214078-92-9Relevant articles and documents
Complexation of Ln3+ Ions with Cyclam Dipicolinates: A Small Bridge that Makes Huge Differences in Structure, Equilibrium, and Kinetic Properties
Rodríguez-Rodríguez, Aurora,Regueiro-Figueroa, Martín,Esteban-Gómez, David,Tripier, Rapha?l,Tircsó, Gyula,Kálmán, Ferenc Krisztián,Bényei, Attila Csaba,Tóth, Imre,Blas, Andrés De,Rodríguez-Blas, Teresa,Platas-Iglesias, Carlos
, p. 2227 - 2239 (2016)
The coordination properties toward the lanthanide ions of two macrocyclic ligands based on a cyclam platform containing picolinate pendant arms have been investigated. The synthesis of the ligands was achieved by using the well-known bis-aminal chemistry. One of the cyclam derivatives (cb-tedpa2-) is reinforced with a cross-bridge unit, which results in exceptionally inert [Ln(cb-tedpa)]+ complexes. The X-ray structures of the [La(cb-tedpa)Cl], [Gd(cb-tedpa)]+, and [Lu(Me2tedpa)]+ complexes indicate octadentate binding of the ligands to the metal ions. The analysis of the Yb3+-induced shifts in [Yb(Me2tedpa)]+ indicates that this complex presents a solution structure very similar to that observed in the solid state for the Lu3+ analogue. The X-ray structures of [La(H2Me2tedpa)2]3+ and [Yb(H2Me2tedpa)2]3+ complexes confirm the exocyclic coordination of the metal ions, which gives rise to coordination polymers with the metal coordination environment being fulfilled by oxygen atoms of the picolinate groups and water molecules. The X-ray structure of [Gd(Hcb-tedpa)2]+ also indicates exocyclic coordination that in this case results in a discrete structure with an eight-coordinated metal ion. The nonreinforced complexes [Ln(Me2tedpa)]+ were prepared and isolated as chloride salts in nonaqueous media. However, these complexes were found to undergo dissociation in aqueous solution, except in the case of the complexes with the smallest Ln3+ ions (Ln3+ = Yb3+ and Lu3+). A DFT investigation shows that the increased stability of the [Ln(Me2tedpa)]+ complexes in solution across the lanthanide series is the result of an increased binding energy of the ligand due to the increased charge density of the Ln3+ ion.
Monoesterase activity of a purple acid phosphatase mimic with a cyclam platform
Comba, Peter,Gahan, Lawrence R.,Hanson, Graeme R.,Mereacre, Valeriu,Noble, Christopher J.,Powell, Annie K.,Prisecaru, Ion,Schenk, Gerhard,Zajaczkowski-Fischer, Marta
scheme or table, p. 1700 - 1710 (2012/03/27)
The synthesis and characterization of a novel dinucleating ligand L (L=4,11-dimethyl-1,8-bis{2-[N-(di-2-pyridylmethyl)amino]ethyl}cyclam) and its μ-oxo-bridged diferric complex [(H2L){FeIII 2(O)}(Cl)4]2+ are reported. This diiron(III) complex is the first example of a truly functional purple acid phosphatase (PAP) mimic as it accelerates the hydrolysis of the activated phosphomonoester 2,4-dinitrophenyl phosphate (DNPP). The spectroscopic and kinetic data indicate that only substrates that are monodentately bound to one of the two ferric ions can be attacked by a suitable nucleophile. This is, most probably, a terminal iron(III)-bound hydroxide. DFT calculations support this assumption and also highlight the importance of secondary interactions, exerted by the protonated cyclam platform, for the positioning and activation of the iron(III)-bound substrate. Similar effects are postulated in the native enzyme but addressed in PAP mimics for the first time. Copyright
Metal Complexes of Macrocyclic Ligands: Part XLVII - Copper(II) and Nickel(II) Complexes of 'trans'-Difunctionalized Tetraaza Macrocycles
Comparone, Antonio,Kaden, Thomas A.
, p. 1765 - 1772 (2007/10/03)
Reductive cleavage of the bis-aminal 1 of 1,4,8,11-tetraazacyclotetradecane allows a new synthesis of 1,8-dimethyl-1,4,8,11-tetraazacyclotetradecane (3), which is an ideal starting compound for preparing 'trans'-difunctionalized derivatives. Thus, 3 was reacted to give the macrocyclic diacetonitrile 5 and dipropanenitrile 9. These were reduced with Raney-Ni and H2 to the corresponding diamines 6 and 10, respectively. In addition, 5 was selectively hydrolysed to the diacetamide 7 and fully hydrolysed to the diacetic acid 8. The Cu2+ and Ni2+ complexes of these new ligands were prepared and their spectral and structural properties studied. Whereas 3 yielded square planar species, the functionalized derivatives gave penta- or hexacoordinate complexes. The ligands with amino groups in their side chains (6 and 10) formed square planar species at acidic pH (amino groups protonated), but pentacoordinate geometries resulted at alkaline pH, where one amino group underwent coordination. In contrast, the diacetic acid 8 gave distorted octahedral Cu2+ and Ni2+ complexes.
