Discotic derivatives of 6-oxoverdazyl radical

Substitution of each phenyl in 1,3,5-triphenyl-6-oxoverdazyl with three alkoxy groups induces an ordered columnar hexagonal phase (Col_h(o)) below 130°C in 1b[n], while in the alkylsulfanyl analogues 1a[n] additional periodicity along the columns was found rendering the phase a true three-dimensional columnar hexagonal phase (Col_h(3D)) below 60°C. Both series exhibit broad absorption bands in the visible region with maxima at 540 and 610 nm in series 1a[n] and at 486 and 614 nm in series 1b[n]. Unusual reversible thermochromism is observed in series 1b[n], in which the dark green isotropic phase turns red in the discotic phase. Analysis of 1a[8] revealed redox potentials E^0/+1_1/2 = +0.99 V and E^{0/ ?1}_1/2 = –0.45 V vs. saturated calomel electrode (SCE), while the potentials in the alkoxy analogue 1b[8] are shifted cathodically by 0.16 V. Photovoltaic studies of 1a[8] demonstrated hole mobility of μ_h = 1.52 × 10^?3 cm² V^?1 s^?1 in the mesophase with an activation energy E_a = 0.06 ± 0.01 eV. Magnetisation studies of 1a[8] revealed nearly ideal paramagnetic behaviour in either the solid or fluid phase above 200 K and weak antiferromagnetic interactions at low temperatures. In contrast, a noticeable drop of about 4% in μ_eff was observed during the I→Col phase transition in 1b[8], which coincide with the thermochromic effect.     

Phase behaviour of three homologues of the discotic hexa‐n‐alkoxyanthraquinones under pressure

The phase transition behaviour of three homologous discotic mesogens, the hexa‐n‐alkoxyanthraquinones HOAQ(n), n indicating the number of carbon atoms in the alkoxy group, was investigated under hydrostatic pressures up to 500?MPa using a high pressure differential thermal analyser. The T vs. P phase diagrams of HOAQ(6), HOAQ(8) and HOAQ(9) were constructed for solution‐ (Cr₀) and melt‐crystallized (Cr₁) samples of the compounds. HOAQ(6) shows the reversible Cr₀–rectangular columnar phase (Col_r)–hexagonal columnar phase (Col_h)–isotropic liquid (I) phase sequence at atmospheric pressure. The stable Col_r phase of HOAQ(6) has a decreased temperature range with increasing pressure and then the Col_r phase disappears under pressures above about 350?MPa; instead the Cr₀–Col_h–I phase sequence is exhibited. For HOAQ(8), the solution‐grown sample exhibits the stable Cr₀–Col_h–I phase sequence at atmospheric pressure. Applying pressure to the solution‐grown sample induces the formation of the stable Col_r phase in the pressure region between 10 and 350?MPa, leading to the Cr₀–Col_r–Col_h–I phase sequence. The pressure‐induced Col_r phase disappears under higher pressures. The melt‐cooled sample of HOAQ(8) shows the formation of the metastable crystal (Cr₁), unknown mesophase (X) and Col_r phases at lower temperatures under atmospheric pressure, and exhibits the reversible Cr₁–X–Col_r–Col_h–I phase sequence on subsequent thermal cycles. The metastable phase sequence was observed under pressures up to 100?MPa, but the phase transitions were too small to be detected under higher pressures. In HOAQ(9) the stable Cr₀–Col_h–I phase sequence is observed at all pressures, while the melt‐cooled sample shows the metastable Cr₁–Col_r–Col_h–I phase sequence under pressures up to 300?MPa. The metastable Col_r phase disappears under higher pressures.     

