Single-crystal X-ray Diffractometry Research Articles

A Rare Example of a Gallium-Based Lewis Superacid: Synthesis and Reactivity of Ga(OTeF5)3.

The Lewis superacid Ga(OTeF5)3 has been synthesized and characterized, revealing a monomeric structure in solution and a dimeric structure in the solid state. Isolated adducts of Ga(OTeF5)3 with strong and weak Lewis bases have been characterized spectroscopically as well as by single-crystal X-ray diffractometry. The Lewis acidity of this new species has been evaluated by means of different experimental and theoretical methods, which has allowed to classify it as one of only a few examples of a gallium-based Lewis superacid. The high Lewis acidity of Ga(OTeF5)3 was used to amplify the strength of the Brønsted acid HOTeF5, leading to the protonation of diethyl ether. Furthermore, Ga(OTeF5)3 was utilized to access the strong oxidizing system Ga(OTeF5)3/Xe(OTeF5)2 in SO2ClF, which was successfully employed in the synthesis of the dimethyl chloronium salt [Cl(CH3)2][Ga(OTeF5)4], a strong electrophilic methylation reagent.

Synthesis, crystal structure and sulphide ion sensing study of a Cu(II) complex of aroyl hydrazone

Herein, we report a Cu(II) complex {[CuII(HL)(H2O)2]Cl} of a benzoylhydrazone Schiff base ligand (4-((2-benzoylhydrazineylidene)methyl)-3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-1-ium chloride) (H2L). The molar conductance in solution, magnetic susceptibility, ESI-MS and EPR spectroscopy have been performed to justify the structure of the complex. The solid-state structure of the complex has also been solved by single crystal X-ray diffractometry. Cu(II) centre is penta-coordinated with imine-N, phenoxide-O and deprotonated amide-O donor of the ligand and two H2O molecules occupying the coordination sphere forming a distorted square pyramidal geometry (τ = 0.32). We have studied the anion sensing property of the complex by monitoring the changes in the UV–Vis and fluorescence spectra of the complex in aqueous Tris-HCl buffer medium with incremental addition of various anions of tetrabutylammonium salt. The complex shows appreciable sensitivity toward sulphide ion, among various other anions, with association constant (Kb) for binding of the complex with S2− and lowest detection limit (L.O.D) value of 6.87 × 104 M−1 and 6.9 × 10−7 M, respectively. Thus, the complex can be used as an efficient S2− probe. The mechanism of sensing is found to be displacement of the fluorescent ligand from the Cu(II) complex by the sulphide ion.

Synthesis, structure, and solution chemistry of mixed-ligand oxidovanadium(IV) complexes incorporating ONO donor hydrazone ligands

Four mixed-ligand oxidovanadium(IV) complexes, [VIVO(L1-4)(phen)], 1-4, incorporating tridentate dibasic ONO donor hydrazone ligands (H2L1-4, general abbreviation H2L) derived from the condensation of 2-picolinyl hydrazide with 2-hydroxy acetophenone and its 5-substituted derivatives as primary ligands and 1,10-phenanthroline (phen) as auxiliary ligand have been synthesized in excellent yields. The complexes were characterized by elemental analyses, magnetic susceptibility measurements, and various spectral (e.g. IR, UV–Vis and EPR) studies. The molecular structure of one of the four complexes has been determined by single-crystal X-ray diffractometry. In 1, the hydrazone ligand is meridionally disposed of, coordinating through one enolic-O, one phenolic-O, and one imine-N. The other basal position is occupied by one pyridine-N of the phen moiety. The axial positions are occupied by one oxido-O atom and the other pyridine-N atom of the phen moiety. The complexes are paramagnetic with one unpaired electron (μeff ≈ 1.73 BM), suggesting no interaction with the neighboring molecules and are EPR active. The complexes display two d-d transitions, one near 725 and the other near 840 nm due to d xy → d xz , d yz and d xy → d x 2 − y 2 transitions, respectively. The other d-d transition associated with d xy → d z 2 transition was not observed as it falls in the UV region, which is masked by highly intense intra-ligand transitions. The complexes display one-electron oxidation peaks in the +0.75 to +0.89 V vs. Ag/AgCl region in the CH3CN solution that show a linear relationship with the Hammett parameter (σ) of the substituents in the aryloxy ring.

