Di- and trinuclear organotin(IV) complexes, in which the metal atoms are separated by large aromatic connectors, are useful building blocks for self-assembly. This is demonstrated by the preparation of [1+1], [2+2], and [2+3] macrocyclic and cage-type structures in combination with organic aromatic dicarboxylates. The linkage of the metal atoms by organic binders and the option of varying the number of reactive M-X sites generate versatile building blocks enabling molecular tectonics instead of the node-based strategy generally employed in metallo-supramolecular self-assembly.

No abstract

Four secondary diamines with aromatic spacer groups derived from α,α′-dibromo-p-xylene and 4,4′-bis(chloromethyl)-1,1′-biphenyl have been transformed into bis-dithiocarbamate ligands and each combined with dimethyl-, di-nbutyl-, and diphenyltin(IV) dichloride to yield a total of 12 mononuclear diorganotin(IV) bis-dithiocarbamate complexes with six-coordinate metal coordination geometries and either 23-or 27-membered macrocyclic structures. The products were fully characterized by IR and NMR ( 1 H, 13 C, 119 Sn) spectroscopy and high-resolution ESI + -TOF mass spectrometry. A representative selection of the macrocyclic complexes was further examined by DFT computational studies and the relative binding [a] 3429 Scheme 1. Synthesis of the macrocyclic diorganotin(IV) bis-dithiocarbamates 1-12. The numbering scheme for the assignment of the NMR spectroscopic data is included. 3431Scheme 3. Illustration of the stereochemical differences found in the molecular structures of the four trans conformers that were geometry-optimized by DFT quantum chemical calculations by using the B3LYP/def2-TZVP method for the dimethyltin complex 1. 3432In all the structures, the Sn-S cov bonds point towards the interior of the macrocycle cavity. The organic groups attached to Eur.Titration Experiments: For the titration experiments, the receptor was employed at fixed concentrations of 1 × 10 -5 M for 3, 4, 6, and 9 and 2 × 10 -5 M for 12 using chloroform as the solvent. 0.1 M (0.2 M for 12) stock solutions of the anions were prepared in the same solvent from the corresponding tetramethyl ammonium salts. Spectral changes were observed at λ = 300-302 nm and the spectrometric titration curves were analyzed and fitted on the basis of a 1:1 host-guest complexation model using Equation (1) and the Microcal Origin 8.0 program. [23] DFT Calculations: DFT quantum chemical calculations were performed with the quantum mechanical program Gaussian 09 (version B.01) [27] using the B3LYP hybrid functional [28] in combination with the def2-TZVP basis set. [29] Geometry optimizations were realized for different starting geometries of the molecular structures, which were established by molecular modelling considering variations in the metal coordination environment (cis and trans coordina-

Crystalline framework materials have gained interest because of their many potential applications. A novel chiral tetrandrine salt (DNT) has been synthesized and characterized by conventional analytical techniques and single‐crystal X‐ray diffraction analysis, and its self‐assembly behavior studied. In the solid state, 48 molecules of the compound self‐assemble into an organic framework based on nanospherical aggregates formed exclusively through weak noncovalent interactions. Additionally, it was demonstrated by UV‐vis spectroscopy and TGA that assembled DNT can include the Nile Red dye, giving a fluorescent material. To the best of our knowledge, these spherical assemblies are the largest among the purely synthetic organic self‐assembled molecular crystals reported to date.

Ligands derived from 2,x- and 3,y-pyridinedicarboxylic acid (x = 3–6; y = 4–5) are widely used building blocks for the formation of metal-coordination polymers (MCPs), as they show a large variety of bridging modes and angles. Metal complexation occurs either only with the carboxylate groups or through N,O-chelate ring formation. In this contribution, the supramolecular chemistry and solvatomorphism of diorganotin complexes with 2,5-pyridinedicarboxylate (25pdc) formed in the presence of a series of coordinating and noncoordinating solvents were explored in detail. Five novel diorganotin 25pdc’s of composition [Me2Sn­(25pdc)­(py)]3­·3.04C5H5N­·1.86H2O (1), {[Me2Sn­(25pdc)]­·[Me2Sn­(25pdc)­(H2O)]} n ­2nC7H8O (2), {[nBu2Sn­(25pdc)]4} n ­·4nC6H5NO2 (3), [nBu2Sn­(25pdc)­(gly)] n (4), and {[nBu2Sn­·(25pdc)]3} n ­·nCHCl3 (5) were achieved and analyzed in the context of previously reported tri- and diorganotin complexes with the same ligand. The comparative study revealed that upon coordination to diorganotin species the ligand exhibits N,O-chelate ring formation with the carboxylate group in the 2-position and bridging to other tin atoms primarily by the 5-carboxylate group, giving macrocyclic, one-, two-, or three-dimensional MCPs. On the contrary, triorganotin moieties are mostly bound only by the ligand carboxylate groups without N→Sn binding. The assemblies of diorganotin 25pdc’s mostly contain trinuclear or tetranuclear macrocycles with a large predominance of the generally uncommon [3 + 3] metal–organic aggregates. For the trinuclear macrocycles, different configurations having 12-, 18-, 21-, or 27-membered rings were encountered. The metal atoms in diorganotin 25pdc’s prefer pentagonal-bipyramidal environments, which are achieved through coordination by solvent molecules (H2O, DMSO, py) or intermolecular O→Sn bond formation. In solution, di-n-butyltin 25pdc exhibits supramolecular isomerism, giving a tetrameric aggregate in the noncoordinating solvent chloroform and a trimeric species in the presence of coordinating solvents, such as DMSO, pyridine, or methanol, due to solvent→Sn bond formation.