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DOE OSTI2022

Ferromagnetic MnBi 4 Te 7 obtained with low-concentration Sb doping: A promising platform for exploring topological quantum states

The tuning of the magnetic phase, chemical potential, and structure is crucial to observe diverse exotic topological quantum states in Mn Bi 2 Te 4 (Bi 2 Te 3 ) m (m = 0–3). Here we show a ferromagnetic (FM) phase with a chiral crystal structure in Mn (Bi 1–x Sb x ) 4 Te 7 , obtained via tuning the growth conditions and Sb concentration. Unlike previously reported Mn (Bi 1–x Sb x ) 4 Te 7 , which exhibits FM transitions only at high Sb doping levels, our samples show FM transitions (T C = 13.5 K) at 15%–27% doping levels. Furthermore, our single-crystal x-ray-diffraction structure refinements find Sb doping leads to a chiral structure with the space group of P3, contrasted with the centrosymmetric $P\bar{3}m1$ crystal structure of the parent compound MnBi 4 Te 7 . Through angle-resolved photoemission spectroscopy measurements, we also demonstrated that the nontrivial band topology is preserved in the Sb-doped FM samples. Given that the nontrivial band topology of this system remains robust for low Sb doping levels, our success in making FM Mn(Bi 1–x Sb x ) 4 Te 7 with x = 0.15, 0.175, 0.2, and 0.27 paves the way for realizing the predicted topological quantum states, such as the axion insulator and Weyl semimetals. Additionally, we also observed magnetic glassy behavior in both antiferromagnetic MnBi 4 Te 7 and FM Mn (Bi 1–x Sb x )4 Te 7 samples, which we believe originates from cluster spin-glass phases coexisting with long-range antiferromagnetic/FM orders. Further, we have also discussed how the antisite Mn ions impact the interlayer magnetic coupling and how FM interlayer coupling is stabilized in this system.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Single crystal synthesis and magnetic properties of a Shastry-Sutherland lattice compound BaNd 2 ZnS 5

In this study, single crystals of a Shastry-Sutherland magnetic semiconductor, BaNd 2 ZnS 5 , were synthesized through a high-temperature solution growth technique. Physical properties were characterized by powder and single crystal x-ray diffraction, temperature- and field-dependent magnetization, and temperature-dependent specific heat measurements. BaNd 2 ZnS 5 orders antiferromagnetically at 2.9 K, with magnetic moments primarily aligned within the $ab$ -plane. Magnetic isothermal measurements show metamagnetic transitions at ~ 15 kOe for the [110] direction and ~ 21 kOe for the [100] direction. Estimated magnetic entropy suggests a double ground state for each neodymium ion.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Unconventional magnetotransport and antiferromagnetic order in Eu 2 ⁢InTe 5

Here, we report on the structural characterization and physical properties of Eu 2 ⁢InTe 5 , a distorted square-net motif antiferromagnetic semiconductor. Single crystal x-ray diffraction measurements reveal a distortion of the Te square-net layers such that an orthorhombic supercell is necessary to accurately describe the structure. Magnetization, resistivity, and specific heat measurements confirm antiferromagnetic ordering at 𝑇 𝑁 = 7.3K. Anisotropy in magnetization data suggests the magnetic moments are oriented parallel to the 𝑐 axis. We observe an unconventional transverse magnetoresistance and Hall resistivity in the paramagnetic state (𝑇 ≤ 80K), indicating strong coupling between localized Eu 2+ magnetic moments and conduction electrons. Resistivity and Hall measurements indicate the material is a heavily doped semiconductor, with impurity states related to disorder. Our findings highlight a relatively unexplored Eu-based antiferromagnetic semiconductor with unconventional magnetotransport behavior.

