Cover Picture: Photo‐Induced Spin Transition of Iron(III) Compounds with π–π Intermolecular Interactions (Chem. Eur. J. 14/2009)

Introduction of strong intermolecular interactions leads to the observation of the LIESST effect even for iron(III) spin‐crossover (SCO) compounds. For LIESST iron(III) compounds, both stretching and bending modes are considered in the reaction coordinate diagram. The picture depicts the LIESST mechanism in the reaction coordinate diagram considering both stretching and bending modes for SCO iron(III) compounds. For more information see the Full Paper by S. Hayami, O. Sato et al. on page 3497 ff.

     

Crystal structures of (azido)(pentamethylcyclopentadienyl)iridium(III) complexes containing various types of bidentate ligands

Several (azido)iridium(III) complexes having a pentamethylcyclopentadienyl (Cp∗) group, [Cp∗Ir(N₃)₂(Ph₂Ppy-κP)] (1: Ph₂Ppy = 2-diphenylphosphinopyridine), [Cp∗Ir(N₃)(Ph₂Ppy-κP,κN)]CF₃SO₃ (2), [Cp∗Ir(N₃)(dmpm)]PF₆ (3: dmpm = bis(dimethylphosphino)methane), [Cp∗Ir(N₃)(Ph₂Pqn)]PF₆·$·$CH₃OH (4·$·$CH₃OH: Ph₂Pqn = 8-diphenylphosphinoquinoline), and [Cp∗Ir(N₃)(pybim)] (5: Hpybim = 2-(2-pyridyl)benzimidazole) have been prepared and their crystal structures have been analyzed by X-ray diffraction. In complex 1, the Ph₂Ppy ligand is only coordinated via the P atom (-κP), while in 2 it acts as a bidentate ligand through the P and N atoms (-κP,κN) to form a four-membered chelate ring. Comparing the structural parameters of the chelate ring in 2 with those of a similar five-membered chelate ring formed by Ph₂Pqn in 4, it became apparent that the angular distortion in the Ph₂Ppy-κP,κN ring was remarkable, although the Ir–P and Ir–N bonds in the Ph₂Ppy-κP,κN ring were not elongated very much from the corresponding bonds in the Ph₂Pqn-κP,κN ring. In the pybim complex 5, the five-membered chelate ring was coplanar with the pyridine and benzimidazolyl rings. With the related (azido)iridium(III) complexes analyzed previously, comparison of the structural parameters of the Ir–N₃ moiety in [Cp∗Ir^III(N₃)(L–L′)]^+/0 complexes reveals an anomalous feature of the 2,2′-bipyridyl (bpy) complex, [Cp∗Ir(N₃)(bpy)]PF₆.     

Instrumental neutron activation analysis of hafnium in zirconium metal using internal standardization

Instrumental neutron activation analysis with the internal standard correction was applied to determination Hf in high purity Zr metal. Zirconium, which was a matrix element, was used as an internal standard to compensate for inhomogeneity of the neutron flux through an irradiation capsule and to improve the gamma ray measurement uncertainty. It was found that the linearity of the calibration curves of Hf was improved with using an internal standard. The analytical result of Hf in Zr metal was in good agreement with that obtained by ICP-SFMS. The relative expanded uncertainty (k = 2) was 2.1%, and it was comparable to that of ICP-SFMS.     

Topochemical synthesis of co-fe layered double hydroxides at varied fe/co ratios: unique intercalation of triiodide and its profound effect

Co-Fe layered double hydroxides at different Fe/Co ratios were synthesized from brucite-like Co(2+)(1-x)Fe(2+)(x)(OH)(2) (0 ≤ x ≤ 1/3) via oxidative intercalation reaction using an excess amount of iodine as the oxidizing agent. A new redoxable species: triiodide (I(3)(-)), promoted the formation of single-phase Co-Fe LDHs. The results point to a general principle that LDHs with a characteristic ratio of total trivalent and divalent cations (M(3+)/M(2+)) at 1/2 may be the most stable in the oxidative intercalation procedure. At low Fe content, e.g., starting from Co(2+)(1-x)Fe(2+)(x)(OH)(2) (x < 1/3), partial oxidation of Co(2+) to Co(3+) takes place to reach the M(3+)/M(2+) threshold of 1/2 in as-transformed Co(2+)(2/3)-(Co(3+)(1/3-x)-Fe(3+)(x)) LDHs. Also discovered was the cointercalation of triiodide and iodide into the interlayer gallery of as-transformed LDH phase, which profoundly impacted the relative intensity ratio of basal Bragg peaks as a consequence of the significant X-ray scattering power of triiodide. In combination with XRD simulation, the LDH structure model was constructed by considering both the host layer composition/charge and the arrangement of interlayer triiodide/iodide. The work provides a clear understanding of the thermodynamic and kinetic factors associated with the oxidative intercalation reaction and is helpful in elucidating the formation of LDH structure in general.     

