Chelating Behaviour of 2, 4, 9, 11−Tetraphenyl−1, 5, 8, 12− Tetraazacyclotetradeca −1, 4, 8, 11−Tetraene towards Cu(II), Ni(II), Fe(II), Co(II) Metal Ions

The chelating behavior of 2, 4, 9, 11−tetraphenyl−1, 5, 8, 12 tetraazacyclo tetradeca 1, 4, 8, 11−tetraene towards Fe(II), Co(II), Ni(II) & Cu(II). The synthesis of metal legand complex of Fe(II), Co(II), Ni(II) and Cu(II) of [2, 4, 9, 11−tetraphenyl−1, 5, 8, 12−tetraaza−cyclotetradeca−1, 4, 8, 11−tetraene] was made by using methanol, metal salt nitrate and 1, 3−diphenyl−1, 3−propanedione. Melting point of the complex was found out to be in the range 145−260°C. Yield 55−60%. The IR spectra of the complex in methanol have shown the characteristic band due to ν(C=N) at ∼1660 cm⁻¹. The presence of 1, 3−diphenyl−1, 3−propanedione moiety was indicated by the appearance of bands at 2993, 1584, 1419, 657 cm⁻¹. ¹H NMR of the Cu−Complex in DMSO gave singlets in the region 2.24−3.16 ppm and 6.88−7.56 ppm attributable to CH₂ (4H) protons and C₆H₅ (20H) protons of 1, 3−diphenyl−1, 3−propanedione. The electronic spectra confirmed the square planar geometry. The observed magnetic moment value of 5.2 B.M. for the complex under discussion suggested the tetrahedral geometry for the Fe(C₃₄H₃₂N₄)(NO₃)₂. The electronic spectrum of cobalt complex Co(C₃₄H₃₂N₄)(NO₃)₂ exhibited very weak band in the near infrared region at 1800 nm, which is characteristic of a square planar Co(II) species. This result was corroborated by its magnetic data (2.02 B.M.). The spectrum of nickel complex displayed a relatively weak band at 560 nm with a shoulder at 500 nm. This low intensity band was described to (d−d) transitions, in square planar complexes. On the basis of the analytical, spectral (IR, UV−visible) and magnetic data, it is inferred that the bonding of the metal ions takes place through aza group and the ligand acts as neutral tetradentate.