(4)AI. In the 4-acetylpyridine ligands the acetyl group is twisted from the pyridine ring plane by 14.1 (1) °. There is extensive intermolecular hydrogen bonding between the water groups and the thiocyanates and acetyl groups in adjacent molecules.
CaII, SrII, BaII, and PbII are effective templates ALTHOUGH it has not previously been synthesised, the for the synthesis of a conjugated, 18-membered, hexaconjugated macrocycle L (1) containing the 18-membered dentate 'N6' macrocycle; the crystal and molecular inner large ring, has been the subject of theoretical calculastructures of a PbII complex, and of a CdII complex tions by Honeybournel who predicted that (i) the six prepared by metal exchange, have been determined.nitrogen atoms would define a hexagon with a face dimension of ca. 2.8 A, (ii) when co-ordinated, the length of any
The product from the reaction of 2,6-diacetylpyridine with o-phenylenediamine contains one 1 2-membered and two 7-membered inner rings and not a single 18-membered inner ring as proposed by others.We have previously describedl some mononuclear nontransition metal complexes of the conjugated 18-membered hexadentate 'NB' macrocycle L1 derived from the cyclic (2 + 2) Schiff base condensation of 2,6-diformylpyridine with o-phenylenediamine. X-Ray analysis of the CdII and PbII complexes established that the co-ordinated macrocycle has a near planar hexagonal structure of hole radius ca. 2.7 A suitable for the complexation of large metal ions (ionic diameter ca. 2.2-2.7 A) but not for first row transition metal ions2 having ionic diameters less than 2.0 A. Attempts to
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