Inclusion of Polymers within the Crystal Structure of Tris(o-phenylenedioxy)cyclotriphosphazene

Abstract

Tris(o-phenylenedioxy)cyclotriphosphazene was found to form hexagonal host-guest inclusion adducts (clathrates) with the polymers: cis-1,4-polybutadiene, trans-1,4-polyisoprene, polyethylene, poly(ethylene oxide), and polytetrahydrofuran. Single-crystal X-ray diffraction studies of both the polyethylene and poly(ethylene oxide) inclusion adducts revealed the presence of individual polymer chains extended along tunnel-like voids within the host lattice. Both polyethylene and poly(ethylene oxide) were incommensurate within the tunnel-like voids preventing the exact elucidation of the polymer conformation. Average repeat unit lengths calculated for these polymers suggest that both are in an extended conformation. Both the polyethylene and poly(ethylene oxide) adducts crystallized from benzene in the space group P6 3 /m. Inclusion adducts of the five different polymers were examined by differential scanning calorimetry (DSC) and powder X-ray diffraction. In each case, the melting point of the inclusion adduct was higher than either the melting point of the pure polymer or the pure host. The melting points of oligomeric polyethylene and poly-(ethylene oxide) inclusion adducts increased as the molecular weight of the included oligomers increased. Removal of cis-1,4-polybutadiene and poly(ethylene oxide) from the host lattice was achieved through chemical decomposition of tris(o-phenylenedioxy)cyclotriphosphazene. Linear polybutadiene was separated from a mixture with highly branched polybutadiene through selective adduct formation.

A Phthalocyanine Clathrate of Cubic Symmetry Containing Interconnected Solvent‐Filled Voids of Nanometer Dimensions

“…Since the middle of the last century, the crystal structures of a vast number of organic inclusion compounds (namely, clathrates) have been determined 1. In most cases, only one or two guest molecules reside at well‐defined sites within the unit cell of the crystal; however, for a number of structures, such as those derived from urea,2 thiourea,2 or tris( o ‐phenylenedioxy)cyclotriphosphazene,3 extended channels are formed within which the guest molecules, usually the solvent of recrystallization, are contained. Recent extensive research that involves rigid and extended organic components linked through hydrogen‐bonding interactions4 or by coordination to metal ions (namely, metal–organic frameworks (MOFs))5 has resulted in structures in which solvent‐filled channels occupy over 70 % of the total volume of the crystal.…”

A Phthalocyanine Clathrate of Cubic Symmetry Containing Interconnected Solvent‐Filled Voids of Nanometer Dimensions

“…[1] In most cases, only one or two guest molecules reside at well-defined sites within the unit cell of the crystal; however, for a number of structures, such as those derived from urea, [2] thiourea, [2] or tris(ophenylenedioxy)cyclotriphosphazene, [3] extended channels are formed within which the guest molecules, usually the solvent of recrystallization, are contained. Recent extensive research that involves rigid and extended organic components linked through hydrogen-bonding interactions [4] or by coordination to metal ions (namely, metal-organic frameworks (MOFs)) [5] has resulted in structures in which solvent-filled channels occupy over 70 % of the total volume of the crystal.…”

“…The macrocycles are arranged so that their Zn 2+ ion and its axial ligand point towards the center of the cube. Based upon the distance between the protruding Zn 2+ ions on opposite sides of the cube, the minimum diameter of the cube is 2.33 nm, which gives a cavity volume of at least 8 nm 3 , even if the width, calculated from the sum of the van der Waals radii, of the phthalocyanine unit (0.33 nm) is taken into account. In addition to the axial water ligand attached to the Zn 2+ center of 1, there are a further 24 water molecules per unit cell that appear to be associated through hydrogen-bonding interactions to the meso nitrogen atoms of the phthalocyanine ring (Figure 1 d) [18] indicate a solvent-accessible void volume of 20.5 nm 3 per unit cell (namely, 38.2 % of the total volume).…”

Stereoisomer Discrimination Through π‐Stacking Interactions in Spirocyclic Phosphazenes Bearing 2,2′‐Dioxybiphenyl Units

“…The spirocyclotriphosphazenes, bearing one to three dioxyaryl or other nucleophilic groups that cyclize to form rings with the phosphorus atoms,4,5 are optimal candidates for such applications. They represent a unique class of highly tailorable host molecules,6,7 and they have received much attention for the synthesis of new, high‐molecular‐weight spiropolyphosphazenes containing functionalized and optically active groups 8,9. The basic research interest in the structural characterization of spirocyclotriphosphazenes stems from their ability to form inclusion adducts with polymers,6 their ability, in some cases, to induce polymerization of a guest,7 and, especially, their potential for stereoisomer discriminaton.…”