in Langmuir–Blodgett films

The complexation in LB films induces the linearly polarized luminescence of europium by the excited 1-naphtoate ligand.

Luminescent lanthanide (Eu(iii)) cross-linked supramolecular metallo co-polymeric hydrogels: the effect of ligand symmetry

Two lanthanide luminescent naphthyl-dipicolinic amide (dpa) methacrylate monomers for the synthesis of grafted supramolecular co-polymer gels (hydrogels), and their use as additional crosslinks in robust covalently cross-linked HEMA hydrogels is presented.

Ligand-to-Ligand Interactions That Direct Formation of D2-Symmetrical Alternating Circular Helicate

This work demonstrates that ligand-to-ligand interactions between achiral bis-β-diketonate (BTP) and chiral bis(4-phenyl-2-oxazolinyl)pyridine [( R)- or ( S)-Ph-Pybox] are successfully directed to the fabrication of a D₂-symmetrical alternating circular helicate with the general formula [( R)- or ( S)-Ph-Pybox]₄(Ln^III)₄(BTP)₆. The lanthanide(III) Ln^III assemblies (Ln^III₄- RRRR and Ln^III₄- SSSS) have a nanometer-size squarelike grid (interatomic distances > 10 Å). X-ray structure analysis revealed that the circular helicate contains two double helicate Ln^III₂L₂ units, where both show ( M)-helicity for Ln^III₄- RRRR and ( P)-helicity for Ln^III₄- SSSS, where π-π stacking interaction is present between the side arm of ( R)-Ph-Pybox (Ph₁) and the adjacent BTP ligand around the Eu^III metal center ( d_ππ = 3.636 Å: the diketonate plane···Ph₁ distance). The newly obtained circular lanthanide(III) helicate exists as single and homochiral diastereomers in solution (Ln^III₄- RRRR and Ln^III₄- SSSS), exhibiting circularly dichroism (CD) and circularly polarized luminescence (CPL). Conversely, the circular helicate favors the heterochiral arrangement (i.e., Ln^III₄- RRRR/Ln^III₄- SSSS).

Surface-based molecular self-assembly: Langmuir-Blodgett films of amphiphilic Ln(III) complexes

The unique photophysical properties of the Ln(III) series has led to significant research efforts being directed towards their application in sensors. However, for “real-life” applications, these sensors should ideally be immobilised onto surfaces without loss of function. The Langmuir-Blodgett (LB) technique offers a promising method in which to achieve such immobilisation. This mini-review focuses on synthetic strategies for film formation, the effect that film formation has on the physical properties of the Ln(III) amphiphile, and concludes with examples of Ln(III) LB films being used as sensors.

Towards multifunctional lanthanide-based metal-organic frameworks

We report the synthesis, structure and physicochemical attributes of a new holmium(III)-based metal-organic framework whose 3D network structure gives rise to porosity; the reported structure-type can be varied using a range of different lanthanide ions to tune the photophysical properties and produce ligand-sensitised near-infrared (NIR) and visible light emitters.

Lanthanide-directed synthesis of luminescent self-assembly supramolecular structures and mechanically bonded systems from acyclic coordinating organic ligands

Herein some examples of the use of lanthanide ions (f-metal ions) to direct the synthesis of luminescent self-assembly systems (architectures) will be discussed. This area of lanthanide supramolecular chemistry is fast growing, thanks to the unique physical (magnetic and luminescent) and coordination properties of the lanthanides, which are often transferred to the resulting supermolecule. The emphasis herein will be on systems that are luminescent, and hence, generated by using either visibly emitting ions (such as Eu(III), Tb(III) and Sm(III)) or near infrared emitting ions (like Nd(III), Yb(III) and Er(III)), formed through the use of templating chemistry, by employing structurally simple ligands, possessing oxygen and nitrogen coordinating moieties. As the lanthanides have high coordination requirements, their use often allows for the formation of coordination compounds and supramolecular systems such as bundles, grids, helicates and interlocked molecules that are not synthetically accessible through the use of other commonly used templating ions such as transition metal ions. Hence, the use of the rare-earth metal ions can lead to the formation of unique and stable species in both solution and in the solid state, as well as functional and responsive structures.

