An oxovanadium(IV) complex containing a pentacoordinate Schiff-base ligand: synthesis and crystal and molecular structure of N,N′-(3,3′-dipropylamine)bis (3-methoxysalicylideneiminato)oxovanadium(IV) dihydrate

Crystals ofN,N-(3,3-dipropylamine)bis(3-methoxysalicylideneiminato) oxovanadium(IV) dihydrate are monoclinic, space groupP2₁/n (No. 14) with four molecules in the unit cell of dimensionsa=8.667(4),b=20.617(4),c=12.744(3) Å,=91.48(3)°. The structure was solved by the heavy-atom method and refined by block diagonal least-squares calculations with anisotropic thermal parameters for nonhydrogen atoms.R=0.038 for 1457 reflections withI>3(I). This structure is the first reported for an oxovanadium(IV) complex involving complexation of a pentacoordinate Schiff-base ligand. The coordination polyhedron is based on a distorted octahedron. Three nitrogen and one oxygen atom from the ligand form an equatorial plane around vanadium with V-N(1) 2.096(4), V-N(2) 2.180(4), V-N(3) 2.088(4), V-O(2) 1.961(3) Å, and octahedral coordination is completed by the vanadyl oxygen [V-O(1) 1.617(3) Å] and the remaining ligand oxygen [V-O(3) 2,098(3) Å]. The relatively long V-O(1) distance correlates well with the low value ofv(V=O) of 919 cm^–1. The molecules of the complex are linked by water molecules of crystallization to form infinite hydrogen-bonded chains parallel toa.     

Quenching Behavior of the Electrochemiluminescence of Ru(bpy)32+/TPrA System by Phenols on a Smartphone-Based Sensor

Phenolic compounds such as vanillic and p-coumaric acids are pollutants of major concern in the agro-industrial processing, thereby their effective detection in the industrial environment is essential to reduce exposure. Herein, we present the quenching effect of these compounds on the electrochemiluminescence (ECL) of the Ru(bpy)₃²⁺/TPrA (TPrA=tri-n-propylamine) system at a disposable screen-printed carbon electrode. Transient ECL profiles are obtained from multiple video frames following 1.2 V application by a smartphone-based ECL sensor. A wide range of detection was achieved using the sensor with limit of detection of 0.26 μM and 0.68 μM for vanillic and p-coumaric acids, respectively. The estimated quenching constants determined that the quenching efficiency of vanillic acid is at least two-fold that of p-coumaric acid under the current detection conditions. The present ECL quenching approach provided an effective method to detect phenolic compounds using a low-cost, portable smartphone-based ECL sensor.     

Chlorpromazine binding to Na+, K+-ATPase and photolabeling: involvement of the ouabain site monitored by fluorescence

This work reports the results of ultraviolet irradiation on the interaction of the phototoxic antipsychotic drug chlorpromazine (CPZ) with the sodium pump Na+, K+-ATPase. The study was performed by monitoring the fluorescence modifications of CPZ itself and of the specific probe anthroylouabain (AO). CPZ association with Na+, K+-ATPase was found to modify the kinetics of CPZ-photodegradation. It was demonstrated that UV irradiation produces a stable fluorescent photoproduct of CPZ covalently bound to Na+, K+-ATPase. The fluorescent probe AO, which specifically binds to the extracellular ouabain site of the pump, was used to localize the CPZ binding site. UV-irradiation of AO-labeled Na+, K+-ATPase treated with CPZ at concentration about 20 microM produced dose-dependent modifications of the AO fluorescence, e.g. increased quantum yield and blue shift. The results demonstrated that CPZ binds near the ouabain site. The photo-induced reaction of CPZ with AO-labeled Na+, K+-ATPase protected the ouabain site from the aqueous environment. It was also found that UV irradiation of CPZ-treated enzyme obstructs the binding of AO, which suggested occlusion of the ouabain site. This effect can be evaluated for a potential use of CPZ in photochemotherapy.     

Fluorogenic Bifunctional trans-Cyclooctenes as Efficient Tools for Investigating Click-to-Release Kinetics

The inverse electron demand Diels–Alder pyridazine elimination reaction between tetrazines and allylic substituted trans-cyclooctenes (TCOs) is a key player in bioorthogonal bond cleavage reactions. Determining the rate of elimination of alkylamine substrates has so far proven difficult. Here, we report a fluorogenic tool consisting of a TCO-linked EDANS fluorophore and a DABCYL quencher for accurate determination of both the click and release rate constants for any tetrazine at physiologically relevant concentrations.     

STERIC AND ELECTRONIC DESTABILIZATION OF THE P—Se BOND IN TRIARYLPHOSPHINE SELENIDE SYSTEMS

Abstract

Electronic and steric effects in SeP(Ar), compounds are discussed with the assistance of ¹J(⁷⁷Se-³¹P) correlations with d(P—Se) values and the pKa of the arylphosphines.     

Elektroanalytische Bestimmungen und Trennungen

Ohne Zusammenfassung     

Synthesis and Antibacterial Activity of Cefixime Metal Complexes

Cefixime (H₂cefixi) reacts with transition metal(II) ions to give [M(cefixi)(H₂O)₂] complexes (M = Mn, Co, Ni and Cd) and [Fe(cefixi)Cl(H₂O)], which were characterized by physicochemical and spectroscopic methods, and an octahedral geometry is suggested for their structure. The complexes are polymers with high temperature decomposition points and are insoluble in water and common organic solvents. The complexes have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of cefixime.