Studies of Organotin(iv) Derivatives of Thiosemicarbazones

Synthesis, structural characterization, biological activity and thermal study of tri‐ and diorganotin(IV) complexes of Schiff base derived from 2‐aminomethylbenzimidazole

“…Absence of ν(OH) mode in all of the studied complexes suggests the deprotonation of phenolic -OH of Hsal-ambmz and its subsequent coordination through the oxygen atom. [16,19,20,22,23] Two strong bands around 1530 ± 10 and 1313 ± 6 cm −1 in the complexes were observed at lower wave numbers as compared with uncoordinated Hsal-ambmz (1561 and 1320 cm −1 ), indicating the participation of phenolic oxygen in bonding with tin. [20] Further, the IR spectrum of Hsal-ambmz showed a very sharp and strong band due to the ν(-C N-) of azomethine at 1638 cm −1 .…”

“…Since the imidazole ring has an aromatic character, a shoulder at 1615 cm −1 may be assigned to ν(C N) of the imidazole ring. [16,19,20,22,24] In the IR spectra of the studied complexes, a single sharp band at 1621 ± 8 cm −1 was observed because the azomethine ν(C N) merges with ν(C N) of imidazole ring, indicating the coordination of azomethine nitrogen to tin. Moreover, the presence of two medium intensity bands in the regions 3052-3064 and 2954-3044 cm −1 in Hsal-ambmz as well as in most of the complexes indicates that the N-H of imidazole ring does not participate in the coordination.…”

“…Moreover, there were a few sharp bands observed in the region 240-270 nm in the spectra of complexes, which could be assigned to charge transfer bands. [16,18 -21] It has been reported [16,20] that a metal/metalloid is capable of forming dπ -pπ bonds with ligands containing nitrogen as donor atom. The tin atom has its 5d orbitals completely vacant and hence L → M bonding can take place by the acceptance of pair of electron from nitrogen or oxygen donor atom of the ligands.…”

“…oxygen and nitrogen in (sal-ambmz) −1 , are not in axial positions, as one would expect from the steric properties of the bidentate ligand. [16,20] Hence the triorganotin(IV) chelates of monofunctional bidentate Schiff base (HL) with ON donor site exhibit trigonal-bipyramidal geometry with either fac or mer configuration (Fig. 2).…”

“…The absence of such a signal in all of the organotin(IV) complexes suggests the deprotonation of the phenolic OH of Schiff base on complexation. [16,20,28] In the 1 H NMR spectra of the complexes, a signal at δ 8.63 ± 0.04 ppm for triorganotin(IV) complexes and δ 8.72 ± 0.09 ppm for diorganotin(IV) complexes has been assigned to the azomethine proton (-CH N-). It appears at low frequency in all of the studied complexes as compared with the corresponding signal of uncoordinated Schiff base (8.69 ppm in CD 3 OD/8.96 ppm in DMSO-d 6 ), indicating thereby the coordination of the ligand to the tin via azomethine nitrogen (Sn ← N).…”