Modification of glassy carbon electrode by the electrochemical oxidation of 3‐aminophenylcalix[4]pyrrole in nonaqueous media

3‐Aminophenylcalix[4]pyrrole (3APCP) was grafted to a glassy carbon (GC) surface during the electrochemical oxidation process in 0.1 M tetrabutylammoniumtetra‐fluoroborate (TBATFB) containing acetonitrile solution. The presence of a surface film was confirmed electrochemically by comparing voltammograms of dopamine and ferricyanide redox probes at the bare and modified electrodes. Reflection‐absorption infrared spectroscopy (RAIRS), XPS, atomic force microscopy (AFM), ellipsometry and the contact angle measurements were also employed to characterize 3APCP film on GC electrode. RAIRS analysis revealed that calix[4]pyrrole was bonded to the glassy carbon surface via the etheric linkage. The stability of the modified GC electrode was also studied. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and electrochemical properties of calix[4]arene derivatives containing ferrocene units in the cone and 1,3-alternate conformation

Two novel calix[4]arene receptors containing ferrocene units in cone (L₁) and 1,3-alternate (L₂) conformations have been synthesized from 25,27-dihydroxy-26,28-bis[(3-aminopropyl)oxy]calix[4]arene 4 or 25,26,27,28-tetra[(3-aminopropyl)oxy]calix[4]arene 6 and ferrocenecarboxaldehyde via condensation, respectively. Their structures have been characterized by ¹H, ¹³C, APT, COSY NMR, FTIR, HSMR, and UV–vis spectral data. The electrochemical behavior of L₁ and L₂ has been investigated in the presence of F^?, Cl^?, Br^?, H₂PO₄^?, CH₃COO^? anions. Electrochemical studies show that these receptors electrochemically recognize CH₃COO^?, H₂PO₄^?, and Cl^?, anions. Using an UV–vis study, the selectivity to these anions in DMSO solution was confirmed.     

Measurements of indoor radon concentration levels in Kilis,Osmaniye and Antakya,Turkey during spring season

The fact that 50% of the natural radiation dose to which humans are exposed is caused by radon gas makes indoor radon measurements important. In this study, levels of indoor radon gas were measured in 204 houses in Kilis, Osmaniye and Antakya using passive nuclear track detectors. Cr-39 radon detectors were left in the living rooms of participants’ houses, then analyzed at the Radon Laboratory of Health Physics Department in Çekmece Nuclear Research and Training Center (ÇANEM) of Atomic Energy Agency of Turkey (TAEK). Average indoor radon activity concentrations for Kilis, Osmaniye and Antakya were 50 Bq/m³ (1.26 mSv/y), 51 Bq/m³ (1.29 mSv/y) and 40 Bq/m³ (1.01 mSv/y), respectively.     

Phosphorus–nitrogen compounds: part 16. Synthesis, stereogenism, anisochronism and the relationship between 31P NMR spectral and crystallographic data of monotopic spiro-crypta phosphazene derivatives

The condensation reactions of N₂O₃-donor type coronands (1–3) with hexachlorocyclotriphosphazatriene, N₃P₃Cl₆, resulted in the formation of spiro-crypta phosphazene derivatives (4–6). These compounds with excess morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) afford fully substituted morpholino (7 and 10) and 1,4-dioxa-8-azaspiro[4,5]deca (8)-substituted phosphazene derivatives, respectively. Whilst, in the same conditions, the reactions of 4, 5 and 6 with pyrrolidine, morpholine and DASD also produce partially pyrrolidino-substituted geminal (9 and 11), mono-substituted pyrrolidino (12), morpholino (13) and 1,4-dioxa-8-azaspiro[4,5]deca (14) phosphazenes. It has been clearly observed that the chloride replacement reactions of 4, 5 and 6 with pyrrolidine lead to the geminal products. Compounds 7, 8 and 10 are the first examples of anisochronic tetrakis (amino) phosphazenes according to ³¹P NMR data. The structures of 7, 8 and 10–14 have been determined by FTIR, MS, ¹H, ¹³C and ³¹P NMR, DEPT, and HETCOR spectral data. The solid-state structures of 9, 13 and 14 have been examined by X-ray diffraction techniques. The sums of the bond angles around the spiro cyclic nitrogen atoms [344.8(4)° and 347.6(4)°] of 9, indicate that the nitrogen atoms have pyramidal geometries. Thus, the N atoms seem to have stereogenic configurations. Compounds 12–14 also have two stereogenic P-atoms, and they are expected to be in the mixture of enantiomers. The relationships between NPN (α and α′) bond angles and δP_spiro values and the correlation of Δ(P–N) with δP_spiro and Δ(δP) values are presented.     

Synthesis of 15‐, 16‐, and 17‐Membered Bis‐C‐Pivot Macrocycles Consisting of N2O2 Donor‐Type Crown Ethers and Dialkyl Phosphonates

Bis‐C‐pivot macrocycles containing aminophosphonate functions ( 5–10 ) have been synthesized and characterized by elemental analysis, FTIR, MS, 1D ¹H, ¹³C and ³¹P NMR, and 2D HETCOR techniques. The phosphorylation reaction of dibenzo‐bis‐imino crown ethers ( 1–4 ) with dimethyl and diethyl phosphite used here has the potential to provide bis‐C‐pivot macrocycles ( 5–10 ), which possess two stereogenic C‐centers giving rise to diastereoisomers (meso and racemic). Detailed spectral assignments for the meso and racemic forms of the compounds are reported on the basis of chemical shifts, signal intensities, spin–spin coupling constants, and splitting patterns. The bis‐C‐pivot macrocycles ( 5–10 ) may serve as a potential new class of supramolecular host molecules.     

Phase diagrams of the spin-2 Ising model in the presence of a quenched diluted crystal field distribution

We have investigated the random crystal field effects on the phase diagrams of the spin-2 Blume-Capel model for a honeycomb lattice using the effective-field theory with correlations.To do so,the thermal variations of magnetization are studied via calculating the phase diagrams of the model.We have found that the model displays both second-order and first-order phase transitions in addition to the tricritical and isolated points.Reentrant behavior is also observed for some appropriate values of certain system parameters.Besides the usual ground-state phases of the spin-2 model including ±2,±1,and 0,we have also observed the phases ±3/2 and ±1/2,which are unusual for the spin-2 case.     

Experimental and numerical study of omega type bianisotropic metamaterials combined with a negative permittivity medium

We report on the transmission properties of the omega (Ω) type metamaterials. Transmission through the periodic Ω-only and Ω-wire metamaterials are studied experimentally and numerically. A resonance band gap is observed for the periodic Ω medium around the resonance frequency of the single Ω unit cell. A transmission band is observed below the resonance band gap, when the periodic Ω structure is embedded in a negative permittivity medium composed of thin metallic wire arrays. We also studied the effect of periodicity on the transmission spectra of Ω type metamaterials.     

Trimodal random-field spin- Ising systems in a transverse field

The trimodal random-field spin- Ising system in a transverse field is investigated by combining the pair approximation with the discretized path-integral representation by introducing a parameter p to simulate the fractions of the spins not exposed to the external longitudinal magnetic field. The variation of the critical reduced transverse field and longitudinal magnetic field with the parameter p is studied for different coordination numbers and it is found that the system does not exhibit any tricritical points for p>0.22. The phase diagrams with respect to the external longitudinal random-field and the second-order phase transition temperature are obtained for given values of the transverse field, coordination numbers and the parameter p. It is found that for appropriate values of the system parameters the system does present tricritical points and reentrant phase transitions, which may be caused by the competition between the quantum effects and randomness.