Macrocyclic and Acyclic Molecules Synthesized from Dipyrrolylmethanes: Receptors for Anions (original) (raw)
Inorganic Chemistry, 2012
The [2 + 2] Schiff base condensation reactions between the newly synthesized dialdehyde, N,N-di(α-formylpyrrolyl-α-methyl)-N-methylamine), and ethylenediamine or p-phenylenediamine dihydrochloride readily afforded the 30-and 34-membered large size macrocycles in very high yields. Subsequent reduction reactions of these macrocycles with NaBH 4 gave the corresponding saturated macrocyclic hexaamines in good yields. The analogous reaction of the new dialdehyde with a triamine molecule afforded the [3 + 2] Schiff base macrobicycle in high yield, which was then reduced by reaction with NaBH 4 to give the saturated macrobicycle. All these compounds were characterized by spectroscopic methods. The anion binding properties of the saturated macrocycles having the ethylene and the phenylene linkers in CDCl 3 were studied by NMR titration methods. Although they have similar pyrrolic and amine NH groups their binding properties are different and interesting, owing to the conformational flexibility or rigidness rendered by the ethylene or phenylene groups, respectively. The macrocycle having the ethylene linkers binds anions in a 1:1 fashion, while the other receptor having the phenylene linkers prefers to bind anions in a sequential 1:2 fashion and has a multiple equilibria between a 1:1 and a 1:2 complexes, as shown by their binding constants, curve fittings by EQNMR, and Job plots. The X-ray structures of the 1:2 methanol, the aqua and the benzoate anion complexes of the macrocycles show two cavities in which the guests are bound, correlating with the high affinity found for the formation of stable 1:2 complexes in solution. The X-ray structure showed that the macrobicycle Schiff base adopts an eclipsed paddle-wheel shaped conformation and exhibits an out-out configuration at the bridgehead nitrogen atoms.
Synthesis and anion recognition properties of pyrrole-bearing acyclic receptors
Tetrahedron, 2007
We report on the synthesis and characterization of novel shape-persistent, optically active arylamide macrocycles, which can be obtained using a one-pot methodology. Resolved, axially chiral binol scaffolds, which incorporate either methoxy or acetoxy functionalities in the 2,2' positions and carboxylic functionalities in the external 3,3' positions, were used as the source of chirality. Two of these binaphthyls are joined through amidation reactions using rigid diaryl amines of differing shapes, to give homochiral tetraamidic macrocycles. The recognition properties of these supramolecular receptors have been analyzed, and the results indicate a modulation of binding affinities towards dicarboxylate anions, with a drastic change of binding mode depending on the steric and electronic features of the functional groups in the 2,2' positions.
Chemistry - An Asian Journal, 2014
as dyes or photosensitizers, [2] as metal ion or anion recognition elements in sensors, [3] as potential ligands for metal ions and especially for the macrocyclic encapsulation and extraction of larger lanthanide or actinide ions, [2e, 3d, f, 4] and simply for the challenge of their syntheses and the testing of theoretical understanding of aromaticity. [4c, 5] Of relevance to the research reported herein, phenanthroline chromophores are also employed as sensitizers to afford strongly fluorescent lanthanide complexes. [5g, 6] Although macrocycles with a bis(phenanthrolinyl-pyrrole) core are attractive targets for all of these reasons, the first examples were only recently reported: In this Journal in 2011, Müllen and co-workers reported four tetraalkoxy-substituted bis(phenanthrolinyl-pyrrole) macrocycles, each obtained by a demanding synthesis (over 8 steps) in very low yield (< 2 % overall), and demonstrated mesogenic behavior dependent on alkyl side-chain length. The electronic and fluorescence spectra of one example and a density functional theory (DFT) calculation on the macrocyclic core were briefly described. Other properties were not reported. Following our recent development of a useful one-pot procedure to di(2-pyridyl)pyrrolato ligands from condensation of a a-methylenecarbonyl derivative, 2-formyl-pyridine (2 equiv), and ammonia, we wondered if extension through use of a pyridyl-dicarboxaldehyde derivative would afford macrocyclic product(s). This proved to be the case as we report herein. the solid-state structures of similar macrocycles. [5a, c, 11] The Abstract: This paper reports a convenient, one-pot, easily scalable and readily modifiable synthesis of a novel large-ring bis(1,10-phenanthrolinyl-2,5-pyrrole) macrocycle, H 2 L MC , and describes its spectroscopic and electrochemical properties, protonation, cooperative amine binding, electrocatalysis of the oxidation of primary amines, photosensitization of the decomposition of dichloromethane, and the first lanthanide complexes of the hexaaza-dianion L MC 2À including the novel dimer, [(NO 3 )
Proceedings of the National Academy of Sciences of the United States of America, 2002
Two neutral macrobicyclic anion receptors 4 and 6, containing a calix[4]arene in the cone conformation, two L-alanine units, and a 2,6-diacylpyridine or a phthaloyl bridge, are described. The x-ray crystal structure of the acetone complexes of the pyridine containing macrocycle 6 shows the four amide NH groups to be in close proximity to the chiral pocket delimited by the pyridine and one aromatic nucleus of the calix[4]arene. This conformation is also the most stable in acetone-d6 solution, as proven by one-and twodimensional NMR spectral measurements. Electrospray ionization-MS and 1 H NMR experiments reveal that the two ligands strongly bind carboxylate anions in acetone solution. H-bonding interactions between the carboxylate anions and the amide NH groups, together with ͞ stacking, are invoked to explain the efficiency and the selectivity of these anion receptors.
