Self-assembled Transition Metal Coordination Frameworks of ...

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v(Ni—S), further supports sulfur coordination [34]. Bands ranging from 1600-1400 cm'
', attributed to v(C=C) and v(C=N) vibration modes, in the spectra of complexes
suffer significant shifts and their mixing patterns are different from that in the spectra
of respective ligands. The azomethine v(C=N) vibrations at 1580 and 1630 cm" in the
free ligands HL7 and HL8 respectively suffered negative shifts. These bands are seen
at 1561 cm" in the spectrum of 5 and at 1553 and 1537 cm" in the spectra of
compounds 6 and 7 respectively. The new bands at frequencies 1590 and 1594 cm"
for 6 and 7 are assigned the vibration of newly formed v(2N=C) bond and is absent in
the spectrum of 5. The coordination through azomethine nitrogen is further evidenced
by the v(Ni—N,,°) [35] peaks at ~440 cm" for these compounds. The shifts in the v(N­
N) frequencies also support the coordination through azomethine nitrogen in all the
complexes. Coordination of the pyridine nitrogen atom is seen by the shift in
frequencies of the deformation mode bands that appear in the range 649 and 455 cm"
in the spectrum of HL8 [32]. This is further supported by v(Ni-_Npy/qu) bands [36] seen
at ~250 cm" for all these compounds. The perchlorate complex 6 shows a broad band
| '1
Compds. v(C= N) v('N=C) v(N—N) v(C_S) v(C—H)
at 1090 cm" and strong band at 625 cm", indicating the presence of ionic perchlorate
[37]. The former band is assignable to v3(C1O4) and unsplit band at 625 cm"
assignable to v4(ClO4). These indicate that C104 species is not coordinated (T ,1). The
other bands at 938 and 467 cm", assignable to v, and v2 of C104, are very week.
Table 3.3. IR spectral features of thiosemicarbazones and their Ni(H) complexes.
94
HL7 1580
5 1561
HL8 1630
6 1553
7 1537
1590
1594
1102
1110
1118
1145
1150
1282
1278
1342
1337,
1283
1296
2970,2870
2969,2870
2964,2876
2969,2876
V(Nl_Nazo)v
v(Ni—S),
v(PJi—1JQn@u)
459,352,240
430,354,251
433,351,270