Synthesis and characterisation of thioether crown hydrazones, and palladium(II) and platinum(II) complexes of 6-(2,4-dinitrophenylhydrazono)-1,4,8,11-tetrathiacyclotetradecane
Abstract
Reaction of the functionalised thioether crowns [14]aneS4-6-one (1,4,8,11-tetrathiacyclotetradecan-6-one, L1) and [10]aneS3-9-one (1,4,7-trithiacyclodecan-9-one, L2) with 2,4-dinitrophenylhydrazine in a protic solvent under acidic catalysis afforded the corresponding hydrazones L3 and L4, respectively, in high yield. Reaction of [14]aneS4-6-one with p-nitrophenylhydrazine under similar conditions affords the hydrazone L5. Reaction of L3 with [Pd(MeCN)4][BF4]2 in MeCN yielded the complex [Pd(L3)][BF4]2, while reaction of this ligand with [Pt(EtCN)4][CF3SO3]2 in MeCN afforded [Pt(L3)][CF3SO3]2. The single-crystal structures of L3–L5 and of [Pd(L3)][BF4]2 have been determined. In all cases, π–π stacking is observed, the free macrocycles crystallising as polymeric arrays of face-sharing hydrazone moieties. In [Pd(L3)]2+, π–π interactions alternate with face sharing between planar [PdS4]2+ units constructing a one-dimensional polymeric array. The hydrazone function forces distortions of the respective macrocyclic rings and imparts chirality to the [Pd(L3)]2+ cation. The potential of these molecules as building blocks for macrocyclic liquid crystals and extended supramolecular arrays is discussed, as is the need to consider steric factors in rationalising the reactivity of keto-functionalised thioether crowns.