Mn Distance Research Articles

Structural Design of Hybrid Manganese(II) Halides for High Quantum Efficiency and Specific Response to Methanol.

Manganese(II) halides have been a new generation of optoelectronic materials due to their fascinating luminescent properties, however, lacking specific solvent-responsive analogues with high quantum efficiency. Herein, we prepared three single crystals, [Pr(MIm)2][MnBr4] ([Pr(MIm)2]2+ = 1,3-di(methylimidazolium)-propane, Compound 1), [Pr(EIm)2][MnBr4] ([Pr(EIm)2]2+ = 1,3-di(ethylimidazolium)-propane, Compound 2), and [Bu(MIm)2][MnBr4] ([Bu(MIm)2]2+ = 1,4-di(methylimidazolium)-butane, Compound 3), where different Bola-type cations were chosen as organic components to separate [MnBr4]2- tetrahedrons. All three compounds emitted bright green light with excellent quantum yields of 95.3, 80.0, and 96.2%, benefiting from the large Mn···Mn distance. More interestingly, Compound 3 showed a highly selective response to methanol in a series of tested organic solvents, with a rapid and reversible change in emission color from green to red. The single crystal of [Bu(MIm)2][MnBr4]·CH3OH with red emission proved that the luminescence switching was attributed to the adsorption of CH3OH molecules into the lattice space in the form of the O-H···Br hydrogen bonds. To our knowledge, for tetrahedrally coordinated Mn(II) species, the reversible emission color switching between green and red triggered by a solvent without the change of coordination number is achieved for the first time, providing promising applications for the specific detection of methanol.

Quantitative Decoupling of Strong Mn─Mn Coupling on Photoluminescence of Zero‐Dimensional Hybrid Manganese Chlorides Single Crystals

AbstractStrong Mn─Mn coupling interactions, including dipolar and exchange interactions, significantly affect the photoluminescence quantum yields (PLQYs) in Mn2+‐based luminescent materials. However, clarifying the individual effects of dipole–dipole and exchange interactions on photoluminescence (PL) is challenging because these interactions may have similar effects on PL properties, and there is a lack of materials with precisely tunable Mn─Mn distances over a wide range. In this study, the influence of dipolar and exchange coupling on PLQY is quantitatively decoupled by designing a series of hybrid manganese chlorides single crystals with a wide tuning range of Mn─Mn distances, from 6.0 to 9.5 Å. It is found that the PLQY can be enhanced from 2.1% to 57.1%, and the PL lifetime increased from 0.21 to 3.81 ms as the Mn─Mn distance increased. This enhancement is solely attributed to the decreased energy transfer dominated by dipole–dipole interactions. At the shortest Mn─Mn distance of 6 Å, exchange coupling becomes dominant, resulting in an additional red‐side PL band with negligible effects on PLQY and lifetime. This work provides valuable insights into the mechanisms underlying the regulation of PLQY in Mn2⁺‐based luminescent materials.

Synthesis, crystal structure and Hirshfeld surface analysis of Mn(II) coordination compounds with ONO-donor ligands derived from ampyrone

Four manganese(II) coordination compounds, [Mn2(L1)2(NCS)2(MeOH)2] (1) [Mn(HL2)2(NCS)2(MeOH)2] (2) [Mn2(L3)2(NCS)2(MeOH)2] (3) and [Mn(HL3)2(NCS)2(MeOH)2] (4) have been synthesized from the reaction of MnCl2·4H2O, KSCN and Schiff base ligands derived from 4-aminoantipyrine (HL1= (E)-4-((2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL2 = (E)-4-((2-hydroxy-3-methoxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one and HL3 = (E)-4-((5-bromo-2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one) in methanol and the products have been characterized with single crystal X-ray diffraction (SC-XRD). The detailed studies involve the synthesis, crystal structure, FT-IR spectroscopy, UV–Vis spectroscopy, bond sum valence calculations, elemental and Hirshfeld surface analyses. In the case of 1 and 3, the phenolate bridged dinuclear MnII complexes are formed by chelating two Schiff base ligands, two thiocyanates and two methanol molecules and two crystallographically equivalent MnII ions are connected together by phenolate oxygen with the Mn···Mn distance of 3.1618(4) (in 1) and 3.1910(6) Å (in 3). In the case of 2 and 4, the octahedral coordination geometry of the MnII center in these mononuclear species is formed by chelating two Schiff base ligands, two thiocyanates and two methanol molecules. The presence of intermolecular hydrogen bond in 2 leads to the formation of molecular chains within the layers. Also, the presence of efficient π···π interactions between pyrazolone and phenyl rings and intermolecular hydrogen bonding in 4 lead to the formation of molecular chains within the layers. All of the intermolecular and intramolecular interactions have been studied by Hirshfeld surface analyses.

