Design of selective macrocyclic ligands for the divalent first-row transition-metal ions †

Costa, Judite; Delgado, Rita; Drew, Michael G. B.; Félix, Vítor

doi:10.1039/a706434i

Cited by 34 publications

(56 citation statements)

References 37 publications

(45 reference statements)

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“…DELGADO et al The overall basicity of the compounds having methylphosphonate arms is very high compared with that of the N-acetate derivative, ac 3 py14 [6,8]. This is explained by electrostatic effects and hydrogen-bonding formation [6].…”

Section: -Membered Tetraazamacrocycles Containing Pyridinementioning

confidence: 91%

“…In general, the ligands studied in this work exhibit very high thermodynamic stability constants with the first-row transition-metal [6,[8][9][10] and lanthanide ions [5,7,12,[14][15][16][17], although the K LnL and pLn values decrease with the increase of the number of atoms of the macrocyclic ring and for those including acetate arms. Therefore, the 12-membered macrocycles, dota and dotp, have the highest values of thermodynamic stability constants.…”

Section: Discussionmentioning

confidence: 99%

“…The later ligands exhibit larger K ML values for the complexes with lanthanide ions than the corresponding acetate derivative [6][7][8]. Differently, the Ni 2+ , Cu 2+ , and Zn 2+ complexes of the same ligands present K ML of the same order for the acetate and methylphosphonate derivatives, see in Table 2 the values for the Cu(II) complexes [6][7][8]. However, as the direct comparison of stability constants involving ligands with rather different overall basicity can lead to erroneous conclusions, because the competition of metals and proton for ligands is not taken into account, the pM val-…”

Section: -Membered Tetraazamacrocycles Containing Pyridinementioning

confidence: 99%

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Lanthanide complexes of macrocyclic derivatives useful for medical applications

Delgado

Costa

Guerra

et al. 2005

Pure and Applied Chemistry

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Abstract:The protonation constants of two series of tetraazamacrocyclic ligands with acetate and methylphosphonate pendant arms, as well as their stability constants with Cu 2+ , La 3+ , Sm 3+ , and Ho 3+ , were determined. All the values were determined in aqueous solution at 298.0 K and 0.10 mol dm -3 in N(CH 3 ) 4 NO 3 . In the first series, the effect of both types of pendant arms was observed by appending them in the same macrocyclic backbone, a 14-membered tetraazamacrocycle containing pyridine (ac 3 py14, p 2 py14, and p 3 py14). In the second series, two effects were taken into account, the increase of the cavity size of the macrocycle, from 12-to 14-membered, and the appending of acetate (dota, trita, and teta) or methylphosphonate (dotp, tritp, and tetp) arms. The ligands containing methylphosphonate arms have higher thermodynamic stability compared to the corresponding ones with acetate arms, especially in the series of compounds containing pyridine, even upon correction of the different basicity values of the ligands. On the other hand, the ligands with smaller macrocyclic cavity size, namely, dota and dotp, exhibit the largest values of stability constants. In contrast, ac 3 py14 presents low stability constants with lanthanides. An interpretation of these features based on the known adopted arrangement of dota and teta when free or coordinated with lanthanides is evaluated.

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Section: -Membered Tetraazamacrocycles Containing Pyridinementioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: -Membered Tetraazamacrocycles Containing Pyridinementioning

confidence: 99%

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Lanthanide complexes of macrocyclic derivatives useful for medical applications

Delgado

Costa

Guerra

et al. 2005

Pure and Applied Chemistry

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“…The strong, unresolved band in the high-field region of the EPR spectrum overlaps the fourth line. The hyperfine coupling constants and g values of glassy solutions of these complexes, obtained by simulation of the spectrum [22], are compiled in Table 4, together with [24]. The parameters of these species are typical of Cu II complexes of an axially elongated rhombic symmetry, and with a d x2Ày 2 ground state, consistent with elongated rhombic-octahedral or distorted square-based pyramidal configurations [25].…”

mentioning

confidence: 99%

“…The EPR A values were obtained from an unrestricted calculation, and the g values from a spinrestricted calculation with spinÀorbit correction. The starting geometries were taken from the crystal structures of the complexes with the ligand 2 (described in this work) and the published structure of [Cu II -10] 0 [24]. Graphical representations of molecular orbitals were drawn with MOLEKEL [39].…”

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confidence: 99%

Structure, Characterization, and Metal‐Complexation Properties of a New Tetraazamacrocycle Containing Two Phenolic Pendant Arms

Cui

Costa

Delgado

et al. 2004

Helvetica Chimica Acta

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The new tetraazamacrocycle 2 ( 2,2'- 7,11,.1]heptadeca-1(17),13,15-triene-3,11-diyl]bis(methylene)]bis(4-bromophenol)) was synthesized and used as a ligand for different metalion complexes. The X-ray crystal structures of the complexes of the general formula [M(H-2)] NO, in which only one of the two pendant phenolic OH groups of 2 is deprotonated, were determined. In both complexes, the coordination environment is of the [5 1] type, the four N-atoms of the macrocyclic framework defining a square-planar arrangement around the metal center, with similar NiÀN and ZnÀN distances of 1.961(9) to 2.157(9) ä and 2.021(9) to 2.284(8) ä, respectively. In contrast, the MÀO distances are markedly different, 2.060(6) and 2.449(8) ä in the Ni II complex, and 2.027(7) and 2.941(9) ä in the Zn II complex. The UV/VIS spectra of the Ni II and Cu II complexes with ligand 2, and the EPR spectra of the Cu II system, suggest the same type of structure for the complexes in solution as in the solid state. Theoretical studies by means of density functional theory (DFT) confirmed the experimental structures of the Ni II and Zn II complexes, and led to a proposal of a similar structure for the corresponding Cu II complex. The calculated EPR parameters for the latter and comparison with related data support this interpretation. The singly occupied molecular orbital (SOMO) in these systems is mainly made of a d orbital of Cu, with a strong antibonding (s*) contribution of the axially bound phenolate residue.

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