Single-crystal X-ray Diffractometry Research Articles

Umpolung in a Pair of Cobalt(III) Terminal Imido/Imidyl Complexes.

Reaction of the CoI complex [(TIMMNmes)CoI](PF6) (1) (TIMMNmes= tris‐[2‐(3‐mesityl‐imidazolin‐2‐ylidene)‐methyl]amine) with mesityl azide yields the CoIII imide [(TIMMNmes)CoIII(NMes)](PF6) (2). Oxidation of 2 with [FeCp2](PF6) provides access to a rare CoIII imidyl [(TIMMNmes)Co(NMes)](PF6)2 (3). Single‐crystal X‐ray diffractometry and EPR spectroscopy confirm the molecular structure of 3 and its S=1/2 ground state. ENDOR, X‐ray absorption spectroscopy and computational analyses indicate a ligand‐based oxidation; thus, an imidyl‐radical electronic structure for 3. Migratory insertion of one ancillary NHC to the imido ligand in 2 gives the CoI N‐heterocyclic imine (4) within 12 h. Conversely, it takes merely 0.5 h for 3 to transform to the CoII congener (5). The migratory insertion in 2 occurs via a nucleophilic attack of the imido ligand at the NHC to give 4, whereas in 3, a nucleophilic attack of the NHC at the electrophilic imidyl ligand yields 5. The reactivity shunt upon oxidation of 2 to 3 confirms an umpolung of the imido ligand.

Ancillary ligand-assisted self-assembly of a pyrenylpyridine with Zn(II), Cu(II), Ni(II), and Co(II): Syntheses, structural characterization, and photoluminescence properties

4-(Pyren-1-yl)pyridine (L) with luminescence properties was self-assembled with β-diketone-based transition metal compounds to produce five new hexacoordinated metal complexes: [Zn(acac)2L2] (1), [Zn(hfacac)2L2] (2), [Ni(hfacac)2L2] (3), [Cu(hfacac)2L2] (4), and [Co(acac)2L2] (5) [L = 4-(pyren-1-yl)pyridine, acac = acetylacetone, and hfacac = hexafluoroacetylacetone]. The structures of these complexes were characterized by single-crystal and powder X-ray diffractometry; elemental analysis; electrospray ionization masss pectrometry; and nuclear magnetic resonance, infrared, and fluorescence spectroscopies. The β-diketone ancillary ligands and pyrenylpyridine functional ligands were bonded to Zn(II)/Ni(II) /Cu(II)/Co(II) metal ions in an O^O and two N chelating fashion, leading to the formation of mononuclear coordination complexes where one-dimensional chains and two-dimensional sheet structures were formed via π···π stacking and hydrogen bonding interactions. In addition, the solid state photoluminescence properties of these new crystalline materials were examined, with obvious differences observed between the metal complexes.

Nitrogen-Embedded Quintuple [7]Helicene: A Helicene-Azacorannulene Hybrid with Strong Near-Infrared Fluorescence.

Herein, a nitrogen-embedded quintuple [7]helicene (N-Q7H) with an azapentabenzocorannulene core, which can be considered to be a helicene/azacorannulene hybrid π-system, was synthesized from azapentabenzocorannulene in a three-step process. N-Q7H is the first example of a multiple helicene with an azabuckybowl core. Single-crystal X-ray diffractometry unambiguously confirmed the structure of the propeller-shaped hybrid π-system. Owing to nitrogen-atom doping in the multiple helicenes and effective hybridization between the helicene and azacorannulene, N-Q7H exhibits considerably redshifted absorption and emission (yellow-to-green color change and green-to-near-infrared fluorescence change) relative to the azapentabenzocorannulene core. The broad absorption from the ultraviolet-visible to the NIR region is ascribable to the allowed transition between the highest occupied molecular orbital and the lowest unoccupied molecular orbital after symmetry breaking, as revealed by density functional theory calculations. Compared to previous propeller-shaped multiple helicenes with corannulene or hexabenzocoronene (etc.) as cores, N-Q7H demonstrates a significantly higher NIR fluorescence quantum efficiency of 28%. Additionally, the chiral-resolution and redox properties of N-Q7H were investigated. The excellent photophysical and inherent chiral properties of N-Q7H suggest that azapentabenzocorannulene can be used as an outstanding nitrogen-embedded core to construct novel multiple helicenes with wide application potential, including as NIR fluorescent bio-probes.

