C2 Axis Research Articles

Magnetic circular dichroism of f-f electron transitions in Ho3+ and Nd3+ ions in antiferromagnetic crystal Ho0.75Nd0.25Fe3(BO3)4 in the region of spin-reorientation transition

Absorption and magnetic circular dichroism (MCD) spectra have been studied in the region of 5I8 → 5F2, 5S2, 5F3, and 5F5 absorption bands of the Ho3+ ion and in the region of 4I9/2→4G7/2, 2K13/2, 4S3/2, 4F7/2, 4F5/2 and 2H9/2 absorption bands of the Nd3+ ion in an antiferromagnetic trigonal crystal Ho0.75Nd0.25Fe3(BO3)4 in the temperature range from 5 to 90 K. A qualitative change in the shape of the MCD spectra of Ho3+ ion was revealed during the spin-reorientation transition at TR = 6.9 К. Below TR, in the easy-axis state of the crystal, the MCD spectrum has a shape typical for paramagnets, i.e., it consists of diamagnetic and paramagnetic parts. Just above TR, in the easy-plane state of the crystal, MCD of Ho3+ ion has a spectrum similar to the absorption spectrum, which is typical for the paramagnetic part of the MCD. It was shown, that in the easy-plane state the exchange field of iron, being perpendicular to the external field directed along the C3 axis, quenches the usual paramagnetic and diamagnetic MCD in Ho3+ ion, but creates a condition for the appearance of a large paramagnetic MCD of mixing (B-term). With temperature increasing, the MCD spectrum of Ho3+ ion gradually turns into a spectrum typical for paramagnets with the predominance of the sign-changing diamagnetic part, because the influence of the exchange field decreases. The shape of the MCD spectra of Nd3+ ions are typical for paramagnets but does not change during the reorientation transition in the rest of the crystal. This means that the magnetic moment of the Nd3+ ion does not make a reorientation transition simultaneously with the Fe3+ and Ho3+ ions of the rest of the crystal. This phenomenon is accounted for by a strong local magnetic anisotropy of the Nd3+ ion and by a weak exchange interaction Fe-Nd, which is not enough for rotation of the Nd3+ ion moment synchronously with that of the Fe3+ ion. The magneto-optical properties of neodymium are controlled by the easy-axis anisotropy of neodymium.

Osmium(III) Acetylacetonate and Its Missing Polymorph: A Magnetic and Structural Investigation.

Despite the potential for their application, the magnetic behavior of complexes containing 4d and 5d metal ions is underexplored, evidencing the need for benchmark multi-technique studies on simple molecules. We report here a structural and magnetic study on osmium(III) acetylacetonate [Os(acac)3]. X-ray single crystal diffraction did not allow us to determine the structure of the β-polymorph of [Os(acac)3]. The combined magnetic (dc magnetic measurements on powder and cantilever torque magnetometry on single crystal) and spectroscopic (electron paramagnetic resonance, EPR) characterization is here used to provide further evidence that its structure is indeed the one of the orthorhombic "missing polymorph", analogous to the ruthenium(III) derivative. Our study shows that all acetylacetonate complexes of the eighth group of the periodic table show dimorphism and are isomorphic. The EPR characterization allowed the experimental assessment of the easy axis nature of the ground doublet and the determination of the first hyperfine coupling in an osmium complex. Torque magnetometry, applied here for the first time on an osmium-based molecule, determined the orientation of the easy axis along the pseudo C3 axis of the complex. Ac magnetometric measurements revealed in-field slow relaxation of the magnetization further slowed by the suppression of dipolar fields via magnetic dilution in the isostructural gallium(III) analogue.

Ab Initio Investigation of Tetrel Bonds in Isolated Complexes Formed Between a Lewis Acid H3MX, M-O or M-S (M = Si, Ge, or Sn) and the Lewis Bases B = N2, CO, HCCH, PH3, C2H4, HCN, CS, HNC, NP, H2O, and NH3.

