Endowing Metal-Organic Coordination Materials with Chiroptical Activity by a Chiral Anion Strategy.

Recently, chiral metal-organic coordination materials have emerged as promising candidates for a wide range of applications in chiroptoelectronics, chiral catalysis, and information encryption, etc. Notably, the chiroptical effect of coordination chromophores makes them appealing for applications such as photodetectors, OLEDs, 3D displays, and bioimaging. The direct synthesis of chiral coordination materials using chiral organic ligands or complexes with metal-centered chirality is very often tedious and costly. In the case of ionic coordination materials, the combination of chiral anions with cationic, achiral coordination compounds through noncovalent interactions may endow molecular materials with desirable chiroptical properties. The use of such a simple chiral strategy has been proven effective in inducing promising circular dichroism and/or circularly polarized luminescence signals. This concept article mainly delves into the latest advances in exploring the efficacy of such a chiral anion strategy for transforming achiral coordination materials into chromophores with superb photo- or electro-chiroptical properties. In particular, ionic small-molecular metal complexes, metal clusters, coordination supramolecular assemblies, and metal-organic frameworks containing chiral anions are discussed. A perspective on the future opportunities on the preparation of chiroptical materials with the chiral anion strategy is also presented.

Near-Unity Green Luminescent Hybrid Manganese Halides as X-ray Scintillators.

The increasing demands in optoelectronic applications have driven the advancement of organic-inorganic hybrid metal halides (OIMHs), owing to their exceptional optical and scintillation properties. Among them, zero-dimensional (0D) low-toxic manganese-based scintillators have garnered significant interest due to their exceptional optical transparency and elevated photoluminescence quantum yields (PLQYs), making them promising for colorful light-emitting diodes and X-ray imaging applications. In this study, two OIMH single crystals of (Br-PrTPP)2MnBr4 (Br-PrTPP = (3-bromopropyl) triphenylphosphonium) and (Br-BuTPP)2MnBr4 (Br-BuTPP = (4-bromobutyl) triphenylphosphonium) were prepared via a facile saturated crystallization method. Benefiting from the tetrahedrally coordinated [MnBr4]2- polyhedron, both of them exhibited strong green emissions peaked at 517 nm owing to the d-d electron transition of Mn2+ with near-unity PLQYs of 99.33 and 86.85%, respectively. Moreover, benefiting from the high optical transparencies and remarkable luminescence properties, these manganese halides also exhibit excellent radioluminescent performance with the highest light yield of up to 68,000 photons MeV-1, negligible afterglow (0.4 ms), and linear response to X-ray dose rate with the lowest detection limit of 45 nGyair s-1. In X-ray imaging, the flexible film made by the composite of (Br-PrTPP)2MnBr4 and PDMS shows an ultrahigh spatial resolution of 12.78 lp mm-1, which provides a potential visualization tool for X-ray radiography.

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.

Rapid and Low-Cost Quantification of Adulteration Content in Camellia Oil Utilizing UV-Vis-NIR Spectroscopy Combined with Feature Selection Methods.

This study aims to explore the potential use of low-cost ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy to quantify adulteration content of soybean, rapeseed, corn and peanut oils in Camellia oil. To attain this aim, test oil samples were firstly prepared with different adulterant ratios ranging from 1% to 90% at varying intervals, and their spectra were collected by an in-house built experimental platform. Next, the spectra were preprocessed using Savitzky-Golay (SG)-Continuous Wavelet Transform (CWT) and the feature wavelengths were extracted using four different algorithms. Finally, Support Vector Regression (SVR) and Random Forest (RF) models were developed to rapidly predict adulteration content. The results indicated that SG-CWT with decomposition scale of 25 and the Iterative Variable Subset Optimization (IVSO) algorithm can effectively improve the accuracy of the models. Furthermore, the SVR model performed best for predicting adulteration of camellia oil with soybean oil, while the RF models were optimal for camellia oil adulterated with rapeseed, corn, or peanut oil. Additionally, we verified the models' robustness by examining the correlation between the absorbance and adulteration content at certain feature wavelengths screened by IVSO. This study demonstrates the feasibility of using low-cost UV-Vis-NIR spectroscopy for the authentication of Camellia oil.