Solvent media as the driving force in the formation of one-dimensional silver(I) coordination polymers with 2-methylidene-1,3-bis(nicotinoyloxy)propane.

Two kinds of silver(I) coordination polymers consisting of the same chemical composition, [Ag(CF3SO3)(L)] [L is 2-methylidene-1,3-bis(nicotinoyloxy)propane], were synthesized and characterized by infrared (IR) and photoluminescence (PL) spectroscopy, elemental and thermal analyses, and single-crystal X-ray diffractometry; these are catena-poly[[(trifluoromethanesulfonato-κO)silver(I)]-μ-2-methylenepropane-1,3-diyl dinicotinate-κ2N:N'], [Ag(CF3SO3)(C16H14N2O4)]n, and its chloroform monosolvate, {[Ag(CF3SO3)(C16H14N2O4)]·CHCl3}n. The X-ray crystallographic measurements revealed that the silver(I) compounds exhibit one-dimensional sinusoidal or helical molecular structures depending on the solvent used for crystallization. Self-assembly in a methanol/chloroform mixture produces the sinusoidal molecular strand, whereas recrystallization from acetonitrile medium affords a racemic mixture of the helical strands. These compounds display a fluorescence emission arising from both the ligand-centred transition and the ligand-to-metal charge transfer (LMCT) in the solid state under ambient conditions.

Fabrication and characterization of lysine hydrochloride Cu(ii) complexes and their potential for bombing bacterial resistance

Abstract The emergence of drug-resistant bacteria and the lack of effective antimicrobial agents have posed a threat to public safety, so a new efficient strategy is needed to deal with the increasing severity of bacteria. Herein, a substitute antibacterial agent with high stability and biocompatibility was synthesized by incorporating lysine hydrochloride and copper sulfate pentahydrate following the liquid-phase synthesis method. The composition and structure of the Cu(ii) complex (Lys–Cu) were characterized by performing ultraviolet-visible spectrophotometry, Fourier-transform infrared spectroscopy, X-ray diffractometry (XRD), thermogravimetric analysis-differential scanning calorimetry, and single-crystal XRD. The crystal structure of Lys–Cu belongs to a monoclinic system, space group P21, with cell parameters of a = 5.14350(10), b = 16.8308(2), c = 11.4915(2) Å, Z = 2, and D = 1.548 g·cm−3. Bacteriostatic tests were carried out on Escherichia coli and Staphylococcus aureus. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of Lys–Cu against S. aureus were 0.3125 and 0.9250 mg·mL−1, respectively. The MIC and MBC values of Lys–Cu against bacterial strain E. coli were 0.4685 and 0.9250 mg·mL−1, respectively.

Multi-stimuli-engendered radical-anionic MOFs: Visualization of structural transformation upon radical formation

<h2>Summary</h2> Understanding the dynamic structural changes accompanying radical formation provides detailed insights into the design of stimuli-responsive redox-active materials. In this study, we develop a metal-organic framework (MOF) comprising a π-acidic 1,4,5,8-naphthalenediimide (NDI)-based ligand and Nd³⁺, viz. X-DGIST-4 (X = synthesis temperature in °C, DGIST=Daegu Gyeongbuk Institute of Science and Technology). The reduction of the NDI moieties to the radical-anionic state (NDI^·−) in 75-DGIST-4 can be triggered by various stimuli (heat, X-rays, and ultraviolet, visible, and infrared light), indicating the presence of structure-guided multiple electron transfer pathways. The single-crystal-to-single-crystal transformation of 75-DGIST-4 upon X-ray-induced radical formation reveals sequential structural changes. The solvothermally synthesized radical-anionic MOF, viz. 150-DGIST-4, offers a more complete structural understanding of the radical-anionic state. Importantly, the stabilization of radical-anionic NDI^·− by adjacent benzoates allows this state to be visualized by single-crystal X-ray diffractometry; the pendant benzoate is twisted to optimize the electrostatic interaction between NDI^·− and the benzoate phenyl group.