Understanding the effect of foreign atoms occupation on the metamagnetic behaviors in MnCoSi-based alloys: taking Pt-doping as an example

Present research on TiNiSi-type MnCoSi-based alloys focuses on finding a suitable doping element to effectively reduce the critical magnetic field (μ 0 H cri) required to induce a metamagnetic transition. This paper provides a guide to achieve this goal through an experimental investigation of Mn1−x Pt x CoSi and MnCo1−x Pt x Si alloys. In Mn1−x Pt x CoSi, as x increases, μ 0 H cri at room temperature decreases, while in MnCo1−x Pt x Si, it increases. This phenomenon can be attributed to the fact that larger Pt atoms prefer Co sites over Mn sites, as predicted by our density-functional theory. Consequently, in Mn1−x Pt x CoSi, larger Co atoms are extruded into the Mn atoms chain, increasing the nearest Mn–Mn distance and resulting in a reduced μ 0 H cri. This finding suggests that transition-metal atoms with more valence electrons preferably occupy the Co site, while those with fewer valence electrons preferably occupy the Mn site. Adhering to this rule, one can easily obtain a low μ 0 H cri and large magnetostrain under a low magnetic field by selecting a suitable foreign element and chemical formula, as demonstrated by the Mn1−x Pt x CoSi alloy.

First-principles study of magnetic properties and electronic structure of 3d transition-metal atom-adsorbed SnSSe monolayers.

We investigated the electronic structure and magnetic characteristics of 3d transition metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) adsorbed onto monolayer SnSSe by employing first-principles calculations. After the calculation, we found that Sc, Ti, V, Cu, and Zn atoms adsorbed onto monolayer SnSSe do not have magnetic moments, while the rest of the atoms adsorbed onto SnSSe are able to produce magnetic moments, and their magnetic moments in the adsorption systems are in the range of 1.0-3.0 μB, in which the magnetic distance of Mn is the largest. The results of MAE calculations indicate that there is a big difference in the MAE of the systems with TM atoms adsorbed to the S-side and the Se-side; for V adsorbed to the S-side on the Sn atoms, the MAE is the largest, which reaches 8.277 meV f.u.-1, showing an in-plane magnetic anisotropy, and for Co adsorbed to the Se-side on the Sn atoms, the MAE is the smallest, which is -0.673 meV f.u.-1, showing a perpendicular magnetic anisotropy. Calculations of binding energies show that all atoms are able to adsorb stably. Our results indicate the potential application of TM-adsorbed SnSSe monolayers in spintronics and magnetic memory devices.