Cook, Matthew S. [Oak Ridge National Laboratory (O↗

DOE OSTI2016

Observation of a re-entrant phase transition in the molecular complex tris(μ 2 -3,5-diisopropyl-1,2,4-triazolato-κ 2 N 1 : N 2 )trigold(I) under high pressure

We report a molecular crystal that exhibits four successive phase transitions under hydrostatic pressure, driven by aurophilic interactions, with the ground-state structure re-emerging at high pressure. The effect of pressure on two polytypes of tris(μ 2 -3,5-diisopropyl-1,2,4-triazolato-κ 2 N 1 : N 2 )trigold(I) (denoted Form-I and Form-II) has been analysed using luminescence spectroscopy, single-crystal X-ray diffraction and first-principles computation. A unique phase behaviour was observed in Form-I, with a complex sequence of phase transitions between 1 and 3.5 GPa. The ambient C 2/c mother cell transforms to a P 2 1 /n phase above 1 GPa, followed by a P 2 1 /a phase above 2 GPa and a large-volume C 2/c supercell at 2.70 GPa, with the previously observed P 2 1 /n phase then reappearing at higher pressure. The observation of crystallographically identical low- and high-pressure P 2 1 /n phases makes this a rare example of a re-entrant phase transformation. The phase behaviour has been characterized using detailed crystallographic theory and modelling, and rationalized in terms of molecular structural distortions. The dramatic changes in conformation are correlated with shifts of the luminescence maxima, from a band maximum at 14040 cm –1 at 2.40 GPa, decreasing steeply to 13550 cm –1 at 3 GPa. A similar study of Form-II displays more conventional crystallographic behaviour, indicating that the complex behaviour observed in Form-I is likely to be a direct consequence of the differences in crystal packing between the two polytypes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Crystal structure across the β to α phase transition in thermoelectric Cu 2– x Se

Here, the crystal structure uniquely imparts the specific properties of a material, and thus provides the starting point for any quantitative understanding of thermoelectric properties. Cu 2–x Se is an intensely studied high performing, non-toxic and cheap thermoelectric material, and here for the first time, the average structure of β-Cu 2–x Se is reported based on analysis of multi-temperature single-crystal X-ray diffraction data. It consists of Se–Cu layers with additional copper between every alternate layer. The structural changes during the peculiar zT enhancing phase transition mainly consist of changes in the inter-layer distance coupled with subtle Cu migration. Just prior to the transition the structure exhibits strong negative thermal expansion due to the reordering of Cu atoms, when approached from low temperatures. The phase transition is fully reversible and group–subgroup symmetry relations are derived that relate the low-temperature β-phase to the high-temperature α-phase. Weak superstructure reflections are observed and a possible Cu ordering is proposed. The structural rearrangement may have a significant impact on the band structure and the Cu rearrangement may also be linked to an entropy increase. Both factors potentially contribute to the extraordinary zT enhancement across the phase transition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Evolution of structure and spectroscopic properties of a new 1,3-diacetylpyrene polymorph with temperature and pressure

A new polymorph of 1,3-diacetylpyrene has been obtained from its melt and thoroughly characterized using single-crystal X-ray diffraction, steady-state UV–Vis spectroscopy and periodic density functional theory calculations. Experimental studies covered the temperature range from 90 to 390 K and the pressure range from atmospheric to 4.08 GPa. Optimal sample placement in a diamond anvil cell according to our previously presented methodology ensured over 80% data coverage up to 0.8 Å for a monoclinic sample. Unrestrained Hirshfeld atom refinement of the high-pressure crystal structures was successful and anharmonic behavior of carbonyl oxygen atoms was observed. Unlike the previously characterized polymorph, the structure of 2°AP-β is based on infinite π-stacks of antiparallel 2°AP molecules. 2°AP-β displays piezochromism and piezofluorochromism which are directly related to the variation in interplanar distances within the π-stacking. The importance of weak intermolecular interactions is reflected in the substantial negative thermal expansion coefficient of -55.8 (57) MK -1 in the direction of C—H∙∙∙O interactions.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Crystal structure refinements of tetragonal (OH,F)-rich spessartine and henritermierite garnets

