An ethylene cross-bridged pentaazamacrocycle and its Cu2+ complex: constrained ligand topology and excellent kinetic stability

Diagnosis of Melanoma with 61Cu-Labeled PET Tracer

Until the recent years, substances containing radioactive 61Cu were strongly considered as potential positron-emitting radiopharmaceuticals for use in positron emission tomography (PET) applications; however, due to their suitably long half-life, and generator-independent and cost-effective production, they seem to be economically viable for human imaging. Since malignant melanoma (MM) is a major public health problem, its early diagnosis is a crucial contributor to long-term survival, which can be achieved using radiolabeled α-melanocyte-stimulating hormone analog NAPamide derivatives. Here, we report on the physicochemical features of a new CB-15aneN5-based Cu(II) complex ([Cu(KFTGdiac)]-) and the ex vivo and in vivo characterization of its NAPamide conjugate. The rigid chelate possesses prompt complex formation and suitable inertness (t1/2 = 18.4 min in 5.0 M HCl at 50 °C), as well as excellent features in the diagnosis of B16-F10 melanoma tumors (T/M(SUVs) (in vivo): 12.7, %ID/g: 6.6 ± 0.3, T/M (ex vivo): 22).

61Cu-Labelled radiodiagnostics of melanoma with NAPamide-targeted radiopharmaceutical

Malignant melanoma is a major public health problem with an increasing incidence and mortality in the Caucasian population due to its significant metastatic potential. The early detection of this cancer type by imaging techniques like positron emission tomography acts as an important contributor to the long-term survival. Based on literature data, the radio labelled alpha-MSH analog NAPamide molecule is an appropriate diagnostic tool for the detection of melanoma tumors. Inspired by these facts, a new radiotracer, the [⁶¹Cu]Cu-KFTG-NAPamide has been synthesized to exploit the beneficial features of the positron emitter ⁶¹Cu and the melanoma specificity of the NAPamide molecule. In this work, we report a new member of the CB-15aneN₅ ligand family (KFTG) as the chelator for ⁶¹Cu(II) complexation. On the basis of the thorough physico-chemical characterization, the rigid [Cu(KFTG)]⁺ complex exhibits fast complex formation (t_1/2 = 155 s at pH 5.0 and 25 °C) and high inertness (t_1/2 = 2.0 h in 5.0 M HCl at 50 °C) as well as moderate superoxide dismutase activity (IC₅₀ = 2.3 μM). Furthermore, the [⁶¹Cu]Cu-KFTG-NAPamide possesses outstanding features in the diagnostics of B16-F10 melanoma tumors by PET imaging: (T/M(SUVs) (in vivo): appr. 14, %ID/g: 7 ± 1 and T/M (ex vivo): 315 ± 24 at 180 min).

Synthesis and Characterization of Late Transition Metal Complexes of Mono-Acetate Pendant Armed Ethylene Cross-Bridged Tetraazamacrocycles with Promise as Oxidation Catalysts for Dye Bleaching

Ethylene cross-bridged tetraazamacrocycles are known to produce kinetically stable transition metal complexes that can act as robust oxidation catalysts under harsh aqueous conditions. We have synthesized ligand analogs with single acetate pendant arms that act as pentadentate ligands to Mn, Fe, Co, Ni, Cu, and Zn. These complexes have been synthesized and characterized, including the structural characterization of four Co and Cu complexes. Cyclic voltammetry demonstrates that multiple oxidation states are stabilized by these rigid, bicyclic ligands. Yet, redox potentials of the metal complexes are modified compared to the "parent" ligands due to the pendant acetate arm. Similarly, gains in kinetic stability under harsh acidic conditions, compared to parent complexes without the pendant acetate arm, were demonstrated by a half-life seven times longer for the cyclam copper complex. Due to the reversible, high oxidation states available for the Mn and Fe complexes, the Mn and Fe complexes were examined as catalysts for the bleaching of three commonly used pollutant model dyes (methylene blue, methyl orange, and Rhodamine B) in water with hydrogen peroxide as oxidant. The efficient bleaching of these dyes was observed.

Recent Advances in the Chemistry of Saturated Annulated Nitrogen-Containing Polycyclic Compounds

This review is devoted to the analysis of works published over the past 20 years on the chemistry of saturated annulated nitrogen-containing polycyclic compounds, the molecules of which consist of four, five, six, and seven cycles, and contain from one to eight endocyclic nitrogen atoms.

The critical role of ligand topology: strikingly different properties of Gd(iii) complexes with regioisomeric AAZTA derivatives

Two regioisomeric Gd(III) complexes with heptadentate AAZTA-like ligands show different hydration state (q = 1 and 2) and astonishingly different thermodynamic stability and dissociation kinetics.

Expanding and quantifying the crystal chemistry of the flexible ligand 15aneN5

15aneN5 is structurally characterized complexed to Cr3+, Mn3+, Fe3+, Co3+, and Cu2+ for the first time. Ru3+ complexation yields a Ru2+ diimine structure. A geometric factor quantifies the coordination geometry of the ligand in its complexes.

Exceptionally fast formation of stable rigidified cross-bridged complexes formed with Cu(II) isotopes for Molecular Imaging

64Cu is considered to be one of the most promising radioisotope in radiotheragnostics (combining therapeutics with diagnostics) because its positron emission is suitable for PET imaging while the combination of...