Assembly of a trinuclear metallo-capsule from a tripodal tris(beta-diketone) derivative and copper(II)

A new metallo-capsule has been synthesised that consists of three copper(II) ions and two molecules of a tris-deprotonated tripodal ligand in which three 2,4-pentanedione groups are linked via their gamma-carbons through thioether spacers to the 1,3,5-positions of a triazine core.     

Europium-directed self-assembly of a luminescent supramolecular gel from a tripodal terpyridine-based ligand

Eu(III), the last piece in the puzzle: Europium-induced self-assembly of ligands having a C(3)-symmetrical benzene-1,3,5-tricarboxamide core results in the formation of luminescent gels. Supramolecular polymers are formed through hydrogen bonding between the ligands. The polymers are then brought together into the gel assembly through the coordination of terpyridine ends by Eu(III) ions (blue dashed arrow: distance between two ligands in the strand direction).     

Assembly of supermolecular complexes from the tripodal ligand titmb: assembly of a large M6L8 cage from 14 components

The coordinatively saturated, nanometer-sized M6L8 complex [Pd6(titmb)8]Cl(12).2H2O (titmb = 1,3,5-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene) was obtained by assembly of six Pd(II) ions with eight flexible titmb tripodal ligands; structural analysis shows that these eight titmb are in a disordered cube configuration and the six Pd atoms are in a disordered octahedral configuration; the inner cavity of the cage is estimated to have a volume of 1000 A3, large enough to encapsulate eight Cl- anions.     

Complexation of lanthanide(III) with a tripodal polyaza polycatecholate ligand

The interaction of La(III), Gd(III), and Yb(III) with Tris((2,3-dihydroxybenzylamino)ethyl)amine) (TRENCAT) was investigated by means of potentiometric measurements in 0.1 mol dm⁻³ aqueous solution of sodium perchlorate at 25 °C. The formation of complexes between the partially protonated ligand and lanthanides has been observed and the values of their formation constants are reported.     

Aromatic guest inclusion by a tripodal ligand: Fluorescence and structural studies

The newly synthesized simple tripodal ligand tris-[2-(naphthalen-2-yloxy)-ethyl]-amine (L₁) act as a fluorescence signaling system for aromatic guest. It forms inclusion complexes with several electron deficient aromatic compounds. This inclusion phenomenon has been studied by steady-state fluorescence spectroscopy and solid-state structural analysis. Electron-rich L₁ shows dramatic color change and a concomitant quenching of luminescence in solution as well as solid phase when titrated with several other electron deficient aromatic guest molecules. Rather high selectivity towards the picric acid was observed. L₁ simultaneously forms inclusion complex and organic salt co-crystal with the composition [(L₁H⁺) (Pic⁻)]  PicH (PicH = picric acid) when crystallized in the presence of picric acid. In the solid state, it forms a strong π–π, C–Hπ and C–HO type interactions.     

Dioxygen activation by a low-valent cobalt complex employing a flexible tripodal N-heterocyclic carbene ligand

The novel versatile cobalt(I) tris-carbene complex [(TIMEN(xyl))Co]Cl (1) (where TIMEN = (tris[2-(3-arylimidazol-2-ylidene)ethyl]amine) reacts with CO, one-electron oxidizers such as CH(2)Cl(2), and O(2) to yield the cobalt complexes [(TIMEN(xyl))Co(CO)]Cl (2), [(TIMEN(xyl))Co(Cl)]Cl (3), and peroxo species [(TIMEN(xyl))Co(O(2))](BPh(4)) (5). All new complexes were fully characterized by (1)H NMR, UV/vis, and IR spectroscopy as well as superconducting quantum interference device (SQUID) magnetization measurements and single-crystal X-ray crystallography. The nucleophilic character of the eta(2)-bound dioxygen ligand in 5 was confirmed by density functional theory (DFT) studies and allows for oxygen-transfer reactions with electron-deficient organic substrates, such as benzoyl chloride.     