Ion polarisation-assisted hydrogen-bonded ferroelectrics in liquid crystalline domains

An alkylamide-substituted (−NHCOC₁₀H₂₁) hydrogen-bonded dibenzo[18]crown-6 derivative (1) was prepared to stabilise the ionic channel structure in a discotic hexagonal columnar (Col_h) liquid crystal. The introduction of simple M⁺X⁻ salts such as Na⁺PF₆⁻ and K⁺I⁻ into the ionic channel of 1 enhanced the ionic conductivity of the Col_h phase of the M⁺·(1)·X⁻ salts, with the highest ionic conductivity reaching ∼10⁻⁶ S cm⁻¹ for K⁺·(1)·I⁻ and Na⁺·(1)·PF₆⁻ at 460 K, which was approximately 5 orders of magnitude higher than that of 1. The introduction of non-ferroelectric 1 into the ferroelectric N,N′,N′′-tri(tetradecyl)-1,3,5-benzenetricarboxamide (3BC) elicited a ferroelectric response from the mixed Col_h phase of (3BC)_x(1)_1−x with x = 0.9 and 0.8. The further doping of M⁺X⁻ into the ferroelectric Col_h phase of (3BC)_0.9(1)_0.1 enhanced the ferroelectric polarisation assisted by ion displacement in the half-filled ionic channel for the vacant dibenzo[18]crown-6 of (3BC)_0.9[(M⁺)_0.5·(1)·(X⁻)_0.5]_0.1.

An alkylamide-substituted (−NHCOC₁₀H₂₁) hydrogen-bonded dibenzo[18]crown-6 derivative (1) was prepared to stabilise the ionic channel structure in a discotic hexagonal columnar (Col_h) liquid crystal.     

A novel dimeric discotic liquid crystal based on anthraquinone

A novel dimer based on the disc-like anthraquinone core-bis[1-(4-nitrobenzyloxy)-2,3,6,7-tetrapentyloxy-9,10-anthraquinon-5-oxy]do and its corresponding monomer 1-hexyloxy5-(4-nitrobenzyloxy)-2,3,6,7-tetrapentyloxy-9,10-anthraquinone, have been synthesized and characterized. X-ray diffraction studies show that this novel dimer exhibits a hexagonal columnar phase (Col_h) with correlation among the molecular cores along the column. The Col_h phase of the dimer exists over a very wide temperature range, extending from 176°C down to at least 60°C (the lowest temperature reached in DSC), whereas the monomer exhibits a Col_h phase at high temperature and a three-dimensionally ordered columnar phase (Col_x) at low temperature.     

Effect of Axial Ligands on Easy-Axis Anisotropy and Field-Induced Slow Magnetic Relaxation in Heptacoordinated FeII Complexes

A rational approach to modulating easy-axis magnetic anisotropy by varying the axial donor ligand in heptacoordinated Fe^II complexes has been explored. In this series of complexes with formulae of [Fe(H₄L)(NCS)₂] ⋅ 3 DMF ⋅ 0.5 H₂O ( 1 ), [Fe(H₄L)(NCSe)₂] ⋅ 3 DMF ⋅ 0.5 H₂O ( 2 ), and [Fe(H₄L)(NCNCN)₂] ⋅ DMF ⋅ H₂O ( 3 ) [H₄L=2,2′-{pyridine-2,6-diylbis(ethan-1-yl-1-ylidene)}bis(N-phenylhydrazinecarboxamide)], the axial positions are successively occupied by different nitrogen-based π-donor ligands. Detailed dc and ac magnetic susceptibility measurements reveal the existence of easy-axis magnetic anisotropy for all of the complexes, with 1 [U_eff=21 K, τ₀=1.72×10⁻⁶ s] and 2 [U_eff=25 K, τ₀=2.25×10⁻⁶ s] showing field-induced slow magnetic relaxation behavior. However, both experimental studies and theoretical calculations indicate the magnitude of the D value of complex 3 to be larger than those of complexes 1 and 2 due to the axial bond angle being smaller than that for an ideal geometry. Detailed analysis of the field and temperature dependences of relaxation time for 1 and 2 has revealed that multiple relaxation processes (quantum tunneling of magnetization, direct, and Raman) are involved in slow magnetic relaxation for both of these complexes. Magnetic dilution experiments support the role of intermolecular short contacts.     

