Spin-State Patterning in an Iron(II) Tripodal Spin-Crossover Complex

A mononuclear iron(II) complex that displays a gradual two-step spin-crossover (SCO) transition is reported. The intermediate plateau (IP) occurs between HS0.40LS0.60 and HS0.30LS0.70 (HS = high spin; LS = low spin) ratios over the region of ca. 190-170 K. A phase change occurs at the IP, breaking the symmetry, resulting in six independent SCO sites compared to one at the 100% HS and LS plateau regions, respectively. Variableerature X-ray photoelectron spectroscopy shows that the SCO behavior is completely reversible among the HS, IP, and LS regions. The results both confirm and extend the related results for the above system described by Halcrow et al. (Kulmaczewski, R.; Cespedes, O.; Halcrow, M. A. Gradual Thermal Spin-Crossover Mediated By a Reentrant Z′ = 1 Z′ = 6 Z′ = 1 Phase Transition, Inorg. Chem. 2017, 56, 3144-3148) in a recent report

Polyamide-Scorpion Cyclam Lexitropsins Selectively Bind AT-Rich DNA Independently of the Nature of the Coordinated Metal

Cyclam was attached to 1-, 2- and 3-pyrrole lexitropsins for the first time through a synthetically facile copper-catalyzed “click” reaction. The corresponding copper and zinc complexes were synthesized and characterized. The ligand and its complexes bound AT-rich DNA selectively over GC-rich DNA, and the thermodynamic profile of the binding was evaluated by isothermal titration calorimetry. The metal, encapsulated in a scorpion azamacrocyclic complex, did not affect the binding, which was dominated by the organic tail

Investigation of novel bis- and tris-tetraazamacrocycles for use in the copper-64 (Cu-64) radiolabeling of antibodies with potential to increase the therapeutic index for drug targeting.

The 64Cu complexes of a series of mono-, bis-, and tris-tetraazamacrocycles have been prepared, and their stability in human sera has been assessed. The ligands forming the most stable Cu2+ complexes were then conjugated to the B72.3 antibody (mAb). Conditions for conjugation of the ligands to the mAb were optimized for the concentration of protein, ligand, pH, temperature, and time. The optimum moles of Cu2+ attached to the mAb were as high as 3.5 for L2 and 5.5 or 2.7 for L5, and the immunoreactivity was ≥80%. Biodistribution of the radioimmunoconjugates showed good tumor localization and target-to-background ratios that were significantly enhanced compared to those achieved with monotetraazamacrocyclic derivatives. © 2009, American Chemical Societ