The paramagnetic gadolinium(III) ion is used as contrast agent in magnetic resonance (MR) imaging to improve the lesion detection and characterization. It generates a signal by changing the relaxivity of protons from associated water molecules and creates a clearer physical distinction between the molecule and the surrounding tissues. New gadolinium-based contrast agents displaying larger relaxivity values and specifically targeted might provide higher resolution and better functional images. We have synthesized the gadolinium(III) complex of formula [Gd(thy)2(H2O)6](ClO4)3·2H2O (1) [thy = 5-methyl-1H-pyrimidine-2,4-dione or thymine], which is the first reported compound based on gadolinium and thymine nucleobase. 1 has been characterized through UV-vis, IR, SEM-EDAX, and single-crystal X-ray diffraction techniques, and its magnetic and relaxometric properties have been investigated by means of SQUID magnetometer and MR imaging phantom studies, respectively. On the basis of its high relaxivity values, this gadolinium(III) complex can be considered a suitable candidate for contrast-enhanced magnetic resonance imaging.
A series
of six novel RuIV compounds of formula (H2bpy)2[{RuCl5}2(μ-O)]
(1), (PPh4)2[{RuCl4(H2O)}2(μ-O)]·4H2O (2), (PPh4)2[{RuCl4(MeCN)}2(μ-O)] (3), (PPh4)2[{RuCl4(dmf)}2(μ-O)] (4), (PPh4)2[{RuCl4(py)}2(μ-O)] (5), and [{RuCl3(bpym)}2(μ-O)]·6H2O (6) [H2bpy2+ = 4,4′-bipyridine-1,1′-diium
cation; PPh4
+ = tetraphenylphosphonium cation;
dmf = N,N′-dimethylformamide;
py = pyridine; bpym = 2,2′-bipyrimidine] have been prepared
and spectroscopically, electrochemically, and magnetically characterized.
Compounds 1, 2, 5, and 6 crystallize in the triclinic system with space group P1̅, whereas 3 and 4 crystallize
in the monoclinic system with space group P21/c. While 1–5 are salts based on anionic dinuclear RuIV species, 6 is a neutral diruthenium(IV) complex. The Ru–O–Ru
core is present in 1–6 [with values
of the Ru–Ooxo bond length covering the range of
1.774(1)–1.816(1) Å and the values of the Ru–O–Ru
angle (θ) varying in the range of 164.3–180.0°].
In their crystal lattice, intermolecular RuIV–Cl···Cl–RuIV halogen bonds (1 and 6), Cl···π
(1 and 3–6), and π···π
(5 and 6) type interactions as well as hydrogen
bonds (1, 2, and 6) are present.
These intermolecular interactions generate novel supramolecular structures
based on the self-assembly of (μ-oxo)diruthenium(IV) complexes.
Magnetic susceptibility measurements performed on microcrystalline
samples of 1–6 confirmed the diamagnetic
nature for the six compounds, which are strongly antiferromagnetically
coupled. The study of the electrochemical properties of 2–6 through cyclic voltammetry (CV) in dmf allowed
us to evaluate the effect of the ligand nature on the rich redox features
along this series of (μ-oxo)diruthenium(IV) complexes.
Two novel one-dimensional dysprosium(iii) complexes based on α-glycine (gly) and β-alanine (β-ala) amino acids have been synthesised and characterised structurally and magnetically. Both compounds exhibit field-induced slow relaxation of magnetisation.
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