Electrically Amplified Circularly Polarized Luminescence by a Chiral Anion Strategy.

The development of circularly polarized electroluminescence (CPEL) is currently hampered by the high difficulty and cost in the syntheses of suitable chiral materials and the notorious chirality diminishment issue in electrical devices. Herein, diastereomeric IrIII and RuII complexes with chiral (±)-camphorsulfonate counteranions are readily synthesized and used as the active materials in circularly polarized light-emitting electrochemical cells to generate promising CPELs. The addition of the chiral ionic liquid (±)-1-butyl-3-methylimidazole camphorsulfonate into the active layer significantly improves the device performance and the electroluminescence dissymmetry factors (≈10-3 ), in stark contrast to the very weak circularly polarized photoluminescence of the spin-coated films of these diastereomeric complexes. Control experiments with enantiopure IrIII complexes suggest that the chiral anions play a dominant role in the electrically-induced amplification of CPELs.

Organoplatinum(II) Cruciform: A Versatile Building Block to Fabricate 2D Microcrystals with Full-Color and White Phosphorescence and Anisotropic Photon Transport.

Conventional square-planar platinum complexes typically form one-dimensional assemblies as a result of unidirectional metallophilic and/or π⋅⋅⋅π intermolecular interactions. Organoplatinum(II) complexes with a cruciform shape are presented herein to construct two-dimensional (2D) microcrystals with full-color and white phosphorescence. These 2D crystals show unique monocomponent π⋅⋅⋅π stacking, from either the cyclometalating or noncyclometalating ligand, and the bicomponent alternate π⋅⋅⋅π stacking from both ligands along different facet directions. Anisotropic tri-directional waveguiding is further implemented on a single hexagonal microcrystal. These results demonstrate the great capability of the organoplatinum(II) cruciform as a general platform to fabricate 2D phosphorescent micro-/nanocrystals for advanced photonic applications.

Dual-Band-Tunable White-Light Emission from Bi3+ /Te4+ Emitters in Perovskite-Derivative Cs2 SnCl6 Microcrystals.

Luminescent metal halides have attracted considerable attention in next-generation solid-state lighting because of their superior optical properties and easy solution processibility. Herein, we report a new class of highly efficient and dual-band-tunable white-light emitters based on Bi3+ /Te4+ co-doped perovskite derivative Cs2 SnCl6 microcrystals. Owing to the strong electron-phonon coupling and efficient energy transfer from Bi3+ to Te4+ , the microcrystals exhibited broad dual-band white-light emission originating from the inter-configurational 3 P0,1 →1 S0 transitions of Bi3+ and Te4+ , with good stability and a high photoluminescence (PL) quantum yield of up to 68.3 %. Specifically, a remarkable transition in Bi3+ -PL lifetime from milliseconds at 10 K to microseconds at 300 K was observed, as solid evidence for the isolated Bi3+ emission. These findings provide not only new insights into the excited-state dynamics of Bi3+ and Te4+ in Cs2 SnCl6 , but also a general approach to achieve single-composition white-light emitters based on lead-free metal halides through ns2 -metal ion co-doping.

Selective, Anisotropic, or Consistent Polarized-Photon Out-Coupling of 2D Organic Microcrystals.

Nano- and micromaterials with anisotropic photoluminescence and photon transport have widespread application prospects in quantum optics, optoelectronics, and displays. But the nature of the polarization information of the out-coupled light, with respect to that of the source luminescence, has never been explored in active optical-waveguiding organic crystals. Herein, three different modes (selective, anisotropic, and consistent) of polarized-photon out-coupling are proposed and successfully implemented in a set of 2D organic microcrystals with highly linearly-polarized luminescence. It is found that the polarization direction and degree of the luminescence out-coupled through different waveguiding channels can either be essentially retained or distinctly changed with respect to those of the original luminescence, depending on the molecular arrangement and the orientation of transition dipole moments of the crystal. This work demonstrates the promising potential of 2D emissive microcrystals in multi-channel polarized photon transport.

A Carbazole-Bridged Biscyclometalated Diplatinum Complex: Synthesis, Characterization, and Dual-Mode Aggregation-Enhanced Phosphorescence.

