Organopalladium Complexes 5-Amino-3H-1,3,4-thiadiazoline-2-thione as Metalloreceptor

Abstract

Macrocycles containing two 5-amino-3H-1,3,4-thiadiazoline-2-thione 5 linking the 2- and 5-positions of the heterocycle unit and one 1,3-benzenedimethanethiol were prepared via the regiospecific S-alkylation of 5-amino-3H-1,3,4-thiadiazoline-2-thione. The 1,3-benzenedimethanethiol sites chelated to palladium metal ion to afford an organopalladium metalloreceptor. The structures of the macrocycles and metalloreceptors were established using 1 H and 13 C NMR, IR, MS spectrometry, and elemental analysis. The molecular recognition of the metalloreceptors (5a and 5b) was examined for some DNA/RNA nucleobases and some amino acid methyl ester by 'H NMR spectrometry. In case of 5a, the complexation ability increased in the order pyrazine / uracil /acetanilide < adenine < cytosine < phenylalanine methyl ester / tyrosine methyl ester. With 5b, the complexation ability also increased in the same order as 5a pyrazine / uracil <acetanilide <adenine < cytosine, however, the formation constants are larger than in case of 5a.