Isolated complexes of the type B⋯A in which the noncovalent interaction is a tetrel bond have been characterized by ab initio calculations at the CCSD(T)(F12c)/cc-pVDZ-F12 level. The Lewis bases B involved were N2, CO, HCCH, PH3, C2H4, HCN, CS, HNC, NP, H2O and NH3. Two types of Lewis acid A were examined, each containing one of the tetrel atoms M = Si, Ge or Sn, The Lewis acids in the first series were the H3MX (X = F, Cl, CN, H), in each of which the most electrophilic region was found to lie on the C3 axis of the C3v molecules, near to the tetrel atom M. In the second series the Lewis acids were M-O and M-S. Graphs, consisting of calculated equilibrium dissociation energies De of each B⋯H3MX complex plotted against the nucleophilicities NB of the Lewis bases B, were used to obtain the electrophilicity EH3MX of each molecule H3MX (M = Si, Ge, Sn). The molecular electrostatic surface of potentials of the molecules M-S and M-O (M = Si, Ge, Sn) revealed that many of the B⋯M-S and B⋯M-O complexes should have a tetrel bond to M in which the axis of the M-S or M-O subunit should be approximately perpendicular to the axis of the nonbonding or π-bonding electron pair carried by B, a novel type of tetrel bond confirmed by geometry optimizations of the complexes.

Jahn-Teller effect and features of divalent copper ion behavior in multicomponent borate crystals

Crystals of YGa3(BO3)4, YAl3(BO3)4, EuGa3(BO3)4 and EuAl3(BO3)4 with copper alloy were studied by electron paramagnetic resonance and X-ray diffraction analysis. The lattice parameters and coordinates of copper-doped boron atoms were determined. The study of EPR spectra showed that copper is in the divalent state and replaces aluminum ions with C2 node symmetry. In YAl3(BO3)4:Cu crystals, a ligand structure exists due to the interaction of copper electrons with yttrium nuclei. The parameters of the spin Hamiltonian describing the behavior of the Cu2+ spectrum have been determined. The deviation of the Z-axis spectra from the C3 axis by 54(1)° is due to Jahn-Teller vibronic interaction and monoclinic distortion. In the EuGa3(BO3)4 crystal, a new spectrum 2 was found, which also belongs to divalent copper but is observed at an excited state 31 cm−1 away from the ground state. Above 70 K, an isotropic EPR line with a width of 450 Gs, g = 2.1, appears and exists up to room temperature.

High-resolution spectroscopy of LaAlO3-Pr3+ pseudo-cubic perovskite single crystals: Crystal-field parameters, hyperfine and deformation splittings

We report high-resolution measurements and analysis of the optical transmission and emission spectra of a concentration series of La(1-x)PrxAlO3 (x = 10−3, 9 ⋅ 10−3, and 2 ⋅ 10−2) single crystals in a wide frequency range ((2-27) ⋅ 103 cm−1) at temperatures 5–300 K, below the structural phase transition from the cubic Pm3‾m to the rhombohedral R3‾c phase. Pr3+ ions substitute for La3+ ions at sites with point symmetry D3. All recorded spectral lines are assigned to specific initial and final crystal-field (CF) energy levels, the scheme of CF levels is constructed and described by an appropriate set of CF parameters. The structural phase transition is accompanied by shear strains and the formation of ferroelastic twin domains of four types compressed along one of the four C3 axes in the parent cubic crystal lattice. Specific features of the measured spectra, namely, anomalous broadening of spectral lines and doublet structure of some lines corresponding to transitions between CF singlets and doublets, are considered as a result of interaction of 4f electrons with the field of random shear deformations competing at the boundaries of twin domains. Modeling of the observed line shapes was performed taking into account both hyperfine interactions and random lattice strains, as well as the effect of temperature. The width (6.6 ± 0.7)⋅10− 4 of the introduced two-dimensional distribution function of random strains was found from a comparison of simulated and measured profiles of the split spectral lines. The results of this work can be applied for quantitative assessment of crystal quality.

