Béla Ágai

Chromogenic calix[4]arene as ionophore for potentiometric and optical sensors

Chromogenic calix[4]arene derivative was synthesized and tested as an ionophore for potentiometric and optical sensors. Distinct sodium selectivity was observed with this ionophore based, plasticized PVC membranes in potentiometric measurements suggesting their utility for biological applications. Optode membranes exhibited sodium sensitivity in the 5 x 10(-2) -10(-4)M concentration range. The optical sensitivity was improved by the use of an internal, lipophilic base (TDDA). The operation of the optical sensor is in accordance with the ion-exchange theory.

Indole-2-carboxamides as Novel NR2B Selective NMDA Receptor Antagonists

A novel series of indole-2-carboxamide derivatives was prepared and identified as NR2B selective NMDA receptor antagonists. The influence of the number and position of OH groups on the indole skeleton as well as the substitution of the piperidine ring on the biological activity of the compounds was studied.

Zinc Selective Ionophores for Potentiometric and Optical Sensors

Abstract Iminodiacetamide derivatives were synthesized and studied as ionophores in plasticized poly(vinyl chloride) membranes with potentiometric and optical transduction. The N-benzyl and N-phenyl derivatives proved to have a distinct zinc selectivity preferring Zn2+ over Ca2+, Na+ by factors of 6×105 and 3×104. respectively. All ionophores exhibit a serious proton interference (log KPot Zn ++, H + - 6) which suggests that all application of this type of ionophores based sensors are limited to hydrogen ion buffer solution at pH ≥ 6.

An easy access to tetra-o-alkylated calix[4]arenes of cone conformation

Abstract Fully O-alkylated calix[4]arenes have been synthesized by the alkylation of p-tertbutylcalix[4]arene and its 1,3-dialkylated derivatives in liquid-liquid phase-transfer catalytic process. 1H 4 and 1H 2 R 2 could effeciently be deprotonated by aqueous NaOH (50% w/w)-toluene system and alkylated with alkyl (aralkyl, allyl) halogens in good yields affording calix[4]arene tetraethers of cone conformation.

Novel bis (crown ether)-based potassium sensor for biological applications

Based on structure-selectivity studies on bis-benzo-crown ether derivatives, 2,2′-bis[3,4-(15-crown-5)-2-nitrophenylcarbamoxymethyl]tetradecane (BME-44) was designed and synthesized. The performance characteristics of this new, highly lipophilic ionophore of the group of bis-nitrobenzo-15-crown-5 derivatives with urethane linkage when used in liquid membrane electrodes are evaluated with special regard to the requirements of biological and clinical applications. Potentiometric steady-state and flow-through dynamic data are presented to prove the sensor capabilities for clinical and physiological potassium determinations.

Novel bis-crown-ether derivatives for potassium sensors

Abstract A variety of bis-benzo-15-crown-5 derivatives were designed and studied with the aim of developing potassium sensors of biological relevance. the significant advantages of bis-/o-nitrophenyl/urethanes have been explained by the existence of NO2-NH hydrogen bonds proved indirectly. the performance characteristics of the prime ligands based sensors were compiled together with potassium assays in biological matrices.

Acylation of Resorcinol on Clay Catalysts

Abstract Using a series of clay based catalysts (KSF, KSF/0, KP10, K10, K0, KS), resorcinol is acylated in 1,2-dichloroethane by phenylacetyl chloride with a heterogeneous catalytic procedure. The yield of 1-(2,4-dihydroxyphenyl)-2-phenyl-ethanone is in correlation with the specific surface area of the catalyst.

Bis-crown ether derivatives as ionophores for potassium selective electrodes

ZusammenfassungDie Beziehung zwischen der chemischen Struktur und der potentiometrischen Ionen-Selektivität einer neuen Gruppe von Bis-Kronenether-Derivaten wurde eingehend untersucht. Es ergab sich, daß bei Bis-benzo-15-krone-5-Derivaten mit einer Urethanbindung die NO2-Substitution an beiden Benzolringen für die potentiometrische Effektivität von großer Bedeutung ist. Hinweise werden gegeben zur Interpretation der Selektivitäts-steigernden Wirkung des NO2-Substituenten. Die Leistungsfähigkeit der neuen Elektroden auf Ligandenbasis wird mit der von üblichen K-selektiven Sensoren verglichen.SummaryThe correlation between the chemical structure and potentiometric ion-selectivity of a new group of biscrown ether-derivatives has been studied in detail. It was concluded that with bis-benzo-15-crown-5 derivatives with a urethane linkage, NO2-substitution on both benzene rings is of utmost importance with respect to potentiometric performance. Hints have been given for the interpretation of the selectivity increasing effect of the NO2-substituent. The performance characteristics of the new ligand based electrodes were compared with those of the existing potassium selective sensors.

Thermoanalytical studies on crown ether-alkali complexes

Solid samples prepared from benzo-15-crown-5, its nitro, acetylamino and decanoylamino derivatives (Group I), and chloro-dibenzo-aza-crown ethers (Group II) with alkali metal salts were studied. The existence of solid adducts between LiBr, NaSCN, KSCN and crown ethers of group I was proved by DSC. The melting points of adducts of the same ligand were found to increase in KSCN<NaSCN<LiBr order. DSC and TG results suggested a ligand scission mechanism of thermal decomposition for all the complexes except that of benzo-15-crown-5 and KSCN where a dissociation and evaporation process took place. The samples prepared from crown ethers belonging to group II were found to be mechanical mixtures of the alkali salts and crown compounds.

Selectivity of C- Versus O-acylation of diphenols by clay catalysts. I. Acylation of resorcinol with phenylacetyl chloride

Resorcinol was acylated by phenylacetyl chloride with a set of catalysts consisting of the montmorillonite-based K-series and their cation-exchanged forms. The selectivity of C-acylation over O-acylation could be significantly increased by an appropriate ion exchange and by a solvent-free reaction mode, resulting in a 60% preparative yield of 1-(2,4-dihydroxyphenyl)-2-phenyl-ethanone.