Photophysical Tuning of Imidazolium Tetrahalidomanganate(II) Complexes towards Highly Efficient Green Emitters with Near‐Unity Quantum Yield

AbstractTen ionic manganese(II) complexes of [EMIm]2[MnX2Y2] (EMIm=1‐ethyl‐3‐methylimidazolium ion; X, Y=Cl, Br or I) and [BnMIm]2[MnX2Y2] (BnMIm=1‐benzyl‐3‐methylimidazolium ion; X, Y=Cl, Br or I) types were synthesized and studied in terms of their thermal and photophysical properties. Complexes with [BnMIm]+ cation were found to exhibit higher crystallinity, owing to the aromatic π‐stacking, and superior photoluminescent quantum yields, promoted by the increased Mn⋅⋅⋅Mn distance. For complexes with chlorine and bromine ligands efficient tunability of photophysical parameters was demonstrated. Out of all complexes, [BnMIm]2[MnBr4] was found to have the highest photoluminescence quantum yield at room temperature (Φ=0.59). To highlight the importance of a large Mn⋅⋅⋅Mn distance for achieving high Φ values, a mixed‐anion analog of complex [BnMIm]2[MnBr4] was prepared, with the suggested formula of [BnMIm]4[MnBr4]Br2. The latter have shown a significant improvement in d–d absorption efficiency and a reduction in nonradiative deactivation, which led to an outstanding Φ value of 0.97. Finally, the optical band gap of [BnMIm]4[MnBr4]Br2 was estimated to describe its applicability as light‐emitting material.

Modelling of chemical and magnetic order in Ni-Mn-Al shape memory alloys using Monte Carlo simulations

A model for the description of atomic and magnetic ordering in NiMnAl shape memory alloys is presented. The parameters characterizing the energies of the chemical and magnetic interactions were obtained from fitting to experimental data. Monte Carlo simulations based on this model correctly reproduces the critical B2↔L21 ordering temperatures as a function of composition for three pseudobinary composition lines, as well as the nature of the low temperature magnetic transition. A ferromagnetic configuration is predicted for alloys in the stable L21 structure, whereas an antiferromagnetic state is obtained for metastably retained B2 order; this is in agreement with experimental observations. It is verified that atomic ordering is strongly dominated by the interactions between Ni and Al atoms in nearest neighbours. As a consequence, the formation of B2 order can delay the stabilization of the L21 configuration at low temperatures. Since the magnetic interactions change sign with the Mn–Mn distance, the type of stable magnetic configuration depends on atomic ordering.

Magnetic and crystallographic properties of Heusler alloy Ni2Mn1.48Sn0.52

The results of experimental investigations of the crystal structure and magnetization of the magnetic shape memory alloy Ni2Mn1.48Sn0.52 are reported. This alloy undergoes the martensitic transition from the cubic L21-type structure to the orthorhombic 4O-type one with decreasing temperature. The Curie temperature TCA in the austenite phase is 310 K. The magnetic state just below the martensitic transition temperature TM is the low magnetization state or something like that. With further decrease of temperature, this alloy regains the ferromagnetism. The unit cell volume contracts discontinuously at TM with decreasing temperature. The percentage of the volume change was estimated to be ∼0.7%. The nearest neighbor Ni–Mn and Mn–Mn distances in both austenite and martensite phases of Ni2Mn1.48Sn0.52 were estimated using the X-ray diffraction analysis. On the basis of the experimental results, the magnetic properties of Ni2Mn1.48Sn0.52 are discussed.

Emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic in MnCo1−y Fe y Ge1−x Si x alloys

The emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic and magnetocaloric effect (MCE) have been investigated by X-ray diffraction, differential scanning calorimetry and magnetization measurements. Applying the isostructural alloying principle, the martensitic transition temperature (T M) increases effectively and the Curie temperatures of the two phases increase slightly by substituting the Si content (x). With an appropriate amount of Fe and Si content, an emergent first-order antiferromagnetic–ferromagnetic magnetoelastic transition with thermal hysteresis in the martensitic state occurs for MnCo0.7Fe0.3Ge1–x Si x (x = 0.15–0.40) alloys, which results from the decrease in the nearest-neighbor Mn–Mn distance. Moreover, the values of magnetic entropy change (ΔS M), refrigeration capacity (RC) and temperature-averaged entropy change (TEC, 10 K) with ΔH = 50 kOe reach −12.2 J kg−1 K−1, 112.8 J kg−1 and 11.4 J kg−1 K−1 for MnCo0.7Fe0.3Ge0.8Si0.2 undergoing the ferromagnetic magneto-structural transition in the Curie temperature window. The results facilitate the magnetocaloric/magnetoelastic performance and tunability of multiple phase states in a wider temperature range.

