engleski

SYNTHESIS AND STRUCTURAL CHARACTERISATION OF A N4O4-DONOR SCHIFF BASE MACROCYCLE. HOST-GUEST INTERACTION WITH IODINE

There is a great interest in macrocycles that can form open tubular structures. These materials can be classified as organic zeolites. Most of the investigations in this particular research area are based on the shape-persistent macrocycles that have a noncollapsible backbone and a well defined inner void in the size range from less than 1 up to several nanometers [1]. Because of their rigid structure, organic zeolites have potential application as host materials. Furthermore, size of voids can be rationally designed by utilization of supramolecular forces or by simple increase or decrease of number of atoms in the macrocyclic ring. The promising field of research in this area are macrocyclic Schiff bases that can be relatively easily synthesized by simple condensation reactions of suitable formyl and amino precursors. There are several examples of these types of compounds with selective uptake of gaseous species [2]. This paper addresses synthetic procedures for obtaining a macrocyclic Schiff base, essentially built from dialdehyde and diamine precursors and host-guest interactions with iodine vapors. In this paper we report synthesis of a large macrocyclic Schiff base, derived from p-phenylendiamine and 2-[5-(2-formylphenoxy)pentoxy]benzaldehyde. The crystal and molecular structure of the compound was determinated by single crystal X-ray analysis. The molecule crystallizes in the monoclinic crystal system, P 21/c space group. In the crystal, the molecules are linked with very weak C-H•••N interactions along the a-axis, thereby forming a tubular structure. The derived compound is a large macrocyclic Schiff base with 38 atoms in the inner macrocyclic ring and a well-defined inner void of 441, 8 Å3. Also, the diagonal distances between donor atoms are around 1.3 nm. Therefore, this compound can be considered as a nano-tubular material. In addition, we have studied absorption of iodine vapors inside the tubular voids. The compound was treated with iodine vapors inside a sealed chamber for 24 hours to form a host-guest complex with iodine. Small amount of solid material (around 10 mg) was subsequently treated with ethanol to remove iodine species on the crystal surface and the amount of absorbed iodine was determined by TGA. The host: guest ratio was found to be approximately 2:1. In addition, the guest-free compound and iodine-loaded compound were characterized by FTIR and Raman spectroscopy in order to verify the stability of organic framework.

macrocyclic Schiff base; host-guest; iodine

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