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Crystal structure, Hirshfeld surface analysis and contact enrichment ratios of 5,5-dimethyl-2-(2,4,6-tris(trifluoromethyl)phenyl)-1,3,2-dioxaborinane

The title compound C14H12BF9O2 (1) was obtained as the sole product during a failed attempt to make a new organoboron compound. Characterization of the title compound by NMR (1H, 13C{1H}, 19F{1H}, and 11B) spectroscopy and single crystal X-ray diffractometry confirmed the formation of 1. Compound 1 crystallizes in the triclinic space group P-1, with a = 8.275(5) Å, b = 8.611(5) Å, c = 10.910(5) Å, α = 89.634(5)°, β = 89.637(5)°, γ = 87.403(5)°, V = 776.6(7) Å3, and Z = 2. The intermolecular interactions in 1 were analyzed using the Hirshfeld surface method including 2 D fingerprint plots and enrichment ratios (E), which shows that the most favorable intermolecular contacts are the Cπ···F–C and C–H···F–C interactions. The interaction energies between molecular pairs revealed the importance of these weak non-covalent interactions in stabilizing the molecular structure of 1. The title compound was also studied by DFT calculations and UV-Vis spectroscopy.

Thiacalixarenes with Sulfur Functionalities at Lower Rim: Heavy Metal Ion Binding in Solution and 2D-Confined Space.

Sulfur-containing groups preorganized on macrocyclic scaffolds are well suited for liquid-phase complexation of soft metal ions; however, their binding potential was not extensively studied at the air–water interface, and the effect of thioether topology on metal ion binding mechanisms under various conditions was not considered. Herein, we report the interface receptor characteristics of topologically varied thiacalixarene thioethers (linear bis-(methylthio)ethoxy derivative L2, O2S2-thiacrown-ether L3, and O2S2-bridged thiacalixtube L4). The study was conducted in bulk liquid phase and Langmuir monolayers. For all compounds, the highest liquid-phase extraction selectivity was revealed for Ag+ and Hg2+ ions vs. other soft metal ions. In thioether L2 and thiacalixtube L4, metal ion binding was evidenced by a blue shift of the band at 303 nm (for Ag+ species) and the appearance of ligand-to-metal charge transfer bands at 330–340 nm (for Hg2+ species). Theoretical calculations for thioether L2 and its Ag and Hg complexes are consistent with experimental data of UV/Vis, nuclear magnetic resonance (NMR) spectroscopy, and single-crystal X-ray diffractometry of Ag–thioether L2 complexes and Hg–thiacalixtube L4 complex for the case of coordination around the metal center involving two alkyl sulfide groups (Hg2+) or sulfur atoms on the lower rim and bridging unit (Ag+). In thiacrown L3, Ag and Hg binding by alkyl sulfide groups was suggested from changes in NMR spectra upon the addition of corresponding salts. In spite of the low ability of the thioethers to form stable Langmuir monolayers on deionized water, one might argue that the monolayers significantly expand in the presence of Hg salts in the water subphase. Hg2+ ion uptake by the Langmuir–Blodgett (LB) films of ligand L3 was proved by X-ray photoelectron spectroscopy (XPS). Together, these results demonstrate the potential of sulfide groups on the calixarene platform as receptor unit towards Hg2+ ions, which could be useful in the development of Hg2+-selective water purification systems or thin-film sensor devices.