The 12-layer trimer-based hexagonal perovskite Cs4Ca0.7Mn3.3Cl12

We describe the crystal structure and basic magnetic properties of Cs4Ca0.7Mn3.3Cl12, a previously unreported twelve layer (12L-) hexagonal (R-3m) chloride perovskite. Its crystal structure features face sharing MnCl6 octahedra that form Mn3Cl12 trimers. The trimers, which form a triangular array, are separated by corner sharing to layers of disordered single Ca(Mn)Cl6 octahedra. The decreased intratrimer Mn–Mn distance yields stronger magnetic coupling within trimers than between trimers. The dominant magnetic interactions are antiferromagnetic (θCW = −105 K), the effective magnetic moment per Mn2+ is 6.5 μB, and potential signatures of magnetic frustration are observed. Behavior consistent with short- and long-range magnetic order is exhibited at approximately 37 and 0.7 K, respectively.

Synthesis, crystal structure and Hirshfeld surface analysis of the hybrid salt bis-(2-methyl-imidazo[1,5-a]pyridin-2-ium) tetra-chlorido-manganate(II).

The 0-D hybrid salt bis-(2-methyl-imidazo[1,5-a]pyridin-2-ium) tetra-chlorido-manganate(II), (C8H9N2)2[MnCl4] or [L]2[MnCl4], consists of discrete L + cations and tetra-chlorido-manganate(II) anions. The fused heterocyclic rings in the two crystallographically non-equivalent monovalent organic cations are almost coplanar; the bond lengths are as expected. The tetra-hedral MnCl4 2- dianion is slightly distorted with the Mn-Cl bond lengths varying from 2.3577 (7) to 2.3777 (7) Å and the Cl-Mn-Cl angles falling in the range 105.81 (3)-115.23 (3)°. In the crystal, the compound demonstrates a pseudo-layered arrangement of separate organic and inorganic sheets alternating parallel to the bc plane. In the organic layer, pairs of centrosymmetrically related trans-oriented L + cations are π-stacked. Neighboring MnCl4 2- dianions in the inorganic sheet show no connectivity, with the minimal Mn⋯Mn distance exceeding 7 Å. The Hirshfeld surface analysis revealed the prevalence of the non-conventional C-H⋯Cl-Mn hydrogen bonding in the crystal packing.

Ultrahigh Photoluminescence Quantum Yield Organic Manganese Halide Scintillator for X-ray Imaging

X-ray indirect detection based on metal halide scintillators has great potential in various applications, such as medical diagnosis, computerized tomography, and quality inspection. However, there are still many limitations in metal halide scintillation materials, such as toxicity, high production costs, and strong self-absorption caused by a band-edge transition limiting the photoluminescence quantum yield (PLQY). Here, (TEA)2MnCl4 and (TBA)2MnCl4 single crystals as scintillators with advanced properties were synthesized from TEAC (tetraethylammonium chloride), TBAC (tetrabutylammonium chloride), and manganese chloride by an antisolvent method at room temperature. These two zero-dimensional organometallic halides exhibit green emission peaking at 512 nm ((TBA)2MnCl4) and 524 nm ((TEA)2MnCl4) with high PLQYs of 99.96% and 65.07%, respectively. The ultrahigh PLQY of (TBA)2MnCl4 benefits from the long Mn–Mn distance in (TBA)2MnCl4. (TBA)2MnCl4 shows an outstanding scintillation performance with a high light yield of 21000 photons/MeV, a low detection limit of 381 nGy/s, and a spatial resolution of 5.6 lp/mm. X-ray imaging experiments demonstrate that the flexible scintillators based on (TEA)2MnCl4 and (TBA)2MnCl4 could be used in high-resolution X-ray imaging.

