Proton-Induced Spin State Switching in an FeIII Complex

Reversible proton-induced spin state switching of an Fe^III complex in solution is observed at room temperature. A reversible magnetic response was detected in the complex, [Fe^III(sal₂323)]ClO₄ ( 1 ), using Evans’ method ¹H NMR spectroscopy which indicated cumulative switching from low-spin to high-spin upon addition of one and two equivalents of acid. Infrared spectroscopy suggests a coordination-induced spin state switching (CISSS) effect, whereby protonation displaces the metal-phenoxo donors. The analogous complex, [Fe^III(4-NEt₂-sal₂323)]ClO₄ ( 2 ), with a diethylamino group on the ligand, was used to combine the magnetic change with a colorimetric response. Comparison of the protonation responses of 1 and 2 reveals that the magnetic switching is caused by perturbation of the immediate coordination sphere of the complex. These complexes constitute a new class of analyte sensor which operate by magneto-modulation, and in the case of 2 , also yield a colorimetric response.     

Oscillation of 2nd-order Nonlinear Noncanonical Difference Equations with Deviating Argument

The purpose of this paper is to establish some new criteria for the oscillation of the second-order nonlinear noncanonical difference equations of the form \[ \Delta \left( a\left( n\right) \Delta x\left( n\right) \right) +q(n)x^{\beta }\left( g(n)\right) =0,\text{ \ \ }n\geq n_{0} \] under the assumption \[ \sum_{s=n}^{\infty }\frac{1}{a\left( s\right) }<\infty \text{.} \] Corresponding difference equations of both retarded and advanced type are studied. A particular example of Euler type equation is provided in order to illustrate the significance of our main results.     

Electroanalytical performance of a Bismuth/Antimony composite glassy carbon electrode in detecting lead and cadmium

This work reports on the electroanalytical performance of a glassy carbon electrode (GCE) modified with antimony and bismuth (Sb/Bi-GCE) in detecting heavy metal ions using lead and cadmium as model analytes. The electroanalytical performance of the Sb/Bi-GCE surface was compared to the bismuth modified glassy carbon electrode (Bi-GCE) as well as the antimony modified glassy carbon electrode (Sb-GCE). The Sb/Bi-GCE exhibited excellent figures of merit compared to Bi-GCE and Sb-GCE surfaces. For example, the limit of detection for lead was 0.01 ppb using Sb/Bi-GCE and 0.1 and 1 ppb on Bi-GCE and Sb-GCE, respectively.     

New amidino‐benzimidazolyl thiophenes: Synthesis and photochemical synthesis

New amidino‐benzimidazolyl‐substituted bis‐1,2‐(2‐thienyl)ethenes ( 4, 5 , and 6 ) and benzo[1,2‐ b:4,3‐ b′]dithiophenes ( 8, 9 , and 10 ) were prepared by the condensation of amidino‐substituted o‐phenylene diamines with corresponding dialdehydes ( 3 and 7 ). All prepared amidino‐benzimidazolyl‐substituted compounds are of particular interest, because they can serve as intercalators or groove binders on DNA in anticancer therapy. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:218–222, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10126