A cationic carbazole-bridged biscyclometalated diplatinum complex 4 has been synthesized and characterized. Single-crystal X-ray analysis demonstrates that complex 4 displays a dimeric structure with noncovalent π-π stacking and unique double Pt-Pt interactions. In aerated dilute CH3CN, complex 4 is characterized by a very weak monomeric yellow emission (λemi = 547 nm; Φ = 0.51%), which is attributed to the triplet intraligand (3LC) excited state mixing with some charge transfer characters. In contrast, under aerated conditions, the dispersion of 4 in a mixed solvent of CH3CN/Et2O (1/9, v/v) or CH3CN/H2O (1/9, v/v) displays intense yellow (λemi = 550 nm; Φ = 35.5%; τ = 11.10 µs) and red emission (λemi = 635 nm; Φ = 14.1%; τ = 7.00 µs), respectively. These aggregation-induced phosphorescent emission enhancements are considered being caused by the oxygen-shielding effect and the molecular rigidification-induced decrease of nonradiative decays in the aggregate state. The morphology and size of the aggregates under these two conditions are examined by scanning electron microscope and dynamic light scattering analysis. The absorption and emission properties of 4 are further rationalized by time-dependent density functional theory calculations on a model compound.

Dual-Emissive Tris-Heteroleptic Ruthenium Complexes: Tuning the DNA-Triggered Ratiometric Emission Response by Ancillary Ligands.

Three tris-heteroleptic mononuclear Ru(II) complexes with dual fluorescence and phosphorescence-[Ru(dpma)(bpy)(phen)]2+ (12+), [Ru(dpma)(bpy)(dppz)]2+ (22+), and [Ru(dpma)(phen)(dppz)]2+ (32+)-have been designed and used as ratiometric light-response probes for DNA, where dpma is di(pyrid-2-yl)(methyl)-amine, bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline, and dppz is dipyridophenazine, respectively. Single crystals of complex 2(PF6)2 have been obtained and studied by X-ray analysis. The interactions of these complexes with different DNAs are investigated by means of spectroscopic methods, viscosity measurements, and molecular modeling. In the presence of calf thymus DNA, complexes 2(PF6)2 and 3(PF6)2 show the emergence of a new lower-energy phosphorescence emission band; meanwhile, the higher-energy fluorescence emission band is essentially unchanged, functioning as an intrinsic internal reference. These two complexes exhibit stronger preference for calf thymus DNA over single-strand DNA (d(A)16 and d(C)16). In contrast, no binding interaction between 1(PF6)2 and calf thymus DNA is observed. The intrinsic binding constants (Kb) of 2(PF6)2 and 3(PF6)2 with calf thymus DNA are determined to be (1.4 ± 0.4) × 105 and (9.5 ± 0.15) × 104 M-1, respectively. In addition, these spectroscopic results are compared with those of the prototype complex [Ru(bpy)2(dppz)]2+ (42+), and density functional theory and time-dependent density functional theory calculations are employed to elucidate these experimental findings.

Full-Color and White Circularly Polarized Luminescence of Hydrogen-Bonded Ionic Organic Microcrystals.

A simple and general method is presented herein for the in situ preparations of circularly polarized luminescence (CPL)-active microcrystals with a large luminescence dissymmetry factor glum , high fluorescence quantum efficiency (ΦFL ), wide emission color tenability, and well-ordered morphology. The reactions of pyridine-containing achiral molecules 1-7 with chiral camphor sulfonic acid ((±)-CSA) gave crystalline microplates formed by hydrogen bonding interactions between the protonated pyridinium units and the sulfonic anions. The chiral information of CSA are effectively transferred to the microcrystals by hydrogen bonding to afford full-color CPL from deep-blue to red with glum in the order of 10-2 and ΦFL up to 80 %. Moreover, organic microcrystals with high-performance white CPL (ΦFL =46 %; |glum |=0.025) are achieved via the light-harvesting energy transfer between blue and yellow emitters.

Engineering the Bandgap and Surface Structure of CsPbCl3 Nanocrystals to Achieve Efficient Ultraviolet Luminescence.

