Synthesis and coordination properties of a new ligand designed for surface functionalization of carbon substrates

Savastano, Matteo; Zoppi, Carlotta; Bianchi, Antonio; Bazzicalupi, Carla

doi:10.1016/j.ica.2020.119793

Cited by 6 publications

(10 citation statements)

References 28 publications

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“…In the studied pH range, H 3 L behaves as an heptaprotic molecule. In agreement with the behavior of analogous polyamines functionalized with the same pyrimidine derivative [27][28][29][30][31][32][33][34][35][36], the secondary amines directly connected to the pyrimidine residues can be deprotonated at pH ≈ 11, while the pyrimidine nitroso groups are protonated below pH 2.5. These protonation equilibria are generally easily followed through UV-Vis measurements, as they significantly alter π-π* transitions of the chromophore.…”

Section: Ligand Protonation Equilibriasupporting

confidence: 73%

“…These protonation equilibria are generally easily followed through UV-Vis measurements, as they significantly alter π-π* transitions of the chromophore. The characteristic absorption wavelengths have been commented elsewhere [27,28,31,34,36,51,52], and they are only affected slightly by the nature of appended polyamine. Uv-Vis spectra of the ligand at different pHs, as reported in Figure 2, clearly show three absorption bands at 328, 271, and 230 nm.…”

Section: Ligand Protonation Equilibriamentioning

confidence: 98%

“…While the grafting moiety, a convenient pyrimidine derivative with an extremely electron-deficient character, could, in principle, also be replaced, we tried to improve the stability of our catalysts by adding a second identical pyrimidine moiety for each metal complex in order to achieve a firmer chemisorption. Linear commercial ligands, despite interesting, tend to form metal complexes of various stoichiometry, which complicate the picture and conflict with the idea of single identical catalytic active sites [36]. A more stable catalyst adsorbed via two pyrimidine moieties per metal center has been recently reported for the Sonogashira cross-coupling: no desorption issues were observed; yet, as the complex nature of the non-commercial (and thus sub-optimal, price-wise) polyaminic portion of the ligand offered further binding sites stabilizing Pd(0) NPs, deactivation still happened over time due to Pd(II) reduction [28].…”

Section: Introductionmentioning

confidence: 99%

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Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

et al. 2020

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Lowering the platinum group metal content of oxygen reduction reaction catalysts is among the most prevalent research focuses in the field. This target is herein approached through supported Pd(II) complexes. Starting from a commercial macrocycle, a new ligand is synthesized, its solution behavior and binding properties briefly explored (potentiometry, UV-Vis) and then used to prepare a new catalyst. A supramolecular approach is used in order to obtain homogeneous decoration of carbon nanotubes surfaces, fostering novel possibilities to access single-ion active sites. The novel catalyst is characterized through X-ray photoelectron spectroscopy and scanning transmission electron microscopy and its promising oxygen reduction reaction performance is evaluated via rotating ring-disk electrode and rotating disk electrode in half-cell studies.

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Section: Ligand Protonation Equilibriasupporting

confidence: 73%

Section: Ligand Protonation Equilibriamentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

et al. 2020

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“…Then, the adsorption of PdCl 4 2– on these hybrids was carried out until a 1:1 ligand/Pd molar ratio was obtained, thus providing the catalysts G-L1-Pd and MWCNT-L2-Pd in which most of the Pd(II) was adsorbed via complexation by the common macrocyclic polyamine function of the corresponding ligand. The adsorption of L1 and L2 on the carbon substrates was ensured by the π–π stacking interaction of the 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxo-pyrimidine ligand moieties (two in L1, one in L2) with the graphene surfaces of MWCNTs and G. The use of this adhesive pyrimidine residue was initially introduced by some of us for the functionalization of activated carbon (AC) aimed at the removal of chromate anions from aqueous solutions and was later extended to the generation of new materials for further remediation purposes (cation and anion sequestration) − as well as for applications in fuel cells (oxygen reduction reactions), − hydrogenation processes, and the photochemical generation of hydrogen …”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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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 4 2– . Ligands are more efficiently adsorbed on the flat surfaces of G and GNPTs than on the curved surfaces of MWCNTs. All catalysts work very efficiently under mild conditions (50 °C, aerobic, 7 h), giving a similar high yield (90% or greater) in the coupling of iodobenzene with phenylacetylene to form diphenylacetylene in one catalytic cycle, but catalysts based on G and GNPTs (especially on GNPTs) provide greater catalytic efficiency in reuse (four cycles). The study also revealed that the active centers of the ligand-Pd type decorating the support surfaces are much more efficient than the Pd(0) and PdCl 4 2– centers sharing the same surfaces. All of the results allow a better understanding of the structural factors to be controlled in order to obtain an optimal efficiency from similar catalysts based on graphene supports.

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“…Other polydentate ligands that were functionalized with this pyrimidine group have been shown to form stable complexes with various metal ions. For all these complexes [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ] as well as for DFO–Pm [ 18 ], metal complexation is manifested by evident modifications in the UV-vis adsorption spectra of the ligand.…”

Section: Introductionmentioning

confidence: 99%

Metal Coordination Properties of a Chromophoric Desferrioxamine (DFO) Derivative: Insight on the Coordination Stoichiometry and Thermodynamic Stability of Zr4+ Complexes

Savastano¹,

Boscaro

Bianchi³

2021

Molecules

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Desferrioxamine (DFO) is the current “gold standard” chelator for 89Zr4+, which is used to label monoclonal antibodies for applications in immunopositron emission tomography. Recently, controversial data have been reported regarding the speciation and the stability of the complexes formed by DFO with Zr4+ in solution. To shed some light on this point, we studied the coordination properties in solution ofa chromophoric DFO derivative bearing a substituted pyrimidine residue (DFO–Pm) toward several metal ions (Zr4+, Cu2+, Zn2+, Mg2+, Ca2+, Na+, K+). Potentiometric titrations showed that DFO–Pm and pristine DFO form complexes with very similar stoichiometry and stability. DFO–Pm, which can consequently be taken as a model system for DFO, provides a photochemical response to metal coordination that can be used to further define the complexes formed. In the critical case of Zr4+, spectrophotometric measurements allowed the verification of the formation of 1:1 and 2:3 complexes that, together with 2:2 complexes form the coordination model that was obtained through the use of our potentiometric measurements. Additionally, mass spectrometry measurements verified the formation of 1:1 and 2:3 complexes and showed that 1:2 species can be easily generated through the fragmentation of the 2:3 species. In conclusion, the results obtained with DFO–Pm validate the complexation model of Zr4+/DFO composed of 1:1, 2:2, and 2:3 metal-to-ligand complexes. Convergences and conflicts with other works are addressed.

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Synthesis and coordination properties of a new ligand designed for surface functionalization of carbon substrates

Cited by 6 publications

References 28 publications

Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

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

Metal Coordination Properties of a Chromophoric Desferrioxamine (DFO) Derivative: Insight on the Coordination Stoichiometry and Thermodynamic Stability of Zr4+ Complexes

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