The First Crystal Structure of an Anti-Geometric Homoleptic Zinc Complex from an Unsymmetric Curcuminoid Ligand

Curcuminoids are widely studied due to their well-recognized therapeutic properties. These molecules are often derivatized with metals, producing their corresponding homoleptic metal complexes. Numerous crystal structures of homoleptic symmetric curcuminoids with physiologically essential metals are known, although the literature lacks reports of homoleptic metal complexes of unsymmetric curcuminoids (or hemi-curcuminoids) as ligands. Three unknowns must be solved when an unsymmetric curcuminoid ligand is reacted with a metal ion: (a) the degree of coordination (MLn); (b) the spatial geometry; and (c) the conformational nature (syn or anti) of the complex. Herein, we report the structure of the anti-isomer of the Zn complex of the hemi-curcuminoid 5-hydroxy-1-(4-methoxyphenyl)hexa-1,4-dien-3-one. While the NMR shows only one set of signals for this homoleptic complex, the unambiguous stereochemistry was established through single-crystal X-ray diffractometry, revealing an anti-hexacoordinated octahedral ML2 structure.

Development of pivalic acid conjugated Nafion modified glassy carbon electrode for sensitive detection of Cu(II) by electrochemical approach

In this work, pivalic acid (pivH) molecule is employed for an electrochemical sensing of copper cations in an aqueous medium. For sensitive as well as selective potential sensor application, pivH was fabricated onto a glassy carbon electrode (GCE) facilitated by adhesive conducting binder, nafion, so as make it selective and effective electrochemical probe (pivH/Nafion/GCE) towards specific heavy metal cations. This newly fabricated pivH/Nafion/GCE reveals enhance electrochemical activity toward copper ions in the presence of other interfering heavy metal cations in phosphate buffer solution (PBS) of pH=7. The calibration plot was linear (r2 = 0.9879) across broad linear dynamic range (LDR) spanning Cu2+ concentration from 0.1 nM to 0.01 M. The sensitivity and detection limit was found to be 0.0212 × 10−2 µAµM−1cm−2 and 0.014 nM, respectively. So, this newly fabricated GCE as selective electrochemical probe offers a sensitive as well as selective detection of Cu2+ cations in real environmental samples using a novel electrochemical, current–potential (I-V), approach, for the first time. Further, we explored pivalic acid for the preparation of new di-nuclear copper complex, [Cu2(piv)4(pivH)2] (where piv = pivalate; pivH=pivalic acid) and characterized by Fourier transform infrared spectroscopy (FTIR) spectroscopy, elemental analysis and single crystal X-ray diffractometry. Density functional theory (DFT) calculations were carried out to confirm the interactions and these calculations well-support to experimental data. In case of deprotonated form of pivH, Molecular Electrostatic Potential (MEP) analysis exhibits electrostatic potential equals to −148.4 kcal/mol which suggest about the strong interaction of –COOH with copper centers. Similarly, interaction energies, the quantum theory of atoms in molecules (QTAIM) study and Natural Bond Orbital (NBO) analysis also favor to experimental work. Thus, this novel study demonstrates an excellent approach for highly selective and sensitive detection of Cu2+ cations in short response time with low detection limit and good reproducibility by using I-V method based on newly designed pivH/Nafion/GCE as selective Cu2+ cationic electrochemical sensor. The experimental data was compactable with theoretical calculations.

New proportion of levofloxacin citrate: Structural, physicochemical properties, and potency studies

Stability and potency improvement have been reported by reacting levofloxacin (LF) with citric acid (CA) in a (1:1) molar ratio. However, CA is known to be irritant to the gastrointestinal tract and should be minimized. In a novel approach, this experiment aimed to prepare LF – CA salt with reduced CA, the (2:1) molar ratio, study the structure, and investigate its solubility, stability, and potency improvement. Solvent-dropped grinding and slow evaporation methods were used to prepare the new ratio composition salt, characterized by electrothermal, differential scanning calorimetry, and powder X-ray diffractometry to confirm the physically new solid-state formation. Next, Fourier transform spectrophotometry identified the chemical interaction between LF and CA. After that, a comprehensive structural study using single-crystal X-ray diffractometry determined the 3D structure of the new salt, which determined the solid physicochemical behavior. Finally, stability, solubility, and potency tests were done to investigate the benefits of the new LF-CA composition. As a result, this experiment successfully synthesized the salt, which bound 4.5 water molecules, named LFCA (2:1) - 4.5 hydrate. This new solid-state salt was comparable with the established (1:1) molar ratio in solubility, stability, and potency, higher than LF alone. Hereafter, with a reduced CA portion, this new composition holds potential for further development in drug formulation as a stable, safer, and more efficient antibiotic.