Cubic garnet (space group Ia\overline 3 d) has the general formula X 3 Y 2 Z 3 O 12 , where X , Y and Z are cation sites. In the tetragonal garnet (space group I 4 1 / acd ), the corresponding cation sites are X 1 and X 2, Y , and Z 1 and Z 2. In both space groups only the Y site is the same. The crystal chemistry of a tetragonal (OH,F)-rich spessartine sample from Tongbei, near Yunxiao, Fujian Province, China, with composition X (Mn 2.82 Fe^{2+}_{0.14}Ca 0.04 ) Σ3 Y {Al 1.95 Fe^{3+}_{0.05}} Σ2 Z [(SiO 4 ) 2.61 (O 4 H 4 ) 0.28 (F 4 ) 0.11 ] Σ3 (Sps 94 Alm 5 Grs 1 ) was studied with single-crystal X-ray diffraction and space group I 4 1 / acd . The deviation of the unit-cell parameters from cubic symmetry is small [ a = 11.64463(1), c = 11.65481 (2) Å, c / a = 1.0009]. Point analyses and back-scattered electron images, obtained by electron-probe microanalysis, indicate a homogeneous composition. The Z 2 site is fully occupied, but the Z 1 site contains vacancies. The occupied Z 1 and Z 2 sites with Si atoms are surrounded by four O atoms, as in anhydrous cubic garnets. Pairs of split sites are O1 with F11 and O2 with O22. When the Z 1 site is vacant, a larger [(O 2 H 2 )F 2 ] tetrahedron is formed by two OH and two F anions in the O22 and F11 sites, respectively. This [(O 2 H 2 )F 2 ] tetrahedron is similar to the O 4 H 4 tetrahedron in hydrogarnets. These results indicate ^{X}{{\rm Mn}^ {2+}_{3}}\,^{Y}{\rm Al}_{2}^{Z}[({\rm SiO}_{4})_{2}({\rm O}_{2}{\rm H}_{2})_{0.5}({\rm F}_{2})_{0.5}]_{\Sigma3} as a possible end member, which is yet unknown. The H atom that is bonded to the O22 site is not located because of the small number of OH groups. In contrast, tetragonal henritermierite, ideally ^{X}{\rm Ca}_{3}\,^{Y}{\rm Mn}^{3+}_{2}\,^{Z}[({\rm SiO}_{4})_{2}({\rm O}_{4}{\rm H}_{4})_1]_{\Sigma3}, has a vacant Z 2 site that contains the O 4 H 4 tetrahedron. The H atom is bonded to an O3 atom [O3—H3 = 0.73 (2) Å]. Because of O2—Mn 3+ —O2 Jahn–Teller elongation of the Mn 3+ O 6 octahedron, a weak hydrogen bond is formed to the under-bonded O2 atom. This causes a large deviation from cubic symmetry ( c / a = 0.9534).

Antao, Sytle M.↗

DOE OSTI2022

Effects of composition and growth parameters on phase formation in multicomponent aluminum garnet crystals

The effects of composition on the phase formation of multicomponent garnet crystals grown via directional solidification by the micro-pulling-down method are studied. A relatively wide range of rare-earth (RE) average ionic radii (AIR) is explored by formulating ten compositions from the system (Lu,Y,Ho,Dy,Tb,Gd) 3 Al 5 O 12 . Crystals were grown at either 0.05 or 0.20 mm min -1 . The hypothesis is that multicomponent compounds with large AIR will form secondary phases as the single-RE aluminum garnets formed by larger Tb 3+ or Gd 3+ ; this will result in crystals of poor optical quality. Crystals with large AIR have a central opaque region in optical microscopy images, which is responsible for their reduced transparency compared to crystals with small AIR. Slow pulling rates suppress the formation of the opaque region in crystals with intermediate AIR. Powder and single-crystal X-ray diffraction and electron probe microanalysis results indicate that the opaque region is a perovskite phase. Scanning electron microscopy and energy dispersive spectroscopy measurements reveal eutectic inclusions at the outer surface of the crystals. Finally, the concentration of the eutectic inclusions increases with increasing AIR.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Polymorphism of Pb 5 (PO 4 ) 3 OH δ within the LK-99 mixture

During the synthetic exploration targeting the polycrystalline compound LK-99, an unexpected phase, Pb 5 (PO 4 ) 3 OH δ , was identified as a byproduct. We elucidated the composition of this compound through single-crystal X-ray diffraction analysis. Subsequent synthesis of the target compounds was achieved via high-temperature solid-state pellet reactions. The newly identified Pb 5 (PO 4 ) 3 OH δ has an orthorhombic crystal structure with space group Pnma , representing a unique structure differing from the hexagonal apatite phases of Pb 10 (PO 4 ) 6 O and Pb 5 (PO 4 ) 3 OH. Comprehensive temperature- and magnetic-field-dependent magnetization studies unveiled a temperature-independent magnetic characteristic of Pb 5 (PO 4 ) 3 OH δ . Solid-state nuclear magnetic resonance spectroscopy was employed to decipher the origins of the phase stability and confirm the presence of hydrogen atoms in Pb 5 (PO 4 ) 3 OH δ . These investigations revealed the presence of protonated oxygen sites, in addition to the interstitial water molecules within the structure, which may play critical roles in stabilizing the orthorhombic phase.

