Self-assembled Transition Metal Coordination Frameworks of ...

W 7 N A _ gm g_ g Manganesefll) complexes
reported for the first time. The MALDI MS spectra reveal sensible fragmentation
peaks of tetranuclear molecular squares, and it is found that the Mn(II) squares are not
so stable like their Ni(Il) counterparts in solution or under ionization conditions of
MALDI. The Mn(II) complexes were organized by mono and dideprotonated
thiocarbohydrazones and by monodeprotonated and neutral carbohydrazones.
Variable temperature magnetic studies of all the Mn(ll) square grids exhibit
intramolecular antiferromagnetic coupling between electrons, consistent with the
expected bridging structural arrangement, by a super exchange mechanism through
intervening sulfur/oxygen atoms. Magnetic data have been rationalized successfully
on the basis of expected square grid structures, as supported by MALDI MS and other
data, in the absence of single crystal X-ray studies. The theoretical simulations of
isotropic patterns of characteristic fragmentation peaks were achieved well, confirm
the proposed structural formulae and this is found inevitable in the absence of single
crystal X-ray studies. The molar conductance, magnetic studies and elemental
analyses along with other spectral studies differentiate the square grid frameworks
from mononuclear metal complexes. However, the complex 20 was found to be a
dimanganese(ll) complex, may be due to the effect of concentration or the preference
of azide ion to coordinate to metal center. The magnetic complexes, especially the
colorless materials derived from carbohydrazones would find applications.
References
l. N.N. Greenwood, A. Eamshaw, Chemistry of the Elements, 2'“ ed., Reed
Educational and Professional, Oxford (1997).
2. T.G. Carrel], A.M. Tyryshkin, G.C. Dismukes, J. Biol. lnorg. Chem. 7 (2002)
2.
3. J.-Z. Wu, E. Bouwman, A.M. Mills, A.L. Spek, J. Reedijk, lnorg. Chim. Acta
225