Caught in the Act of Substitution: Interadsorbate Effects on an Atomically Precise Fe/Co/Se Nanocluster.

Directing groups guide substitution patterns in organic synthetic schemes, but little is known about pathways to control reactivity patterns, such as regioselectivity, in complex inorganic systems such as bioinorganic cofactors or extended surfaces. Interadsorbate effects are known to encode surface reactivity patterns in inorganic materials, modulating the location and binding strength of ligands. However, owing to limited experimental resolution into complex inorganic structures, there is little opportunity to resolve these effects on the atomic scale. Here, we utilize an atomically precise Fe/Co/Se nanocluster platform, [Fe3(L)2Co6Se8L'6]+ ([1(L)2]+; L = CN t Bu, THF; L' = Ph2PN(-)Tol), in which allosteric interadsorbate effects give rise to pronounced site-differentiation. Using a combination of spectroscopic techniques and single-crystal X-ray diffractometry, we discover that coordination of THF at the ligand-free Fe site in [1(CN t Bu)2]+ sets off a domino effect wherein allosteric through-cluster interactions promote the regioselective dissociation of CN t Bu at a neighboring Fe site. Computational analysis reveals that this active site correlation is a result of delocalized Fe···Se···Co···Se covalent interactions that intertwine edge sites on the same cluster face. This study provides an unprecedented atom-scale glimpse into how interfacial metal-support interactions mediate a collective and regiospecific path for substrate exchange across multiple active sites.

Photocurrent, electrochemical characteristic and photodegradation of two Ag20 cage isomers co-constructed by thiol and carboxylate/sulfonate and induced by CO32– template

Assembly of AgStBu and PhCOOH ligands with the assistance of soluble silver salt CH3COOAg/CF3SO3Ag in methanol, N, N-dimethylformamide (DMF) and dichloromethane solution, yielded two Ag20 cage isomers co-constructed by thiol and carboxylate/sulfonate ligands encapsulating a CO32– anion template, [(CO32–)@Ag20(StBu)10(PhCOO)4(CH3COO)4(DMF)4] (1) and [(CO32–)@Ag20(StBu)10(PhCOO)6(CF3SO3)2(DMF)4]·2DMF (2). The CO32– anion template was generated in situ by fixing atmospheric CO2. The precise structures of 1 and 2 were confirmed by single-crystal X-ray diffractometry (SCXRD). The thermal stability of compounds 1 and 2 was proved by thermogravimetric (TG) analysis, and their solution stability was characterized by nuclear magnetic resonance hydrogen spectroscopy (1H NMR). The absorption spectra, photocurrent responses, and luminescence of compounds 1 and 2 were investigated. In addition, the photodegradation of methylene blue (MB) and cyclic voltammetry characteristic curves of 1 and 2 were also studied.

N‒N hydrazonyl bond cleavage in benzothiazolyl-hydrazino-phenathrenequinone mediated by ruthenium(II) via an anion radical intermediate

The complexes [Ru(LBenz)H(CO)(PPh3)2] 2, [Ru(LBenz)Cl(CO)(PPh3)2] 3, (ligand behaving as bidentate monoanionic) and [Ru(LBenz)Cl(CO)(PPh3)] 4, (ligand is tridentate monoanionic) have been synthesized starting from benzothiazolyl-hydrazino-phenathrenequinone (HL) 1 and [RuH(CO)Cl(PPh3)3]. These are characterized by electrochemical and spectral methods as well as single crystal X-ray diffractometry (SCXRD). Upon treating with NaBH4, 3 accepts an electron within the coordinated ligand framework and the anionic hydrazonyl-N takes up a proton to be transformed to meta-stable hydrazinoquinone anion radical complex of ruthenium(II) [Ru(HLBenz•‒)Cl(CO)(PPh3)2] 5, possibly via concerted proton electron transfer process (CPET). Thus, the redox non-innocent character of the ligand upon complexation with ruthenium(II), has been disclosed and it is attributed to presence of low lying π* orbitals of almost entirely of phenanthraquinone and hydrazone character. In 5, the π‒acceptor ability of the ligand donor centres are reduced due to the existence of an odd electron in SOMO and hence the M-L distances around the coordination sphere are altered. The N‒N (hydrazonyl bond length increases from 1.296(6) Å in 3 to 1.429 Å in 5, leading to lesser thermodynamic stability of the latter and upon standing, the N‒N bond is cleaved to be transformed to 6+, possibly via the formation of iminoquinone anion radical complex, [6] (reported elsewhere). Also, it is via the dissociation of N‒N (hydrazonyl) bond, the biologically important molecule 2-aminobenzothiazole is formed along with 6+, so as to provide a novel route for its synthesis.

