Search

In the structure of the title compound, cooperative C—H⋯O=C, C—H⋯π and offset π–π inter­actions generate supra­molecular nanotubes which accommodate the 2,3-di­chloro­benzene solvent mol­ecules., The asymmetric unit of the title compound, C56H50N6O8S2·3C6H4Cl2, contains two half-mol­ecules of the parent, A and B, which both have crystallographic inversion symmetry, together with three 2,3-di­chloro­benzene mol­ecules of solvation. Mol­ecules A and B are conformationally similar, with dihedral angles between the central naphthalenedi­imide ring and the peripheral naphthalene and benzyl rings of 2.43 (7), 81.87 (7)° (A) and 3.95 (7), 84.88 (7)° (B), respectively. The conformations are stabilized by the presence of intra­molecular π–π inter­actions between the naphthalene ring and the six-membered di­imide ring of the central naphthalenedi­imide moiety, with ring centroid-to-centroid distances of 3.5795 (8) Å (A) and 3.5640 (8) Å (B). In the crystal, C—H⋯O hydrogen bonds link the mol­ecules into infinite supra­molecular chains along the c axis. These chains are inter­connected through C—H⋯π and offset π–π inter­actions, generating supra­molecular nanotubes which are filled by 1,2-di­chloro­benzene mol­ecules.

Fluorescent responses and conformational changes against pH were studied on four new water-soluble 1-pyrene and 1-methylpyrene bichromophores, (ttha1py)H4, (edta1mpy)H2, (dtpa1mpy)H3 and (ttha1mpy)H4, with the objective of modifying pH–fluorescence profiles and other solution properties of 1-pyrene bichromophores, (edta1py)H2 and (dtpa1py)H3, developed previously by our group; the abbreviations with acidic protons stand for pyrenyl moieties interlinked by an EDTA, DTPA (diethylenetriaminepentacetic acid) or TTHA (triethylenetetraminehexaacetic acid) chain through amide linkages. The new derivatives exhibit emission bands of monomeric pyrene and an intense structureless excimer band; the latter responds to pH sensitively. The pH dependence of the emission intensity of the DTPA and TTHA derivatives is well correlated with species distribution determined by potentiometry. In every derivative, the completely deprotonated species Ln− is the most efficient for excimer emission, followed by the corresponding monoprotonated species LH(n−1)−. In the latter, the acidic hydrogen is located on the central amine, as confirmed by 1H NMR. The resulting hydrogen bond between amino nitrogen atoms makes the aliphatic chain rigid. Further protonation stretches the interlinking chain due to electrostatic repulsion. These conformational changes with protonation result in fluorescent on–off cycles against pH window. The switching cycles of the methylpyrene derivatives are reverse to those of the corresponding pyrene derivatives, as the CH2 spacer between the amide and aromatic groups defines the orientation of pyrene rings. The sensitiveness of amide group to environment leads to a sharp change in excimer emission above pH ∼11. The combined functions of amide and amino groups lead to the novel pH-responses.

The title compound possesses twofold rotation symmetry, with the planes of the phthalimide moieties inclined to one another by 73.53 (7)° and by 78.62 (9)° to that of the urea unit. In the crystal, mol­ecules are linked via N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional framework structure., The whole mol­ecule of the title compound, C17H10N4O5·2H2O, is generated by twofold rotation symmetry and it crystallized as a dihydrate. The planes of the phthalimide moieties and the urea unit are almost normal to one another, with a dihedral angle of 78.62 (9)°. In the crystal, mol­ecules are linked by N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional framework structure. The crystal packing also features C—H⋯O hydrogen bonds and slipped parallel π–π inter­actions [centroid–centroid distance = 3.6746 (15) Å] involving the benzene rings of neighbouring phthalimide moieties.

Interactions of protonated forms of kanamycin A with nucleotides and several simple phosphate anions have been studied by potentiometric and NMR titrations. The affinity of kanamycin A to anions is comparable to that observed with other aliphatic polyammonium receptors of similar charge, but it discriminates triphosphate nucleotides with different nucleobases with binding constants following the order GTP≫CTP ≈ ATP. Kanamycin A also binds the respective uncharged nucleosides with the same selectivity. Binding of ATP is exothermic with a negative entropic contribution in contrast to what is expected for simple ion pairing. Other tested aminoglycosides, amikacin and streptomycin, bind ATP less efficiently than kanamycin A. Models of structures of kanamycin A complexes with ATP and GTP obtained by molecular mechanics (OPLS-2005) calculations based on 1H and 31P NMR data confirm the possibility of nucleotide discrimination by simultaneous ion pairing of terminal nucleotide phosphate groups with ammonium sites...