Xu, Mingyu (ORCID:0000000171386009)↗

DOE OSTI2017

Two novel bimetallic transition metal–uranyl one-dimensional coordination polymers with manganese(II) and cobalt(II) incorporating bridging diglycolate (2,2'-oxydiacetate) ligands

The crystal structures of two new bimetallic uranyl–transition metal compounds with diglycolic acid [or 2-(carboxymethoxy)acetic acid] have been hydrothermally synthesized and structurally characterized via single-crystal X-ray diffraction. The compounds, namely catena -poly[[[tetraaquamanganese(II)]-μ-2,2'-oxydiacetato-[dioxidouranium(VI)]-μ-2,2'-oxydiacetato] dihydrate], {[MnU(C 4 H 4 O 5 ) 2 O 2 (H 2 O) 4 ]·2H 2 O} n , and catena -poly[[[tetraaquacobalt(II)]-μ-2,2'-oxydiacetato-[dioxidouranium(VI)]-μ-2,2'-oxydiacetato] dihydrate], {[CoU(C 4 H 4 O 5 ) 2 O 2 (H 2 O) 4 ]·2H 2 O} n , both crystallize in the triclinic space group P -1. These compounds form one-dimensional chains via alternating uranyl and transition metal building units. The chains then assemble into three-dimensional supramolecular networks through several hydrogen bonds between water molecules and diglycolate ligands. Luminescence measurements were conducted and no uranyl emission was observed in either compound.

nuclear (including radiation effects), materials a↗

DOE OSTI2018

On the effect of Ga and In substitutions in the Ca 11 Bi 10 and Yb 11 Bi 10 bismuthides crystallizing in the tetragonal Ho 11 Ge 10 structure type

The Ga- and In-substituted bismuthides Ca 11 Ga x Bi 10– x , Ca 11 In x Bi 10– x , Yb 11 Ga x Bi 10– x , and Yb 11 In x Bi 10– x ( x < 2) can be readily synthesized employing molten Ga or In metals as fluxes. They crystallize in the tetragonal space group I 4/ mmm and adopt the Ho 11 Ge 10 structure type (Pearson code tI 84; Wyckoff sequence n 2 m j h 2 e 2 d ). The structural response to the substitution of Bi with smaller and electron-poorer In or Ga has been studied by single-crystal X-ray diffraction methods for the case of Ca 11 In x Bi 10– x [ x = 1.73 (2); octabismuth undecacalcium diindium]. The refinements show that the In atoms substitute Bi only at the 8 h site. The refined interatomic distances show an unconventional – for this structure type – bond-length distribution within the anionic sublattice. The latter can be viewed as consisting of isolated Bi 3- anions and [In 4 Bi 8 20- ] clusters for the idealized Ca 11 In 2 Bi 8 model. Formal electron counting and first-principle calculations show that the peculiar bonding in this compound drives the system toward an electron-precise state, thereby stabilizing the observed bond-length pattern.