Chiral discotic derivatives of 1,3,5-triphenyl-6-oxoverdazyl radical

Two derivatives of 1,3,5-aryl-6-oxoverdazyl containing two 3,4,5-trioctyloxyphenyl and one 3,4,5-tri((S)-3,7-dimethyloctyloxy)phenyl group in position C(3) (1b) or N(1) (1c) were investigated by thermal, X-ray diffraction and magnetic methods. The results were compared to those obtained for achiral derivative 1a containing three 3,4,5-trioctyloxyphenyl groups. All three compounds exhibit an ordered columnar hexagonal phase, Col_h(o), and for chiral derivatives, 1b and 1c, a superstructure with doubled periodicity was found. The introduction of the three chiral alkoxy substituents in 1a lowered the mesophase stability by about 50 K and induced a Col_h phase in 1c. Thermochromic analysis showed a hypsochromic shift upon formation of the Col_h(o) phase similar for all three derivatives 1 (~0.3 eV), which coincides with a 5% drop in effective magnetic moment, μ_eff, for 1c. Analysis of magnetisation data in a range of 2–370 K at 200 Oe revealed weak antiferromagnetic interactions (θ = – 4 K) in the Col_h(o) phase.     

2,3,7,8,12,13-Hexakis[2-(2-methoxyethoxy)ethoxy]tricycloquinazoline: a discogen which allows enhanced levels of n-doping

A synthesis has been developed for 2,3,7,8,12,13-hexakis[2-(2-methoxyethoxy)ethoxy]-tricycloquinazoline (TCQ6EO2M) in which the ethylenoxy side chains are introduced before elaboration of the heterocylic core. This discogen gives a hexagonal columnar phase (Col_h) between 77 and 233°C. n-Doping using potassium metal is facilitated firstly by the electron poor/π-deficient nature of the core and secondly by the polyethylenoxy side chains which complex the potassium K⁺ counter-ions. The conductivity of the Col_h phase of TCQ6EO2M doped with 10 mol % potassium (σ _∥ = 1.1 x 10^-3 S m^-1) is substantially higher than that previously reported for 2,3,7,8,12,13-hexa(hexylthio)tricycloquinazoline doped with 6 mol % potassium (σ _∥ = 2.9 x 10^-5 S m^-1). Photoconductivity studies of TCQ6EO2M using a time of flight sample configuration show transient photocurrents for both holes and electrons. From these an upper limit on the mobility for the electrons is estimated as ~10^-4 cm² V^-1 s^-1 at 150°C which is of the same magnitude as that for hole mobilities in other columnar discotic liquid crystals.     

Order-Unity 13C Nuclear Polarization of [1-13C]Pyruvate in Seconds and the Interplay of Water and SABRE Enhancement

Signal Amplification By Reversible Exchange in SHield Enabled Alignment Transfer (SABRE-SHEATH) is investigated to achieve rapid hyperpolarization of ¹³C₁ spins of [1-¹³C]pyruvate, using parahydrogen as the source of nuclear spin order. Pyruvate exchange with an iridium polarization transfer complex can be modulated via a sensitive interplay between temperature and co-ligation of DMSO and H₂O. Order-unity ¹³C (>50 %) polarization of catalyst-bound [1-¹³C]pyruvate is achieved in less than 30 s by restricting the chemical exchange of [1-¹³C]pyruvate at lower temperatures. On the catalyst bound pyruvate, 39 % polarization is measured using a 1.4 T NMR spectrometer, and extrapolated to >50 % at the end of build-up in situ. The highest measured polarization of a 30-mM pyruvate sample, including free and bound pyruvate is 13 % when using 20 mM DMSO and 0.5 M water in CD₃OD. Efficient ¹³C polarization is also enabled by favorable relaxation dynamics in sub-microtesla magnetic fields, as indicated by fast polarization buildup rates compared to the T₁ spin-relaxation rates (e. g., ∼0.2 s⁻¹ versus ∼0.1 s⁻¹, respectively, for a 6 mM catalyst-[1-¹³C]pyruvate sample). Finally, the catalyst-bound hyperpolarized [1-¹³C]pyruvate can be released rapidly by cycling the temperature and/or by optimizing the amount of water, paving the way to future biomedical applications of hyperpolarized [1-¹³C]pyruvate produced via comparatively fast and simple SABRE-SHEATH-based approaches.     