One-Pot Synthesis of Diverse Anion-Binding Macrocycles

AbstractA one-pot synthetic protocol to access a diverse library of diamide–diester macrocycles from the same starting materials is reported. The molecular symmetry can be readily tuned based on the reaction sequence, while the core structure can be varied using amino acids and aromatic building blocks. The first class of macrocycles with C2 axes in their molecular plane were obtained in 24 h with 40–70% yield, while another class with C2 axes perpendicular to the plane were synthesized in 18 h in 10–30% yield. The phenyl- and serine-derived macrocycles of the first class could bind acetate, chloride, and phosphate ions. These macrocycles can be functionalized with hydrophobic groups and potentially be used as ion transporters.

Classical versus Collective Interactions in Asymmetric Trigonal Bipyramidal Alkaline Metal-Boron Halide Complexes.

Collective interactions are a novel type of chemical bond formed between metals and electron-rich substituents around an electron-poor central atom. So far only a limited number of candidates for having collective interactions are reported. In this work, we extend the newly introduced concept of collective bonding to a series of neutral boron complexes with the general formula M2BX3 (M=Li, Na, and K; X=F, Cl, and Br). Our state-of-the-art ab initio computations suggest that these complexes form trigonal bipyramidal structures with a D3h to C3v distortion along the C3 axis of symmetry. The BX3 unit in the complexes distorts from planar to pyramidal akin to a sp3 hybridized atom. Interestingly, the interaction of the metals with the pyramidal side of BX3, where the lone pair in a hypothetical [BX3]2- should be located, is weaker than the interactions of metals with the inverted side, i. e., the middle of three halogen atoms. The origin of this stronger interaction can be explained by the formation of collective interactions between metals and halogen atoms as we explored via energy decomposition within the context of the theory of interacting quantum atoms, IQA.

Engineering Clock Transitions in Molecular Lanthanide Complexes.

Molecular lanthanide (Ln) complexes are promising candidates for the development of next-generation quantum technologies. High-symmetry structures incorporating integer spin Ln ions can give rise to well-isolated crystal field quasi-doublet ground states, i.e., quantum two-level systems that may serve as the basis for magnetic qubits. Recent work has shown that symmetry lowering of the coordination environment around the Ln ion can produce an avoided crossing or clock transition within the ground doublet, leading to significantly enhanced coherence. Here, we employ single-crystal high-frequency electron paramagnetic resonance spectroscopy and high-level ab initio calculations to carry out a detailed investigation of the nine-coordinate complexes, [HoIIIL1L2], where L1 = 1,4,7,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraaza-cyclododecane and L2 = F- (1) or [MeCN]0 (2). The pseudo-4-fold symmetry imposed by the neutral organic ligand scaffold (L1) and the apical anionic fluoride ion generates a strong axial anisotropy with an mJ = ±8 ground-state quasi-doublet in 1, where mJ denotes the projection of the J = 8 spin-orbital moment onto the ∼C4 axis. Meanwhile, off-diagonal crystal field interactions give rise to a giant 116.4 ± 1.0 GHz clock transition within this doublet. We then demonstrate targeted crystal field engineering of the clock transition by replacing F- with neutral MeCN (2), resulting in an increase in the clock transition frequency by a factor of 2.2. The experimental results are in broad agreement with quantum chemical calculations. This tunability is highly desirable because decoherence caused by second-order sensitivity to magnetic noise scales inversely with the clock transition frequency.

Reorientational Dynamics in Y(BH4)3·xNH3 (x = 0, 3, and 7): The Impact of NH3 on BH4- Dynamics.

The reorientational dynamics of Y(BH4)3·xNH3 (x = 0, 3, and 7) was studied using quasielastic neutron scattering (QENS) and neutron spin echo (NSE). The results showed that changing the number of NH3 ligands drastically alters the reorientational mobility of the BH4- anion. From the QENS experiments, it was determined that the BH4- anion performs 2-fold reorientations around the C2 axis in Y(BH4)3, 3-fold reorientations around the C3 axis in Y(BH4)3·3NH3, and either 2-fold reorientations around the C2 axis or 3-fold reorientations around the C3 axis in Y(BH4)3·7NH3. The relaxation time of the BH4- anion at 300 K decreases from 2 × 10-7 s for x = 0 to 1 × 10-12 s for x = 3 and to 7 × 10-13 s for x = 7. In addition to the reorientational dynamics of the BH4- anion, it was shown that the NH3 ligands exhibit 3-fold reorientations around the C3 axis in Y(BH4)3·3NH3 and Y(BH4)3·7NH3 as well as 3-fold quantum mechanical rotational tunneling around the same axis at 5 K. The new insights constitute a significant step toward understanding the relationship between the addition of ligands and the enhanced ionic conductivity observed in systems such as LiBH4·xNH3 and Mg(BH4)2·xCH3NH2.

