THE SYNTHESIS AND CHARACTERIZATION OF TRIPODAL COMPLEXES OF ALUMINIUM (III) AND THALLIUM (III) SALEN SCHIFF BASES WITH BRIDGING 2, 4, 6–TRIS (4–CARBOXYBENZIMINO)–1, 3, 5–TRIAZINE

Metalloligands of aluminium(III) and thallium(III) were synthesized with N,N’–bis(salicylidene)ethylenediamine. 2,4,6–s–Triazine (Melamine) reacted separately with 4–carboxybenzaldehyde in benzene under reflux to form 2,4,6–tris(4–carboxybenzimino)–1,3,5–trazine; Melamine Core Tripodal Ligand = MTPL (6.32 g, 81%). The metalloligands were reacted with MTPL in absolute ethanol under reflux to form the tripodal – trinuclear complexes; aluminium(III) Melamine Core Tripodal Complex; AlMTPC, (0.21 g, 58%) and thallium(III) Melamine Core Tripodal Complex; TlMTPC, (0.17 g, 63%). The compounds were characterized by means of ultraviolet – visible spectroscopy, elemental analysis, atomic absorption spectrometry (AAS), nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR) and fourier transform Infrared spectroscopy (FTIR). The UV – vis spectra shows two moderately intense absorption bands at (323 nm and 407 nm) for AlMTPC and (323 nm and 485 nm) for TlMTPC, which were ?→?* and n→?* transitions of the organic ligands. The FTIR spectra of MTPL reveals two strong bands at 1604.23 cm–1 and 1573.05 cm–1 corresponding to the azomethine (C=N) and triazine (C=N) stretching vibration modes. The band at 2995.49 cm–1 indicates the presence of the O–H of the carboxylic acid. In the complexes, the O–H bands of the COOH were missing thus indicating chelation of the oxygen atom to the metal. A downward shift indicates that the nitrogen and oxygen atoms of the tripodal ligand are coordinated to the ligand complexes and that a capped coordination was formed. In addition, the spectra bands at 541.38 – 521.53 cm–1 and 458.35 cm–1 respectively in the tripodal complexes indicates the M–N and M–O stretching modes. The broad bands between 3316.78 and 3524.03 cm– 1 are evidence that the complexes have water molecule coordinated to the metal centres. The signals in the 1H NMR spectrum of MTPL at singlet δ 9.77 ppm and 10.07 ppm correspond to three (–N=CH–) groups. 13C NMR spectrum of MTPL at δ 39.06 – 40.733 ppm indicates the presence of C-O, C– N group while values at δ 165.75 – 193.47 ppm indicates the presence of C=O group. This is also co – related with the 13C NMR signal at δ163.7 ppm for (C=N) group for the complexes: AlSC, TlSC, AlSLC and TlSLC. The values reveals a three directional linkage to the melamine core. Similarly, 1H NMR spectra of the tripodal complexes at singlet δ 8.30 – 8.99 ppm corresponds to six (–N=CH–) groups. These novel complexes are bridged by the carboxylate anion to the aluminium and thallium centre and the results obtained show that all the melamine core complexes are tripodal – trinuclear.