Assembly of multilayer films incorporating a viral protein cage architecture

Protein cage architectures such as viral capsids, heat shock proteins, ferritins, and DNA-binding proteins are nanoscale modular subunits that can be used to expand the structural and functional range of composite materials. Here, layer-by-layer (LbL) assembly was used to incorporate cowpea chlorotic mottle virus (CCMV) into multilayer films. Three types of multilayer films were prepared. In the first type, ionic interactions were employed to assemble CCMV into triple layers. In the second type, complementary biological interactions (streptavidin/biotin) were used for this purpose. In a third variation of LbL assembly, complementary biological interactions were employed to produce nanotextured films that exhibit in-plane order over a micron scale without the need to adsorb onto a prepatterned template.     

Study of metal complexes of a tripodal hydroxypyridinone ligand by electrospray tandem mass spectrometry

The tripodal ligand N,N,N-tris[(1,hydroxy-2-pyridinon-6-yl)amide]propylamine was synthesized. It is composed of an anchor (nitrogen atom), a functional group (hydroxamate), and also a spacer of variable length defined by the number of methylene groups linking the anchor and the functional group. The characterization of this ligand in the presence of several divalent metal cations (Fe(II), Mn(II), Co(II) and Cu(II)), performed by electrospray ionization mass spectrometry (ESI-MS and ESI-MS/MS), allowed elucidation of oxidation states and also of different fragmentation patterns. The importance of the spacer length was studied in the case of the iron binary complex by comparing this ligand with another with a shorter spacer. In this way the stabilizing conditions, in which hydrogen bonds are implicated, were clarified.     

A novel dimeric zinc(II) complex with a tripodal peptide ligand: a structure stabilized by ligand sharing

The crystal structure of a novel dimeric zinc(II) complex, [ZnL(H₂O)]₂(ClO₄)₂·4H₂O (L?=?N-(bis(2-pyridyl)methyl)-2-pyridinecarboxamide), has been determined by X-ray diffraction. In this complex each planar N_py–N_amido–N_py moiety of the ligand coordinates to one zinc ion and the pendant pyridine of one [ZnL] unit completes the coordination sphere of a [ZnL] neighbor. Units of the complex are connected in a two-dimensional network by intermolecular hydrogen bonds. The thermodynamic properties of the ligand with bivalent metal ions Co(II), Ni(II), Cu(II) and Zn(II) were studied by potentiometric titration and the order of the stability constants is in agreement with the Irving–Williams series. The dimeric complex is stabilized through ligand sharing, as confirmed by the crystal structure and thermodynamic properties.     

Trigonal bi- and monopyramidal cobalt(II) complexes of a novel guanidine-based tripodal ligand

The novel ligand DIG(3)tren has three N',N'-diisopropylguanidinyl (DIG) moieties. We report on the structures of two cobalt complexes that show how an isopropylamino group from each DIG acts as a flap that can either close over the metal or rotate away from the metal to open up a site for auxiliary ligand binding. Two of the -NH(iPr) flaps are open in pink [Co(DIG(3)tren)(OAc)]OAc (1), and each of these flaps provides a hydrogen bond to stabilize acetate binding to trigonal bipyrimidal cobalt. The flaps are closed in blue [Co(DIG(3)tren)][BPh(4)](2) (2), yielding a rare example of a trigonal (mono)pyramidal [ML](2+) ion.     

Supramolecular and coordination polymer complexes supported by a tripodal tripyridine ligand containing a 1,3,5-triethylbenzene spacer

By By combining a tripodal tripyridine ligand containing a 1,3,5-triethylbenzene spacer (L) with several divalent transition-metal chlorides, we have selectively prepared a capsule-type supramolecular complex, [PdII3(L)2Cl6] x 2H2O, and one-dimensional (1D) coordination polymer complexes, ([CuII(L)Cl2] x C2H5OH)n, ([CoII3(L)2Cl6] x 2CH2Cl2)n, and ([ZnII3(L)2Cl6] x 2H2O)n, with a zigzag polymer chain, a linear polymer chain, and a ladder polymer chain structure, respectively. All the structures were established in detail by single-crystal X-ray diffraction analysis, and the factors inducing the structural differences among the complexes are discussed by taking account of the differences in coordination geometry (square planar vs tetrahedral) as well as metal-ligand binding strength in the complexes.     