Atlanto-occipital fusion: Case report

The article discusses cranio-cervical joints, specifically the atlanto-occipital and atlantoaxial joints. The atlanto-occipital joints include the occipital condyle and the superior articular surfaces of the first cervical vertebra (C1 or Atlas), allowing flexion, extension and lateral tilt of the head. The atlantoaxial joints include C1 and C2 (Axis) vertebrae, enabling rotation. Atlanto-occipital fusion is a rare congenital condition in which C1 fuses with the occipital bone of the skull. This can lead to narrowing of the Foramen Magnum, with or without compression of central structures (spinal cord or brain stem). Although this condition can be asymptomatic, when associated with other cranio-cervical anomalies, such as Basilar Invagination and Platybasia, it can bring instability to the neck, in addition to tonsillar herniation, neural compression and cerebral ischemia. This condition is related to an embryonic malformation of the Pro Atlas, which can occur in different regions of the joint. Furthermore, the type of fusion can vary, eventually resulting in stress at the C1-C2 junction, leading to subluxations and neurovascular complications. Despite its rarity, preoperative diagnosis using computed tomography or magnetic resonance imaging is essential to identify these changes and avoid injuries during surgery. In conclusion, atlanto-occipital fusion is a rare condition that, when associated with other anomalies, can cause damage to the central nervous system, highlighting the importance of adequate diagnosis and treatment. The objective of the study is to illustrate, discuss and investigate the prevalence of atlanto-occipital fusion in human skulls, which the authors found one case among the 117 skulls analyzed.

Opticheskiy lineynyy dikhroizm v ab-ploskosti ferroborata NdFe3(BO3)4

he high-resolution optical absorption spectra of NdFe3(BO3)4 single crystals have been recorded at temperatures from 4 to 40 K in the IR range of f–f transitions in a Nd3+ ion. Light linearly polarized at different angles to the C2 axes in the basal plane has been passed along the trigonal C3 axis. Below the temperature of magnetic moment ordering into a collinear antiferromagnetic structure (TN ≈ 30 K), dichroism, that is, the absorption versus polarization dependence, arises. The temperature and angular dependences of dichroism indicate that the magnetic moments of iron are directed along the C2 axes up to about 17 K, the number of domains with variously directed C2 axes being different. The mechanism of linear dichroism has been discussed. Below 17 K, a smooth transition to the helicoidal magnetic phase has been observed, with the collinear phase coexisting with the helicoidal one. Data presented in this article contradict the earlier concept of magnetic moments fluctuating in the low-temperature phase near the C2 axis within the ±10° interval.

Reactivity Studies of Cyclic Alkyl(Amino) Carbene (cAAC)‐Supported Phosphinidenide with AuCl

AbstractA neutral octa‐nuclear AuI‐cluster (2) with molecular formula [(Cy‐cAACPAu)4(AuCl)4] [Cy‐cAAC=:C(N‐2,6‐iPr2C6H3)(C6H10)(CMe2)(CH2)] has been isolated, and structurally characterized by single‐crystal X‐ray diffraction. 2 has been further studied by NMR and ESI‐MS. The μ3‐P bridged AuI‐cluster 2 possesses a C2 axis that passes through the two Au atoms positioned oppositely of the central AuI4P4 core, and two carbene‐P chromophores. The emission spectrum of 2 exhibited a broad band with λem at 720 nm, and an average lifetime of 3.36 ns when excited at 388 nm in solid state at room temperature. Cyclic voltammetry (CV) studies revealed that 2 can undergo reversible one‐electron oxidation at 0.76 V. The electronic transition in 2 has been further studied by computational methods.

