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 {R_nSn} (n = 2 and 3)

Abstract

Pro-ligand 5-[(E)-2-(3-pyridyl)-1-diazenyl]-2hydroxybenzoic acid, H′HL meta , was employed for the synthesis of four organotin(IV) complexes, using suitable tri-and diorganotin (IV) precursors, [nBu 3 Sn(HL meta )] n (1), [Bz 3 Sn(HL meta )] n •C 6 H 5 CH 3 (2), [Ph 3 Sn(HL meta )] 4 •C 6 H 5 CH 3 (3), and {[nBu 2 Sn(L meta )] 2 } n •2nDMSO (4). The coordination behavior of compounds 1−3 in solution was judged from the results of the 119 Sn NMR spectroscopic characterization, while the 119 Sn 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, [HL meta ] − , 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 [HL meta ] − 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 Sn 2 O 2 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.

Triorganotin(IV) derivatives with semirigid heteroditopic hydroxo‐carboxylato ligands: Synthesis, characterization, and cytotoxic properties

“…The Fourier transform infrared spectra of the 10 triorganotin complexes showed characteristic bands in the regions 1625–1650 and 1390–1425 cm −1 for compounds 1 – 4 and at ~1640 and ~1400 cm −1 for compounds 5 – 10 , corresponding to the asymmetric and symmetric stretching vibrations ν asym (OCO) and ν sym (OCO) of the carboxylate group, indicating anisobidenate coordination to the organotin fragments (Figures S1–S13). [ 19,21 ] Compounds 1 – 10 displayed the anticipated 1 H and 13 C NMR signals and proton NMR integration values for the ligand and Sn‐R moieties in 1:1 metal–ligand complexes (Figures S14–S39). The molecular structures of compounds 1 – 10 in solution were assessed by 119 Sn NMR spectroscopy (Figure S40).…”

“…Although macrocyclic structures are quite commonly found in organotin complexes, [ 7,82–84 ] so far, there are only few examples for assemblies based on large heteroditopic ligands. [ 5,17,19,21,85 ]…”

“…Because heteroditopic ligands can facilitate the generation of heterodimetallic assemblies [12,13] and reduce occurrences related to structural diversification, the development of such ligands is being explored in metal coordination chemistry. [14][15][16][17][18][19][20][21] Salicylaldehyde, 2-aminophenol, and 2-aminobenzoic acid are common organic reagents and can be easily converted into Schiff bases by reactions with amines and aldehydes or ketones, respectively (Figure 1a). [22][23][24][25][26][27] The resulting potentially bidentate ligands are ideal for coordination with a large number of metal ions and complexes.…”

“…[45,46] In the presence of additional oxygen or nitrogen donor atoms, the coordination number is F I G U R E 1 (a) Schematic drawings for Schiff bases derived from salicylaldehyde, 2-aminophenol, and 2-aminobenzoic acid in comparison with (b) structurally related azo compounds enhanced to five, giving a trigonal-bipyramidal polyhedron, in which generally the organic substituents occupy the equatorial and the N/O donor atoms the axial positions. [19,21] When carboxylate groups are bound to R 3 Sn groups, generally, four-membered SnO 2 C rings are formed due to a secondary SnÁÁÁO contact. This anisobidentate coordination mode not only strengthens the M-carboxylate binding but also provides directionality for the metal-ligand bonds and structural organization, which is important for crystal engineering purposes.…”

“…[47,48] Moreover, the steric and electronic properties of the tin atoms are easily modified by variation of the organic substituents. [18][19][20][21][28][29][30]49] To explore the influence of the Sn-R groups on self-assembly products, the organotin fragments employed typically carry methyl, n-butyl, or phenyl groups.…”