Association of amino acids and some other low molecular weight compounds with rifamycin SV in water has been studied by 1H NMR titrations. Rifamycin binds aromatic amino acids with pronounced enantioselectivity in favor of l-enantiomers and forms complexes with heterocyclic compounds but does not interact with simple benzene derivatives. Binding constants correlate with LUMO energies and hydrophobicities (expressed as log P values) of guest molecules indicating contributions to the binding free energy from aromatic stacking interactions with the naphthohydroquinone fragment of rifamycin SV and from hydrophobic interactions. Proposed mode of binding is supported by semiempirical calculations of structures of host–guest complexes.

A new water soluble 26-membered macrocyclic pyridinophane functionalized by amide and carboxymethyl groups has been synthesized in a single step reaction and characterized by elemental analysis, mass spectrometry (FAB+), UV-vis, fluorescence, and 1H NMR spectroscopy as well as single-crystal X-ray diffraction analysis. Its complexation properties with the nucleobases thymine and uracil have been explored in aqueous media by performing 1H NMR titration experiments and potentiometric studies. The binding constants of the 1:1 host-guest complexes were determined as 103 M− 1 by proton NMR and 102–103 M− 1 by potentiometry. Semiempirical molecular modelling studies have shown that the nucleobases are included within the cavity of the macrocyclic receptor and that the complexes are stabilized by hydrogen bonding.

Glycine and N,N-dimethylglycine stabilize La(III) hydroxide complexes of the type La2L2(OH)4 which possess phosphodiesterolytic activity close to that observed with most active tetravalent cations like Ce(IV).

Diphenylmethane underwent oxidative coupling in the presence of di-t-butyl peroxide and formed 1,1,2,2-tetraphenylethane. This coupling reaction resulted in the formation of a copolymer of diphenylmethane andp-xylene. The new copolymer was soluble in common organic solvents and had a molecular weight of 32,000 (polystyrene base).

In the title compound, C14H10N2O2, the phtalimide and 2-pyridylmethyl units are almost perpendicular, with an interplanar angle of 85.74 (2)°. In the crystal, molecules are linked by weak C—H...O interactions, forming chains running along the b axis. The packing is further stabilized by offset π–π interactions between adjacent pyridine rings, with a centroid–centroid distance of 3.855 (2) Å.

The alkali metal (Na+, K+, Rb+, Cs+) bis-dithiocarbamate (bis-dtc) salts of N,N′-dibenzyl-1,2-ethylenediamine have been prepared from the reaction of N,N′-dibenzyl-1,2-ethylenediamine with carbon disulfide in the presence of two equivalents of the corresponding alkali metal hydroxide. Additionally, the analogous triethylammonium derivative has been obtained. The resulting compounds have been analyzed as far as possible by elemental analysis, FAB+ mass spectrometry, IR, UV-Vis and NMR (1H, 13C) spectroscopy, and single-crystal X-ray diffraction, showing that the composition of the metal salts can be described by the general formula [{[(H2O)xM-µ-(H2O)yM(H2O)x][bis-dtc]}n] (1, M = Na+, x = 3, y = 2; 2, M = K+, x = 1, y = 2; 3, M = Rb+, x = 0, y = 1; 4, M = Cs+, x = 0, y = 1; 5, M = Et3HN+, x = 0, y = 0). The solid-state and solution studies showed that all alkali metal ions participate in the formation of M–O and cation-π(arene) interactions, while M–S interactions are only observed for the larger alkali metals K+, Rb+ and Cs+. As expected, within the alkali metal group there is a clear tendency for a decreasing number of M–O bonds in favor of M–S and cation–π(arene) interactions, however, only K+ forms a semi-sandwich type complex with η6-coordination.

Oxidation of aniline with ammonium peroxodisuffate in aqueous solutions containing poly(3-sutfonato-4-hydroxystyrene) gave polymer alloys (or polymer blends) with a general composition of {(—C6H4NH—)[—CH2—CH(C6H3·OH·SO3–)—]x(H2SO4)y·zH2O}n. Their electrical conductivities depended on the composition and varied between 10–5 and 0.5 S cm–1 at 300 K. The polyaniline salts were soluble in water and exhibited an electronic absorption band characteristic of emeraldine salts at 800 nm. The corresponding alkaline solutions showed a band due to emeraldine bases at 600 nm. These bands showed a pH dependence that is a consequence of an interchain interaction between two kinds of polymer chains. A polymer with x= 04, y= 1.2 and z= 3.6 was soluble enough to observe EPR spectra, whose pH dependence showed that, with increasing pH, deprotonation occurs at polarons prior to deprotonation at bipolarons.

Two bis crown ether receptors were synthesized and tested as host molecules for protonated forms of alkyl amines and amino acid esters. Molecular recognition studies were conducted in CH2Cl2:MeOH (92:8) by spectrophotometric UV/Vis titrations andby spectrometric 1H NMR titrations in CDCl3. The calculated binding constants are in the range 102-105 M-1. A high affinity for L-amino acid methyl ester derivatives was found. A theoretical study at the DFT level of the synthesized receptor and some analog ligands with three different ammonium ions helps to rationalize the experimentally found trends.