A strategy for designing temperature-sensitive complexes based on ligand vibration rotation mode control

Copper(I) and 3,5-dimethyl-1,2,4-triazole ligands construct the isomers α-Cu(mdtz) and β-Cu(mdtz), respectively. In α-Cu(mdtz), the hexagonal ring structure composed of Cu(I) and N atoms restricts the vibrational rotation of the triazole ring structure and reduces the nonradiative transition, achieving a high internal quantum efficiency at room temperature and pressure (IQY = 72.3%). As for β-Cu(mdtz), the triazole ring can rotate back and forth along its own C2 axis within a certain angle. We investigated the comparison of the luminescence spectra of α-Cu(mdtz) and β-Cu(mdtz) at different temperatures, confirmed that the vibrational rotation of the triazole ring improved the sensitivity of the luminescence intensity and spectral broadening to the temperature response, especially at low temperatures. In addition, we found that the decay time of Cu(mdtz)s varies linearly with temperature in a certain temperature interval, which provides strategy for temperature measurement based on the luminescence lifetime. Besides, the non-porous structure of Cu(mdtz)s prevents oxygen from entering the structure and protects the luminescent center from oxygen, thus improving the accuracy of temperature measurement in atmospheric environments.

Synthesis, crystal structure, and intrinsic reactivity descriptors of coordination complexes of [(cis-PdCl2·L-proline) L-proline] and [trans-PdCl2·(glycine-OMe)2

This work describes the synthesis and structural characterization of two palladium (II) complexes elucidated by infrared spectroscopy, dispersive energy analysis (EDS) with Scanning Electron Microscopy (SEM) and X-ray single-crystal diffraction analysis. The first chiral complex is derivatized from l-proline amino acid, obtaining [Cis-PdCl2·L-proline(L-proline)] (1), in which the structure does not have symmetry elements and crystallized in a triclinic crystal system on a non-centrosymmetric space group P1. The comparison with the structural complex of [trans-PdCl2·(glycine-OMe)2] (3) becomes necessary due to the anticancer activity of its analog, cis-platinum, and the catalytic activity caused by Pd as a metallic center. Complex 1 is therefore made up of a free proline molecule linked by a single hydrogen bond to a PdCl2 molecule forming a 5-member chelate ring of the COO···Pd···NH type with another proline molecule and displaying distorted angles and bond sizes to the square planar geometry of the palladium (Pd) center. Ring formation generates a new stereogenic center chemically correlated with the induction caused by the absolute configuration S of the initial amino acid. The crystal results strongly indicate the confirmed configuration by the Flack parameter and its crystal packing stabilization by an intermolecular H-bond network, highlighting as a secondary mimicking structure the β sheets formed by hydrogen bonding interaction of the N—H···Cl type responsible for the disorder moldered on pyrrolidine ring.Furthermore, the Pd(II) complex obtained by the glycine was [trans-PdCl2·(glycine-OMe)2] (3). Regarding its chemical structure, this complex is constituted by the union of two glycine methyl ester molecules binding to a Pd in a trans disposition concerning the almost perfect square plane, which also contains a C2 axis of rotation. Complex 3 crystallized in a monoclinic system and centrosymmetric space group P21/c, the packing is favored by four strong hydrogen bond type interactions presenting helices with 90° rotations between each layer.Owing to their great interest and relevance in Pd—N amino acid in catalytic and medicinal chemistry, the electronic and global reactivity properties of complexes 1 and 3 were further explored by computational methods in the framework of Density Functional Theory, finding 1 as the most reactive complex due to the narrower E-LUMO/E-HOMO energy gap, having this band gap in agreement with the lowest hardness value compared to those shown for 3, in which band gap and hardness are higher with a tendency to kinetic stability and controlled reactivity.

