Riccardo Serra

Ammonium aminomethylphosphonate monohydrate was synthesized via aqueous neutralization of aminomethylphosphonic acid with ammonium carbonate. The compound was fully characterized by FT-IR and NMR spectroscopy, as well as single-crystal X-ray diffraction (SC-XRD). Structural analysis confirmed the zwitterionic nature of the aminomethylphosphonate anion and revealed an extensive 3D supramolecular network of charge-assisted N–H···O and O–H···O hydrogen bonds.

Amide bond formation remains central to pharmaceutical and fine-chemical synthesis, yet it still relies largely on organic solvents and on waste-intensive work-up and purification.

A simple heterogeneous copper catalyst was prepared by adsorbing Cu(II) ions from an aqueous CuSO ₄ solution onto calcium carbonate (CaCO ₃ ) and marble waste microfine dust from the Carrara production area. The resulting materials (CaCO ₃ –Cu and Carrara–Cu) were characterized by FTIR, PXRD, SEM–EDX, TGA, and zeta potential measurements, confirming copper uptake while preserving the carbonate framework. The catalytic activity of the materials was evaluated in the copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction. Using glucose as a reducing agent, the reactions were performed in water under ultrasound irradiation at 30 °C, generating the active Cu(I) species in situ. A model three‐component reaction between benzyl bromide, sodium azide, and phenylacetylene afforded the corresponding 1,4‐disubstituted 1,2,3‐triazole in 81% isolated yield after 1 h. The scope of the methodology was evaluated across a range of substituted aryl alkynes and benzyl bromides as reaction partners, affording the corresponding triazoles in moderate to good yields. The catalyst was recovered by simple filtration and reused in subsequent reaction cycles. The use of water as the reaction medium, mild operating conditions, catalyst recyclability, and the successful application of marble waste as a catalyst support make this methodology a practical and sustainable approach for the synthesis of 1,2,3‐triazoles.

Ammonium N-ethyloxamate (AmEtOxam) was synthesized, fully characterized by microanalytical and spectroscopic means, and assayed as a precursor of calcium oxalate, acting as a protecting agent for white Carrara marble. The monohydrate form of AmEtOxam shows a water solubility of 1.5 mol·L⁻¹ (~23% w/w), significantly higher than that of common calcium oxalate precursors (CaOx), such as ammonium oxalate (0.4 mol·L⁻¹, ~5% w/w). While AmEtOxam is stable in water solution and in the solid state in its monohydrate form, during the application on carbonate stone it undergoes a complete hydrolysis resulting in the formation of a uniform weddellite layer (CaC₂O₄·2H₂O) on carbonate stone surfaces. Application of 5% w/w aqueous solutions by spraying, brushing, and immersion resulted in different effects. Spraying yielded the most balanced performance, improving mechanical strength, reducing water absorption, recovering superficial tension, and limiting chromatic alteration. Brushing achieved significant gain in surface hardness with minimal esthetic impact. Immersion most effectively reduced porosity and increased surface tension. These results, coupled with the negligible chromatic changes induced in all cases, make AmEtOxam a promising candidate for the conservation of stone cultural heritage.

Ammonium N-ethyloxamate (AmEtOxam) was synthesized, fully characterized by microanalytical and spectroscopic means, and assayed as a precursor of calcium oxalate, acting as a protecting agent for white Carrara marble. The monohydrate form of AmEtOxam shows a water solubility of 1.5 mol·L–1 (~23% w/w), significantly higher than that of common calcium oxalate precursors (CaOx), such as ammonium oxalate (0.4 mol·L–1, ~5% w/w). While AmEtOxam is stable in water solution and in the solid state in its monohydrate form, , during the application on carbonate stone it undergoes a complete hydrolysis resulting in the formation of an uniform weddellite layer (CaC2O4·2H2O) on carbonate stone surfaces. Application of 5% w/w aqueous solutions by spraying, brushing, and immersion resulted in different effects. Spraying yielded the most balanced performance, improving mechanical strength, reducing water absorption, recovering superficial tension, and limiting chromatic alteration. Brushing achieved significant gain in surface hardness with minimal aesthetic impact. Immersion most effectively reduced porosity and increased surface tension. These results, coupled with the negligible chromatic changes induced in all cases, make AmEtOxam a promising candidate for the conservation of stone cultural heritage.

Ammonium oxathioamidate (1) was synthesised by the reaction between O-ethyl-thioxamate (oxalic acid-1-amide-2-O-ethyl ester) and ammonium hydrogen carbonate in water solution. Compound 1 was fully characterised by both microanalytical (elemental analysis, melting point determination) and spectroscopic means (FT-IR and NMR spectroscopy). Crystals suitable for single-crystal X-ray diffraction were isolated by slow evaporation of an ethanol solution of the compound. The analysis of the crystal packing reveals the prominent role exerted by intermolecular hydrogen bonding (HB) and chalcogen bonding (ChB) interactions.