Endo- and Exocyclic Supramolecular Complexes of Mixed-Donor Macrocycles via [1:1] and [2:2] Cyclizations

Abstract

A 20-membered N2O2S2 macrocycle (L(1)) and a 40-membered N4O4S4 macrocycle (L(2)) obtained from the mixed products via respective [1:1] and [2:2] cyclization are employed, and a comparative investigation of the coordination behavior of these macrocyclic ligands with nickel(II), cadmium(II), and silver(I) is reported. The X-ray structures of seven complexes (1-7) have been determined, and a range of structural types and coordination modes, including mono- to multinuclear and endo- to exocyclic coordination, is presented. The cation-dependent endocyclic 1:1 (metal-to-ligand) complex [Ag(L(1))]NO3 (1) and a sandwich-like 1:2 [Cd(L(1))2](NO3)2 (2) complex exhibiting different stoichiometries and metal positions in the complexes were obtained by the reactions of the smaller macrocycle L(1) with AgNO3 and Cd(NO3)2, respectively. Meanwhile, the reactions of L(1) with Ni(ClO4)2·6H2O and Ni(NO3)2·6H2O afforded the anion-dependent perching-type mononuclear solvato-complex [Ni(L(1))(CH3CN)3](ClO4)2·2CH3CN (3) and the sandwich-like complex [Ni(L(1))2(NO3)2] (4), respectively. In the complexations of the larger macrocycle L(2) with AgNO3, two endocyclic dinuclear complexes [Ag2(L(2))(CH3CN)2](NO3)2 (5) and [Ag2(L(2))](NO3)2 (6) with different coordination environments were isolated as a kinetic (5) and thermodynamic controlled (6) products in neutral condition. The identical reaction in acidic condition afforded a stairtype one-dimensional (1-D) coordination polymer {[Ag2(H4L(2))(μ2-NO3)(NO3)2](NO3)3·CH3CN·3H2O}n (7) in which the disilver(I) complex cation units are connected by nitrate ions. From these results, the effects of the cation, anion, and size ratio on the topologies of the resulting solid complexes are discussed. NMR titrations of L(1) and L(2) with silver(I) nitrate were also carried out to explore their complexation behaviors in solution and for comparison with the solid state structures.