Chiral one- and two-dimensional silver(I)–biotin coordination polymers

Abstract

Reaction of biotin {C 10 H 16 N 2 O 3 S, H L ; systematic name: 5-[(3a S ,4 S ,6a R )-2-oxohexahydro-1 H -thieno[3,4- d ]imidazol-4-yl]pentanoic acid} with silver acetate and a few drops of aqueous ammonia leads to the deprotonation of the carboxylic acid group and the formation of a neutral chiral two-dimensional polymer network, poly[[{μ 3 -5-[(3a S ,4 S ,6a R )-2-oxohexahydro-1 H -thieno[3,4- d ]imidazol-4-yl]pentanoato}silver(I)] trihydrate], {[Ag(C 10 H 15 N 2 O 3 S)]·3H 2 O} n or {[Ag( L )]·3H 2 O} n , (I). Here, the Ag I cations are pentacoordinate, coordinated by four biotin anions via two S atoms and a ureido O atom, and by two carboxylate O atoms of the same molecule. The reaction of biotin with silver salts of potentially coordinating anions, viz. nitrate and perchlorate, leads to the formation of the chiral one-dimensional coordination polymers catena -poly[[bis[nitratosilver(I)]-bis{μ 3 -5-[(3a S ,4 S ,6a R )-2-oxohexahydro-1 H -thieno[3,4- d ]imidazol-4-yl]pentanoato}] monohydrate], {[Ag 2 (NO 3 ) 2 (C 10 H 16 N 2 O 3 S) 2 ]·H 2 O} n or {[Ag 2 (NO 3 ) 2 (H L ) 2 ]·H 2 O} n , (II), and catena -poly[bis[perchloratosilver(I)]-bis{μ 3 -5-[(3a S ,4 S ,6a R )-2-oxohexahydro-1 H -thieno[3,4- d ]imidazol-4-yl]pentanoato}], [Ag 2 (ClO 4 ) 2 (C 10 H 16 N 2 O 3 S) 2 ] n or [Ag 2 (ClO 4 ) 2 (H L ) 2 ] n , (III), respectively. In (II), the Ag I cations are again pentacoordinated by three biotin molecules via two S atoms and a ureido O atom, and by two O atoms of a nitrate anion. In (I), (II) and (III), the Ag I cations are bridged by an S atom and are coordinated by the ureido O atom and the O atoms of the anions. The reaction of biotin with silver salts of noncoordinating anions, viz. hexafluoridophosphate (PF 6 − ) and hexafluoridoantimonate (SbF 6 − ), gave the chiral double-stranded helical structures catena -poly[[silver(I)-bis{μ 2 -5-[(3a S ,4 S ,6a R )-2-oxohexahydro-1 H -thieno[3,4- d ]imidazol-4-yl]pentanoato}] hexafluoridophosphate], {[Ag(C 10 H 16 N 2 O 3 S) 2 ](PF 6 )} n or {[Ag(H L ) 2 ](PF 6 )} n , (IV), and catena -poly[[[{5-[(3a S ,4 S ,6a R )-2-oxohexahydro-1 H -thieno[3,4- d ]imidazol-4-yl]pentanoato}silver(I)]-μ 2 -{5-[(3a S ,4 S ,6a R )-2-oxohexahydro-1 H -thieno[3,4- d ]imidazol-4-yl]pentanoato}] hexafluoridoantimonate], {[Ag(C 10 H 16 N 2 O 3 S) 2 ](SbF 6 )} n or {[Ag(H L ) 2 ](SbF 6 )} n , (V), respectively. In (IV), the Ag I cations have a tetrahedral coordination environment, coordinated by four biotin molecules via two S atoms, and by two carboxy O atoms of two different molecules. In (V), however, the Ag I cations have a trigonal coordination environment, coordinated by three biotin molecules via two S atoms and one carboxy O atom. In (IV) and (V), neither the ureido O atom nor the F atoms of the anion are involved in coordination. Hence, the coordination environment of the Ag I cations varies from AgS 2 O trigonal to AgS 2 O 2 tetrahedral to AgS 2 O 3 square-pyramidal. The conformation of the valeric acid side chain varies from extended to twisted and this, together with the various anions present, has an influence on the solid-state structures of the resulting compounds. The various O—H...O and N—H...O hydrogen bonds present result in the formation of chiral two- and three-dimensional networks, which are further stabilized by C—H... X ( X = O, F, S) interactions, and by N—H...F interactions for (IV) and (V). Biotin itself has a twisted valeric acid side chain which is involved in an intramolecular C—H...S hydrogen bond. The tetrahydrothiophene ring has an envelope conformation with the S atom as the flap. It is displaced from the mean plane of the four C atoms (plane B ) by 0.8789 (6) Å, towards the ureido ring (plane A ). Planes A and B are inclined to one another by 58.89 (14)°. In the crystal, molecules are linked via O—H...O and N—H...O hydrogen bonds, enclosing R 2 2 (8) loops, forming zigzag chains propagating along [001]. These chains are linked via N—H...O hydrogen bonds, and C—H...S and C—H...O interactions forming a three-dimensional network. The absolute configurations of biotin and complexes (I), (II), (IV) and (V) were confirmed crystallographically by resonant scattering.