Nitrogen- and sulfur-containing models for metallo-enzymes. Part I. Synthesis and physical studies of 2(2-pyridyl)-1,3-dithioalkyl-2-propanols, 2(2-pyridyl)- and 2(2-imidazolyl)-1,3-dimercapto-2-propanols

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Abstract
Several compounds of the title class have been synthesized as small-molecule analogues for the metal-binding sites in such biochemical systems as ADH. The ligands containing pyridine and two thioethers do not bind divalent metals (Co2+, Zn2+, Cu2+, Ni2+), strongly suggesting that thioethers are poorly chelated. However, the analogues containing free SH groups bind divalent metals very strongly, producing complexes with limited solubility at pH values in excess of 6. Titration of the latter ligands in the presence of 1 equiv. Zn2+ indicates the consumption of 3 equiv. OH− by pH 6, one for the [Formula: see text] ionization, and one for each S—H bound to Zn2+. On the basis of these data the resulting complexes are considered to neutral bis-thiolates. The relationship of these data to the state of ionization of the Zn2+-cysteine SH's in ADH is discussed.

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