Self-assembled Transition Metal Coordination Frameworks of ...

25' 06
2.0­M00­
00-‘. ­ I
Ni(ll) complexes
..;.*..s.*.a.*..;.*1a°*.a.".¢..
'
mmwowovwwm
l ‘ I ‘ l ‘ 1 ' I ' l
Wavelength (nm) wa"°'°"9th mm)
3 in l0‘5M DMF 4i"1°'5M DMF
Fig. 3.15. Electronic spectra of Ni(II) carbohydrazone complexes.
3.3.2.1. IR and electronic spectral studies of thiosemicarbazone complexes
The characteristic IR bands of the complexes 5, 6 and 7 differ from their free
ligands HL7 and HL8, provide significant indications regarding the coordination and
bonding sites of the ligands. Relevant characteristic bands of these compounds are
listed in Table 3.3 and selected spectra are given in Figs. 3.16 and 3.17. The ligand
HL7 shows a broad peak at 3442 cm" is attributed to v(2N—H) vibration with a
possible hydrogen bond. In compound 5, this peak is shifted slightly downwards but is
indicative of the presence of ZN-I-I. However in compounds 6 and 7 due to the
presence of lattice water broad bands are seen at frequencies 3415 and 3440 cm"
respectively. No other bands in the nearby region may be due to the absence of N—H
hydrogens. Also the strong peak at 1282 cm" assigned as v(C=S) vibration for HL7
shows only marginal shift in compound 5, supports the coordination through thione
form. However for compound 6 two strong bands seen at 1337 and 1283 cm" are
assigned v(C=S) and v(C—S) frequencies, show the shift from 1342 cm" assigned for
v(C=S) of HL8 [32]. In compound 7 the strong band at 1296 cm" is assigned to v(C­
S) band. Besides, no band due to the SH group is observed between 2600 and 2500
cm" [33], in agreement with the deprotonated thiolate form of the ligand in these
complexes 6 and 7. The bands seen at ~350 cm" for these complexes are assigned as
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