Self-assembled Transition Metal Coordination Frameworks of ...

3.3.1. MALDI MS spectral studies of molecular square grids
Ni(lI) complexes
For the unequivocal characterization of large molecules, mass spectrometry
was found useful as complementary. The structure and stability of coordination
complexes under ionization conditions are dependent on various factures like the
ligand itself, metal ions, counter ions, solvent, temperature, concentration, etc.
MALDI mass spectra in dichloromethane as DCTB mix on positive ion mode have
been found useful to get excellent results for stable Ni(II) square grids of both
thiocarbohydrazones and carbohydrazones.
MALDI MS spectrum of compound 1 (Fig. 3.1) in dichloromethane shows the
presence of three main peaks centered at m/z 495.0602, 991.1073 and 1981.2342. The
peak centered at l98l.2342 is assigned as the molecular ion peak expected for
[Ni4(HL')L'3]+ (calc. m/z 1981, Fig. 3.2), well agreement with the simulation. The
base peak at m/z 495.0602 is assigned as [Ni(HL')]+ (calc. 495) and the other major
ao- 1 '
1
peak is assigned as [Ni2(HL')L']+ (calc. 991, Fig. 3.2).
. so
991
497
495 0602 I“Y mo 495 1931
so-; 70i * 1<
‘ l 498499
__ 496
l
4° l\Iass!Cha.rge
w._
1 l,,.l,?9°. ..
30
20
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104
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41]) 600 800 1000 1200 1400 1600 1000 Z000
MasaIChu9o
R.
0 ' 7'7" 1 1'] >1 - ; 1 - ~ | - - 1 | . .'. ‘ 1" xi li 1‘: x‘: ; r*' F1 ; ; - '1 v‘ '"*-'""—v—I:1'i"'i—T"*—*T*T ~r1-{"1-.""'r"r'1—{"r‘
Fig. 3.1. MALDI mass spectrum of the compound 1. The insets are isotropic
distribution pattem of base peak (left) and its theoretical simulation (right).
83