Synthesis and characterization of tetradentate bis -Schiff base complexes of di- and tri-valent transition metals

Synthesis, spectral, thermal and magnetic studies of Mn(II), Ni(II) and Cu(II) complexes with some benzopyran-4-one Schiff bases

“…The 1651-1662 cm −1 band in the free ligands is assigned to the benzopyrone carbonyl in position four [11,12]. This band does not show significant change in 1:1 (M:L) chelates confirming that this group does not participate in the chelation.…”

“…This band does not show significant change in 1:1 (M:L) chelates confirming that this group does not participate in the chelation. The Schiff bases H 2 La, H 2 Lb and H 4 La show the stretching vibration of azomethine group at 1620 cm −1 [11,12]. On other hand the IR spectrum of Schiff base H 4 Lb displays this band at 1612 cm −1 [11,12].…”

“…On other hand the IR spectrum of Schiff base H 4 Lb displays this band at 1612 cm −1 [11,12]. The infrared spectra of Mn-H 2 Lb, Cu a,c -H 4 Lb, Ni p,c -H 4 La and Ni p -H 4 Lb complexes show a shift of the C N band towards lower wave numbers, Table 2, indicating the coordination of azomethine group to the metal ions [12]. But in the infrared spectra of Mn-H 2 La, Cu a,c -H 4 Lb and Ni c -H 4 Lb complexes, the band due to the azomethine group show shift to higher wave number, Table 2.…”

“…The Schiff bases H 2 La, H 2 Lb and H 4 La show the stretching vibration of azomethine group at 1620 cm −1 [11,12]. On other hand the IR spectrum of Schiff base H 4 Lb displays this band at 1612 cm −1 [11,12]. The infrared spectra of Mn-H 2 Lb, Cu a,c -H 4 Lb, Ni p,c -H 4 La and Ni p -H 4 Lb complexes show a shift of the C N band towards lower wave numbers, Table 2, indicating the coordination of azomethine group to the metal ions [12].…”

“…Also the complexes of Ni(II) and Cu(II) with ligands H 2 La and H 2 Lb were prepared and characterized [12].…”