Coordination-Driven Self-Assembly of Macrocycles and 1D or 2D Coordination Polymers Using Heteroditopic Pyridyl-Carboxylate Ligands: The Case Study of 5-[(E)-2-(3-Pyridyl)-1-Diazenyl]-2-Hydroxybenzoate in Combination with {RnSn} (n=2 and 3)

Pro-ligand 5-[(E)-2-(3-pyridy1)-1-diazenyl]-2-hydroxybenzoic acid, H'HLmeta, was employed for the synthesis of four organotin(IV) complexes, using suitable tri- and diorganotin (IV) precursors, [nBu(3)Sn(HLmeta)](n) (1), [Bz(3)Sn(HLmeta)](n)center dot C6H5CH3 (2), [Ph3Sn(HLmeta)](4)center dot C6H5CH3 (3), and {[nBu(2)Sn(L-meta)](2)}(n)center dot 2nDMSO (4). The coordination behavior of compounds 1-3 in solution was judged from the results of the Sn-119 NMR spectroscopic characterization, while the Sn-119 MAS NMR technique was utilized to probe 4, owing to its low-solubility issue. The solid-state structures of 1-4 were determined from single-crystal X-ray diffraction data. The structural analysis revealed that by changing the Sn-R. substituents, the molecular coordination geometries and supramolecular structural motifs in the resulting compounds are widely affected. However, one common feature in the crystal structures of these compounds is a strong tendency for the terminal pyridyl nitrogen to bind with the tin atom of an adjacent complex molecule, which influences the ligand bonding interactions and leads to either macrocycle or polymer formation. In compounds 1-3, the triorganotin moieties are embedded in trigonal bipyramidal coordination polyhedra arising from the ligand in the monodeprotonated salicylate form, [HLmeta]-, by complexation through the carboxylate group, resulting in 1D coordination polymers with a zigzag-type topology for compounds 1 and 2, and a tetranuclear 44-membered macrocyclic ring structure in the case of 3. The different outcome is a result of the all anti-conformation of the [HLmeta](-) ligands in compounds 1 and 2, compared with alternating syn- and anti-conformation of the four ligands in 3, and is without doubt related to the variation of the triorganotin functionality. In compound 4, the tin atoms coordinate to the salicylate group of dianionic [L-meta](2-) by chelate ring formation with both the carboxylate and phenolate groups. The combination of syn-conformation of the ligand and secondary building block formation through 4-membered Sn2O2 rings gives rise to 1D tapes containing 22-membered tetranuclear macrocycles. The case study reported herein showed that heteroditopic pyridyl-carboxylate ligands derived from salicylic acid by diazonium coupling are providing an interesting ligand family for complexation and self-assembly studies with a large number of single main group and transition ions and preformed di- or oligonuclear tectons.