Theoretical studies on the g-factors and the local structure of W5+ ions in tungsten phosphate glasses

In this work, we adopt the three-order perturbation formulae for g-factors (g//, g^) of d1 ions in the octahedral environment to calculate the g-factors of W5+ ions in tungsten phosphate glasses containing lithium (P2O5-Li2WO4-Li2O). In the light of the high valence state of the studied W5+ centers and hence the strong covalency of the studied octahedral [WO6]7- cluster, we consider the contributions to g-factors from the ligand orbital and spin-orbit (SO) coupling interactions based on the cluster approach. The required tetragonal crystal-field parameters are calculated from the local structure of W5+ ions based on the superposition model. According to the theoretical calculations, we find that the octahedral [WO6]7- clusters possess the tetragonally compressed distortion with a shorter W-O bond length (≈1.54 Å) and a longer one (≈2.26 Å) along C4 axis and four normal W-O bond length (≈1.94 Å) in the perpendicular plane, which infers that the W5+ ions are in the form of tungstyl ions (i.e., WO3-). Based on the local structural data, the theoretical values of g// and g^ agree well with the experimental values.

Structural Evolution of Paramagnetic Lanthanide Compounds in Solution Compared to Time- and Ensemble-Average Structures.

Anisotropy in the magnetic susceptibility strongly influences the paramagnetic shifts seen in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) experiments. A previous study on a series of C3-symmetric prototype MRI contrast agents showed that their magnetic anisotropy was highly sensitive to changes in molecular geometry and concluded that changes in the average angle between the lanthanide-oxygen (Ln-O) bonds and the molecular C3 axis due to solvent interactions had a significant impact on the magnetic anisotropy and, consequently, the paramagnetic shift. However, this study, like many others, was predicated on an idealized C3-symmetric structural model, which may not be representative of the dynamic structure in solution at the single-molecule level. Here, we address this by using ab initio molecular dynamics simulations to simulate how the molecular geometry, in particular the angles between the Ln-O bonds and the pseudo-C3 axis, evolves over time in the solution, mimicking typical experimental conditions. We observe large-amplitude oscillations in the O-Ln-C̃3 angles, and complete active space self-consistent field spin-orbit calculations show that this leads to similarly large oscillations in the pseudocontact (dipolar) paramagnetic NMR shifts. The time-averaged shifts show good agreement with experimental measurements, while the large fluctuations suggest that an idealized structure provides an incomplete description of the solution dynamics. Our observations have significant implications for modeling the electronic and nuclear relaxation times in this and other systems where the magnetic susceptibility is exquisitely sensitive to the molecular structure.

Rotational Spectroscopy Probes Lone Pair···π-Hole Interactions in Hexafluorobenzene-Tertiary Alkylamines Complexes.

We employed microwave spectroscopy to investigate the 1:1 complexes of hexafluorobenzene with trimethylamine and quinuclidine, respectively. These complexes exhibit a C3v symmetry and are stabilized by nitrogen lone pair···π-hole interactions along the C3 axes. The N···π-center distances were determined to be 3.110(1) and 3.040(2) Å, respectively, which are shorter than that of hexafluorobenzene-ammonia at 3.2685(3) Å. Additionally, the strength of the intermolecular interaction increases with cluster size. While it was initially expected that the electron-donating effect of alkyl groups was responsible for changing the N···π interaction, the symmetry-adapted perturbation theory analysis revealed that, from hexafluorobenzene-ammonia to both hexafluorobenzene-alkylamines, electrostatic interaction actually decreases while dispersion interaction increases and becomes dominant. Interestingly, dispersion interaction decreases while electrostatic interaction increases from C6F6-N(CH3)3 to C6F6-NC7H13. The splitting pattern of the spectra indicates hexafluorobenzene rotates freely relative to its partners along the axis of the N···π-hole interactions.