Broad Hexagonal Columnar Mesophases Formation in Bioinspired Transition‐Metal Complexes of Simple Fatty Acid meta‐Octaester Derivatives of meso‐Tetraphenyl Porphyrins

A series of meta‐substituted fatty acid octaester derivatives and their transition‐metal complexes of meso‐ tetraphenyl porphyrins (TPP‐8OOCR, with R=C_n?1H_2n?1, n=8, 12, or 16) have been prepared through very simple synthesis protocols. The thermotropic phase behavior and the liquid crystalline (LC) organization structures of the synthesized porphyrin derivatives were systematically investigated by a combination of differential scanning calorimetry (DSC), polarized optical microscopy (POM), and variable‐temperature small‐angle X‐ray scattering/wide‐angle X‐ray scattering (SAXS/WAXS) techniques. The shorter octanoic acid ester substituted porphyrin (C8‐TPP) did not show liquid crystallinity and its metal porphyrins exhibited an uncommon columnar mesophase. The lauric acid octaester (C12‐TPP) and the palmitic acid octaester (C16‐TPP) series porphyrins generated hexagonal columnar mesophase Col_h. Moreover, the metal porphyrins C12‐TPPM and C16‐TPPM with M=Zn, Cu, or Ni, exhibited well‐organized Col_h mesophases of broad LC temperature ranges increasing in the order of TPPNi<TPPCu≤TPPZn with their increased effective ionic radii in the square‐planar coordination. The simplicity in synthesis, the well intercolumnar organization of Col_h mesophase, the broadness of the discotic LC range, and the specific UV/Vis absorption and fluorescence emission behaviors make the symmetrically substituted fatty acid octaester porphyrins and their metal complexes very attractive for variant applications.     

Octacarbonyl Ion Complexes of Actinides [An(CO)8]+/− (An=Th,U) and the Role of f Orbitals in Metal–Ligand Bonding

The octacarbonyl cation and anion complexes of actinide metals [An(CO)₈]^+/− (An=Th, U) are prepared in the gas phase and are studied by mass-selected infrared photodissociation spectroscopy. Both the octacarbonyl cations and anions have been characterized to be saturated coordinated complexes. Quantum chemical calculations by using density functional theory show that the [Th(CO)₈]⁺ and [Th(CO)₈]⁻ complexes have a distorted octahedral (D_4h) equilibrium geometry and a doublet electronic ground state. Both the [U(CO)₈]⁺ cation and the [U(CO)₈]⁻ anion exhibit cubic structures (O_h) with a ⁶A_1g ground state for the cation and a ⁴A_1g ground state for the anion. The neutral species [Th(CO)₈] (O_h; ¹A_1g) and [U(CO)₈] (D_4h; ⁵B_1u) have also been calculated. Analysis of their electronic structures with the help on an energy decomposition method reveals that, along with the dominating 6d valence orbitals, there are significant 5f orbital participation in both the [An]←CO σ donation and [An]→CO π back donation interactions in the cations and anions, for which the electronic reference state of An has both occupied and vacant 5f AOs. The trend of the valence orbital contribution to the metal–CO bonds has the order of 6d≫5f>7s≈7p, with the 5f orbitals of uranium being more important than the 5f orbitals of thorium.     

Reactivity of Semivolatile Organic Compounds with Hydroxyl Radicals,Nitrate Radicals,and Ozone in Indoor Air