Hyper-stable organo-Eu(III) luminophore under high temperature for photo-industrial application

Novel organo-Eu(III) luminophores, Eu(hfa)x(CPO)y and Eu(hfa)x(TCPO)y (hfa: hexafluoroacetylacetonate, CPO: 4-carboxyphenyl diphenyl phosphine oxide, TCPO: 4,4',4″-tricarboxyphenyl phosphine oxide), were synthesized by the complexation of Eu(III) ions with hfa moieties and CPO or TCPO ligands. The thermal and luminescent stabilities of the luminophores are extremely high. The decomposition temperature of Eu(hfa)x(CPO)y and Eu(hfa)x(TCPO)y were determined as 200 and 450 °C, respectively. The luminescence of Eu(hfa)x(TCPO)y under UV light irradiation was observed even at a high temperature, 400 °C. The luminescent properties of Eu(hfa)x(CPO)y and Eu(hfa)x(TCPO)y were estimated from emission spectra, quantum yields and lifetime measurements. The energy transfer efficiency from hfa moieties to Eu(III) ions in Eu(hfa)x(TCPO)y was 59%. The photosensitized luminescence of hyper-stable Eu(hfa)x(TCPO)y at 400 °C is demonstrated for future photonic applications.

Very bright, enantiopure europium(iii) complexes allow time-gated chiral contrast imaging

Chiral image contrast is reported with very bright enantiopure europium complexes that emit circularly polarized light.

Recent advances in the development of synthetic chemical probes for glycosidase enzymes

The emergence of synthetic glycoconjugates as chemical probes for the detection of glycosidase enzymes has resulted in the development of a range of useful chemical tools with applications in glycobiology, biotechnology, medical and industrial research. Critical to the function of these probes is the preparation of substrates containing a glycosidic linkage that when activated by a specific enzyme or group of enzymes, irreversibly releases a reporter molecule that can be detected. Starting from the earliest examples of colourimetric probes, increasingly sensitive and sophisticated substrates have been reported. In this review we present an overview of the recent advances in this field, covering an array of strategies including chromogenic and fluorogenic substrates, lanthanide complexes, gels and nanoparticles. The applications of these substrates for the detection of various glycosidases and the scope and limitations for each approach are discussed.

The btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] binding motif: a new versatile terdentate ligand for supramolecular and coordination chemistry

Ligands containing the btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] motif have appeared with increasing regularity over the last decade. This class of ligands, formed in a one pot ‘click’ reaction, has been studied for various purposes, such as for generating d and f metal coordination complexes and supramolecular self-assemblies, and in the formation of dendritic and polymeric networks, etc. This review article introduces btp as a novel and highly versatile terdentate building block with huge potential in inorganic supramolecular chemistry. We will focus on the coordination chemistry of btp ligands with a wide range of metals, and how it compares with other classical pyridyl and polypyridyl based ligands, and then present a selection of applications including use in catalysis, enzyme inhibition, photochemistry, molecular logic and materials, e.g. polymers, dendrimers and gels. The photovoltaic potential of triazolium derivatives of btp and its interactions with anions will also be discussed.

Healable luminescent self-assembly supramolecular metallogels possessing lanthanide (Eu/Tb) dependent rheological and morphological properties

Herein we present the use of lanthanide directed self-assembly formation (Ln(III) = Eu(III), Tb(III)) in the generation of luminescent supramolecular polymers, that when swelled with methanol give rise to self-healing supramolecular gels. These were analyzed by using luminescent and (1)H NMR titrations studies, allowing for the identification of the various species involved in the subsequent Ln(III)-gel formation. These highly luminescent gels could be mixed to give a variety of luminescent colors depending on their Eu(III):Tb(III) stoichiometric ratios. Imaging and rheological studies showed that these gels prepared using only Eu(III) or only Tb(III) have different morphological and rheological properties, that are also different from those determined upon forming gels by mixing of Eu(III) and Tb(III) gels. Hence, our results demonstrate for the first time the crucial role the lanthanide ions play in the supramolecular polymerization process, which is in principle a host-guest interaction, and consequently in the self-healing properties of the corresponding gels, which are dictated by the same host-guest interactions.