Chemistry↗

DOE OSTI2018

Zirconium tetrachloride revisited

We present that zirconium tetrachloride, ZrCl 4 , is a strategic material with wide-ranging applications. Until now, only one crystallographic study on ZrCl 4 has been reported [Krebs (1970). Z. Anorg. Allg. Chem. 378 , 263–272] and that was more than 40 years ago. The compound used for the previous determination was prepared from ZrO 2 and Cl 2 –CCl 4 , and single-crystal X-ray diffraction (SCXRD) studies on ZrCl 4 obtained from Zr metal have not yet been reported. In this context, we prepared ZrCl 4 from the reaction of Zr metal and Cl 2 gas in a sealed tube and investigated its structure at 100, 150, 200, 250, and 300 K. At 300 K, the SCXRD analysis indicates that ZrCl 4 crystallizes in the orthorhombic space group Pca 2 1 [ a = 6.262 (9), b = 7.402 (11), c = 12.039 (17) Å, and V = 558.0 (14) Å 3 ] and consists of infinite zigzag chains of edge-sharing ZrCl 6 octahedra. This chain motif is similar to that observed previously in ZrCl 4 , but the structural parameters and space group differ. Finally, in the temperature range 100–300 K, no phase transformation was identified, while elongation of intra-chain Zr...Zr [3.950 (1) Å at 100 K and 3.968 (5) Å at 300 K] and inter-chain Cl...Cl [3.630 (3) Å at 100 K and 3.687 (9) Å at 300 K] distances occurred.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Synthesis, structural characterization and luminescence properties of 1-carboxymethyl-3-ethylimidazolium chloride

A microcrystalline carboxyl-functionalized imidazolium chloride, namely 1-carboxymethyl-3-ethylimidazolium chloride, C 7 H 11 N 2 O 2 + ·Cl – , has been synthesized and characterized by elemental analysis, attenuated total reflectance Fourier transform IR spectroscopy (ATR-FT-IR), single-crystal X-ray diffraction, thermal analysis (TGA/DSC), and photoluminescence spectroscopy. In the crystal structure, cations and anions are linked by C—H...Cl and C—H...O hydrogen bonds to create a helix along the [010] direction. Adjacent helical chains are further interconnected through O—H...Cl and C—H...O hydrogen bonds to form a (101¯) layer. Finally, neighboring layers are joined together via C—H...Cl contacts to generate a three-dimensional supramolecular architecture. Thermal analyses reveal that the compound melts at 449.7 K and is stable up to 560.0 K under a dynamic air atmosphere. Photoluminescence measurements show that the compound exhibits a blue fluorescence and a green phosphorescence associated with spin-allowed ( 1 π← 1 π*) and spin-forbidden ( 1 π← 3 π*) transitions, respectively. As a result, the average luminescence lifetime was determined to be 1.40 ns for the short-lived ( 1 π← 1 π*) transition and 105 ms for the long-lived ( 1 π← 3 π*) transition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Niobium-bearing arsenides and germanides from elemental mixtures not involving niobium: a new twist to an old problem in solid-state synthesis

Three isostructural transition-metal arsenides and germanides, namely niobium nickel arsenide, Nb 0.92(1) NiAs, niobium cobalt arsenide, NbCoAs, and niobium nickel germanide, NbNiGe, were obtained as inadvertent side products of high-temperature reactions in sealed niobium containers. In addition to reporting for the very first time the structures of the title compounds, refined from single-crystal X-ray diffraction data, this article also serves as a reminder that niobium containers may not be suitable for the synthesis of ternary arsenides and germanides by traditional high-temperature reactions. Synthetic work involving alkali or alkaline-earth metals, transition or early post-transition metals, and elements from groups 14 or 15 under such conditions may yield Nb-containing products, which at times could be the major products of such reactions.

Chemistry↗

DOE OSTI2018

Crystal structure of the layered arsenide Rb 3 Cu 3 As 2

The crystal structure of a new arsenide, Rb 3 Cu 3 As 2 (trirubidium tricopper diarsenide), has been established from single-crystal X-ray diffraction data. This compound crystallizes in the K 3 Cu 3 P 2 type, with layers of interlinked CuAs 2 units. The partitioning of the available valence electrons yields the charge-balanced composition (Rb + ) 3 (Cu + ) 3 (As 3– ) 2 , placing this phase in a broad field of transition-metal-containing Zintl phases. First-principles calculations confirm a semiconducting ground state, in accordance with electron-counting considerations. Chemical bonding analysis reveals strong covalent Cu—As bonds and ionic Rb...As interactions. In addition, a weak attraction is found between the Cu atoms, possibly pointing toward cuprophilic interactions.