Synthesis and Structure of Unsymmetrical Anthracenyl-Isoxazole Antitumor Agents Via the Diastereoselective Bromination of 3-(9′-Anthryl)-Isoxazole Esters

In pursuit of unsymmetrical precursors for the novel series of anthracenyl-isoxazole amide (AIM) antitumor agents, a series of substituted anthracenes were subjected to bromination and re-aromatization in our study, during which we solved four single crystal X-ray diffractometry (Sc-xrd) structures which we report herein. The C-9 nitrile oxide, after its reaction with bromine, was isolated, but when subjected to re-aromatization, it returned to the starting 10-bromo nitrile oxide 1, which did provide an accurate crystal structure, with R = 0.018. The 10-halogenated 3-(9’-anthryl)-isoxazole esters were subjected to bromination and re-aromatization. Surprisingly, the yields obtained in the presence of the isoxazole were reasonably good (62–68% isolated yields), and the major diastereomers allowed for the characterization using Sc-xrd. The penta bromo product 2 showed a trans, trans, cis relationship for the four bromines on the A-ring of the anthracene, and we observed that for the unit cell, the atropisomers displayed a 1:1 ratio at the chiral axis between the isoxazole and anthrancene rings. Similarly, the 10-chloro 3 indicated a ratio of 1:1 at the chiral axis in the crystal structure. A base-induced re-aromatization afforded 3,10-dihalogenated analogues selectively in very good yields (X = Cl, 89%; X = Br 92%), of which the dibromo 4 was characterized using Sc-xrd. The improved yields of the unique diastereomeric bromination products suggested the consideration of a novel electrophilic aromatic substitution mechanism driven by the stereo-electronic environment, imposed by the isoxazole ester substituent. The promise of the application of this chemistry in the future development of AIM antitumor agents is suggested.

Three Ways to (Pseudo)cubic Structure Models: Phase Transition and Pseudosymmetry in Orthorhombic Cs3MO4 (M = V, Nb, or Ta).

The new oxometalates Cs3NbO4 and Cs3TaO4 together with Cs3VO4 crystallize with the K3NO4 structure type [Pnma, a = 12.495(2) Å, b = 9.0183(14) Å, and c = 6.6529(10) Å for the V compound; a = 12.928(2) Å, b = 9.177(3) Å, and c = 6.739(4) Å for the Nb; and a = 12.963(4) Å, b = 9.122(2) Å, and c = 6.774(1) Å for the Ta compound]. Their crystal structures were evaluated on the basis of single-crystal and powder X-ray diffractometry, assisted by vibrational spectroscopy, thermoanalysis, and DFT calculations. The crystal structures contain tetrahedral [M5+O4]3- anions, representing the first occurrence of Nb and Ta in a tetrahedral oxidic environment. Many representatives of the orthorhombic K3NO4 structure type have been described in the literature with a cubic structure model with disordered O atomic positions. Based on studies on Cs3MO4 (M = P, V, Nb, or Ta), we show here three different effects which can lead to (pseudo)cubic data sets. Two of them are problems of crystallographic nature (overlooked twinning or adverse atomic form factor ratios), but the third one, phase transformation into a plastic crystalline high-temperature modification, leads to a "truly" cubic structure with dynamically disordered (freely rotating) oxometalate anions. This might be of interest with respect to a large and growing number of sulfido- and selenidometalate materials which are today in discussion as solid-state electrolytes and to the mechanism of the unusually efficient ion transport therein.

A Linear Two-Coordinate Cr(II) Complex: Synthesis, Characterization, and Reactivity.

