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PubMed2002

Tetranuclear manganese complexes with dimer-of-dimer and ladder structures from the use of a bis-bipyridyl ligand.

The reaction of the bis-chelating ligand 1,2-bis(2,2'-bipyridine-6-yl)ethane (L) with the trinuclear species of formula [Mn(3)O(O(2)CR)(6)(py)(3)](ClO(4)) (R = Me (1); R = Et (2); R = Ph (3)) has afforded the new tetranuclear mixed-valent complexes [Mn(4)O(2)(O(2)CR)(4)L(2)](ClO(4))(2) (R = Me (4); R = Et (5); R = Ph (6)) and [Mn(4)O(2)(OMe)(3)(O(2)CR)(2)L(2)(MeOH)](ClO(4))(2) (R = Me (7); R = Et (8); R = Ph (9)). Complexes 4-6 were obtained in yields of 20%, 44%, and 37%, respectively. They are mixed-valent, with an average Mn oxidation state of +2.5. Complexes 7-9 were obtained in yields of 57%, 65%, and 70%, respectively. They are also mixed-valent, but with an average Mn oxidation state of +2.75. Complexes 4 x 2THF and 9 x 3MeOH x H(2)O crystallize in the triclinic space group P1 macro and contain [Mn(4)(mu(3)-O)(2)](6+) and [Mn(4)(mu(3)-O)(2)(mu-OMe)(2)](5+) cores, respectively, the latter being a new structural type in the family of Mn(4) complexes. Reactivity studies of 4-9 have shown that 4-6 can be converted into 7-9, respectively, and vice versa. The magnetic properties of 5 and 9 have been studied by dc and ac magnetic susceptibility techniques. Complex 5 displays antiferromagnetic coupling between its Mn ions resulting in a spin ground state of S = 0. Complex 9 also displays antiferromagnetic coupling, but the resulting ground state is S = (7)/(2), as confirmed by fitting magnetization versus field data collected for 9 at low temperatures, which gave S = (7)/(2), D = -0.77 cm(-1), and g = 1.79. Complex 9 exhibits a frequency-dependent out-of-phase ac susceptibility peak, indicative of the slow magnetization relaxation that is diagnostic of single-molecule magnetism behavior.

Journal Article↗
PubMed1997

Usefulness of residual fractions of L,L-ethylcysteinate dimer (Neurolite) for the preparation of 99Tc(m)-L,L-ethylcysteinate dimer.

According to the reconstitution instructions for the Neurolite labelling kit, the contents of vial A (containing the ligand) is dissolved in 3 ml of saline and 1 ml of the solution is added to vial B (containing 1 ml of phosphate buffer) to which 2 ml of 99Tc(m) generator eluate had previously been added. This implies that 2 out of 3 ml of the ligand solution is not used. We have investigated the radiochemical purity of 99Tc(m)-ECD reconstituted from fractions of the residual solution after storage in a freezer. Fractions of 0.25 ml or 0.5 ml were reconstituted with 1.11 GBq or 3.7 GBq 99Tc(m)-pertechnetate, respectively, after storage at -20 degrees C for periods ranging from 1 day to 4 weeks. In each test situation, except when 0.25 ml fractions were labelled with 3.7 GBq 99Tc(m), 99Tc(m)-ECD was obtained with a radiochemical purity > 95% up to 6 h after reconstitution, as determined using two-strip TLC and reverse-phase HPLC. The results demonstrate that residual portions of Neurolite kits can be efficiently labelled after fractionation and storage in a freezer.

Brain↗