Indoor semivolatile organic compounds (SVOCs) originate from indoor and outdoor sources. These SVOCs partition among different phases and available surfaces, which increases their residence time indoors to several years. SVOCs may also react with indoor oxidants, such as hydroxyl radicals (OH), nitrate radicals (NO₃), and ozone. In the present study, the second‐order reaction rate constants of 72 SVOCs in indoor air (gas and particle phases) at room temperature and ambient air pressure were retrieved from the literature. The pseudo–first‐order reaction rate constants of these SVOCs were calculated for the indoor concentration ranges of OH, NO₃, and ozone. Then, the extent to which the chemical reaction had a meaningful impact on the removal of SVOCs from the indoor environment was quantitatively analyzed. The orders of magnitude of the second‐order rate constant ranged between 10⁻¹⁵ and 10⁻¹⁰ cm³/(molecule·s) for OH/SVOC reactions, 10⁻¹⁷ and 10⁻¹² cm³/(molecule·s) for NO₃/SVOC reactions, and 10⁻²⁰ and 10⁻¹⁶ cm³/(molecule·s) for ozone/SVOC reactions in indoor air. Assuming that the highest indoor reactant concentrations were 1.8 × 10⁶ molecules/cm³ (7.3 × 10⁻⁵ ppb) for OH, 2.5 × 10⁸ molecules/cm³ (10⁻² ppb) for NO₃, and 1.4 × 10¹² molecules/cm³ (58 ppb) for ozone, the highest pseudo–first‐order rate constants in the gas phase for the studied reactions of OH/SVOCs (n = 72), NO₃/SVOCs (n = 3), and ozone/SVOCs (n = 14) reached 1.5 h⁻¹ (OH/benzo[a]pyrene), 0.41 h⁻¹ (NO₃/acenaphthene), and 1.0 h⁻¹ (ozone/aldrin and ozone/heptachlor), respectively. The pseudo–first‐order rate constants in the particle phase for the studied reactions of OH/SVOCs (n = 13), NO₃/SVOCs (n = 6), and ozone/SVOCs (n = 14) at the high indoor reactant concentrations reached 0.09 h⁻¹ (OH/DEHP), 5.8 h⁻¹ (NO₃/pyrene), and 11 h⁻¹ (ozone/benzo[a ]pyrene), respectively. These results indicate that the chemical reactions of some SVOCs in indoor air have a meaningful impact compared to the air exchange rate, which should be considered in future studies on indoor air quality modeling.     

Tunable Emissive Lanthanidomesogen Derived from a Room‐Temperature Liquid‐Crystalline Schiff‐Base Ligand

A novel photoluminescent room‐temperature liquid‐crystalline salicylaldimine Schiff base with a short alkoxy substituent and a series of lanthanide(III) complexes of the type [Ln(LH)₃(NO₃)₃] (Ln=La, Pr, Sm, Gd, Tb, Dy; LH=(E)‐5‐(hexyloxy)‐2‐ [{2‐(2‐hydroxyethylamino)ethylimino]methyl}phenol) have been synthesized and characterized by FTIR, ¹H and ¹³C NMR, UV/Vis, and FAB‐MS analyses. The ligand coordinates to the metal ions in its zwitterionic form. The thermal behavior of the compounds was investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The ligand exhibits an enantiotropic hexagonal columnar (Col_h) mesophase at room temperature and the complexes show an enantiotropic lamellar columnar (Col_L) phase at around 120 °C with high thermal stability. Based on XRD results, different space‐filling models have been proposed for the ligand and complexes to account for the columnar mesomorphism. The ligand exhibits intense blue emission both in solution and in the condensed state. The most intense emissions were observed for the samarium and terbium complexes, with the samarium complex glowing with a bright‐orange light (ca. 560–644 nm) and the terbium complex emitting green light (ca. 490–622 nm) upon UV irradiation. DFT calculations performed by using the DMol3 program at the BLYP/DNP level of theory revealed a nine‐coordinate structure for the lanthanide complexes.     

Columnar liquid crystalline assembly of a U‐shaped molecular scaffold stabilized by covalent or noncovalent incorporation of aromatic molecules

We report on our serendipitous finding of the anomalous behavior of a novel liquid crystalline (LC) molecule U _H/H , containing a U‐shaped handle. While U _H/H itself shows a bicontinuous cubic (Cub_bi) phase, U _H/H in the presence of pyrene molecules as an external guest forms a hexagonal columnar (Col_h) phase without phase separation. Interestingly, even when the pyrene molecules were covalently attached to U _H/H ( U _Py/Py ), the molecule exhibited a Col_h phase, with a similar columnar geometry to that of U _H/H mixed with pyrene molecules (1–4 equiv.). This result means that no matter how the pyrene moieties are incorporated in the LC system, the resultant material exhibited a similar molecular assembly with a columnar geometry. This finding is interesting because U _H/H and pyrene molecules do not seem to have specific interactions or shape complementarity to form a columnar assembly, as in the case of U _Py/Py . © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 342–351     

Efficient singlet oxygen generation by luminescent 2-(2′-thienyl)pyridyl cyclometalated platinum(II) complexes and their calixarene derivatives

