Noncovalent Assembly and Catalytic Activity of Hybrid Materials Based on Pd Complexes Adsorbed on Multiwalled Carbon Nanotubes, Graphene, and Graphene Nanoplatelets.

Green catalysts with excellent performance in Cu-free Sonogashira coupling reactions can be prepared by the supramolecular decoration of graphene surfaces with Pd(II) complexes. Here we report the synthesis, characterization, and catalytic properties of new catalysts obtained by the surface decoration of multiwalled carbon nanotubes (MWCNTs), graphene (G), and graphene nanoplatelets (GNPTs) with Pd(II) complexes of tetraaza-macrocyclic ligands bearing one or two anchor functionalities. The decoration of these carbon surfaces takes place under environmentally friendly conditions (water, room temperature, aerobic) in two steps: (i) π-π stacking attachment of the ligand via electron-poor anchor group 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxo-pyrimidine and (ii) Pd(II) coordination from PdCl.

Non-covalent Functionalization of Graphene to Tune Its Band Gap and Stabilize Metal Nanoparticles on Its Surface.

Controlling graphene conductivity is crucial for its potential applications. With this focus, this paper shows the effect of the non-covalent bonding of a pyrimidine derivative (HIS) on the electronic properties of graphene (G). Several G-HIS hybrids are prepared through mild treatments keeping unaltered the structures of both G and HIS.

A New Heterogeneous Catalyst Obtained via Supramolecular Decoration of Graphene with a Pd Azamacrocyclic Complex.

A new G-(HL)-Pd heterogeneous catalyst has been prepared via a self-assembly process consisting in the spontaneous adsorption, in water at room temperature, of a macrocyclic HL ligand on graphene (G) (G + HL = G-(HL)), followed by decoration of the macrocycle with Pd ions (G-(HL) + Pd = G-(HL)-Pd) under the same mild conditions. This supramolecular approach is a sustainable (green) procedure that preserves the special characteristics of graphene and furnishes an efficient catalyst for the Cu-free Sonogashira cross coupling reaction between iodobenzene and phenylacetylene. Indeed, G-(HL)-Pd shows an excellent conversion (90%) of reactants into diphenylacetylene under mild conditions (50 °C, water, aerobic atmosphere, 14 h).

Polyfunctional Tetraaza-Macrocyclic Ligands: Zn(II), Cu(II) Binding and Formation of Hybrid Materials with Multiwalled Carbon Nanotubes.

The binding properties of HL1, HL2, and HL3 ligands toward Cu(II) and Zn(II) ions, constituted by tetraaza-macrocyclic rings decorated with pyrimidine pendants, were investigated by means of potentiometric and UV spectrophotometric measurements in aqueous solution, with the objective of using the related HL-M(II) (HL = HL1-HL3; M = Cu, Zn) complexes for the preparation of hybrid MWCNT-HL-M(II) materials based on multiwalled carbon nanotubes (MWCNTs), through an environmentally friendly noncovalent procedure. As shown by the crystal structure of [Cu(HL1)](ClO), metal coordination takes place in the macrocyclic ring, whereas the pyrimidine residue remains available for attachment onto the surface of the MWCNTs via π-π stacking interactions. On the basis of equilibrium data showing the formation of highly stable Cu(II) complexes, the MWCNT-HL1-Cu(II) material was prepared and characterized.

Thermodynamics of anion-π interactions in aqueous solution.

Thermodynamic parameters (ΔG°, ΔH°, TΔS°), obtained by means of potentiometric and isothermal titration calorimetry (ITC) methods, for the binding equilibria involving anions of high negative charge, like SO(4)(2-), SeO(4)(2-), S(2)O(3)(2-) and Co(CN)(6)(3-), and nitroso-amino-pyrimidine receptors in water suggested that anion-π interactions furnish a stabilization of about -10 kJ/mol to the free energy of association. These anion-π interactions are almost athermic and favored by large entropic contributions which are likely due to the reduced hydrophobic pyrimidine surface exposed to water after anion aggregation, and the consequent reduced disruptive effect on the dynamic water structure. The crystal structure of the {H(4)L[Co(CN)(6)]}·2H(2)O complex showed strong anion-π interactions between Co(CN)(6)(3-) and the protonated H(4)L(3+) receptor.

