Mercaptothiazolinyl functionalized hexapodal and tripodal receptors on benzene platform: formation of silver ion assisted hexanuclear metallocage vs metal–organic polymer

Abstract

Mercaptothiazolinyl functionalized hexapodal (L¹ ) and tripodal (L²) receptors on the benzene platform have been synthesized easily in good yields and structurally characterized by a single-crystal X-ray crystallographic study. In the solid state, L¹ shows an orientation of six arms in 1,3,5 vs 2,4,6 facial steric gearing fashion, whereas L² adopted C_2v symmetry where two of its thiazolinyl arms are oriented in one direction and the third arm in the another direction. Two silver complexes of L¹, 1 ([2(L¹)·6(AgClO₄)·2(CHCl₃)·HClO₄]) and 2 ([2(L¹)·6(AgClO₄)]), that are suitable for single-crystal X-ray studies are isolated upon the slow diffusion of a dimethylformamide solution of AgClO₄ to the solution of L¹ in chloroform and dichloromethane, respectively. Similarly, upon the slow diffusion of an acetonitrile solution of AgClO₄ to the chloroform solution of L², colorless crystals of the silver complex of L², 3, are successfully isolated. The structural analyses of 1 and 2 show the formation of a silver ion assisted hexanuclear metallocage Ag₆(L¹)₂ via dimeric assembly of L¹ with multiple clefts and pockets toward guests binding. In 1, two chloroform molecules sit in top and bottom pockets, whereas six perchlorate counteranions are bound in six clefts between the silver ion pillared side arms of the metallocage. Though complex 2 shows the formation of a metallocage like 1, the single crystal structural analysis depicts perchlorate counteranions bonded to the silver atoms of the metallocage. On the contrary, the silver complex of tripodal receptor L², 3, shows the formation of a metallo-organic polymeric network of L² and Ag⁺. To the best of our knowledge, this work represents the first report on the formation of an M₆L₂ type metallosupramolecular cage topology with multiple clefts for guest binding by a semirigid hexapodal receptor.