The structure of a new cardenolide diglycoside and the biological activities of eleven cardenolide diglycosides from Nerium oleander

A new cardenolide diglycoside (1) was isolated from Nerium oleander together with ten known cardenolide diglycosides 2-11. The structure of compound 1 was established on the basis of their spectroscopic data. The in vitro anti-inflammatory activity of compounds 1-11 was examined on the basis of inhibitory activity against the induction of the intercellular adhesion molecule-1 (ICAM-1). Compounds 2-5 were active at an IC(50) value of less than 0.8 μM. The cytotoxicity of compounds 1-11 was evaluated against three human cell lines normal human fibroblast cells (WI-38), malignant tumor cells induced from WI-38 (VA-13), and human liver tumor cells (HepG2). Compound 3 was active toward VA-13 cells, and compounds 2-5 were active toward HepG2 cells at IC(50) values of less than 1.3 μM. The multidrug resistance (MDR)-reversal activity of compounds 1-11 was evaluated on the basis of the amount of calcein in MDR human ovarian cancer 2780AD cells in the presence of each compound. Compounds 1 and 8 showed moderate effects on calcein accumulation.     

On variants of symmetric multiple zeta-star values and the cyclic sum formula

The Ramanujan Journal - The t-adic symmetric multiple zeta values were defined by Jarossay, which have been studied as a real analogue of the $${\varvec{p}}$$ -adic finite multiple zeta values. In...     

Enantioseparation of 1-arylethanols via a supramolecular chiral host consisting of N-(2-naphthoyl)-L-aspartic acid and an achiral diamine

A supramolecular chiral host consisting of N-(2-naphthoyl)-L-aspartic acid (L-1) and meso-1,2-diphenylethylenediamine (2) is effective in enantioseparation of 1-arylethanols (up to 96% ee with 100% inclusion ratio). Here we report three different methods to prepare the inclusion crystals and discuss the chiral recognition mechanism on the basis of X-ray crystallography results.     

The effects of Gd3+ substitution on the crystal structure, site symmetry, and photoluminescence of Y/Eu layered rare-earth hydroxide (LRH) nanoplates

Well crystallized nanoplates of the (Y(0.95-x)Gd(x)Eu(0.05))(2)(OH)(5)NO(3)·nH(2)O ternary layered rare-earth hydroxides (LRHs), synthesized hydrothermally, have been investigated with emphasis on the effects of Gd(3+) substitution for Y(3+) on the structural features and optical properties. Characterizations of the materials were achieved by the combined techniques of XRD, FT-IR, TEM, DTA/TG, and optical spectroscopies. The results showed that Gd(3+) substitution leads to linearly expanded ab plane, shortened interlayer distance (c/2), and reduced hydration (smaller n value) of the crystal structure. As a consequence, the Ln(3+) partially shifts from the C(4v) to C(1) site symmetries and thus leads to systematically altered photoluminescence behaviors. Under the (7)F(0)→(5)L(6) transition excitation of Eu(3+) at 394 nm, both the (5)D(0)→(7)F(2) to (5)D(0)→(7)F(4) and the 595 nm (5)D(0)→(7)F(1) to 590 nm (5)D(0)→(7)F(1) intensity ratios linearly increase towards a higher Gd(3+) content. The incorporated Gd(3+) cations selectively sensitize emission from the C(1)-site Eu(3+) and produce a new charge transfer (CT) excitation band at ～254 nm. With this, the desired 615-nm red emission is obtainable either under intra-4f(6) transition excitation of Eu(3+) or by exciting the CT band. The materials have similar fluorescence lifetimes of 0.85 ± 0.05 ms for the 615-nm emission, irrespective of the Gd(3+) content and excitation wavelength.     

Electronic and Vibrational Coherence Dynamics in a Cyanine Dye Studied Using a Few‐Cycle Pulsed Laser

We report the relaxation times of electronic and vibrational coherence in the cyanine dye 1,1′,3,3,3′,3′‐hexamethyl‐4,4′,5,5′‐dibenzo‐2,2′‐indotricarbocyanine, measured using a 7.1 fs pulsed laser. The vibrational phase relaxation times are found to be between 380 and 680 fs in the ground and lowest excited singlet states. The vibrational dephasing times of the 294, 446, and 736 cm^?1 modes are relatively long among the six modes associated with excited‐state wave packets. The slower relaxations are explained in terms of a coupled triplet of vibrational modes, which preserves coherence by forming a tightly bound group to satisfy the condition of circa conservation of vibrational energy. Using data from the negative‐time range (i.e., when the probe pulse precedes the pump pulse), the electronic phase relaxation time is found to be 31±1 fs. The dynamic vibrational mode in the excited state (1171 cm^?1), detected in the positive‐time range, is also studied from the negative‐time traces under the same experimental conditions.