Preparation of a polymer-supported fluorene-based receptor for quantitative and efficient binding of silver cations

We have designed and synthesized a polymer-supported material in which a versatile fluorene-p-xylene-based receptor is woven onto the backbone of polystyrene. This polymer-supported receptor adopts a pi-prismand-like conformation through a simple C--C bond rotation that results in the quantitative binding of a single silver cation per receptor site with a remarkable efficiency that exceeds the binding abilities of the well-known tris[2.2.2]-p-cyclophane (or pi prismand) by at least a factor of 100. More importantly, the binding event can be readily monitored by 1H NMR spectroscopy, as well as by a more sensitive emission spectroscopic technique in which the quenching of fluorescence of the receptor moiety is quantitatively related to the binding of silver cations.     

Chemistry of the phenylglyoxal-p-diethylaminoanil and/or thiourea substituted ammine complexes

Summary Mixed ligand complexes of chromium(III), cobalt(II), cobalt(III), copper(II) and zinc(II) involving either the phenylglyoxal-p-diethylaminoanil and/or thiourea, and ammonia have been obtained by the partial or complete replacement of the strongly coordinated ammonia of ammine complexes. All the products were characterized by elemental analysis, molar conductance, magnetic susceptibility and i.r. and electronic spectral measurements for their bonding and structures.     

FHBC,a Hexa‐peri‐hexabenzocoronene–Fluorene Hybrid: A Platform for Highly Soluble,Easily Functionalizable HBCs with an Expanded Graphitic Core

Materials based upon hexa‐peri‐hexabenzocoronenes (HBCs) show significant promise in a variety of photovoltaic applications. There remains the need, however, for a soluble, versatile, HBC‐based platform, which can be tailored by incorporation of electroactive groups or groups that can prompt self‐assembly. The synthesis of a HBC–fluorene hybrid is presented that contains an expanded graphitic core that is highly soluble, resists aggregation, and can be readily functionalized at its vertices. This new HBC platform can be tailored to incorporate six electroactive groups at its vertices, as exemplified by a facile synthesis of a representative hexaaryl derivative of FHBC. Synthesis of new FHBC derivatives, containing electroactive functional groups that can allow controlled self‐assembly, may serve as potential long‐range charge‐transfer materials for photovoltaic applications.     

From Intramolecular (Circular) in an Isolated Molecule to Intermolecular Hole Delocalization in a Two‐Dimensional Solid‐State Assembly: The Case of Pillarene

To achieve long‐range charge transport/separation and, in turn, bolster the efficiency of modern photovoltaic devices, new molecular scaffolds are needed that can self‐assemble in two‐dimensional (2D) arrays while maintaining both intra‐ and intermolecular electronic coupling. In an isolated molecule of pillarene, a single hole delocalizes intramolecularly via hopping amongst the circularly arrayed hydroquinone ether rings. The crystallization of pillarene cation radical produces a 2D self‐assembly with three intermolecular dimeric (sandwich‐like) contacts. Surprisingly, each pillarene in the crystal lattice bears a fractional formal charge of +1.5. This unusual stoichiometry of oxidized pillarene in crystals arises from effective charge distribution within the 2D array via an interplay of intra‐ and intermolecular electronic couplings. This important finding is expected to help advance the rational design of efficient solid‐state materials for long‐range charge transfer.     

Lipschitz-Nikolski\imath constants and asymptotic simultaneous approximation on theM n -operatorsconstants and asymptotic simultaneous approximation on theM n -operators

This note is a study of approximation of classes of functions and asymptotic simultaneous approximation of functions by theM _n -operators of Meyer-König and Zeller which are defined by $$(M_n f)(x) = (1 - x)^{n + 1} \sum\limits_{k = 0}^\infty {f\left( {\frac{k}{{n + k}}} \right)} \left( \begin{array}{l} n + k \\ k \\ \end{array} \right)x^k , n = 1,2,....$$ Among other results it is proved that for 0<α≤1 $$\mathop {\lim }\limits_{n \to \infty } n^{\alpha /2} \mathop {\sup }\limits_{f \in Lip_1 \alpha } \left| {(M_n f)(x) - f(x)} \right| = \frac{{\Gamma \left( {\frac{{\alpha + 1}}{2}} \right)}}{{\pi ^{1/2} }}\left\{ {2x(1 - x)^2 } \right\}^{\alpha /2} $$ and if for a functionf, the derivativeD ^m+2 f exist at a pointx∈(0, 1), then $$\mathop {\lim }\limits_{n \to \infty } 2n[D^m (M_n f) - D^m f] = \Omega f,$$ where Ω is the linear differential operator given by $$\Omega = x(1 - x)^2 D^{m + 2} + m(3x - 1)(x - 1)D^{m + 1} + m(m - 1)(3x - 2)D^m + m(m - 1)(m - 2)D^{m - 1} .$$      