Herein, we report the design of novel ultraviolet luminescent CsPbCl3 nanocrystals (NCs) with the emission peak at 381 nm through doping of cadmium ions. Subsequently, a surface passivation strategy with CdCl2 is adopted to improve their photoluminescence quantum yield (PLQY) with the maximum value of 60.5 %, which is 67 times higher than that of the pristine counterparts. The PLQY of the surface passivated NCs remains over 50 % after one week while the pristine NCs show negligible emission. By virtue of density functional theory calculations, we reveal that the higher PLQY and better stability after surface passivation may result from the significant elimination of surface chloride vacancy (VCl ) defects. These findings provide fundamental insights into the optical manipulation of metal ion-doped CsPbCl3 NCs.

Effect of the Fluoro-Substituent Position on the Crystal Structure and Photoluminescence of Microcrystals of Platinum ß-Diketonate Complexes.

Molecular packing has an important effect on the photophysical properties of crystalline materials. We demonstrate in this work the modulation of molecular packing and emission properties of microcrystals by minor molecular structural variations. Four platinum ß-diketonate complexes, with two fluoro substituents (1) or one fluoro atom substituted on different positions of the auxiliary phenylpyridine ligand (2-4) have been synthesized. These complexes were used to prepare one-dimensional microcrystals with well-defined shapes and uniform sizes. Although 1-4 display similar emission spectra in the solution state, the corresponding microcrystals display different emission colors from green to yellow and orange. In addition, different temperature-responsive (80-298 K) emission spectral changes have been observed from these microcrystals, including the intensity variation of the locally excited (LE) emission without obvious wavelength shifts, competition between the LE and metal-metal-to-ligand charge-transfer emissions, and the sole wavelength shift of the π-π excimer emissions. These differences in emission properties are rationalized by different molecular packings of these materials, as revealed by single-crystal X-ray analyses.

Temperature-Triggered Self-Assembled Structural Transformation: From Pure Hydrogen-Bonding Quadrilateral Nanonetwork to Trihexagonal Structures.

Adequate control over the structures of molecular building blocks plays an important role in the fabrication of desired supramolecular nanostructures at interfaces. In this study, the formation of a pure hydrogen-bonding co-assembly supramolecular nanonetwork on a highly oriented pyrolytic graphite surface was demonstrated by means of a scanning tunneling microscope. The thermal annealing process was conducted to monitor the temperature-triggered structural transformation of the self-assembled nanonetwork. On the basis of the single-molecule-level resolution scanning tunneling microscopy images, together with the density functional theory calculations, the formation mechanisms of the formed nanoarrays were proposed. The results have great significance with regard to controlled construction of complex nanostructures on the surface.

Full-Spectrum Persistent Luminescence Tuning Using All-Inorganic Perovskite Quantum Dots.

Applications of persistent luminescence phosphors as night or dark-light vision materials in many technological fields have fueled up a growing demand for rational control over the emission profiles of the phosphors. This, however, remains a daunting challenge. Now a unique strategy is reported to fine-tune the persistent luminescence by using all-inorganic CsPbX3 (X=Cl, Br, and I) perovskite quantum dots (PeQDs) as efficient light-conversion materials. Full-spectrum persistent luminescence with wavelengths covering the entire visible spectral region is achieved through tailoring of the PeQD band gap, in parallel with narrow bandwidth of PeQDs and highly synchronized afterglow decay owing to the single energy storage source. These findings break through the limitations of traditional afterglow phosphors, thereby opening up opportunities for persistent luminescence materials for applications such as a white-emitting persistent light source and dark-light multicolor displays.

A New Class of Blue-LED-Excitable NIR-II Luminescent Nanoprobes Based on Lanthanide-Doped CaS Nanoparticles.

Lanthanide (Ln3+ )-doped luminescent nanoparticles (NPs) with emission in the second near-infrared (NIR-II) biological window have shown great promise but their applications are currently limited by the low absorption efficiency of Ln3+ owing to the parity-forbidden 4f→4f electronic transition. Herein, we developed a strategy for the controlled synthesis of a new class of NIR-II luminescent nanoprobes based on Ce3+ /Er3+ and Ce3+ /Nd3+ co-doped CaS NPs, which can be effectively excited by using a low-cost blue light-emitting diode chip. Through sensitization by the allowed 4f→5d transition of Ce3+ , intense NIR-II luminescence from Er3+ and Nd3+ with quantum yields of 9.3 % and 7.7 % was achieved, respectively. By coating them with a layer of amphiphilic phospholipids, these NPs exhibit excellent stability in water and can be exploited as sensitive NIR-II luminescent nanoprobes for the accurate detection of an important disease biomarker, xanthine, with a detection limit of 32.0 nm.

