Coordination chemistry of amide-functionalised tetraazamacrocycles: structural, relaxometric and cytotoxicity studies
作者:Jonathan Martinelli、Beeta Balali-Mood、Rachael Panizzo、Mark F. Lythgoe、Andrew J. P. White、Patrizia Ferretti、Joachim H. G. Steinke、Ramon Vilar
DOI:10.1039/c0dt00815j
日期:——
determined. A europium(III) complex of one of these ligands (with propargyl substituents) is also presented together with its PARACEST properties. In addition, to gain further insight into the coordination chemistry of the tetra-propargyl substituted ligand, the corresponding zinc(II) and cadmium(II) complexes have been prepared. The X-ray crystal structures of the tetra-propargyl ligand and its corresponding
Contrast agents possessing high temperature sensitivity
作者:Mark Milne、Robert H.E. Hudson
DOI:10.1039/c1cc13073k
日期:——
Contrast agents based on lanthanide tetra-propargyl DOTAM complexes suitable for temperature mapping by magnetic resonance spectroscopy (MRS) are reported. Sensitivity values from 1.05 ppm/°C to 1.76 ppm/°C were determined which represents an improvement of 2–3 times over currently available lanthanide temperature-responsive contrast agents.
Dendrimers up to the fourth generation (G1–G4) were successfully synthesized via the efficient copper catalyzed 1,3-dipolar cycloaddition between primary alkynes and azides (CuAAC), also referred to as a click reaction. The synthetic protocol involved the preparation of presynthesized dendron wedges that subsequently were attached to a tetra-valent alkyne functional cyclen core. These constructed structures integrated stable triazole groups “intra-locked” between the cyclen and dendron wedges. The incorporation of a lanthanide metal ion, europium, into the interior of all cyclen dendrimers was monitored by FT-IR. Interestingly, the photophysical results showed that the proximate triazole not only acts as a stable linker but also as a sensitizers, transferring its singlet–singlet excitation in the ultraviolet region (270–290 nm) to the partially filled luminescent lanthanide 4f shell. An increase of luminescence decay time from the lanthanide 5D0 → 7F2 emission was observed with increasing dendrimer size, indicating that the shielding effect of the dendron wedges is important for the relaxation of the photo-excitation and energy transfer. To the best of our knowledge, this is the first time a set of dendron wedges have successfully been attached to a cyclen metal ion cage via the versatile click reaction. Furthermore, the produced triazoles intra-locked in close proximity to the macrocycle core elucidated an interesting photophysical function.
ParaCEST MRI contrast agents capable of derivatizationvia “click” chemistry
作者:Mark Milne、Kirby Chicas、Alex Li、Robert Bartha、Robert H. E. Hudson
DOI:10.1039/c1ob06162c
日期:——
A comprehensive series of lanthanide chelates has been prepared with a tetrapropargyl DOTAM type ligand. The complexes have been characterized by a combination of 1H NMR, single-crystal X-ray crystallography, CEST and relaxation studies and have also been evaluated for potential use as paramagnetic chemical exchange saturation transfer (ParaCEST) contrast agents in magnetic resonance imaging (MRI). We demonstrate the functionalization of several chelates by means of alkyneâazide âclickâ chemistry in which a glucosyl azide is used to produce a tetra-substituted carbohydrate-decorated lanthanide complex. The carbohydrate periphery of the chelates has a potent influence on the CEST properties as described herein.