Spectroscopic study of copper(II) complexes with 1,4,7-tris(dihydroxyphosphorylmethyl)-1,4,7-triazacyclononane and 1,4,7-tris(?-dihydroxyphosphorylethyl)-1,4,7-triazacyclononane

Investigations on Water‐Soluble Copper Complexes with the Sterically Demanding Triazacyclononane Derivative (tBu)2(nPrSO3)Htacn

“…[16] 1 was obtained as a white powder with a yield of 54 %. 1 H-NMR and 13 C-NMR spectroscopy confirmed the purity of the ligand.…”

“…Synthesis of ( t Bu) 2 ( n PrSO 3 )Htacn: (tBu) 2 tacn (400 mg, 1.66 mmol) and 1,3-Propane sultone (204 mg, 1.67 mmol) were added to 25 mL acetonitrile and was heated to 70 °C for 2 d. Afterward, the solvent was removed under reduced pressure and the received solid 1 was recrystallized in acetonitrile/water (324 mg, 0.891 mmol, Yield: 54 %). 1 H-NMR(δ/ppm): 3.31-3.15 (m, 4H); 3.00-2.94 (m, 2H), 2.86-2.82 (m, 10H), 1.30 (s, 18H); 13 Synthesis of [Cu(1)]OAc, 4: Cu(OAc) 2 (7,5 mg, 0.041 mmol) and 1 (15 mg, 0.041 mmol) were stirred in 1 mL methanol. After 2 h, the resulting turquoise solution was filtered and the solvent was removed.…”

“…The modification of ligands to increase water solubility is not unknown and usually, phosphonic acid, sulphonic acid or carboxylic acid substituents have been used. [12,13] Pasachenik et al, as well as Clegg et al, already investigated the pH dependence of 1,4,7-triazacyclononane derivatives with phosphonic acid substituents. Pasachenik et al measured the pH dependence as a part of the characterization of the copper(II) complexes, while Clegg et al performed NMR studies on small macrocycles with methylenephosphonates.…”

“…Pasachenik et al measured the pH dependence as a part of the characterization of the copper(II) complexes, while Clegg et al performed NMR studies on small macrocycles with methylenephosphonates. [13,14] Furthermore, soluble 1,4,7-triazacyclononane derivatives are applied in bleaching or in medicine where these ligands function as chelators for copper radioisotopes (radiotracers) for positron emission tomography (PET), as a contrast agent in pHresponsive magnetic resonance imaging or emission computed tomography (SPECT). [15]…”

“…Concerning green/sustainable chemistry, our focus was on modifying the 1,4,7‐triazacyclononane system for high solubility and high reactivity in water (or methanol) to develop an environmentally friendly catalyst that could work under mild conditions. The modification of ligands to increase water solubility is not unknown and usually, phosphonic acid, sulphonic acid or carboxylic acid substituents have been used [12,13] . Pasachenik et al ., as well as Clegg et al ., already investigated the pH dependence of 1,4,7‐triazacyclononane derivatives with phosphonic acid substituents.…”