Synthesis, Crystal Structure, and Potentiometry of Pyridine-Containing Tetraaza Macrocyclic Ligands with Acetate Pendant Arms

Kim, Won D.; Hrncir, Duane C.; Kiefer, Garry E.; Sherry, A. Dean

doi:10.1021/ic00112a040

Cited by 73 publications

(88 citation statements)

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“…As noted in the previous section, electronic relaxation can influence low field (<1 MHz) relaxivities; however, the similarity in relaxivity at 20 MHz for [Gd- Tables 20 and 21, relaxivities are collected for a variety of gadolinium(III) chelates. 23,28,[33][34][35]40,49,51,64,65,85,87,144,150,152,159,160,162,185,204,[225][226][227]231,239, Tweedle and co-workers 265 have shown that relaxivity per gadolinium(III) correlates well with molecular weight for a series of monomeric and multimeric gadolinium(III) chelates (Charts 17-19) and this is shown in Figure 38 (data in Table 21). For spheroidal molecules, increases in relaxivity increase approxi- mately with increasing molecular weight.…”

Section: Relaxivitymentioning

confidence: 99%

Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications

et al. 1999

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Section: Relaxivitymentioning

confidence: 99%

Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications

et al. 1999

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“…As the relaxivity of a Gd(III) complex is directly proportional to the number (q) of inner coordinationsphere water molecules, complexes involving heptacoordinating ligands and possibly two water molecules have also been considered. It has been shown that a route to obtaining heptadentate ligands is provided by the inclusion of a pyridine moiety in a triazamacrocycle whose three amine nitrogens are further used as linking sites for three acetate arms [3,4]. Gd(III) complexes of these PCTA (Pyridine-Containing Triaza Macrocyclic TriAcetate) ligands have been obtained with a macrocycle size ranging from twelve to fourteen members.…”

Section: Introductionmentioning

confidence: 99%

Towards MRI contrast agents of improved efficacy. NMR relaxometric investigations of the binding interaction to HSA of a novel heptadentate macrocyclic triphosphonate Gd(III)-complex

et al. 1997

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A novel heptacoordinating ligand consisting of a thirteen-membered tetraazamacrocycle containing the pyridine ring and bearing three methylenephosphonate groups ) has been synthesized. Its Gd(III) complex displays a remarkably high longitudinal water proton relaxivity (7.7 mM P1 s P1 at 25 7C, 20 MHz and pH 7.5) which has been accounted for in terms of contributions arising from (1) one water molecule bound to the metal ion, (2) hydrogen-bonded water molecules in the second coordination sphere, or (3) water molecules diffusing near the paramagnetic chelate. Variable-temperature 17 O-NMR transverse relaxation data indicate that the residence lifetime of the metal-bound water molecule is very short (8.0 ns at 25 7C) with respect to the Gd(III) complexes currently considered as contrast agents for magnetic resonance imaging. Furthermore, GdPCTP-[13] interacts with human serum albumin (HSA), likely through electrostatic forces. By comparing water proton relaxivity data for the GdPCTP-[13]-HSA adduct, measured as a function of temperature and magnetic field strength, with those for the analogous adduct with GdDOTP (a twelvemembered tetraaza macrocyclic tetramethylenephosphonate complex lacking a metal-bound water molecule), it has been possible to propose a general picture accounting for the main determinants of the relaxation enhancement observed when a paramagnetic Gd(III) complex is bound to HSA. Basically, the relaxation enhancement in these systems arises from (1) water molecules in the hydration shell of the macromolecule and protein exchangeable protons which lie close to the interaction site of the paramagnetic complex and (2) the metal bound water molecule(s). As far as the latter contribution is concerned, the interaction with the protein causes an elongation of the residence lifetime of the metal-bound water molecule, which limits, to some extent, the potential relaxivity enhancement expected upon the binding of the paramagnetic complex to HSA.

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“…This finding is in contrast with the expected pKa values of TFA and amines in solution. This rare structural motif of doubly-protonated pyridine rings pointing to a common hydrogen acceptor despite the presence of the more basic aliphatic nitrogen of the bispicolylamine has been described before [52,53]. All compounds were isolated and characterized (see Supplementary Materials).…”

Section: Synthesis Of Chelators For Surface Modificationsmentioning

confidence: 81%

Towards 99mTc- and Re-Based Multifunctional Silica Platforms for Theranostic Applications

et al. 2019

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Taking advantage of the radiation properties of 99mTc and 186/188Re and the photophysical characteristics of the {M(CO)3}+ moiety (M = Re), we developed a multifunctional silica platform with the theranostic pair 99mTc/Re with high potential for (nano)medical applications. Starting with a general screening to evaluate the most suitable mesoporous silica construct and the development of appropriate chelate systems, multifunctional mesoporous silica microparticles (SBA-15) were synthesized. These particles act as a model towards the synthesis of the corresponding nanoconstructs. The particles can be modified at the external surface with a targeting function and labeled with the {M(CO)3}+ moiety (M = 99mTc, Re) at the pore surface. Thus, a silica platform is realized, whose bioprofile is not altered by the loaded modalities. The described synthetic procedures can be applied to establish a target-specific theranostic nanoplatform, which enables the combination of fluorescence and radio imaging, with the possibility of radio- and chemotherapy.

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Synthesis, Crystal Structure, and Potentiometry of Pyridine-Containing Tetraaza Macrocyclic Ligands with Acetate Pendant Arms

Cited by 73 publications

References 0 publications

Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications

Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications

Towards MRI contrast agents of improved efficacy. NMR relaxometric investigations of the binding interaction to HSA of a novel heptadentate macrocyclic triphosphonate Gd(III)-complex

Towards 99mTc- and Re-Based Multifunctional Silica Platforms for Theranostic Applications

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