Synthesis and crystal structure of tris(9,10-phenanthrenedioxy)cyclotriphosphazene. A new clathration system

Tris(9,10-phenanthrenedioxy)cyclotriphosphazene forms inclusion adducts with a wide range of organic small molecules. This novel host molecule crystallized with p-xylene to form a triclinic 1:1 inclusion adduct, space group P1̄ (No. 2), having unit cell of dimensions a = 12.724(3) Å, b = 19.347(5) Å, c = 9.124(5) Å and α = 97.55(3)°, β = 106.13(3)°, γ = 72.46(2)°, Z = 2. In this adduct, p-xylene is confined within both cage and tunnel-like voids of the host lattice. The same host crystallized with 1,2-dichlorobenzene to form an orthorhombic inclusion adduct, space group P2₁2₁2₁ (No. 19), having a unit cell of dimensions a = 14.880(3) Å, b = 23.277(4) Å, c = 13.429(4) Å, and Z = 4. In general, the guest to host molar ratios for the 1,2-dichlorobenzene adduct varied from 1.1:1 to 1.3:1. 1,2-Dichlorobenzene, o-xylene, p-xylene, benzene, tetrahydrofuran, and cyclohexane were directly imbibed by tris(9,10-phenanthrenedioxy)cyclotriphosphazene to form air stable inclusion adducts. Powder X-ray diffraction of these adducts indicated that the crystal lattice formed is highly guest dependent. Inclusion adducts containing 1,2-dichlorobenzene, o-xylene, and p-xylene as guests were more stable than those containing tetrahydrofuran, benzene, or hexane. Selective inclusion of cyclohexane and o-xylene was achieved from hexane/cyclohexane and p-xylene/o-xylene mixtures.