Syntheses, spectroscopic, structural characterization of Co(III) and Co(II) carboxylates and electron transfer reactions with ferrocene derivatives

Herein we report five cobalt compounds; three compounds containing 5-nitroisophthalate viz. Bis{bis(2,2′-bipyridine-ĸ2-N,N')(carbonato-ĸ2-O,O')cobalt(III)}5-nitroisophthalate undeca-hydrate, [Co(bpy)2(CO3)]2(5-nip)·11H2O 1 synthesized by conventional steam bath reaction, while [Co(H2O)3(bpy)(5-nip)]·H2O 2 and polymeric [Co(5-nip)(bpy)(H2O)] 3 prepared under autoclave conditions. The two compounds of 4-nitrobenzoic acid viz. Bis(2,2′-bipyridine-ĸ2-N,N')(carbonato-ĸ2-O,O')cobalt(III)} 4-nitrobenzoate pentahydrate, [Co(bpy)2(CO3)](4-nba)·5H2O 4 and [Co2(4-nba)2(bpy)2(H2O)4](4-nba)25 were also obtained by steam bath and autoclave reactions. These compounds were characterized by single crystal X-ray diffractometry, elemental, spectroscopic, magnetic and thermal methods. Compounds 1 and 4 were studied by XPS, NMR, CV and VSM, revealing +3 oxidation state of Co. 1 showed eleven lattice waters while five waters were observed in 4 due to the change in carboxylate ligand. A large number of O-H···O and C-H···O interactions leading to extended networks were observed in their crystal structures. The thermal behavior of 1–5 was investigated using TG-DTA techniques. Both carbonato Co(III) compounds 1 and 4 were investigated for their oxidizing properties with ferrocene derivatives and the results of these electron transfer reactions are reported.

Challenges in the structure determination of a dimeric impurity found during development of GDC-0326

While developing a synthetic route for GDC-0326, a PI3Kα selective inhibitor, a side product was identified which was adversely impacting process chemistry development. To aid in optimization of a viable synthetic pathway for the drug, it was decided to characterize this impurity. Initial efforts using typical high-resolution mass spectrometry data coupled with NMR analysis were unable to unambiguously identify the structure. The NMR analysis was hampered by a severe lack of protons in the core of the structure. While efforts were being made to produce suitable crystals for definitive x-ray analysis, Raman analysis was undertaken. The vibrational data were compared to DFT calculations for the two most likely structures. This data, along with chemical reasoning, eventually led to successful prediction of structure 2, which was ultimately confirmed by single crystal x-ray diffractometry data.

Synthesis, characterization, crystal structure determination, computational modelling and biological studies of a new tetrakis-(2-hydroxy-5-methylphenyl)(1H-pyrazol-4-yl)methanonezinc(II) complex

A new four-blade-propeller-with-axel kind zinc complex, dichloro-tetrakis-(2‑hydroxy-5-methylphenyl)(1H-pyrazol-4-yl)-methanonezinc(II) complex, [Zn(HMPM)4Cl2], has been synthesized and characterized by spectral, structural and biological studies. Its crystal structure was solved by single crystal X-ray diffractometry. The ligand, (2‑hydroxy-5-methylphenyl)(1H-pyrazol-4-yl)methanone, (HMPM), has been prepared by condensation of 3-formyl-6-methyl chromone with thiosemicarbazide. The [Zn(HMPM)4Cl2] complex crystallizes in the centrosymmetric monoclinic P21/n space group with unit cell dimensions, a=13.2068 Å, b=7.0763 Å, c=23.5910 Å, β = 102.327° From the XRD data it follows that [Zn(HMPM)4Cl2] is a slightly distorted octahedral complex with the 4 HMPMs serving as monodentate ligands through their pyrazoles’ sp2 nitrogens and the 2 chlorides occupying the trans positions. Each of the [Zn(HMPM)4Cl2] molecules in the crystal assumes a ci point group of symmetry. Both [Zn(HMPM)4Cl2] and its ligand, HMPM, have been molecular modelled through DFT studies on XTB platform and the computationally obtained structural parameters were found to be in very good agreement with the XRD data. The calculated electronic spectral bands of HMPM and the Zn(II) complex are also found to be very close to the experimental results. The ligand and the complex are also found to exhibit considerable anti-bacterial activity. Protein-docking studies also have been carried out for both HMPM and [Zn(HMPM)4Cl2].

