The location of p-dichlorobenzene in a single crystal of zeolite H-ZSM-5 at high sorbate loading

The crystal structure of a high-loaded complex of H-ZSM-5 with eight molecules of p-dichlorobenzene per unit cell has been solved by single-crystal X-ray diffraction. The orthorhombic space group P2₁2₁2₁ with a = 20.102 (6), b = 19.797 (9), c = 13.436 (3) Å and V = 5347 (3) ų has four Si_23.92Al_0.08O₄₈.2C₆H₄Cl₂ units per unit cell. D_x = 2.164 Mg m⁻³, λ(MoKα) = 0.71073 Å and μ(Mo Kα) = 0.876 mm⁻¹. The final R(wR) = 0.046 (0.039), w = 1/σ²(F), for 6090 observed reflections with I > 1.0σ(I) measured at 293 K. The straight channel parallel to [010] is slightly corrugated. The elliptical cross sections have limiting apertures of 6.0 × 4.9 Å (r_oxygen = 1.35 Å). The sinusoidal channel parallel to [100] is elliptical with major and minor axes of 6.1 × 4.8 Å, respectively. One of the two independent p-dichlorobenzene molecule lies at the intersection of the straight and sinusoidal channels with its long molecular axis almost parallel to (100) and deviating ~8° from [010]. The second p-dichlorobenzene molecule is in the sinusoidal channel. Its long molecular axis deviates almost 7° from [100] and is practically parallel to (010). The structural aspects are in all details comparable to those in the high-loaded H-ZSM-5/p-xylene complex [van Koningsveld, Tuinstra, van Bekkum & Jansen (1989). Acta Cryst. B45, 423–431] , except for the main interaction forces between the p-dichlorobenzene molecules at the channel intersection.

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