Hexagonal Halide Perovskite Cs2LiInCl6: Cation Ordering, Face-Shared Octahedral Trimers and Mn2+ Luminescence

The In-based double perovskite halides have been widely studied for promising optical-electric applications. The halide hexagonal perovskite Cs2LiInCl6 was isolated using solid-state reactions and investigated using X-ray diffraction and solid-state NMR spectra. The material adopts a 12-layered hexagonal structure (12R) consisting of layered cationic orders driven by the cationic charge difference and has Li+ cations in the terminal site and In3+ in the central site of face-shared octahedron trimers. Such a cationic ordering pattern is stabilized by electrostatic repulsions between the next-nearest neighboring cations in the trimers. The LiCl6 octahedron displays large distortion and is confirmed by 7Li SS NMR in the Cs2LiInCl6. The Cs2LiInCl6 material has a direct bandgap of ~4.98 eV. The Cs2LiInCl6: Mn2+ displays redshift luminescence (centered at ~610-622 nm) from the substituted Mn2+ emission in octahedron with larger PLQY (17.8 %-48 %) compared with that of Cs2NaInCl6: Mn2+. The Mn-doped materials show luminescent concentration quenching and thermal quenching. The composition Cs2Li0.99In0.99Mn0.02Cl6 exhibits the highest PL intensity, a maximum PLQY of 48 %, and high luminescent retention rate of ~86 % below 400 K and is suitable for application for pc-LED. These findings contribute to our understanding of the chloride perovskites and hold potential for widespread optical applications.

Luminescent Behavior of Zn(II) and Mn(II) Halide Derivatives of 4-Phenyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepine 4-Oxide and Single-Crystal X-ray Structure Determination of the Ligand

The two enantiomers of chiral phosphonate 4-phenyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepine 4-oxide, O=PPh(BINOL), were synthesized from the proper 1,1'-bi-2-naphtol (BINOL) enantiomer and characterized. The structure of the (S)-enantiomer was elucidated by means of single-crystal X-ray diffraction. The reaction with anhydrous ZnBr2 afforded complexes having the general formula [ZnBr2{O=PPh(BINOL)}2] that showed intense fluorescence centered in the near-UV region rationalized on the basis of TD-DFT calculations. The corresponding Mn(II) complexes with the general formula [MnX2{O=PPh(BINOL)}2] (X = Cl, Br) exhibited dual emission upon excitation with UV light, with the relative intensity of the bands dependent upon the choice of the halide. The highest energy transition is comparable with that of the Zn(II) complex, while the lowest energy emission falls in the red region of the spectrum and is characterized by lifetimes in the hundreds of microseconds range. Although the emission at lower energy can also be achieved by direct excitation of the metal center, the luminescence decay curves suggest that the band in the red range is possibly derived from BINOL-centered excited states populated by intersystem crossing.

Highly Luminescent Earth-Benign Organometallic Manganese Halide Crystals with Ultrahigh Thermal Stability of Emission from 4 to 623 K

The phosphor-converted light-emitting diode (PC-LED) has become an indispensable solid-state lighting and display technologies in the modern society. Nevertheless, the use of scarce rare-earth elements and the thermal quenching (TQ) behavior are still two most crucial issues yet to be solved. Here, this work successfully demonstrates a highly efficient and thermally stable green emissive MnI₂ (XanPO) crystals showing a notable photoluminescence quantum yield (PLQY) of 94% and a super TQ resistance from 4 to 623 K. This unprecedented superior thermal stability is attributed to the low electron-phonon coupling and the unique rigid crystal structure of MnI₂ (XanPO) over the whole temperature range based on the temperature-dependent photoluminescence (PL) and single crystal X-ray diffraction (SCXRD) analyses. Considering these appealing properties, green PC-LEDs with a power efficacy of 102.5 lm W^-1 , an external quantum efficiency (EQE) of 22.7% and a peak luminance up to 7750 000 cd m^-2 are fabricated by integrating MnI₂ (XanPO) with commercial blue LEDs. Moreover, the applicability of MnI₂ (XanPO) in both micro-LEDs and organic light-emitting diodes (OLEDs) is also demonstrated. In a nutshell, this study uncovers a candidate of highly luminescent and TQ resistant manganese halide suitable for a variety of emission applications.