Temperature-Dependent Reversible Optical Properties of Mn-Based Organic–Inorganic Hybrid (C8H20N)2MnCl4 Metal Halides

Organic-inorganic metal halides (OIMHs) have abundant optical properties and potential applications, such as light-emitting diodes, displays, solar cells, and photodetectors. Herein, we report zero-dimensional Mn-based OIMH (C8H20N)2MnCl4 single crystals synthesized by a simple slow evaporation method, which exhibit intense green emission at 520 nm originating from 4T1-6A1 transition of Mn2+ ions. Large organic cations in the crystal structure result in the isolated [MnCl4]2- tetrahedrons, and the closest Mn-Mn distance reaches 9.07 Å, which effectively inhibits the migration of excitation energy between adjacent Mn2+ emission centers, thus achieving a high quantum yield (∼87%) and a long photoluminescence (PL) lifetime (3.42 ms). The different optical and structural properties at low and high temperatures are revealed by temperature-dependent PL and X-ray diffraction spectra. The PL spectra and lifetimes under the heating and cooling processes indicate that the optical property transitions are reversible at 220/240 K. Our work provides a promising strategy for building multifunctional optoelectronic materials and insights into the understanding convertible photophysical properties from isomers of metal halides.

Highly Efficient, Flexible, and Eco-Friendly Manganese(II) Halide Nanocrystal Membrane with Low Light Scattering for High-Resolution X-ray Imaging.

Scintillators enable invisible X-ray to be converted into ultraviolet (UV)/visible light that can be collected using a sensor array and is the core component of the X-ray imaging system. However, combining the excellent properties of high light output, high spatial resolution, flexibility, non-toxicity, and cost effectiveness into a single X-ray scintillator remains a great challenge. Herein, a novel scintillator based on benzyltriphenylphosphonium manganese(II) bromide (BTP2MnBr4) nanocrystal (NC) membranes was developed by the in situ fabrication strategy. The long Mn-Mn distance provided by the large BTP cation allows the nonradiative energy dissipation in this manganese(II) halide to be significantly suppressed. As a result, the flexible BTP2MnBr4 NC scintillator shows an excellent linear response to the X-ray dose rate, a high light yield of ∼71,000 photon/MeV, a low detection limit of 86.2 nGyair/s at a signal-to-noise ratio of 3, a strong radiation hardness, and a long-term thermal stability. Thanks to the low Rayleigh scattering associated with the dense distribution of nanometer-scale emitters, light cross-talk in X-ray imaging is greatly suppressed. The impressively high-spatial resolution X-ray imaging (23.8 lp/mm at modulation transfer function = 0.2 and >20 lp/mm for a standard pattern chart) was achieved on this scintillator. Moreover, well-resolved 3D dynamic rendering X-ray projections were also successfully demonstrated using this scintillator. These results shed light on designing efficient, flexible, and eco-friendly scintillators for high-resolution X-ray imaging.

Two organic-inorganic manganese(II) halide hybrids containing protonated N,N’-dialkylthioureas with efficient green-emission

Luminescent (C5H13N2S)2[MnBr4] (1) and (C7H17N2S)2[MnBr4] (2) (C5H12N2S = N,N′-diethylthiourea, C7H16N2S = N,N′-diisopropylthiourea) were prepared via solvothermal method, and the structures of these compounds have been resolved using X-ray single crystal diffraction. The structures consist of electrostatically bound MnBr42− anions and organic C5H13N2S+ and C7H17N2S+ cations. The intermolecular N−H···Br and N−H···S hydrogen bonds additionally stabilize crystal structures of 1-2. Upon excitation over broadband covering the range 265 to 515 nm, these compounds show green emission peaking at 526 nm for 1 and 522 nm for 2, which is assigned to the 4T1→6A1 electronic transition of Mn2+ from isolated within the crystal structures MnBr42− tetrahedra. The photoluminescence quantum yield (PLQY) of powder 1 is 97 ± 7% for excitation at 440 nm and that of powder 2 is 83 ± 7% for excitation at 365 nm. The high PLQY indicates the absence of noticeable concentration quenching at shortest Mn···Mn distance of 8.11 and 8.73 Å between Mn2+ ions within the structures of 1 and 2. The high-performance photoluminescence of 0D (C5H13N2S)2[MnBr4] and (C7H17N2S)2[MnBr4] compounds demonstrated promising applications in photonics.