Atropo-enantioselective synthesis of a C3-symmetric tripodal ligand with three axially chiral biaryl subunits

In contrast to the numerous successful applications of C₂-symmetric biaryls as powerful tools for asymmetric synthesis, there have so far been only few reports on combinations of C₃-symmetry with axial chirality. We present here the first enantioselective synthesis of a novel family of tripodal ligands containing three axially chiral biaryl subunits in an (M,M,M)- or, optionally, (P,P,P)-configured form. The incorporation of a PCl₂- and a TiCl-fragment into the central cavity was achieved.     

Electron-transfer kinetics of copper(II/I) tripodal ligand complexes

The electron-transfer kinetics for each of three copper(II/I) tripodal ligand complexes reacting with multiple reducing and oxidizing counter reagents have been examined in aqueous solution at 25 degrees C, mu = 0.10 M. For all of the ligands studied, an amine nitrogen serves as the bridgehead atom. Two of the ligands (PMMEA and PEMEA) contain two thioether sulfurs and one pyridyl nitrogen as donor atoms on the appended legs while the third ligand (BPEMEA) has two pyridyl nitrogens and one thioether sulfur. Very limited kinetic studies were also conducted on two additional closely related tripodal ligand complexes. The results are compared to our previous kinetic study on a Cu(II/I) system involving a tripodal ligand (TMMEA) with thioether sulfur donor atoms on all three legs. In all systems, the Cu(II/I) electron self-exchange rate constants (k(11)) are surprisingly small, ranging approximately 0.03-50 M(-)(1) s(-)(1). The results are consistent with earlier studies reported by Yandell involving the reduction of Cu(II) complexes with four similar tripodal ligand systems, and it is concluded that the dominant reaction pathway involves a metastable Cu(II)L intermediate species (designated as pathway B). Since crystal structures suggest that the ligand reorganization accompanying electron transfer is relatively small compared to our earlier studies on macrocyclic ligand complexes of Cu(II/I), it is unclear why the k(11) values for the tripodal ligand systems are of such small magnitude.     

A tripodal sulfur ligand for the selective ruthenium-catalysed hydrogenation of dimethyl oxalate

The first example of a catalyst utilising a sulfur-based ligand [MeC(CH2SBu)3] for the selective hydrogenation of dimethyl oxalate to methyl glycolate is reported.     

Accessing low denticity coordination modes of a high denticity tripodal ligand to complete its coordinative repertoire

New coordination complexes of the neutral tripodal tetra-amine Me(6)TREN with tBu(3)Ga or tBu(2)Zn have been synthesised and studied with their molecular structures revealing, for the first time, coordination to metal centres via an η(1) or η(2) mode, adding to previously reported η(3) and η(4) ligated examples.     

Synthesis of a macrobicycle incorporating the tris(pyrazolyl)methane ligand

Steric crowding of the 3-position of tris(pyrazolyl)borate and -methane ligands has produced tetrahedral metal complexes with controlled reactivity. As an alternative, we propose to incorporate the tris(pyrazolyl)methane chelate in a macrobicyclic structure in order to create a cavity with well-defined dimensions and shape. Acid-catalyzed equilibration of excess of the new pyrazole 3-(1H-pyrazol-3-yl)benzenemethanethiol acetate with HC(3,5-Me(2)pz)(3) followed by hydrolysis affords a functionalized tris(pyrazolyl)methane, which reacts with 1,3,5-tris(bromomethyl)benzene in K(2)CO(3)/DMF to give the title compound. [structure: see text]