Manganese(II) Bromide Compound with Diprotonated 1-Hydroxy-2-(pyridin-2-yl)-4,5,6,7-tetrahydrobenzimidazole: Dual Emission and the Effect of Proton Transfers

An organic–inorganic cation–anion manganese(II) tetrabromide compound with diprotonated 1-hydroxy-2-(pyridin-2-yl)-4,5,6,7-tetrahydrobenzimidazole, [H3L][MnBr4][H2O], has been synthesized and investigated. The compound has a few possible pathways for proton transfers, which play an important role in the observed luminescence, optical, and magnetic properties. The proton transfers result in the appearance of two-band luminescence. One band is caused by the Mn(II) d-d transitions. The other band is caused by the transition from the triplet state of organic cation and the d-d transition of manganese(II) coupled through {[H3L]}-{[MnBr4]}-{[H2O]} vibrations. The optical absorption spectra of [H3L][MnBr4][H2O] indicate the presence of two direct and one indirect band transitions. The reason for the two-band luminescence and complex optical absorption in [H3L][MnBr4][H2O] were additionally considered using the DFT calculations.

An Efficient Cyan Emission from Copper (II) Complexes with Mixed Organic Conjugate Ligands

Copper (II) complexes containing mixed ligands were synthesized in dimethyl formamide (DMF). The intense cyan emission at an ambient temperature is observed for solid copper (II) complexes with salicylic acid and a 12% quantum yield with a fluorescent lifetime of approximately 10 ms. Hence, copper (II) complexes with salicylic acid are excellent candidates for photoactive materials. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) reveal that the divalent copper metal centers coordinate with the nitrogen and oxygen lone pairs of conjugate ligands. XPS binding energy trends for core electrons in lower-lying orbitals are similar for all three copper (II) complexes: nitrogen 1s and oxygen 1s binding energies increase relative to those for undiluted ligands, and copper 2p3/2 binding energies decrease relative to that for CuCl2. The thermal behavior of these copper complexes reveals that the thermal stability is characterized by the following pattern: Cu(1,10-phenanthroline)(salicylic acid) > Cu(1,10-phenanthroline)(2,2’-bipyridine) > Cu(1,10-phenanthroline)(1-benzylimidazole)2.

Characterization of structural and optical properties of Mn2+ doped Zn2 GeO4 nanorods as an efficient green phosphor for solid-state lighting

A series of Mn²⁺ doped zinc germinate ZGO:xMn²⁺ (x = 0-0.05) nanorods were synthesized successfully by the hydrothermal method. X-ray diffraction, Rietveld refinement were used to describe the structural information of the ZGO:xMn²⁺ nanocrystals. XRD revealed that crystal phases of the ZGO:xMn²⁺ is rhombohedral and in the R-3 space group. The unit cell size did not significantly change as the concentration of Mn²⁺ doping increased. The Williamson-Hall equation was also used to explain the strain, nanocrystalline size, and stacking fault. Green LEDs were successfully fabricated by coating ZGO:Mn²⁺ nanorods onto UV-LEDS chip. High color purity, CIE coordinates of the fabricated green LEDs are (0.2404, 0.5428) which is one of the promising candidate for fabrication of UV-based green LEDs.

