Self-assembled metalla-bowls for selective sensing of multi-carboxylate anions

Abstract

Two new tetranuclear cationic metalla-bowls 4 and 5 were self-assembled from a bis-pyridine amide ligand (H(2)L) (1) and arene-ruthenium acceptors, [(Ru(2)(μ-η(4)-C(2)O(4))(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (2) and [Ru(2)(dhnd)(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (dhnd = 6,11-dihydroxy-5,12-naphthacenedionato) (3), respectively. The metalla-bowls were characterized by multinuclear NMR, ESI-MS, UV-Vis spectroscopy, and single crystal X-ray diffraction study of 4. The crystal structure of 4 reveals unambiguous proof for the molecular shape of the metalla-bowl and the encapsulation of one triflate anion in the cavity through hydrogen bonding. The metalla-bowl 5 has been evaluated for anion binding studies by use of amide ligand as a hydrogen bond donor and arene-Ru acceptor as a signalling unit. UV-Vis titration studies showed that 5 selectively binds with multi-carboxylate anions such as oxalate, tartrate and citrate in a 1 : 1 fashion with high binding constants of 4.0-5.5 × 10(4) M(-1). Furthermore, the addition of multi-carboxylate anions into a solution of 5 gave rise to a large enhancement of fluorescence intensity attributable to the blocking of a photo-induced electron transfer process from the arene-ruthenium moiety to the amidic donor in 5. However, the fluorescence intensity almost remains unchanged upon addition of other anions including F(-), Cl(-), PF(6)(-), MeCOO(-), NO(3)(-) and PhCOO(-), as identically seen in the UV-Vis titration experiments, pointing to the high selectivity of 5 for the sensing of multi-carboxylate anions.

Synthesis and molecular studies of half-sandwich arene ruthenium and Cp*Rh/Cp*Ir complexes containing (3-picolyl)thiourea derivatives as N,S-bidentate donor ligands

“…Nevertheless, new synthetic routes involving mild reaction conditions, high yields, stable complexes, and solubility under aqueous conditions are still desirable [1,2]. These complexes have numerous applications as catalysts for various organic transformations [3][4][5], as sensors in supramolecular chemistry [6], and as products with biological properties [7,8].…”

Pre-organisation or a hydrogen bonding mismatch: silver(I) diamide ligand coordination polymers versus discrete metallo-macrocyclic assemblies

“…20,21,26,[34][35][36][37][38] Such self assembled metallosupramolecular species have been employed as anion sensors. 39 In this latter context, we have directed our attention toward two major types of organic ligand, namely, electron deficient [3]radialene compounds [40][41][42][43][44] and heterocyclic amide ligands, [45][46][47] in an effort to generate simple metallo-supramolecular assemblies and coordination polymers that encapsulate anions. Flexible bis-amide containing ligands (Diagram 1) were chosen to probe the effects of having two different and potential competing, orthogonal, supramolecular synthons in the same component; namely metal donor sites and hydrogen bond donor/acceptor moieties.…”

Self-assembled metal–organic polyhedra: An overview of various applications

“…However, minimal spectral change was observed for monoanionic species such as halide or acetate. Moreover, this kind of selective recognition of multicarboxylate anions (oxalate, tartrate, and citrate) selectivity over monoanions (halides, acetate, and benzoate) was also observed by metalla-bowls prepared by the [2+2] self-assembly of bispyridine amide ligand (L6) and [(Ru 2 (μ-ƞ 4 -C 2 O 4 )(ƞ 6 -p-cymene) 2 ](O 3 SCF 3 ) 2 (B1) and [Ru 2 (dhnd)(ƞ 6 -pcymene) 2 ](O 3 SCF 3 ) 2 (B4) (dhnd = 6,11-dihydroxy-5,12-napthacenedionato) [177]. Cyclotrimethylene-trinitramine (RDX) is an explosive nitroamine even more explosive than TNT (2,4,6-trinitrotoulene).…”