Minimizing Bond Angle Distortion to Improve Thermal Stability of Cr3+ Doped Near‐Infrared Phosphor

AbstractBroadband near‐infrared (NIR) phosphor‐converted light‐emitting diodes are next‐generation smart NIR light sources. However, the NIR phosphor suffers from serious thermal quenching (TQ), resulting in efficiency reduction and spectral shift. Here, a novel strategy is realized to suppress TQ by minimizing bond angle distortion, completely different from the conventional TQ suppression approach through bond length variation. Li(Sr1−xCax)AlF6:Cr3+ NIR phosphor is taken as an example in which rotation between the two parallel fluorine planes perpendicular to the C3 axis in the [AlF6] octahedron is found to dominate TQ. Increasing x from 0 to 1 reduces the amplitude of the rotation from 16.17° to 5.06°, weakening the electron–phonon coupling and, consequently, raising the TQ temperature significantly from 320 to 570 K. This mechanism is elucidated from both theoretical calculations and spectroscopic studies. The findings open a new horizon for the exploration of thermally stable NIR phosphors.

Cross-Cultural Teachings from Cremation Practices: Atmaram for the Departed, Shiva Linga for the Living, and Odontoid Fracture for the Neurosurgeons!

Atmaram bone (C2 axis vertebra) is usually handed over to the family of the deceased on the next day after cremation during the ''Asthi sanchaya '' commemoration. ''Asthi visarajan'' involves the practice of immersing the bones and ashes of the deceased in the Holy Ganges river as per Hindu beliefs. Atmaram bone, which usually does not burn during cremation, is handed over to the family of the departed (asthi sanchaya) after cremation which is then immersed in the holy Ganges river ( asthi visarajan). Atma means soul, Ram means Lord and Atmaram combined means the one who is Lord of his own soul." Worshiping of Lord Shiva (while living) and Asthi sanchaya-Asthi visarajan (of the departed) are two religious venerations in Hinduism. Atmaram bone was handed over to me for immersion in the holy Ganges on November 6, 2020, after conducting the asthi sanchaya of my mother during the coronavirus disease 2019 (COVID-19) pandemic. Atmaram bone looked like a Shivalinga statue to most who looked at it, whereas it resembled the image of the axis vertebrae (C2 vertebra) to me when I saw it that sacred day. Atmaram bone, the Shivalinga, and the C2 axis vertebra are among the most precious and sacred objects that humans can handle as relatives, as devotees, and as neurosurgeons, respectively. Asclepius, possibly a skilled war surgeon/neurosurgeon, was worshipped at Asclepieia. Trephination surgery in neurosurgery and religion are intertwined historically. Though there is no published literature, neurosurgeons in various parts of the world do offer religious prayers prior to major neurosurgical operations. In line with the religious veneration of worshipping Shiva Ling or immersion of bones of the departed soul in the Holy Ganges river, we believe it is the sacred responsibility of the operating neurosurgeon to perform surgery in complex craniovertebral junction. As neurosurgeons, we cannot ignore the axis in the living, the odontoid fracture in the injured, and the Atmaram in the deceased.

Determinative Effect of Axial Linearity on Single-Molecule Magnet Performance in Dinuclear Dysprosium Complexes.

Two dichloride-bridged dinuclear dysprosium(III) complexes based on salen ligands, namely, [Dy(L1 )(μ-Cl)(thf)]2 (1; H2 L1 =N,N'-bis(3,5-di-tert-butylsalicylidene)phenylenediamine) and [Dy2 (L2 )2 (μ-Cl)2 (thf)2 ]2 (2; H2 L2 =N,N'-bis(3,5-di-tert-butylsalicylidene)ethylenediamine) are reported. These two complexes have two short Dy-O(PhO) bonds that exhibit angles of ∼90° for 1 and ∼143° for 2, leading to clear slow relaxation of the magnetization for 2 and not for 1. Compound 2 has a near-identical core to the recently reported compound [Dy2 (L3 )2 (μ-Cl)2 (thf)2 ] (3; H2 L3 =N-(2-pyridylmethyl)-N,N-bis(2'-hydroxy-3',5'-di-tert-butylbenzyl)amine). The only substantial difference is the relative angle of the two O(PhO) -Dy-O(PhO) vectors, which is collinear in 2 owing to inversion symmetry and ∼68° in 3 due to a molecular C2 axis. It is shown that this subtle structural difference leads to large differences in the dipolar ground states, giving rise to open magnetic hysteresis for 3 and not for 2.