Modification of the luminescence spectra of chloro(tetrapyridylcyclotetramine)europium complexes by fine tuning of the Eu-Cl distance with outer-sphere counterions in the solid state, in a polymer matrix and in solution

Controlling the coordination environments and the luminescence properties of Eu(3+) complexes with outer-sphere counterions was achieved in the solid state, in a polymer matrix and in solution.     

Chemical and optical control of peristaltic actuator based on self-oscillating porous gel

We demonstrate the chemical and optical control of the self-sustaining peristaltic motion of a structural colored porous hydrogel.     

Electrochemical activity of nanocrystalline Fe3O4 in aprotic Li and Na salt electrolytes

Fe₃O₄ powders, whose average particle sizes were 400 nm, 100 nm, and 10 nm in diameter, were prepared in order to investigate the effect of particle size on their electrochemical activity. X-ray diffraction and electron microscopy measurements confirmed that all the prepared samples were identified as inverse-spinel type Fe₃O₄, whose crystallite/particle sizes were between 400 nm and 10 nm. We found that the electrochemical activity of Fe₃O₄ in a lithium salt electrolyte was enhanced with a decrease in the particle size from 400 nm to 10 nm. The 10 nm nanocrystalline Fe₃O₄ powder demonstrated the high discharge capacities of about 130 and 160 mAh g⁻¹ with a satisfactory capacity retention as the active cathode material of Li and Na batteries, respectively.     

Synthesis and dynamic structure of multinuclear Rh complexes of porphyrinoids

Large porphyrinoids with three Rh(CO)2 groups at their dipyrrin units shows two-step metal transposition through the macrocycle in solution and the equilibrium between the C3v-isomer and the Cs-isomer depends on the solvent polarity.     

Correlation between surface tension and void fraction in ionic liquids

An effort to systematize published and new data on the surface tension gamma of ionic liquids (ILs) is based on the hypothesis that the dimensionless surface tension parameter gamma V v (2/3)/ kT is a function of the void fraction x v = V v/ V m. The void volume V v is defined as the difference between the liquid volume V m occupied by an ion pair (known from cationic and anionic masses and liquid density measurements) and the sum V (+) + V (-) of the cationic and anionic volumes (known from crystal structures), while kT is the thermal energy. Our hypothesis that gamma V m (2/3)/ kT = G( x v) is initially based on cavity theory. It is then refined based on periodic lattice modeling, which reveals that the number N of voids per unit cell (hence the dimensionless surface tension) must depend on x v. Testing our hypothesis against data for the five ILs for which surface tension and density data are available over a wide range of temperatures collapses all of these data almost on a single curve G( x v), provided that slight (4%) self-consistent modifications are introduced on published crystallographic data for V (+) and V (-). An attempt to correlate the surface tension vs temperature data available for inorganic molten salts is similarly successful, but at the expense of larger shifts on the published ionic radii (8.8% for K; 3.3% for I). The collapsed G( x v) curves for ILs and inorganic salts do not overlap anywhere on x v space, and appear to be different from each other. The existence of a relation between gamma and x v is rationalized with a simple capillary model minimizing the energy. Our success in correlating surface tension to void fraction may apply also to other liquid properties.     

Self-oscillating polymer fueled by organic acid

Here we report the biomimetic polymer that causes self-oscillation driven by the addition of biorelated organic acid. We constructed the built-in system where all of the substrates of the BZ reaction other than biorelated organic substrates were incorporated into the polymer chain. The quarternary copolymer, which includes both of the pH-control and oxidant-supplying sites in the poly(N-isopropylacrylamide-co-Ru(bpy)3) chain was synthesized. By using the polymer, we first succeeded in causing the self-oscillation of the polymer only in the coexistence of organic acid.     