Role of diffusion tensor imaging metrics and in vivo proton magnetic resonance spectroscopy in the differential diagnosis of cystic intracranial mass lesions

The purpose of this study was to determine whether proton magnetic resonance spectroscopy (PMRS) and diffusion tensor imaging (DTI) indices, fractional anisotropy (FA) and mean diffusivity (MD) can be used to distinguish brain abscess from cystic brain tumors, which are difficult to distinguish by conventional magnetic resonance imaging (MRI). Fifty-three patients with intracranial cystic mass lesions and 10 normal controls were studied. Conventional MRI, PMRS and DTI of all the patients were performed on a 1.5-T GE scanner. Forty patients were with brain abscess and 13 with cystic tumors. Cytosolic amino acids (AAs) were present in 32 of 40 brain abscess patients. Out of 13 patients with cystic tumors, lactate and choline were seen in 3 and only lactate was present in 10 patients on PMRS. All 40 cases of abscess had high FA, while all 13 cases of tumor cysts had high MD values. We conclude that FA measurements are more sensitive in predicting the abscess, while PMRS and MD are more specific in differentiating abscess from cystic tumors. We suggest that PMRS should be combined with DTI rather than with diffusion-weighted imaging as FA can be used as an additional parameter for separation of abscess from other cystic intracranial mass lesions.     

The non-pair forces and phonon dispersion in heavy alkali metals

Two types of the non-pair forces, one from the Born-Mayer and other from the Morse potential, are derived to discuss the response of the electrons in heavy alkali metals, i.e. rubidium and caesium. These potentials are added to the two-body potential of Morse to account for the ion-ion interactions as well. The potentials so obtained are employed to predict the phonon dispersion relations in the bcc metals, which are also compared with the recent precise neutron scattering data.     

Laser Raman study of phase transformations in [N(CH3)4]2ZnCI4 single crystals

We report temperature-dependent Raman studies on single crystals of [N(CH₃)₄]₂ZnCI₄ from 300 to 10 K. The observed spectral features suggest that both the N(CH₃)₄ ⁺ and ZnCl^2- ₄ ions are distorted from their regular tetrahedral structure and occupy sites of C_s symmetry in the lattice at room temperature. From the variation of line width of some selected Raman bands and other spectral changes as a function of temperature, it is inferred that both the ZnCl^2- ₄ and—CH₃ groups have high motional freedom at room temperature and the different phase transitions up to 160 K are triggered by the gradual freezing-in of orientational freedom of these groups, while the N—C₄ tetrahedra do not play any significant role in these phase transitions. The monoclinic to orthorhombic superlattice phase transitions at 159 K is triggered by freezing-in of the orientational motions of both the ZnCl^2- ₄ and N(CH₃)⁺ ₄ groups in the lattice.     

Detection of some nitrogen compounds and the semiquantitative determination of diphenylamine with p-dimethylaminobenzaldehyde by capillary solid-state spot-tests

Capillary solid-state spot-tests for nitrogen compounds by reaction with p-dimethylamino-benzaldehyde are described. The tests are neither specific nor universally applicable for nitrogen compounds.     

Amperometric probe for 3-hydroxybutyrate with immobilized 3-hydroxybutyrate dehydrogenase

The enzyme 3-hydroxybutyrate dehydrogenase is immobilized on a graphite electrode suitable for determination of NADH. Of the several procedures tested for the immobilization, direct adsorption on the electrode surface was most satisfactory, with useful lifetimes of up to 3 days. The best calibration graphs for the NADH, and for 3-hydroxybutyrate were obtained at pH 7.5 (phosphate buffer). 3-Hydroxybutyrate was determined in the range 5–100 μmol l^?1 at pH 7.5 with good precision. Interferences are discussed.