Formation of Metal-Based 21- and 22-Membered Macrocycles from Dinuclear Organotin Tectons and Ditopic Organic Ligands Carrying Carboxylate or Dithiocarbamate Groups

Flexible bidentate aluminum Lewis acids for host-guest complex formation

This study investigates the design, synthesis, and reactivity of bidentate aluminum Lewis acids supported by amido and cyclopentadienyl donor sets within a flexible 1,4-disubstituted phenylene framework. The reactivity of these complexes with nitrogen-based ditopic donors was systematically explored, revealing their capacity to form host-guest assemblies. Reactions with equimolar pyrazine or quinoxaline yielded 1 : 1 colored adducts, highlighting the potential of these two systems as colorimetric sensors for ditopic nitrogen donors. The reaction with 4,4'-bipyridine, which features a longer N⋯N distance, resulted in a dimeric 2 : 2 adduct. In contrast, sterically demanding nitrogen donors such as 2,3,5,6-tetramethylpyrazine or phenazine showed no reactivity with these bidentate Lewis acids. The results reveal not only the robust Lewis acidic nature of the aluminum centers but also the pivotal role of ligand flexibility in facilitating diverse molecular interactions.

Temperature-dependent photoluminescence down to 77 K of organotin molecular rotors: eco-friendly synthesis, photophysical characterization, X-ray structures, and DFT studies

Fluorescent organotin compounds are useful in sensing, optoelectronic devices, and in vitro bioimaging. Although in vitro fluorescence bioimaging shows low resolution at room temperature, a better resolution is possible at cryotemperatures. Therefore, the search for new cryoluminescent materials with potential application in high-resolution fluorescence bioimaging remains a great challenge. Herein, we report the cryoluminescence properties of two fluorescent bis-organotin compounds, namely, BisNTHySnBu2 (5) and BisNTHySnPh2 (6), synthesized via microwave irradiation. All compounds were fully characterized using 1H, 13C, and 119Sn NMR spectroscopy, Raman spectroscopy, IR spectroscopy, and HR-MS. The 119Sn δ and 3J(1H,119Sn) of 5 and 6 indicate that two Sn-ligands are chemically and electronically equivalent, as confirmed by cyclic voltammetry. The crystal structure of 6 showed pentacoordinate tin atoms with skeleton ligands. The study of self-assembled monolayers of both Sn-complexes via STM microscopy revealed a similar supramolecular packing in lamella-like patterns, adopting a face-on arrangement, where molecules stay flat lying on HOPG in accordance with the height profile of closely packed monolayers on graphite of about 0.33 nm thickness. However, only the Sn complex 6, which bears phenyls, covers large surface areas. The photophysical properties of bis-organotin compounds were also investigated in solution (room and low temperatures) and in the solid state. Good luminescence properties in solutions with fluorescence quantum yields (Φ) of approximately 35% and 50% were found. Despite this, Φ is quenched in the solid state because of aggregation, as supported by solvent/non solvent fluorescence studies, which is in agreement with STM and AFM investigation.

A Structural Survey of Poly-Functional Dithiocarbamate Ligands and the Aggregation Patterns They Sustain

An overview is presented of the crystal structures of transition metal, main group element, and lanthanide compounds containing poly-functional dithiocarbamate ligands, namely species containing two or more connected NCS2− residues. In all, there are 40 different ligands of this type that have been characterised crystallographically in their heavy-element compounds with up to six NCS2− residues; all are bridging. In most cases, the resulting aggregates are zero-dimensional, often di-nuclear, but aggregates of up to 36 metal (gold) atoms are noted. There are smaller numbers of one-, two-, and three-dimensional architectures sustained by poly-functional dithiocarbamate ligands in their respective crystals. The survey highlights the opportunities afforded by this generally under-studied class of ligand.

New 1D diorganotin(iv) dithiolate coordination polymers: crystallographic, computational, Hirshfeld surface and thermal analyses

Three new 1D coordination polymers of diorganotin(iv) dithiolates synthesized and the nature of their weak interactions addressed using computational techniques.