The tetragonal apohost phase of p-tert-butyltetramethoxythiacalix[4]arene absorbs hydrochloric acid and iodine. These guest molecules occupy different sites in the solid-state structure - either within the small intrinsic voids of the macrocycle or within the interstitial spaces between the host molecules. This study illustrates the dynamic deformation of the host, providing strong mechanistic insight into the diffusion of guests into this seemingly non-porous material.
This work investigates the supramolecular aggregation of Cu(II) complexes based on a combination of the heterocyclic N-donor ligand 2-aminopyrimidine (2-apym) and a variety of different carboxylate ligands, like salicylic acid (H 2 SAL), maleic acid (H 2 MAL), and glycine (HGLY). Four new Cu(II) complexes [Cu(HSAL) 2 (2-apym) 2 ] (I), [Cu(HSAL) 2 (2-apym) 2 ]?(H 2 SAL) 2 (2-apym) (I9), {(H2apym)[Cu(GLY)(m-Cl) 2 Cl]} n (II) and [Cu(m-MAL)(2-apym)] n (III) have been synthesized and characterized by elemental analyses, FT-IR spectra, and X-ray structural analyses. I and I9 appear as molecular clusters whereas II is a 1-D coordination polymer with weak axial Cu-Cl interactions. However the last one shows a 2-D coordination polymer with trigonal bipyramidal geometry for Cu(II) ion. The two last cases have no molecular fragments packed with non-covalent interactions. In these new supramolecular compounds, existent species join together with the cooperation of multiple inter/intra-molecular classical O-H … O/N, N-H … O/N, and non-classical N-H … Cl hydrogen bonds (H-bonds), offset face to face p … p, edge to face C/N-H … p, and lp … p stacking interactions in the form of various homo/hetero-synthons leading to architecturally different structures. DFT calculations were used to estimate the binding energy of the involved non-covalent interactions and whole stabilization energy of related network of I, I9, and II. Theoretical calculations facilitate the comparison of intermolecular interactions, which demonstrate that for all of I-II, N-H … N and N-H … O H-bonds govern the network formation. The equilibrium constants for the three protontransfer systems including SAL/2-apym, GLY/2-apym, MAL/2-apym, the stoichiometry and stability of complexation of these systems with Cu 2+ ion in aqueous solution were investigated by potentiometric pH titration method. The stoichiometries of the most complex species in solution was compared to the crystalline Cu 2+ ion complexes with the cited proton-transfer systems.
We demonstrate that covalently bonded chiral organic hexaamine, rigidified by a methylene bridge, assembles into crystalline inclusion compounds and microporous materials. The inclusion of primary alcohol molecules belonging to the homologous series from ethanol to n-octanol is intrinsic to the triangular molecular shape and columnar stacking of these triangular units. Our studies show that through the choice of differently sized guest molecules (short-or long-chain) we were able to increase the accessible solvent volume from cavities, located inside columnar stacking of triangular units, to one-dimensional undulating channels. While the short-chain molecules occupy voids, the long-chain molecules are included in the channels. By using branched chain solvent during crystallization we were able to isolate dimorphic apohost forms that give rise to two different types of new materials: porous crystals with 1D channels and crystals that possess isolated 0D pockets.
Calixsalens, chiral triangular hexaimines are readily synthesized by [3 + 3] cyclocondensation of trans-(R,R)-1,2-diaminocyclohexane with 2-hydroxyisophthalaldehyde derivatives. The usually rigid calixsalen ring is able to invert its conformation as a consequence of steric repulsion between bulky substituents at the C5 positions of the aromatic rings. The steric and electronic nature of the substituents does not affect only the conformation of the macrocycle. Small polar substituents enforce dimeric self-association to form an apohost where each of the monomers simultaneously serves as the host and the guest of its partner. Non-associating calixsalens form assemblies in which two symmetry-related molecules are arranged in a head-to-head fashion to form a capsule, or unimolecular cages that are able to entrap solvent molecules in their intrinsic voids.
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