Magnetic, metallomesogenic and thermoelectric studies of Cu(II), Ni(II), Co(II), Fe(II) and Mn(II) complexes with benzoates, cyclam and 4 alkyloxypyridines as ligands / Siti Amira Mat Hussin

Siti Amira , Mat Hussin (2016) Magnetic, metallomesogenic and thermoelectric studies of Cu(II), Ni(II), Co(II), Fe(II) and Mn(II) complexes with benzoates, cyclam and 4 alkyloxypyridines as ligands / Siti Amira Mat Hussin. Masters thesis, University of Malaya.

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Abstract

The main objective of the research was to synthesise and characterise thermally stable complexes, designed to be metallomesogenic with spin-crossover (SCO) and thermoelectric properties. 4-Hexadecyloxypyridine and complexes of general formula [M(cyclam)(L)2](4-XC6H4COO)2/3], where M = Cu(II), Ni(II), Co(II), Co(III), Fe(II), Fe(III), Mn(II) and Mn(III), L = 4-tetradecyloxypyridine or 4-hexadecyloxypyridine, X = H, CH3, CH3O and OH were successfully synthesized in good yields, and their structural formulae deduced from combined analytical data (elemental analyses and IR and UV-vis spectroscopies). The magnetic, thermoelectric, thermal, and mesomorphic properties of these complexes were then studied. The ?eff values at room temperature were in the range of 1.47 BM to 1.77 BM for all Cu(II) complexes (1-3), and 1.83 BM for [Ni(cyclam)(L2)2](C6H5COO)2?H2O (4). Based on 1H-NMR spectroscopy, [Co(cyclam)(L1)2](R)2?3H2O (6), [Fe(cyclam)(L2)2](R)3?4H2O?2CH3CH2OH (9), [Mn(cyclam)(L1)2](R)2?4H2O (10) and [Mn(cyclam)(L2)(H2O)](R)3?3H2O (11) were paramagnetic, while [Ni(cyclam)(L1)(H2O)](R)2?H2O (4), [Co(cyclam)(L2)2](R)3?4H2O (7) and [Fe(cyclam)(L1)2](R)2?2H2O (8), where R = C6H5COO, were diamagnetic. The decomposition temperatures for all complexes were in the range of 130 ºC to 206 ºC. Complexes 3, 9, 11 were mesogenic, while the other complexes were non-mesogenic. The Seebeck coefficients (in mV K-1) were in the range of -0.42 to -0.51 for all Cu(II) complexes in chloroform, +0.23 to +0.27 for Ni(II) complexes in ethanol, +0.24 to +0.33 for Co(II/III) complexes in DMSO, +0.33 and -0.8 for Fe(II)/III) complexes in MPN, and +0.22 and +0.24 for Mn(II/III) complexes in DMSO and ethanol.

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