The synthesis and characterization of a linear two-coordinate Cr(II) amido complex, Cr{N(t Bu)Dipp}2 (Dipp=2,6-diisopropylphenyl), from the reaction of 1 molar equivalent (equiv) of CrCl2 and 2 equiv. of LiN(t Bu)Dipp is reported. Single-crystal X-ray diffractometry (SC-XRD) analysis revealed that it has a short Cr-N bond distance of 1.8878(9) Å, which could be attributed to the relatively less bulky nature of the amido ligand compared with reported systems. Furthermore, the oxidation reaction of the two-coordinate Cr(II) complex was explored. The oxidation reaction of Cr{N(t Bu)Dipp}2 with the one-electron oxidants AgOTf and [FeCp2 ][BArF 4 ] (BArF 4 - =[B{C6 H3 -3,5-(CF3 )2 }4 ]- ) afforded the trigonal planar three- and bent two-coordinate Cr(III) complexes Cr{N(t Bu)Dipp}2 (OTf) and [Cr{N(t Bu)Dipp}2 ][BArF 4 ], respectively. The reaction of Cr{N(t Bu)Dipp}2 with 1 equiv. of the organic azides AdN3 (Ad=1-adamantyl) and PhN3 afforded the three-coordinate Cr(IV) imido complexes Cr{N(t Bu)Dipp}2 (NAd) and Cr{N(t Bu)Dipp}2 (NPh), respectively. The reaction of Cr{N(t Bu)Dipp}2 and two equiv. of Me3 NO afforded the Cr(VI) dioxo complex Cr{N(t Bu)Dipp}2 (O)2 . The reaction of Cr{N(t Bu)Dipp}2 with 1 equiv. of CyN=C=NCy resulted in the insertion of the carbodiimide into the Cr-N bond, with the formation of a three-coordinate Cr(II) complex. Finally, density functional theory (DFT) calculations were used to elucidate the electronic structure of these complexes.

Fluorenyl-tethered N-heterocyclic carbene: An effective ancillary support for heteroleptic magnesium organometallics

Judicious designing of ancillary ligands with appropriate stetrolelectronics is critical for the chemistries of electropositive alkaline earths that typically make labile coordination to conventional donor sites. We report here a series of magnesium complexes [(LH)Mg(A)Br(thf)] (A = nBu (1), N(SiMe3)2 (2)), [(L)Mg{N(SiMe3)2}] (3), and [(L)MgMe(thf)] (4) supported by a N-heterocyclic carbene LH ([(Flu)H-(CH2)2-NHCDipp]; Dipp = 2,6-iPr2-C6H3) with a fluorenyl sidearm and its monoanionic version L- ([(Flu)-(CH2)2-NHCDipp] -). Complexes 1, 2, and 4 are characterized by single crystal X-ray diffractometry. 3 and 4 are additionally analyzed by DFT calculations. The pseudo-bidentate L- appears to be quite an effective ancillary support as evident from the monomeric nature of 4 and the thermal stability of 3 and 4 towards the deleterious Schlenk equilibrium. This is also reflected in 4′s catalytic activity in intramolecular hydroamination/cyclization of two primary aminoalkenes as model substrates, for which the presence of a spectator ligand and its ability to thwart the Schlenk equilibrium are critical. It’s also the 1st NHC-based main group catalyst for intramolecular hydroamination. Complex 2 also catalyzes the hydroboration of model substrates of carbonyl, ester, amide, and nitrile functions.

Improvement of the Thermal Stability and Aqueous Solubility of Three Matrine Salts Assembled by the Similar Structure Salt Formers.

Matrine (MAT), a natural Chinese herbal medicine, has a unique advantage in the treatment of various chronic diseases. However, its low melting point, low bioavailability, and high dosage restrict its subsequent development into new drugs. In this study, three kinds of MAT salts, namely, MAT-2,5-dihydroxybenzoic acid (MAT-25DHB), MAT-2,6-dihydroxybenzoic acid (MAT-26DHB), and MAT-salicylic acid-hydrate (MAT-SAL-H2O), were designed and synthesized to improve the drugability of MAT. The three salts were characterized by using various analytical techniques, including single-crystal X-ray diffractometry, powder X-ray diffractometry, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. The results of the thermal stability evaluation showed that the formation of salts improved the stability of MAT; MAT-25DHB is the most stable salt reported at present. The results of aqueous solubility showed that the solubility of MAT-25DHB was higher than that of MAT, while that of MAT-26DHB and MAT-SAL-H2O were less. Given that the MAT-25DHB salt further improved the solubility of MAT, it is expected to be subjected to further research as an optimized salt. Lattice energy and solvation free energy are important factors affecting the solubility of salts; the reasons for the changes of solubility and stability of three kinds of salts are explained by calculating them.

