Self-assembled Transition Metal Coordination Frameworks of ...

Chapter 4
Where ,1’ M is the magnetic susceptibility per Cu(H), Na is the temperature
independent paramagnetism. ,5-Bohr magneton, N -Avogadro number. p is the
mole fraction of the paramagnetic monomeric impurity.
The susceptibility data of all dicopper complexes, however, found cannot be
satisfactorily fitted to Bleaney-Bower equation (2). Around the maximum the fit
departs from the experimental data. Inter-dimer exchange interactions between
neighboring ions may occur [40], possibly having influence in the susceptibility
around Tm“. The existence of other kinds of secondary interactions may also be
present in the compounds. To fit and interpret the magnetic susceptibility data of
complexes, first it is necessary to find all possible magnetic pathways in the complex
structures, and in the absence of X-ray crystallographic structural results it is not
possible to use any magnetic interacting models as that may lead to erroneous
conclusions. Single crystal study is mandatory for a magneto structural correlation
study also.
4.3.6. Characterization of an unusual complex
The Cu(H) complexes of carbohydrazone ligands are found to undergo a color
loss in common organic solvents in lower concentrations on exposure to air for days
attributed to possible dissociation, though they are very stable in their solid form.
Fortunately, we could isolate the single crystals of a new copper compound
[Cu(L4“)2Cl2]- CH3OH- H2O- H3O+Cl' (l3a) by slow evaporation of a solution of 13 in
methanol in air after a month. Where L4” is 3-(2-pyridyl)triazolo[l,5-a]-pyridine. It is
found that the compound 13 suffered degradation of -CO- group and cyclization to
form a chloride copper complex of L4’. A comparable copper complex of 3­
phenyltriazolo[l,5-a]-pyridine has been isolated by the reaction of 1,5-bis(2­
benzoylpyridine) carbohydrazone (HZLS) with CuCl2 [1 1], resulted with a degradation
of -CO- group and cyclization. Also, somewhat similar kind of ligand N’, N’2­
180