New insights into the selective and systematic preparation of arylgermanium hydrides

A series of novel arylgermanium hydrides ArnGeH4–n (n = 1–3) and diaryl(chloro)germanium hydrides Ar2Ge(Cl)H were synthesized and characterized. Systematic preparation and purification were achieved via the lithium chloride–triflic acid and the optimized Grignard route. Arylgermanium hydrides ArnGeH4–n (Ar = 2,5-Me2C6H3, n = 1–3) were characterized by 1H and 73Ge NMR spectroscopy and single crystal X-ray diffractometry.

New picolinate-functionalized titanium-oxide clusters: syntheses, structures and photocatalytic H2 evolution.

Two nanosized titanium-oxide clusters (TOCs), Ti12(μ2-O)14(μ3-O)4PA16 (1; PA = 2-picolinate) and Ti12(μ2-O)18PA18 (2) were synthesized by using 2-picolinic acid and Ti(OiPr)4 in one-pot reactions. Their structures were determined using single-crystal X-ray diffractometry. Although both have the same core composition of Ti12O18, 1 exhibited superior H2 evolution activity of up to 180 μmol h-1 g-1, which is nearly eight times faster than 2. Mechanism studies revealed that 1 could induce the assembly of 2.3 nm PtNPs into 10-30 nm supra-nanoparticle structures, which contributed to the increased H2 evolution rate.

Ring-Opening Polymerization of ε-Caprolactone and Styrene Oxide-CO2 Coupling Reactions Catalyzed by Chelated Dehydroacetic Acid-Imine Aluminum Complexes.

A series of chelated dehydroacetic acid–imine-based ligands L1H~L4H was synthesized by reacting dehydroacetic acid with 2-t-butylaniline, (S)-1-phenyl-ethylamine, 4-methoxylbenzylamine, and 2-(aminoethyl)pyridine, respectively, in moderate yields. Ligands L1H~L4H reacted with AlMe3 in toluene to afford corresponding compounds AlMe2L1 (1), AlMe2L2 (2), AlMe2L3 (3), and AlMe2L4 (4). All the ligands and aluminum compounds were characterized by IR spectra, 1H and 13C NMR spectroscopy. Additionally, the ligands L1H~L4H and corresponding aluminum derivatives 1, 3, and 4 were characterized by single-crystal X-ray diffractometry. The catalytic activities using these aluminum compounds as catalysts for the ε-caprolactone ring-opening polymerization (ROP) and styrene oxide-CO2 coupling reactions were studied. The results show that increases in the reaction temperature and selective solvent intensify the conversions of ε-caprolactone to polycaprolactone. Regarding the coupling reactions of styrene oxide and CO2, the conversion rate is over 90% for a period of 12 h at 90 °C. This strategy dispenses the origination of cyclic styrene carbonates, which is an appealing concern because of the transformation of CO2 into an inexpensive, renewable and easy excess carbon feedstock.

π Back-Donation from a Beryllium Dibromide Fragment at the Expense of Its σ Strength.

It is common knowledge that metal-to-ligand π back-donation requires filled atomic orbitals at the metal center. However, we show through a combined experimental and theoretical approach that Be(II)→N-heterocyclic carbene (NHC) π back-donation is present in the two carbene adducts [(iPr)BeBr2] (1) and [(iPr)2BeBr2] (2) (iPr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene). These complexes were characterized with NMR, IR, and Raman spectroscopy as well as with single-crystal X-ray diffractometry. The unusual bonding situation is understood from the results of energy decomposition analysis in combination with natural orbital for chemical valence and quantum theory of atoms-in-molecules analysis. The obtained findings shed light on the unusually high Be-C bond strength in carbene adducts to beryllium compounds and rationalize their geometry and reactivity.

