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Crystal and molecular structures of two new macrocyclic imine ligands derived from dehydroacetic acid

Recently, much attention has been paid to research on design, synthesis and structure of macrocyclic molecules due to their selectivity for metal ions and ability to mimic various naturally occurring macrocyclic systems. Hence, it is important to investigate some novel macrocyclic ligands containing oxygen and nitrogen donor atoms derived from a physiologically active oxygen heterocyclic compound, dehydroacetic acid (3-acetyl-4-hydroxy- 6-methyl-2H-pyran-2-one). Two new imine ligands were prepared by condensation of 1, 3- diaminopropane or 1, 2-diaminobenzene with dehydroactic acid (1:2). Their structures have been established by X-ray analysis. Crystal data: (I) C19O6N2H22 . 0.5 CH3OH, Mr = 374.39, monoclinic, a = 9.31820(10), b = 15.4152(2), c = 13.8754(2) &Aring ; , beta = 108.6330(10), V = 108.6330(10) &Aring ; 3, Z = 4, space group P21/c Dcalc = 1.317 g cm-3, F(000) = 792, *(MoK*) = 0.7107 &Aring ; . (II) C22O6N2H21 . CH3OH, Mr = 440.44, trigonal, a = 23.9242(3), b = 23.9242(3), c = 20.0525(3) &Aring ; , V = 9939.7(2) &Aring ; 3, Z = 18, space group , Dcalc = 1.324g cm-3, F(000) = 4176, *(MoK*) = 0.7107 &Aring ; . Both molecular structures consist of two beta- enaminone-2-pyrone rings interlaced with either alkyl chain (I) or phenyl ring (II). Corresponding characteristic C-C bond lengths ranging from 1.418(2)-1.437(2) &Aring ; and C-N, from 1.313(2)-1.322(2) &Aring ; are indicative of the enamine C=C-N-H form of both ligands. Owing to the strong N-H...O intramolecular hydrogen bonds, reinforced with &#61552 ; -delocalization along the heterodienic O=C-C=C-NH moiety [d(N...O) of 2.541(2) and 2.561(2)&Aring ; for (I) and 2.542(2) and 2.561(2) for (II) ], in both crystal structures, the enaminonic fragments adopt the form of six membered rings.

macrocyclic imine ligands ; dehydroacetic acid ; crystal and molecular structures

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