Structural Chemistry最新文献

Average crystallographic structures may disguise more complex packing modes, such as commensurate modulations that originate from coherent librational distortions of the lattice. These can be easily overlooked, with striking implications on the understanding of intermolecular interactions, provided that the crystal is described in terms of colorless symmetries. As shown in the 1970s by Kołakowski, lattice modulations with strong librational components can be understood in terms of colored group operations applied to pseudovector quantities, like rotation momenta. Here, we employ Kołakowski’s concepts of dynamic symmetry to computationally predict modulated distortions in crystalline acrylic acid. We show that periodic lattice distortions may indeed originate from a low-frequency phonon instability at the (Gamma) point of the first Brillouin zone. The packing of the corresponding molecular libration momenta is analogue to an antiferromagnetic ordering in the I_cbam Shubnikov group, which can be also described as a commensurate modulation emerging from (3 + 1)D Imcb(00γ)0s0 superspace structure with γ = 1. In the reciprocal lattice, the distortions produce exceptions to the systematic extinction rules, due to the scattering at commensurate Bragg points that derive from the reduced colorless symmetry. This evidence offers an easy strategy to look for such phenomena in X-ray experiments, also taking advantage of the sensitivity of modern area detectors. Implications on the onset of phase transitions in organic crystals are also discussed.

In a 1999 article of Structural Chemistry, the recently deceased J. Fraser Stoddart and two associates surveyed the interplay between the synthesis of functioning supramolecular systems and their X-ray crystallographic investigation. Furthermore, they charted the anticipated development and necessary work for creating “intelligent” materials with predetermined functions. This was part of Stoddart’s discoveries in creating molecular machines that brought him a share of the chemistry Nobel Prize in 2016.

Three new nickel-based representatives of the so-called “layered hydroselenite” family have been characterized by single-crystal X-ray diffraction. In addition to the (enH₂)[Ni(HSeO₃)₂Br₂], the last missing member of the ethylenediammonium – transition metal hydroselenite-halide family, we were able to characterize the first members of a new family of compounds based on the N,N′-dimethylethylenediammonium cations, (dmedaH₂)[Ni(HSeO₃)₂X₂], X = Cl and Br. We compare the structural peculiarities of layered hydroselenites “stuffed” by the (enH₂)²⁺ and (dmedaH₂)²⁺ cations and predict existence of new series in this peculiar layered family.

The current global energy demands and environmental concerns have highlighted the potential of hydrogen as a crucial component of a sustainable energy strategy for the twenty-first century. This research employed first-principles computations to investigate the perovskite-type hydrides NaXH₃ (X = Ni, Cu, Zn). The structural optimizations revealed negative formation energies, indicating their thermodynamic stability and synthesizability. The mechanical stability was studied using elastic constants, while the electronic properties were examined through band structures and partial densities of states, confirming their metallic nature. Bader partial charge analysis shed light on the charge transfer characteristics, and phonon dispersion curves demonstrated their dynamic stability. Importantly, these hydrides exhibit promising hydrogen storage capacities of 3.57, 3.38, and 3.31 wt% for NaXH₃ (X = Ni, Cu, and Zn), respectively. This study represents a novel exploration of these perovskite hydrides, potentially paving the way for further advancements in hydrogen storage technologies.

Two novel complexes, [Ni(dipic)₂](mea)₂(1) and [(dipic)(Cl)(μ-Cl)Cu₂(μ-Cl)(Cl)(dipic)](H₂O) (2), were prepared from mixed ligand in which pyridine-2,6-dicarboxylic acid (PDC or dipicolinic acid, dipic) has reacted with monoethanolamine (MEA) and also hydrochloric acid, respectively. In the complex-1, the dipic ligand containing ONO' donating atoms acted as a monodentate and for complex-2, it was recognized as a neutral state, and both complexes were crystallized in the triclinic space group P ī. The structure of the two complexes was assigned based on elemental and spectroscopic analysis, and also X-ray crystallographic techniques, and finally, the Ni(II) complex confirmed distorted octahedral, and each of the binuclear Cu(II) complexes was also recognized as having the same structure. Hirshfeld surface analysis (HSA) was studied for both complexes as well. According to the analysis report, it expressed the significant intermolecular interactions in packing, with O••H/H••O interactions being the largest (50.9%) for complex-1 and Cl••H/H••Cl interactions (30.1%) followed by H••O/O •••H Interactions (29.8%) of complex-2.

Monomethyl fumarate (MMF) is a harmful substance which could be toxic for healthy cells. Hence, it is a useful drug for treatment of multiple sclerosis (MS). Considering these, its safe transportation to the targeted tissues (applying a suitable carrier) is needed. Thus, in this work, the possibility of using cavitand container-shaped capsule as well as a number of nanosheets (derived from B₄C₅N₃ structure) for delivery and adsorption of MMF have been studied. The results have indicated that (except cavitand) the biggest values for E_ads and for recovery time (τ) belong to MMF + AlB₄C₅N₃ (− 18.04 eV, 17.68 s) and MMF + GaB₄C₅N₃ (− 17.59 eV, 8.22 s), respectively. Therefore, in opposition to the other considered derivatives, both of those two nanosheets (AlB₄C₅N₃ and GaB₄C₅N₃) could be used as sorbents and also as carriers for delivery of the MMF drug. In addition, the results showed that the cavitand structure could be applied as a good capsule for trapping MMF, while it would not be able to sense the existence of this drug.

A 1973 paper described a stable C₆₀ molecule of truncated icosahedral shape from Elena G. Galpern’s computations. It remained in the shadow until after the discovery of buckminsterfullerene in 1985. Ivan V. Stankevich contributed substantially to the computational study but his name did not figure among its authors. He was a pioneer in researching new allotropes of carbon.

A new series of palladium(II) complexes with α-keto-stabilized phosphonium ylide ligands having a general formula [Pd(μ-X)(PPh₃CHC(O)C₆H₄R)]₂ [X = Br, R = m-OCH₃ (C1), p-NO₂ (C2), p-F (C3), X = Cl, R = m-OCH₃ (C4)] was prepared. Also, a single-crystal X-ray diffraction study was performed for the compounds C1 and C4, which revealed a dimeric square-planar geometry around Pd(II) ions for these complexes. The spectroscopic and crystallographic results indicate that the phosphonium ylides coordinate to palladium(II) centers through the coordinatively active ylidic carbon atom and ortho-carbon atom of PPh₃ phenyl ring (ortho-palladation). Using theoretical methods, density function theory (DFT) calculations at the BP86/def2-SVP level of theory, the structures of dimeric palladium(II) [Pd(μ-Br)(PPh₃CHC(O)C₆H₄R)]₂ [R = p-OCH₃ (a), R = p-NO₂ (b), p-F (c)] complexes were investigated. The strength and nature of donor − acceptor bonds between the phosphonium ylide (L) and Pd fragments were analyzed using natural bond orbital analysis (NBO).