Self-assembly formation of a healable lanthanide luminescent supramolecular metallogel from 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) ligands

The self-assembly and rheological studies of self-healing Eu(iii) luminescent metallogels from a btp (2,6-bis(1,2,3-triazol-4-yl)pyridine) ligand is described.

Quantifying the formation of chiral luminescent lanthanide assemblies in an aqueous medium through chiroptical spectroscopy and generation of luminescent hydrogels

Herein we present the synthesis and the photophysical evaluation of water-soluble chiral ligands (2·(R,R) and 2·(S,S)) and their application in the formation of lanthanide directed self-assembled structures. These pyridine-2,6-dicarboxylic amide based ligands, possessing two naphthalene moieties as sensitising antennae, that can be used to populate the excited state of lanthanide ions, were structurally modified using 3-propanesultone and caesium carbonate, allowing for the incorporation of a water-solubilising sulfonate motif. We show, using microwave synthesis, that Eu(iii) forms chiral complexes in 1 : 3 (M : L) stoichiometries (Eu·[2·(R,R)]₃ and Eu·[2·(S,S)]₃) with these ligands, and that the red Eu(iii)-centred emission arising from these complexes has quantum yields (Φ_tot) of 12% in water. Both circular dichroism (CD) and circular polarised luminescence (CPL) analysis show that the complexes are chiral; giving rise to characteristic CD and CPL signatures for both the Λ and the Δ complexes, which both possess characteristic luminescence dissymmetry factors (g_lum), describing the structure in solution. The self-assembly process was also monitored in situ by observing the changes in the ligand absorption and fluorescence emission, as well as in the Eu(iii) luminescence. The change, fitted using non-linear regression analysis, demonstrated high binding affinity for Eu(iii) which in part can be assigned to being driven by additional hydrophobic effects. Moreover, using CD spectroscopy, the changes in the chiroptical properties of both (2·(R,R) and 2·(S,S)) were monitored in real time. Fitting the changes in the CD spectra allowed for the step-wise binding constants to be determined for these assemblies; these matched well with those determined from both the ground and the excited state changes. Both the ligands and the Eu(iii) complexes were then used in the formation of hydrogels; the Eu(iii)-metallogels were luminescent to the naked-eye.

Synthesis of novel lanthanide acylpyrazolonato ligands with long aliphatic chains and immobilization of the Tb complex on the surface of silica pre-modified via hydrophobic interactions

Immobilization of a Tb acylpyrazolonato complex on silica surfaces via hydrophobic interactions.

Potential switchable circularly polarized luminescence from chiral cyclometalated platinum(II) complexes

A series of chiral cyclometalated platinum(II) complexes, [Pt((-)-L1)(Dmpi)]Cl ((-)-1), [Pt((+)-L1)(Dmpi)]Cl ((+)-1), [Pt((-)-L2)(Dmpi)]Cl ((-)-2), [Pt((+)-L2)(Dmpi)]Cl ((+)-2), [Pt3((-)-L2)2(Dmpi)4](ClO4)4 ((-)-3), and [Pt3((+)-L2)2(Dmpi)4](ClO4)4 ((+)-3) [(-)-L1 = (-)-4,5-pinene-6'-phenyl-2,2'-bipyridine, (+)-L1 = (+)-4,5-pinene-6'-phenyl-2,2'-bipyridine), (-)-L2 = (-)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, (+)-L2 = (+)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, Dmpi = 2,6-dimethylphenyl isocyanide], have been designed and synthesized. In aqueous solutions, (-)-1 and (+)-1 aggregate into one-dimensional helical chain structures through Pt···Pt, π-π, and hydrophobic-hydrophobic interactions. (-)-3 and (+)-3 represent a novel helical structure with Pt-Pt bonds. The formation of helical structures results in enhanced and distinct chiroptical properties as evidenced by circular dichroism spectra. Circularly polarized luminescence (CPL) was observed from the aggregates of (-)-1 and (+)-1 in water, as well as (-)-3 and (+)-3 in dichloromethane. The CPL activity can be switched reversibly (for (-)-1 and (+)-1) or irreversibly (for (-)-3 and (+)-3) by varying the temperature.