Chemistry↗

DOE OSTI2020

Fourfold alkyl wrapping of a copper(II) porphyrin thwarts macrocycle π–π stacking in a compact supramolecular package

Porphyrins are valuable constituents in optoelectronic, catalytic, and other applications, yet control of intermolecular π–π stacking is invariably essential to attain the desired properties. Superstructures built onto the porphyrin, often via meso -aryl groups, can afford facial encumbrance that suppresses π–π stacking, although some molecular designs have provided insufficient facial coverage and many have entailed cumbersome syntheses. In this study, a copper(II) porphyrin bearing four meso substituents, namely, {10,20-bis[2,6-bis(octyloxy)phenyl]-5,15-dibromoporphinato}copper(II), [Cu(C 64 H 82 Br 2 N 4 O 4 )], was prepared by metalation of the corresponding free-base porphyrin and was characterized by single-crystal X-ray diffraction. The crystal structure reveals a dihedral angle of 111.1 (2)° for the plane of the meso -aryl group relative to the plane of the porphyrin, with both aryl groups tilted in the same direction. Each of the four octyloxy groups exhibits a gauche conformation for the –OCH 2 CH 2 – unit but is extended with four or five anti (–CH 2 CH 2 –/H) conformations thereafter, causing each octyl group to span the dimension of the macrocycle. In a global frame of reference where the two Br atoms define the north/south poles and the two aryl groups are at antipodes on the equator, two octyl groups of one aryl unit project over the northern hemisphere (covering pyrroles A and B ), whereas those of the other aryl unit project over the southern hemisphere (covering pyrroles C and D ). Together, the four octyl groups ensheath the two faces of the porphyrin in a self-wrapped assembly. The closest approach of the Cu atom to an octyl methylene C atom (position 6) is 3.5817 (18) Å, the mean separations of neighboring porphyrin planes are 8.059 (4) and 4.693 (8) Å along the a and c axes, respectively, and the center-to-center distances between the Cu atoms of neighboring porphyrins are 10.2725 (4), 12.2540 (6), and 12.7472 (6) Å along the a , b , and c axes, respectively. The Hirshfeld surface analysis and two-dimensional (2D) fingerprint plots provide information concerning contact interactions in the supramolecular assembly of the solid crystal.

Chemistry↗

DOE OSTI2020

Synthesis, structural characterization, and electronic structure of the novel Zintl phase Ba 2 ZnP 2

The novel Zintl phase dibarium zinc diphosphide (Ba 2 ZnP 2 ) was synthesized for the first time. This was accomplished using the Pb flux technique, which allowed for the growth of crystals of adequate size for structural determination via single-crystal X-ray diffraction methods. The Ba 2 ZnP 2 compound was determined to crystallize in a body-centered orthorhombic space group, Ibam (No. 72). Formally, this crystallographic arrangement belongs to the K 2 SiP 2 structure type. Therefore, the structure can be best described as infinite [ZnP 2 ] 4– polyanionic chains with divalent Ba 2+ cations located between the chains. All valence electrons are partitioned, which conforms to the Zintl–Klemm concept and suggests that Ba 2 ZnP 2 is a valence-precise composition. In conclusion, the electronic band structure of this new compound, computed with the aid of the TB–LMTO–ASA code, shows that Ba 2 ZnP 2 is an intrinsic semiconductor with a band gap of ca 0.6 eV.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Step-stool conformation of a cyclic Schiff base derived from ethylenediamine and heptane-2,4,6-trione: evidence for partial hydrolysis in metal coordination

A Schiff base derived from ethylenediamine and heptane-2,4,6-trione, namely, 5,9,14,18-tetramethyl-1,4,10,13-tetraazacyclooctadeca-5,8,14,17-tetraene-7,16- dione (C 18 H 28 N 4 O 2 ), abbreviated H 4 daaden, was prepared and characterized for the first time by single-crystal X-ray diffraction. The atoms of the Schiff base occupy two different planes and thus the molecule is essentially nonplanar. An axis running through the C–C atoms of the ethylenediamine groups separate the two planes and these two planes are connected by bridging ethylene groups showing an angle of 117.34 (8)°. As a result, the side view of the molecule shows a ‘step-stool’ conformation. The nonplanar nature of the Schiff base plays an important role in metal coordination, which leads to partial hydrolysis of the ring structure

crystal structure↗