Cooperative Effect of Anion and Mole Ratio on the Coordination Modes of an NO₂S₃-Donor Macrocycle

Abstract

Synthesis of an NO2S3-macrocycle (L) incorporating a pyridine subunit and its anion and/or mole ratio-dependent coordination modes in the formations of mercury(II) complexes is reported. When the mercury(II) salts with different anions (ClO4(-) or Br(-)) were reacted with L, the Hg(ClO4)2 afforded a typical endocyclic complex [HgL](ClO4)2 (1). Meanwhile, the HgBr2 gave an exocyclic complex [HgLBr2] (2) in which the metal ion exists outside the macrocyclic cavity. The observed anion effect on the coordination modes can be explained by the anion coordination ability toward the metal cation. In the mole ratio variation experiments, notably, the use of 1.5 equiv or above of HgBr2 in the same reaction condition gave a unique endo/exocyclic dumbbell-type complex 3, [Hg4L2Br6][Hg2Br6]. However, the formation of the endocyclic Hg(ClO4)2 complex 1 shows no mole ratio dependency. To monitor the observed mole ratio-dependent exocoordination products as well as their reactivities and reversibility, systematic powder X-ray diffraction (PXRD) analysis was also applied. From single crystal X-ray and PXRD analyses, it was found that endocyclic complex 1 is not reactive, but complexes 2 and 3 are reactive and show the reversibility between them in the presence of the corresponding reactants.

Syntheses and Crystal Structures of a Novel 20‐Membered N3O2‐Donor Macrocycle and Its Disilver(I) Bis(Macrocycle) and Monocadmium(II) Complexes

“…However, macrocycles with the 20–23 membered rings are expected to give the unusual coordination topologies, while another advantage is that the latter category is usually relatively easier to prepare than larger analogs. Recently, several kinds of 20‐ to 23‐membered oxathia‐tribenzo macrocycles and their discrete and polymeric complexes showing less common stoichiometric ratios have been reported . To the best of our knowledge, such 20‐membered O 2 N 3 ‐donor analogs have not been reported so far.…”

“…On the other hand, the preparation and structural characterization of the complexes with 20‐ to 23‐membered macrocycles have been less investigated because their cavity sizes are too large for planar complexation with one metal ion but too small for coordination with two metal ions simultaneously . However, macrocycles with the 20–23 membered rings are expected to give the unusual coordination topologies, while another advantage is that the latter category is usually relatively easier to prepare than larger analogs.…”

Endocyclic and Endo–Exocyclic Silver(I) Complexes of Thiaoxaaza Macrocycles: Crystallographic and NMR Studies

“…The thiaoxaaza-macrocycles L 1 and L 2 were synthesised as described previously by us. [20,22] Although the crystal structures of several soft metal complexes of L 1 and L 2 have been reported, [20][21][22] those of the free ligands have not been reported. Thus, determinations of the crystal structures of the macrocycles were carried out as a part of the present study ( Fig.…”

“…[19] As an extension of our previous studies on exo-coordinationbased networking, [8] we expect that the adoption of the endoand exo-coordination modes may be controlled by employing the soft binding site alternation of thiamacrocycles, including the interdonor distance. In the present work, we therefore propose a 19-membered NO 2 S 2 -macrocycle L 1 [20] and a 20membered NO 2 S 3 -macrocycle L 2 , [21,22] which share a rigid NO 2 donor site with one pyridine and two aromatic rings.…”

“…[20] We also introduced the anion-dependent endo-and exocyclic mercury(II) complexes of L 2 (Chart 1). [22] Further, L 2 forms a unique dumbbell-type mercury(II) bromide complex [22] and cadmium(II) iodide complexes [21] via endo-exocyclic coordination. We now report an extension of these studies that form endo-and endo-exocyclic complexes, with emphasis on the different coordination modes associated with the macrocycles.…”