Metal exchange study of pyrogallol[4]arene based dimers

Abstract

The synthesis, the single-crystal X-ray structure, and a metalexchange study of a zinc-seamed C-hexylpyrogallolij4]arene/ PgC 6 Zn dimer are reported. The packing arrangement of the PgC 6 Zn dimer shows interdigitation between the C-hexyl tails. Neighboring dimeric nanocapsules are slightly offset with respect to each other, with CH⋯π interactions between the hexyl tails and the external pyridine ligands. In situ metal exchange with nickel nitrate does not result in expulsion of zinc metal centers from a preformed dimer, a result suggesting a framework robustness that may make formation of (magnetically interesting) mixed-metal dimers difficult. The suggested robustness of zinc-seamed pyrogallol[4]arene-based dimers is supported by quantum chemical calculations on related PgC 0 Zn and PgC 3 Zn dimers.

Metal Organic Nanocapsules as Two-Dimensional Network Building Blocks

“…The affinity 1 exhibits for the ZE 2 models makes it an ideal candidate against which to compare energetic and geometric properties for the ligands screened in this study. It should also be noted that the calculated BDEs for (ZE 2 ) 1,2 1 fall within the range calculated for a variety of experimentally observed capsular exo ligands (80–120 kJ/mol). ,, The cited range is from the M05-2X/B2-PP//PBE0/LANL2DZ BDEs for ZE 2 Y, where Y includes DMF (81.3 kJ/mol), Py (95.3 kJ/mol), and DMSO (121.7 kJ/mol).…”

“…A discrepancy of 6°in the trans bond angles changes the τ5 value by 0.1. Complexes optimized with a smallcore pseudopotential tend to have τ5 values that fall within the 0.37−0.45 range observed experimentally, 28,42,49 and complexes optimized with a large-core pseudopotential do not. The difference in the τ5 values for the (ZE 2 ) 1,2 1 complexes versus the (ZE 2 ) 1,2 2(3) complexes is primarily due to the tilting of the Y ligand in the latter complexes, which maximizes the hydrogen bonding interaction between the ligand and the zinc model complex (Table S2B).…”

“…Although the calculated bond lengths and bond angles generally lie within the ranges observed for the solid-state structures, the calculated τ5 values do not agree with experiment (0.37 ≤ τ5 ≤ 0.45). 28,42,49 As noted previously, 42 however, the discrepancy in calculated and experimental τ5 values is due to the greater flexibility of the model complexes compared with the capsules. In general, the zinc coordination spheres in the model complexes show very little distortion from either trigonal bipyramidal or square pyramidal character.…”

“…It should also be noted that the calculated BDEs for (ZE 2 ) 1,2 1 fall within the range calculated for a variety of experimentally observed capsular exo ligands (80−120 kJ/mol). 28,43,49 The cited range is from the M05-2X/ B2-PP//PBE0/LANL2DZ BDEs for ZE 2 Y, where Y includes DMF (81.3 kJ/mol), Py (95.3 kJ/mol), and DMSO (121.7 kJ/ mol). Another measure by which to compare linked systems is the intercapsular distance.…”

“…Common structural motifs of PgCbased entities include the hexameric (PgC) 6 M 24 and dimeric (PgC) 2 M 8 MONCs formed with transition metal cations 22−28 and the infinite-layered networks formed with alkali cations, 29,30 among others. 31,32 The cage-like coordination complexes formed from transition metal cations are very similar in size and shape to their noncovalently seamed complementary supramolecules 28,33 and feature two distinct coordination patterns: eight distinct trimetal clusters in the hexamer and an "octametal belt" in the dimer. 28,[34][35][36][37][38][39]49 The coordination number of the metal cations is also different in the two motifs, with tetra-or hexacoordinate sites seen in the hexamer and pentacoordinate sites typically seen in the dimer.…”