Adsorption of designed pyrimidine derivative ligands on an activated carbon for the removal of Cu(II) ions from aqueous solution.

The adsorption of five Nalpha-substituted amino acids with a 5-nitroso-6-oxo pyrimidine as substituent on a commercial activated carbon (AC) has been studied in aqueous solution at several pH values. The adsorption processes of these organic compounds have been analyzed on the basis of the electrolytic behavior of the adsorbates. In all cases, the adsorption process is highly irreversible due to strong pi-pi interactions between the arene centers of the AC and the pyrimidine residue of the adsorbates.

N-(6-Amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)leucine: a three-dimensional hydrogen-bonded framework structure.

In the title compound, C11H17N5O4, the bond distances show evidence of a highly polarized molecular-electronic structure. The molecules are linked into a three-dimensional framework by a combination of O-H..

Ligand adsorption on an activated carbon for the removal of chromate ions from aqueous solutions.

The results presented in this work are related to the design of a guideline to develop specific properties at the surface of an activated carbon (AC). For this, two model aromatic compounds have been synthesized and their electrolytic behavior in aqueous solutions was studied by a potentiometric method. The textural characteristics of the activated carbon were determined by porosimetry methods.

Hydrated metal(II) complexes of N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl) derivatives of glycine, glycylglycine, threonine, serine, valine and methionine: a monomeric complex and coordination polymers in one, two and three dimensions linked by hydrogen bonding.

Nine hydrated complexes of Group 2 (alkaline earth) cations with organic ligands which are N-substituted amino acids containing the 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl group have been structurally characterized. The octahydrated calcium glycinate complex, where the six-coordinate Ca cation lies on an inversion centre in the space group P(-)1, forms a finite (zero-dimensional) complex. The hexahydrated barium glycinate complex contains eight-coordinate Ba and it is isostructural with the known Sr analogue, and its one-dimensional coordination polymer takes the form of a simple chain.

Bis[6-amino-3-methyl-5-nitrosopyrimidine-2,4(1H,3H)-dionato]diaquazinc(II) dihydrate, redetermined at 120 K: a three-dimensional hydrogen-bonded framework.

The title compound, whose structure has been redetermined at 120 K, contains almost centrosymmetric trans-[Zn(C(5)H(5)N(4)O(3))(2)(H(2)O)(2)].2H(2)O units, together with two uncoordinated water molecules. An extensive series of O-H.

6-Amino-3-methyl-5-nitrosopyrimidine-2,4(1H,3H)-dione forms a three-dimensional hydrogen-bonded framework structure.

Molecules of the title compound, C(5)H(6)N(4)O(3), are linked into a single three-dimensional framework by a two-centre N-H.O hydrogen bond [H.O = 1.

Barium bis[6-amino-3-methyl-5-nitrosopyrimidine-2,4(1H,3H)-dionate] trihydrate: coordination polymer chains linked by hydrogen bonds.

The title complex, catena-poly[[triaquabarium(II)]-di-mu-6-amino-3-methyl-5-nitrosopyrimidine-2,4(1H,3H)-dionato], [Ba(C(5)H(5)N(4)O(3))(2)(H(2)O)(3)](n), forms a coordination polymer chain in which the two distinct anions use different ligating atoms to bridge pairs of cations. Adjacent pairs of cations are also linked by pairs of bridging water molecules. The chains are linked into a single three-dimensional framework by an extensive series of hydrogen bonds.

Hydrated metal complexes of N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)glycinate: interplay of molecular, molecular-electronic and supramolecular structures.

The title anion, (C(7)H(8)N(5)O(4))(-), L(-), forms hydrated metal complexes with a range of metal ions M(+) and M(2+). Lithium and manganese(II) form finite molecular aggregates [Li(L)(H(2)O)(3)] (1) and [Mn(L)(2)(H(2)O)(4)].6H(2)O (4) in which the molecular aggregates are linked into three-dimensional frameworks by extensive hydrogen bonding.