A multielement alloying strategy to tune magnetic and mechanical properties in NiMnTi alloys via Co and B

The phase stability, martensitic transformation, and magnetic and mechanical properties of (Ni2-xCoxMn1.5Ti0.5)1-yBy (0 ≤ x ≤ 0.625; y = 0.03 and 0.06) alloys are systematically studied through the first-principles calculations method. The Co and B atoms are inclined to be aggregated distribution in the Ni2Mn1.5Ti0.5 alloy, and the phase stability of the austenite and non-modulated (NM) martensite decreases by co-doping. The ferromagnetic activation effect in the austenite occurs when x = 0.03 and y = 0.625. The magnetism of the austenite changes from an antiferromagnetic to a ferromagnetic state, which is ascribed to the elongation of the nearest neighboring distance of Mn–Mn, the nearest Mn–Mn distance increases from 2.50–2.79 to 2.90–2.94 Å, while the NM martensite always shows antiferromagnetism. Additionally, the doped B accelerates the change from antiferromagnetic to ferromagnetic for the austenite, but B-doping decreases the stability of the whole alloy system. The Co and B co-doping increases the stiffness of the NiMnTi alloy but decreases toughness and plasticity. However, the toughness and plasticity of the NiCoMnTiB alloy are better than those of the NiMnTiB alloy, indicating that the Co doping increases the d-orbital hybridization in the NiMnTiB alloy. The above results are expected to support the performance design of the NiMnTi-based alloy.

Spin-Glass-Like Behavior in Mn3Ga0.3Sn0.7N Compound

The magnetic transition, thermal property, and the distance of Mn–Mn of Mn3Ga0.3Sn0.7N compound with the Sn element substitution of Ga in Mn3GaN compounds were investigated. Magnetic measurements indicate that the existence of spin glass system at high temperature (502 K) in Mn3Ga0.3Sn0.7N compound may be attributed to competing antiferromagnetic (AFM) and ferromagnetic (FM) interactions due to the doped Sn inducing ferromagnetic orders in Mn3GaN and the partially random Sn substitute Ga at a corner site of the lattice. It is not clear how much role the pure Sn power, which is not doped into Ga site completely, played in inducing the magnetic characteristic. This finding will be helpful to reveal the mechanism of the antiperovskites’ intriguing physics properties and to develop more smart materials.

Structure, magnetic anisotropy and magnetocaloric effect of Mn5Ge3-xSix single crystals

Magnetocaloric polycrystalline materials based on Mn5Ge3 have been widely studied due to their potential application for room temperature magnetic refrigeration. However, many investigations are performed on polycrystalline materials and thus the strong anisotropy in this layered structure is usually neglected. In this study, Mn5Ge3-xSix (x = 0, 0.7) single crystals were successfully synthesized via Sn flux and characterized by single-crystal X-ray diffraction and magnetic measurements. The Si substitution does not change the structural symmetry, but reduces the shortest Mn − Mn distances. As described by the Bethe-Slater curve, the reduction of the shortest Mn − Mn distances leads to weaker magnetic exchange, accounting for the lower ordering temperature. The magnetocrystalline anisotropy was evaluated by the Sucksmith and Thompson method, and became smaller upon substitution. The anisotropy constants K1 and K2 of Mn5Ge3-xSix (x = 0, 0.7) single crystals are positive, and decrease with the temperature. The electron paramagnetic resonance spectra suggest high spin d5 configuration of manganese in both crystals. The easy magnetization direction yields much larger maximum entropy changes in both crystals: 6.0 J/kg K for the pristine and 5.4 J/kg K for the substituted under an applied field of 30 kOe.