Heterometallic Co–Sr −2,3-pyridinedicarboxylate complex and its related perovskite oxide: Synthesis, structural characterization and magnetic properties

A new heterometallic complex {[CoSr(2,3-pdc)2(H2O)5]3H2O}n (1), where 2,3-H2pdc stands for 2,3-pyridinedicarboxylic acid, has been synthesized and investigated by single crystal X-Ray diffractometry, IR spectroscopy and thermal analysis. The compound is self-organized in a polymeric structure forming a 2D framework. The 2,3-pyridinedicarboxylic acid is fully deprotonated performing several types of coordination: monodentate, bridging chelating, bidentate bridging. Thermal decomposition of the heterometallic 2,3-pyridinedicarboxylate 1 leads to the formation of a perovskite type oxide of brownmillerite series, 2, with 20.8 % yield. Magnetic studies of 1 show the paramagnetic behavior of Co(II) ions with a significant influence of a ground state zero-field splitting at low temperatures. Variable field and temperature magnetic studies of the oxide product 2 (obtained by the controlled heating of 1) indicate the presence of the Sr6Co5O15, detected by the diffraction method. Also, trace amounts of SrCoO2.75 and SrCoO2.5 were revealed by magnetic and DSC methods, respectively.

Mechanical Properties and Temperature and Pressure Effects on the Crystal Structure of (2S,3S,4R)-2,3,4-(Trinitratomethyl)-1-nitroazetidine (TMNA) by Single-Crystal X-ray Diffractometry and Density Functional Theory

Mechanical Properties and Temperature and Pressure Effects on the Crystal Structure of (2S,3S,4R)-2,3,4-(Trinitratomethyl)-1-nitroazetidine (TMNA) by Single-Crystal X-ray Diffractometry and Density Functional Theory

Dioxygen-halogen bonding exemplified by crystalline peroxosolvates of N,N'-bis(haloacetyl) bispidines.

The halogen bonding in molecular crystals and supramolecular assemblies has been widely investigated. Special attention is given to the molecular structures capable of simultaneously exhibiting different types of non-covalent interactions, including conventional hydrogen bonds and halogen bonds. This paper systematically analyzes crystalline peroxosolvates of bispidine-based bis-amide derivatives, containing haloacetic acid residues, namely previously reported 1,1'-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-iodooethanone) peroxosolvate C13H20I2N2O2·H2O2 (1) and four new crystalline compounds, 1,1'-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-bromoethanone) peroxosolvate C13H20Br2N2O2·H2O2 (2), 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-iodoethanone) peroxosolvate C13H20I2N2O5·0.5H2O2 (3), 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-bromoethanone) peroxosolvate C13H20Br2N2O5·H2O2 (4), and 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-chloroethanone) peroxosolvate C13H20Cl2N2O5·H2O2 (5). Compounds 2-5 were synthesized for the first time and their crystal structures were determined by single-crystal X-ray diffractometry (SCXRD). To the best of our knowledge, 3-5 are unprecedented crystalline hydrogen peroxide adducts of organic hydroperoxides (R-OOH). Short intermolecular contacts between halogen and hydroperoxo oxygen atoms were found in 1-3. The halogen bonding of C-I(Br) fragments with dioxygen species in compounds 1-3 as well as in the previously reported cocrystal of diacetone diperoxide with triodotrinitrobenzene (6) was identified through reduced density gradient analysis, Hirshfeld surface analysis, and Bader analysis of crystalline electron density. The interactions were quantified using the electron density topological properties acquired from the periodic DFT calculations and evaluated to lie in the range of 9-19 kJ mol-1. A distinctive spectral feature was revealed for this type of interaction, involving a red shift of the characteristic O-O stretching vibration by about 6 cm-1, which appeared in IR spectra as a narrow low-intensity band in the region 837-872 cm-1.

Solvent-induced structural transformation in a one-dimensional coordination polymer.