Pyrazolyl-based zinc(II) carboxylate complexes: synthesis, characterization and catalytic behaviour in ring opening polymerization of ε-caprolactone and D,L-lactide

1,2-Bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L1) and bis(3,5-dimethylpyrazol-1-yl)methane (L2), react with [Zn(OAc)2] and 4-OH-C6H4COOH, 2-Cl-C6H4COOH, 3,5-(NO2)2-C6H3COOH and C6H5COOH to form the corresponding zinc(II) complexes [Zn(4-OH-C6H4COO)2L1] (1), [Zn(2-Cl-C6H4COO)2L1] (2), [Zn{3,5-(NO2)2-C6H3COO}2L1] (3), [Zn4(C6H5COO)8(L1)2]n (4) and [Zn{3,5-(NO2)2-C6H3COO}2L2] (5). All five zinc complexes were characterized by a combination of NMR and IR spectroscopy, mass spectrometry and elemental analysis. Complexes 4 and 5 were further characterized by single-crystal X-ray diffractometry. Complex 4 is polymeric, with two different pentacoordinate Zn centres in two different coordination environments. Complex 5 has a distorted tetrahedral geometry around the zinc. These Zn(II) complexes (1–5) successfully initiate the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and D,L-lactide at elevated temperatures, and under solvent-free conditions and in toluene, respectively. The polycaprolactone (PCL) and poly(D,L-lactide) (PLA) obtained are of moderate molecular weights and medium polydispersity indices. The end groups of the polymers, determined by MALDI-ToF MS, are mainly hydroxyl groups and the stereochemistry of PLA is predominantly isotactic as determined with 13C{1H} NMR spectroscopy.

Cyan-Emitting Sialon-Polytypoid Phosphor Discovered by a Single-Particle-Diagnosis Approach

Benefiting from a novel phosphor screening method based on single crystal X-ray diffractometry and single-particle spectroscopy, i.e., the single-particle-diagnosis approach, a new Eu2+-activated cyan-emitting oxynitride phosphor (Si2.5Al9.5O0.5N12.5:Eu2+) was discovered. Single crystal X-ray diffraction analysis of the particle revealed that this sialon-polytypoid crystallizes in the Cmcm space group (No. 63) with a = 3.0704 Å, b = 18.6697 Å, c = 35.7178 Å, and Z = 8. The analyzed orthorhombic structure is built up of highly condensed networks that constructed from linked [MX4] (M = Si, Al; X = O, N) tetrahedra. Although there are no obvious crystalline sites able to accommodate larger Eu2+ ions in the host, the time-resolved streak imaging of a single crystalline particle indicates that the cyan-emitting band peaking at ∼500 nm with a relatively narrow full-width at half-maximum (FWHM) of ∼61 nm exhibits a typical Eu2+ fluorescent lifetime (∼0.39 μs) in oxynitrides. Besides, slight lifetime variation (0.32 μs vs 0.47 μs) between shorter wavelength region (450–500 nm) and longer wavelength region (500–550 nm) of the Eu2+ emission band may suggest two different crystalline environments around Eu2+. This sialon-polytypoid cyan-emitting phosphor with efficient excitability at 365 nm may find its potential application as an all-inorganic color-converter in near-ultraviolet (NUV) excited wLEDs.

A Crystalline Iron Terminal Methylidene.

Iron methylidene species are alleged intermediates in the Fischer-Tropsch process and in olefin cyclopropanation, yet iron methylidene complexes with unambiguously established molecular and electronic structures remain elusive. In this study, we characterize an iron terminal methylidene complex by single-crystal X-ray diffractometry (scXRD), CHN combustion elemental analysis, 1H/13C/31P/1H-13C NMR, and zero-field 57Fe Mössbauer spectroscopy and study its reactivity. A series of closely related complexes in different oxidation states were synthesized, isolated and characterized in order to validate the electronic structure of the title methylidene complex. The computational analysis substantiates the proposed Fischer-type electronic description while emphasizing high Fe═CH2 bond covalency, considerable double bond order, and thus, substantial alkylidene character.

Guest-Mediated Hierarchical Self-Assembly of Dissymmetric Organic Cages to Form Supramolecular Ferroelectrics

Guest-Mediated Hierarchical Self-Assembly of Dissymmetric Organic Cages to Form Supramolecular Ferroelectrics