Luminescent cyclometalated platinum(II) complexes, namely [Pt(Thpy)(PPh₃)X]ⁿ⁺ (HThpy = 2-(2′-thienyl)pyridine; X = Cl⁻ ( 1 ), n = 0; X = CH₃CN ( 2 ), pyridine ( 3 ), n = 1) and [Pt(Thpy)(HThpy)Y] ^{n +} (Y = Cl⁻ ( 4 ), n = 0; Y = pyridine ( 5 ), n = 1), exhibit structured emission with peak maximum at ∼556 and 598 nm in degassed acetonitrile and with emission quantum yield and lifetime of up to 0.38 and 26 μs, respectively. These complexes are efficient photosensitizers of singlet oxygen with yields up to >90%. Complex 5 exhibited photocytotoxicity towards cancer cells and fluorescence microscopic images of cells incubated with 5 reveal substantial uptake at the nucleus and mitochondria.     

A Thermally Populated,Perpendicularly Twisted Alkene Triplet Diradical

Variable‐temperature NMR and ESR spectroscopic studies reveal that bis(dibenzo[a,i]fluorenylidene) 1 possesses a singlet ground state, 1 (S₀), while the 90° twisted triplet 1 (T₁) is populated to a small extent already at room temperature. Analysis of the increasing amount of paramagnetic 1 (T₁) at temperatures between 300 and 500 K yields the exchange interaction J_ex/h c=3351 cm⁻¹ and a singlet–triplet energy splitting of 9.6 kcal mol⁻¹, which is in excellent agreement with calculations (9.3 kcal mol⁻¹ at the UKS BP86/B3LYP/revPBE level of theory). In contrast, the zero‐field splitting parameter D is very small (calculated value −0.018 cm⁻¹) and unmeasurable.     

Chiral Pyrrolidinium Ionic Liquids with (−)-Borneol Fragment in the Cation – Synthesis,Physicochemical Properties and Application in Diels-Alder Reaction

A series of chiral pyrrolidinium salts containing (1 S)-endo-(−)-born-2-yloxymethyl substituent in the structure of the cation and six different anions: chloride, tetrafluoroborate [BF₄]⁻, hexafluorophosphate [PF₆]⁻, trifluoromethanesulfonate [OTf]⁻, bis(trifluoromethylsulfonyl)imide [NTf₂]⁻, bis(pentafluoroethylsulfonyl)imide [NPf₂]⁻ and perfluorobutanesulfonate [C₄FS]⁻ were efficiently prepared and extensively characterized. The enantiomeric purity of them was confirmed by NMR analysis with a chemical shift reagent. All salts were characterized with the specific rotation, the solubility in commonly used solvents, thermal properties, including phase transition temperatures and thermal stability. Salts with [PF₆]⁻, [C₄FS]⁻, [NTf₂]⁻ and [NPf₂]⁻ anions were classified as chiral ionic liquids (CILs). Moreover, salts with [NTf₂]⁻ and [NPf₂]⁻ anions were in the liquid state at room temperature and below. Therefore, density and dynamic viscosity, the surface tension and the contact angle on three different surfaces were also measured for them. Additionally, these chiral ionic liquids were tested as solvents in Diels-Alder reaction.     

Octacarbonyl Anion Complexes of the Late Lanthanides Ln(CO)8− (Ln=Tm,Yb, Lu) and the 32-Electron Rule

The lanthanide octacarbonyl anion complexes Ln(CO)₈⁻ (Ln=Tm, Yb, Lu) were produced in the gas phase and detected by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching-frequency region. By comparison of the experimental CO-stretching frequencies with calculated data, which are strongly red-shifted with respect to free CO, the Yb(CO)₈⁻ and Lu(CO)₈⁻ complexes were determined to possess octahedral (O_h) symmetry and a doublet X²A_2u (Yb) and singlet X¹A_1g (Lu) electronic ground state, whereas Tm(CO)₈⁻ exhibits a D_4h equilibrium geometry and a triplet X³B_1g ground state. The analysis of the electronic structures revealed that the metal-CO attractive forces come mainly from covalent orbital interactions, which are dominated by [Ln(d)]→(CO)₈ π backdonation and [Ln(d)]←(CO)₈ σ donation (contributes ≈77 and 16 % to covalent bonding, respectively). The metal f orbitals play a very minor role in the bonding. The electronic structure of all three lanthanide complexes obeys the 32-electron rule if only those electrons that occupy the valence orbitals of the metal are considered.     