Temperature-Responsive Fluorescent Organoplatinum(II) Metallacycles.

The synthesis, characterization, and temperature-responsive properties of two fluorescent organoplatinum(II) metallacycles are reported. Metallacycles M1 and M2 were prepared via the coordination-driven self-assembly of a 120° triarylamine ligand L1 and a 120° diplatinum(II) acceptor Pt-1 or 180° diplatinum(II) acceptor Pt-2, respectively. M1 and M2 are hexagonal metallacycles, comprising of three or six freely rotating anthracene pendants on their periphery, respectively. In response to the temperature variation between -20 and 60 °C, the ligand displays irregular emission changes, whereas both metallacycles show reversible absorption and emission spectral changes in THF. The changes in their green emission intensity also exhibit a linear correlation with the temperature variation, with an average sensitivity of -0.67% and -0.77% per °C for M1 and M2, respectively. Furthermore, in coordinating solvents, such as DMF and CH3CN, M1 and M2 show different behaviors: in the lower temperature range, i.e., below 30 °C, their spectral changes are similar to those observed in THF; however, at a higher temperature the metallacycles were presumably destroyed by the solvents and displayed ratiometric fluorescent responses, including a cyan emission of the ligand L1.

Anion-regulated electronic communication in a cyclometalated diruthenium complex with a urea bridge.

A combined study of electrochemical measurements, intervalence charge transfer analysis, and DFT calculations suggests that the degree of urea-mediated electronic coupling between two cyclometalated ruthenium sites is enhanced by the coordination of urea with Br- or Cl-via hydrogen bonding. In contrast, the redox waves of the diruthenium complex become highly irreversible in the presence of relatively strong basic anions such as H2PO4-, F-, or OAc-. This work demonstrates that the anion-urea interaction can be employed to regulate the electronic coupling and electron transfer between redox-active sites, suggesting the potential applications of the urea-functionalized diruthenium complex in anion sensing and stimuli-responsive molecular electronics.

H2PO4-- and Solvent-Induced Polymorphism of an Amide-Functionalized [Pt(N

A simple [Pt(N^C^N)Cl] complex functionalized with an amide group was prepared, and its absorption and emission properties were examined in different solvents in response to various anions. On the one hand, in the presence of H2PO4-, the solution of the complex shows distinct color changes in CH3CN, together with a ratiometric emission change from a green emission band at 537 nm to a deep red emission band at 680 nm. On the other hand, two-step spectral changes were observed in response to H2PO4- in CH2Cl2, with the green emission being attenuated first followed by the appearance of enhanced and yellow-green emissions at a lower-energy region. These recognition processes are highly selective for H2PO4- against other common anions including F-, Cl-, Br-, I-, OAc-, NO3-, and HSO4-. In addition, the platinum complex displays multistage emission polymorphism in mixed CH3CN/H2O solvent of various ratios. The hydrogen-bonding interaction between H2PO4- and the amide unit was confirmed by NMR analysis. In the solid state, this platinum complex emits red light. However, the composite material of the platinum complex with H2PO4- shows purely monomeric yellow emissions. The solid-state materials were further analyzed by single-crystal X-ray and Fourier-transform IR analysis. These studies suggest that this simple platinum complex is useful for the selective recognition of H2PO4- and as solid-state emitting materials with tunable emission colors.

Molecular Conductance through a Quadruple-Hydrogen-Bond-Bridged Supramolecular Junction.

A series of self-complementary ureido pyrimidinedione (UPy) derivatives modified with different aurophilic anchoring groups were synthesized. Their electron transport properties through the quadruple hydrogen bonds in apolar solvent were probed employing the scanning tunneling microscopy break junction (STMBJ) technique. The molecule terminated with a thiol shows the optimal electron transport properties, with a statistical conductance value that approaches 10(-3)  G0 . The (1) H NMR spectra and control experiments verify the formation of quadruple hydrogen bonds, which can be effectively modulated by the polarity of the solvent environment. These findings provide a new design strategy for supramolecular circuit elements in molecular electronics.