Highly efficient emission in lead-free inorganic vacancy-ordered Sb-Bi-alloyed halide quadruple perovskites

Lead-free vacancy-ordered quadruple perovskites have received extensive attention in optoelectronic applications. We study the optical properties and charge-carrier dynamics of Cs4Mn(Bi1-xSbx)2Cl12 (0 ≤ x ≤ 1) quadruple perovskite single crystals (SCs), which exhibit excellent stability and Mn2+-based photoluminescence (PL) emission. The ratio of Bi:Sb has a great influence on PL intensity. As the Bi3+ content increases, the PL quantum yield (PLQY) shows a monotonically increasing trend and enhances by more than 40 times, attributed to larger energy difference between conduction band minimum and 4T1 state of Mn2+ ions, weaker Mn-Mn coupling interaction due to longer Mn···Mn distance and smaller Jahn-Teller distortion, and lower carrier-phonon coupling. Moreover, Cs4Mn(Bi1-xSbx)2Cl12 nanocrystals were synthesized through top-down ultrasonic crushing method. The PL quenching of Cs4MnBi2Cl12 nanocrystals compared to corresponding SCs arises from surface defect trapping. Our work provides an in-depth understanding of Mn2+-based PL mechanism.

The Renaissance of Functional Hybrid Transition-Metal Halides

ConspectusThere is an extensive history of research on both inorganic and hybrid metal halides, with the latter being first reported in the 1960s. Although work on hybrid systems has progressed steadily over the last 60 years, it has enjoyed a major renaissance during the last 5 years. This has arisen as a consequence of the 2009 discovery of the outstanding optoelectronic properties of hybrid lead halides, such as (MA)PbI3 (MA = methylammonium), and the recognition that there are many opportunities for equally exciting discoveries with compounds of the transition metals. Some of the early work on hybrid transition-metal halides put more emphasis on crystal structures but less on properties. In the modern era, we aim to grasp both the structure and properties, with a new twist. In this Account, we shall explore the recent developments in hybrid transition-metal halides with a focus on work in four main areas: magnetism, photoluminescence, semiconductivity, and spintronics. Our work on magnetism centers on the Ru-based hybrid halides, where the structural types are diversely composed of vacancy-ordered double perovskite, as well as chain-like one-dimensional structures and layered double perovskite (LDP) when paired with a (1+) metal. We explore their magnetic properties and find that their spin–orbit coupling (SOC) behavior can be tuned through changing the A cation and the halide. In the luminescence section, we focus on our recent works on hybrid tetrahedral Mn(II) bromides and Cu(I) and Ag(I) iodides. We correlated our newly discovered 0D AmMnBr4 (A = organic cation, m = 1 or 2) compounds with previous reports, and generated a trend where the photoluminescence quantum yield (PLQY) increases with larger Mn–Mn distances. The flexible organic cation becomes the most important tool here to tune the structure–PLQY relations. Cu(I) and Ag(I) iodides coordinated with iodides and organic ligands produce new crystal structures with intense PL. For the semiconducting properties, we explore the Pt-based vacancy-ordered double perovskite and hybrid bismuth and indium-based LDPs to show the structural evolution with different choices for the organic cation, the metal and the halide; these have a strong influence on the optical properties. The LDPs specifically exhibit high structure tunability, with a wide range of (1+) and (3+) metal choices, and are exempt from some of the limitations of 3D double perovskite. In the last section, we introduce the recent progress on hybrid transition-metal-based ferroelectrics and spintronic materials. We successfully demonstrate the utilization of chiral Cu(II) chlorides for circularly polarized light (CPL) detection, showing the high anisotropy of the photoresponsivity. We also highlight the work that the authors have contributed in these areas and suggest several exciting opportunities for future developments.