2D H-bonding molecular magnets based on [Ni(mnt)2]− monoanion: Syntheses,crystal structures and magnetic properties

Two new H-bonding molecular magnets based on [Ni(mnt)₂]⁻ monoanion have been synthesized and characterized structurally. In crystal of 1, [Ni(mnt)₂]⁻ monoanions form the π-stacked sheets and the neighboring anionic sheets are held together via H-bonding interactions between –NH groups of diprotonated benzene-1,4-diamine and CN groups of mnt²⁻ ligands. In crystal of 2, the neighboring anionic dimers form an anionic column via Ni…S contacting interactions, and these anionic stacks arrange into a sheet which is parallel to crystallographic ab-plane. The H-bonding interactions between diprotonated 1,4-diazabicyclo[2.2.2]octane cations and [Ni(mnt)₂]⁻ monoanions as well as between cations and solvent MeCN molecules stabilize the lattice. Magnetic susceptibility measurement for 1 indicates an activated magnetic behavior in the high-temperature range together with a Curie tail at the lower temperature range, but the magnetic feature deviates from the magnetic exchange model for a spin dimer with S = 1/2. The magnetic nature of 2 reveals the presence of strongly antiferromagnetic interactions between the nearest-neighboring spins, the larger energy gap between spin ground and excited states results in a weakly paramagnetic property.     

Simultaneous endo and exo Complex Formation of Pyridine[4]arene Dimers with Neutral and Anionic Guests

The formation of complexes between hexafluorophosphate (PF₆⁻) and tetraisobutyloctahydroxypyridine[4]arene has been thoroughly studied in the gas phase (ESI‐QTOF‐MS, IM‐MS, DFT calculations), in the solid state (X‐ray crystallography), and in chloroform solution (¹H, ¹⁹F, and DOSY NMR spectroscopy). In all states of matter, simultaneous endo complexation of solvent molecules and exo complexation of a PF₆⁻ anion within a pyridine[4]arene dimer was observed. While similar ternary complexes are often observed in the solid state, this is a unique example of such behavior in the gas phase.     

The evolution of inner-shell multielectronic X-ray spectra from threshold to saturation for low- to high-Z atoms

Inter- and intra-shell electronic correlations in an atom are manifested in, and can be studied through, the X-ray emission spectra of multielectronic transitions. We have measured the spectra of K^hα_1,2 hypersatellites (HS), Kα_3,4 satellites (S), and the 3d electron shake-up satellites (D) accompanying the Kα_1,2 diagram lines, and their evolution from the double-ionization threshold, for selected 4- and 5-row elements of the periodic table. These spectra originate in the [1 s]⁻¹, [2p]⁻¹, and [3d]⁻¹ spectator two-electron transitions [1 s]⁻²→[1s2p]⁻¹, [1s2p]⁻¹→[2p]⁻², and [1s3d]⁻¹→[2p3d]⁻¹ respectively. Photoexcitation by monochromatized synchrotron radiation together with high-resolution crystal spectrometers were employed. Ab initio relativistic multiconfigurational Dirac–Fock (RMCDF) calculations reproduce the spectra very well for all transitions, with the HS spectra showing a strong dependence on QED effects. The excitation thresholds were determined accurately. The threshold-to-saturation energy range of the intensity was found to depend strongly on the principal quantum number n of the spectator hole. For example, for Cu, ranges of 2%, 10%, and 60% of the threshold energy are found for the D, S and HS spectra, respectively. Only the D spectrum's evolution conforms to the Thomas model, indicating a dominant shake up/off process. The S and HS spectra seem to be dominated by the knockout (“two-step-one”) process near threshold. The S spectra show a two-regime behavior. Near threshold both shape and intensity vary with excitation energy, and above that only intensity changes are observed. The lower-than-expected K^hα₁/K^hα₂ intensity ratio found for Z=23–30 and 39–46 indicates that the angular momenta coupling scheme at the regime intermediate between the LS coupling at low-Z and the jj coupling at high-Z may not be fully accounted for by the prevailing theory.