Inorganica Chimica Acta, 2003
Synthesis and characterisation of a new macrobicycle containing two dipyridine units (L) is reported. Protonated forms of L are efficient receptors for inorganic phosphate and nucleotide anions. The binding properties of L toward these substrates have been investigated in aqueous solution by means of potentiometric, microcalorimetric and 1 H NMR measurements. Only 1:1 receptor Á/ anion complexes have been found in solution. The stability of the adducts with inorganic phosphates anions is higher than that found for the nucleotides complexes. The complexation reactions are endothermic, and promoted by invariably favourable entropic contributions, indicating that these pairing processes are mostly determined by the desolvation of the interacting species that occurs upon charge neutralisation. #
Basicity and coordination properties of a new phenanthroline-based bis-macrocyclic receptor
Dalton Transactions, 2006
The synthesis and characterisation of the new macrocyclic ligand 6-methyl-2,6,10-triaza-[11]-12,25-phenathrolinophane (L1), which contains a triamine aliphatic chain linking the 2,9 positions of 1,10-phenanthroline and of its derivative L2, composed by two L1 moieties connected by an ethylenic bridge, are reported. Their basicity and coordination properties toward Cu(II), Zn(II), Cd(II), Pb(II) and Hg(II) have been studied by means of potentiometric and spectroscopic (UV-Vis, fluorescence emission) measurements in aqueous solutions. L1 forms 1 : 1 metal complexes in aqueous solutions, while L2 can give both mono-and dinuclear complexes. In the mononuclear L2 complexes the metal is sandwiched between the two cyclic moieties. The metal complexes with L1 and L2 do not display fluorescence emission, due to the presence of amine groups not involved in metal coordination. These amine groups can quench the excited fluorophore through an electron transfer process. The ability of the Zn(II) complexes with L1 and L2 to cleave the phosphate ester bond in the presence has been investigated by using bis(p-nitrophenyl)phosphate (BNPP) as substrate. The dinuclear complex with L2 shows a remarkable hydrolytic activity, due to the simultaneous presence within this complex of two metals and two hydrophobic units. In fact, the two Zn(II) act cooperatively in substrate binding, probably through a bridging interaction of the phosphate ester; the interaction is further reinforced by p-stacking pairing and hydrophobic interactions between the phenanthroline unit(s) and the p-nitrophenyl groups of BNPP.
Anion and Carboxylic Acid Binding to Monotopic and Ditopic Amidopyridine Macrocycles
The Journal of Organic Chemistry, 2008
Binding of inorganic anions, carboxylic acids, and tetraalkylammonium carboxylates by macrocyclic compounds of different size was studied by NMR in DMSO-d 6 . It has been shown that at least a 15membered ring is necessary for successful recognition of fluoride. Larger macrocycles were shown to bind HSO 4 -, H 2 PO 4 -, Cl -, and carboxylic acid salts. Effects of binding topicity are discussed. The 30membered macrocycles 4 and 4m selectively bind substrates that are size-and shape-complementary: maximum binding is observed for dicarboxylic acids and dicarboxylates with four-carbon chains, and the binding constant for association of fumaric acid and 4 is ca. 5 orders of magnitude higher than that of maleic acid. The 30-membered macrocycle 4m showed selectivity toward R-ketocarboxylic acids. Secondary amino groups were not crucial for binding of fluoride to the macrocycles; however, they proved to be very important for selectivity and strength of carboxylic acid binding. The X-ray structure of the adduct of 4 and nitrobenzoic acid confirmed the guest H-bonding with both the amide and the secondary amino groups of the 30-membered macrocyclic host. SCHEME 1 Korendovych et al.
Pyrrole-Pyridine and Pyrrole-Naphthyridine Hosts for Anion Recognition
Molecules (Basel, Switzerland), 2015
The association constants of the complexes formed by two hosts containing pyrrole, amide and azine (pyridine and 1,8-naphthyridine) groups and six guests, all monoanions (Cl-, CH3CO2-, NO3-, H2PO4-, BF4-, PF6-), have been determined using NMR titrations. The X-ray crystal structure of the host N2,N5-bis(6-methylpyridin-2-yl)-3,4-diphenyl-1H-pyrrole- 2,5-dicarboxamide (1) has been solved (P21/c monoclinic space group). B3LYP/6-31G(d,p) and calculations were carried out in an attempt to rationalize the trends observed in the experimental association constants.