Dipole-Orientation-Dependent Förster Resonance Energy Transfer from Aromatic Head Groups to MnBr42- Blocks in Organic-Inorganic Hybrids

The understanding and visualization of dipole-dipole interaction on molecular scale are scientifically fundamental and extremely of interest. Herein, two new zero-dimensional (0D) Mn hybrids with aromatic head groups and alkyl tails as organic spacers are selected as models. It was found that the dipole interaction between head groups and Mn blocks could have a huge impact on their crystalline structures as well as the luminescent properties. The parallel-oriented dipoles of the head groups and MnBr₄^2- blocks contribute to an efficient Förster Resonance Energy Transfer (FRET) in cetylpyridinium manganese bromide ([C16Py]₂MnBr₄), while the process is absent in 1-methyl-3-hexadecylimidazolium manganese bromide ([C16mim]₂MnBr₄) with perpendicular-oriented dipoles. This work gives insight into the influence of organic spacers on the geometry and the dipole interaction of Mn polyhedron in the hybrids, which could be of great interest in the future optical regulations and structural design.

Synthesis and photoluminescence of manganese(II) naphtylphosphonic diamide complexes

Manganese(ii) halide complexes with N,N,N',N'-tetramethyl-P-naphtalen-2-ylphosphonic diamide were synthesized from anhydrous MnX2 salts (X = Cl, Br, I) and characterized. Single-crystal X-ray diffraction revealed in all the cases slightly distorted tetrahedral geometry of the coordination sphere. The photoluminescence spectra showed the superimposition of a green emission, related to the 4T1(4G) → 6A1(6S) transition of Mn(ii), with a band in the red range. Different possible attributions to the lowest-energy emission were taken into account. The emission spectra of the isolated products are dependent upon the nature of the halide and, in the case of X = Br, also upon the excitation wavelength.

The moisture-responsive structural transformation of manganochlorine for water-soluble luminescent switching ink

CsMnCl3(H2O)2 (CMCH) has been widely investigated for magnetic and optical applications, including anti-Stokes photoluminescence, microwave absorption, and magnon-assisted optical transitions. Herein, CMCH crystals, which are colorless and transparent (unlike the pink crystals reported previously), were obtained through a unique approach. Consequently, a high-resolution optical absorption spectrum and distinct thermal behavior were observed. The reversible (de)hydration of CMCH being accompanied by photoluminescence switching (mainly in terms of the color temperature) was rationalized using crystal structure analysis. As a result, water-soluble CMCH could be applied as a moisture-responsive luminescent ink. Moreover, density functional theory (DFT) calculations were performed to understand the optical absorption of CMCH.

Manganese(ii) bromo- and iodo-complexes with phosphoramidate and phosphonate ligands: synthesis, characterization and photoluminescence

Phosphoramidates and phosphonates are suitable ligands for the preparation of tetrahedral mono- and polynuclear Mn(ii) complexes characterized by green luminescence, influenced by the symmetry of the compounds and by the P-bonded substituents.

Mn2+ luminescence of Gd(Zn,Mg)B5O10 pentaborate under high pressure

The results of X-ray diffraction studies of the Gd(Mg_0.95-x,Zn_xMn_-0.05)B₅O₁₀ down-converting phosphor as a function of Mg-Zn composition are presented. The lattice parameters and unit cell volumes of GdMg_0.95-xZn_xMn_0.05B₅O₁₀ pentaborates are examined. The relationships between the structure and optical properties of these materials are explicated based on the results of theoretical calculations of the energy structure. The effect of pressure on the luminescence of Mn²⁺ in this system was studied up to ca. 32 GPa. The observed quenching of Mn²⁺ luminescence is due to the crossing of the emitting ⁴T_1g level with the non-emitting ²T_2g state. This crossing sets a long-wavelength limit on the possibility of observing the emission of Mn²⁺ ions, which is around 850 nm.

Light harvesting indolyl-substituted phosphoramide ligand for the enhancement of Mn(ii) luminescence

Excitation of the coordinated ligands in tetrahedral complexes having the general formula [MnX₂L₂] (X = Cl, Br, I; L = N,N′,N′-tetramethyl-P-indol-1-ylphosphonic diamide) causes bright green luminescence from the Mn(ii) centre.