Pseudo [M(ii)7] (M = Co, Ni and Zn) metallocalix[6]arene hosts encapsulate a range of organic guest molecules in the solid state

Abstract

We present the successful encapsulation of a number of small organic guest moieties within the molecular cavities of pseudo [M₇] (M = Co(II), Ni(II) and Zn(II)) metallocalix[6]arene hosts and include the complexes [(2-fur)⊂Zn(II)₇(OMe)₆(L)₆](NO₃)₂·3H₂O (1), [(3-fur)⊂Co(II)₇(OH)₆(L)₆](NO₃)₂·4.5H₂O (6), [(bzal)⊂Zn(II)₇(OMe)₆(L)₆](NO₃)₂·5H₂O (7), [(2-acetylfuran)⊂[Ni(II)₇(OMe)₆L₆(NO₃)₂]·3H₂O (12) and [(coumarin)⊂[Ni(II)₇(OH)₆(L)₆(NO₃)₂·3H₂O (20) (where LH = 2-methoxy-6-[(E)-(methylimino)methyl]phenol). Guest inclusion of the species 2- and 3-furaldehyde, benzaldehyde, 2-thiophenecarboxaldehyde, 2-acetylfuran, acetophenone, 1-indanone and coumarin was evidenced through a combination of FT-IR, solid state ¹³C NMR, X-ray diffraction studies and TGA measurements. Guest packing coefficients were produced for a cross-section of these materials to give values ranging from 34% (in [(3-fur)⊂Ni(II)₇(OH)₆(L)₆](NO₃)₂·3H₂O (5)) to 75% (in [(2-acetylfuran)⊂[Co(II)₇(OMe)₆(L)₆](NO₃)₂·7H₂O (13)).