Direction control of chemical wave propagation in self-oscillating gel array

A chemomechanical actuator utilizing a reaction-diffusion wave across gap junction was constructed toward a novel mircoconveyer by micropatterned self-oscillating gel array. Unidirectional propagation of the chemical wave of the Belousov-Zhabotinsky (BZ) reaction was induced on gel arrays. In the case of using a triangle-shaped gel as an element of the array, the chemical wave propagated from the corner side of the triangle gel to the plane side of the other gel (C-to-P) across the gap junction, whereas it propagated from the plane side to the corner side (P-to-C) in the case of the pentagonal gel array. Numerical analysis based on the Keener-Tyson model was done for understanding the mechanism of unidirectional propagation in triangle and pentagonal gel arrays. The swelling and deswelling changes of the gels followed the unidirectional propagation of the chemical wave.     

Substitution, dimerization, metalation, and ring-opening reactions of N-fused porphyrins

A variety of reactions such as substitution, dimerization, rhenium(I) metalation, and ring-opening reactions of N-fused porphyrin (NFP) and optical properties of the products are presented. Palladium-catalyzed cross-coupling reactions under Suzuki or Stille conditions afford aryl and arylethynyl-substituted NFPs (12, 14) and an ethynyl-bridged dimer (15) from 3-bromo-substituted NFP (3b) in 40-98% yields. Treatment of NFP with silver(I) trifluoroacetate in CHCl₃ affords a dimer (22) linked at both C21-positions of the fused rings and its bis-Re(I) metal complex (24) is synthesized. X-ray structures of the 3-trifluoromethyl and 3-phenyl NFP derivatives (9e and 12a) reveal the three-center hydrogen bondings in the core. All the new NFP derivatives display unique absorption spectra, and particularly, ethyne-bridged NFP-dimer (15) shows a remarkable bathochromic shift into a near-infrared region showing an absorption band at 1020 nm with tailing up to 1100 nm. Moreover, alkoxide nucleophiles convert NFP into NCP derivatives by the cleavage of C-N bond in the fused ring, which is useful for the preparation of various C3-substituted NCPs and C21,C21′-linked NCP dimers from NFPs.     

Preparation and XAFS studies of organotin(IV) complexes with adenosine and related compounds and calf thymus DNA

Complexes of adenosine and related compounds (adenosine-5’-monophosphate, adenosine-5’-triphosphate and pyridoxal-5-phosphate) with Bu₂SnO and/or BuSnCl₂ were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain the organotin(IV) moiety and the ligand in a ratio of 1:1. The FT-IR spectra demonstrated that Bu₂SnO reacts with the D-ribose moiety of the ligands, while Bu₂SnCl₂ is coordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mössbauer Δ (quadrupole splitting) values with those calculated on the basis of the pqs concept revealed that the organotin(IV) moiety has Tbp and in some cases also T_h geometry. The adenosine complex contains the organotin(IV) cation in two different surroundings (Tbp and T_h). The local structures of the complexes were determined by means of EXAFS measurements. At the same time a number of organotin(IV) complexes containing different organo moieties of calf thymus DNA were also prepared. Similarly as above, EXAFS data were obtained for these compounds and analyzed by using multishell models up to 300 pm. These results are the first structural data (bond lengths) on complexes formed with organotin(IV)-DNA and related compounds.     

Host-guest Assembly Based on γ-Cyclodextrin-functionalized Multiwalled Carbon Nanotubes for Rutin Electrochemical Sensing

Here, we report multiwalled carbon nanotubes (MWCNTs) functionalized with γ-cyclodextrins (γCD) as a novel electrochemical strategy for Rutin determination, showing superior performance than β-cyclodextrins (βCD) modified MWCNTs, suggesting an adequate environment for host-guest interactions. Under optimized conditions, the sensor showed a linear range of 39–975 nmol L⁻¹ and a limit of detection of 7 nmol L⁻¹. When tested with quercetin, catechin, and caffeine, the platform presented high selectivity with an interference response <10 %. The method was employed to quantify Rutin in spiked pharmaceutical and herbal extracts, providing recovery of 93–98.4 %. Also, HPLC-PDA confirmed the method‘s accuracy.