We have rationally designed a one-dimensional coordination polymer (1D CP), termed 1D-DGIST-18, that exhibits intrinsic structural flexibility. This 1D CP enables its expansion into a three-dimensional network through supramolecular interactions involving coordinated solvents and/or ligands. The strategic selection of solvents for solvent exchange, prior to drying, significantly influences the structures of 1D-DGIST-18 by removing certain coordinating solvents and modulating π-π stacking. Consequently, a hierarchical porosity emerges, ranging from micro- to meso- to macroporous structures, which is attributed to its inherent structural dynamics. Additionally, the formation of excimers endows 1D-DGIST-18, when immersed in acetone, with 'turn-on' fluorescence, as evidenced by fluorescence decay profiles. These structural transitions within 1D-DGIST-18 are further elucidated using single-crystal X-ray diffractometry. The insights from this study provide a foundation for the design of materials with structural dynamics and tunable properties.

Supramolecular Nature of Multicomponent Crystals Formed from 2,2'-Thiodiacetic Acid with 2,6-Diaminopurine or N9-(2-Hydroxyethyl)adenine.

The synthesis and characterization of the multicomponent crystals formed by 2,2'-thiodiacetic acid (H2tda) and 2,6-diaminopurine (Hdap) or N9-(2-hydroxyethyl)adenine (9heade) are detailed in this report. These crystals exist in a salt rather than a co-crystal form, as confirmed by single crystal X-ray diffractometry, which reflects their ionic nature. This analysis confirmed proton transfer from the 2,2'-thiodiacetic acid to the basic groups of the coformers. The new multicomponent crystals have molecular formulas [(H9heade+)(Htda-)] 1 and [(H2dap+)2(tda2-)]·2H2O 2. These were also characterized using FTIR, 1H and 13C NMR and mass spectroscopies, elemental analysis, and thermogravimetric/differential scanning calorimetry (TG/DSC) analyses. In the crystal packing the ions interact with each other via O-H⋯N, O-H⋯O, N-H⋯O, and N-H⋯N hydrogen bonds, generating cyclic hydrogen-bonded motifs with graph-set notation of R22(16), R22(10), R32(10), R33(10), R22(9), R32(8), and R42(8), to form different supramolecular homo- and hetero-synthons. In addition, in the crystal packing of 2, pairs of diaminopurinium ions display a strong anti-parallel π,π-stacking interaction, characterized by short inter-centroids and interplanar distances (3.39 and 3.24 Å, respectively) and a fairly tight angle (17.5°). These assemblies were further analyzed energetically using DFT calculations, MEP surface analysis, and QTAIM characterization.

Electromagnetic wave absorption properties of porous carbon nanocomposite prepared by explosion method derived from energetic CuFe-MOF

An energetic heteronuclear metal–organic framework (MOF), denoted as {[CuIIFeIII3O(tza)6(H2O)3]·Cl·(NO3)2·4H2O}n (CuFe-MOF), was successfully synthesized and characterized using various techniques, including single-crystal X-ray diffractometry (XRD), powder X-ray diffractometry (PXRD), and scanning/transmission electron microscopy (SEM/TEM). The compound crystallized in the P63m space group, forming an infinite 3D cationic network composed of [Fe3O(tza)6]+ clusters and Cu2+ ions. Subsequently, we transformed CuFe-MOF into porous carbon nanocomposites, C/Cu/Fe3N/Fe4N/Fe3O4/CuFe2O4, using an explosion method. We then investigated the electromagnetic wave (EMW) attenuation properties and mechanisms of the carbon nanocomposite. Notably, the synthesized C/Cu/Fe3N/Fe4N/Fe3O4/CuFe2O4 composite material demonstrated exceptional EMW absorption. At a low frequency of 4.1 GHz with a thickness of 5.0 mm, it achieved a minimum reflection loss (RL) of −47.7 dB. Even at a high frequency of 17.8 GHz and a thickness of 1.5 mm, the minimum RL reached −41.8 dB. Moreover, this material exhibited a wide effective absorption bandwidth (EAB; RL ≤ −10 dB) spanning 14.9 GHz (3.1–18 GHz) for thicknesses between 1.0 and 5.5 mm. These attributes position the carbon composite as a strong candidate for absorption applications within the Ku, X, and C bands, making it suitable for both military and civilian usage. Our mechanistic analysis suggests that the excellent absorption performance of C/Cu/Fe3N/Fe4N/Fe3O4/CuFe2O4 results from a combination of mechanisms, including electrical and magnetic loss. This research introduces an innovative approach for the fabrication of high-performance carbon composite materials via the explosive method, utilizing multinuclear energetic materials.