Wolodymyr Zazulak

CHROMOGENIC CRYPTAHEMISPHERAPLEXES FOR THE DETERMINATION OF POTASSIUM IN AQUEOUS SOLUTIONS

Abstract A series of novel chromogenic cryptahemispheraplexes whose core structures are hybrids between those of cryptands and spherands were designed and synthesized for the selective complexation of potassium in aqueous solutions. Two different cavity sizes obtained by combining diaza-18-corand-6, [2.2], and diaza-21-corand-7, [3.2], with the half spherand were explored. These compounds bear various picrylamine-type chromophoric groups for generating a spectrophotometric response. The resulting compounds having the [2.2] cavity are 2,4-dinitro-6-(trifluoromethyl)anilino ( 2 ), 2,6-dinitro-4-(trifluoromethyl)anilino ( 3 ), 4-cyano-2,6-dinitroanilino ( 4 ) and 6-( N,N -diethylsulfonamide)-2,4-dinitroanilino ( 5 ) and having the [3.2] cavity 2,4,6-trinitroanilino ( 6 ). A decrease in the p K a of the chromogenic compound is observed with complexation of potassium ion, which results in an increase in absorbance observed at the characteristic wavelength of the ionized form of the chromophoric group. The p K a values for the NaBr complexes (the original form of the chromogenic cryptahemispheraplexes) ranged from 7.93 to 9.27 with Δp K a [p K a (KL) - p K a (NaL)] values of −0.39 ( 6 ), −0.59 ( 3 ), −0.99 ( 4 ), −1.30 ( 5 ), and −1.69 ( 2 ). The best responses to potassium were obtained with compounds 2 , 5 and 6 , which also had the best molar absorptivities, 1.9 × 10 4 −2.0 × 10 4 l mol −1 cm −1 Compound 6 , owing to the larger cavity size, was less sensitive towards potassium and suitable for use with potassium solutions of higher concentration.

Chromogenic lithium cryptahemispheraplexes for determination of sodium in aqueous solutions

Abstract Three new lithium cryptahemispheraplexes for selective complexation of sodium in aqueous solutions were synthesized. Combining diaza-12-crown-4 or diaza-14-crown-4 with the rigid trianisyl concave produced hosts with two different cavity sizes. These compounds, having the [1.1] cavity, incorporate 2,4-dinitro-6-(trifluoromethyl)anilino ( 2 and 5 ) and 2,6-dinitro-4-(trifluoromethyl)anilino ( 4 ) chromophoric groups for generating a chromogenic and kinetic response to sodium ion. For comparison, the end product of sodium complexation with compound 2 (cryptahemispheraplex 3 ) was isolated and characterized.

Synthesis and metal ion complexing properties of novel chromogenic cryptands

Four novel chromogenic benzocryptands and one side-armed chromogenic cryptand have been synthesized and their complexing abilities for alkali metal cations are described.

New small-cavity cryptand chromoionophores for complexation of lithium and sodium ions

Two new chromoionophores based on small-cavity cryptands with inward-facing phenolic groups have been synthesized. Both compounds incorporate a diaza-12-crown-4 moiety and bear ap-nitrophenylazo chromogenic group attached to the cryptand phenol framework,para to the phenolic group. Chromogenic crytand3 exhibits selectivity for Li+ ions in the extraction mode but shows very little cation response in homogeneous aqueous media. A larger analog, chromogenic cryptand4, acts as a sodium scavenger and cannot be obtained in a sodium-free form.