Made available in DSpace on 2014-10-09T12:32:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:42Z (GMT). No. of bitstreams: 1 03371.pdf: 3959885 bytes, checksum: 92c5eafe280381862d70e980bb9322c9 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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No description available.

To serve well as luminescent labels in biological applications, complexes of the lanthanide ions need to fulfil many criteria, including the requirement of high quantum yields, stability towards dissociation in biological media and preferably, excitation at wavelengths over 350 nm. Herein, a number of aspects regarding the sensitization of europium(III) and terbium(III) ions are discussed with respect to the design and development of novel complexes. The effect of the addition of anions such as fluoride and phosphate to the Eu(III) and Tb(III) complexes of a known tris(bipyridyl) cryptate, are studied with a view to gaining a better understanding of non-radiative deactivation pathways of the lanthanide excited state. Enhancements of Eu3+ emission within the cryptate are noted whilst with the Tb3+ analogue, emission is significantly reduced upon displacement of OH by these ions. A new ligand based on a polyaminocarboxylate structure with a single bipyridyl chromophore is then reported, which displays nine-coordination around the enclosed lanthanide ion. The luminescence properties of the europium complex are very good but the terbium complex shows more complex behaviour, suggestive of a back energy transfer mechanism from the terbium excited state to the ligand triplet level. The development of ligands with mixed N,O pyrido-phenol chromophoric groups, which are expected to be better sensitizers of terbium(III) luminescence, is also outlined. Finally, in the quest to sensitize europium using longer wavelengths, acridone is incorporated into an azamacrocyclic structure and luminescence is observed from the complexed Eu3+. The quantum yield of luminescence is found to increase with decreasing distance between the sensitizer and the ion, and in the presence of coordinating donor atoms.

Made available in DSpace on 2014-10-09T12:49:52Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:36Z (GMT). No. of bitstreams: 1 09984.pdf: 10774307 bytes, checksum: a193fefe92c978f1963dcaad657ea1e2 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:00/08908-1

Made available in DSpace on 2014-10-09T12:49:52Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:36Z (GMT). No. of bitstreams: 1 09984.pdf: 10774307 bytes, checksum: a193fefe92c978f1963dcaad657ea1e2 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:00/08908-1

This thesis is concerned with the synthesis and characterisation of novel TCNQ (7,7,8,8-tetracyanoquinodimethane), TMTCNQ (2,3,5,6-tetramethyl-7,7,8,8-tetracyanoquinodimethane) and TCNQF4 (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) based zwitterionic D-1t-A materials (where D and A are electron donors and acceptors respectively) of which the methylated Z-~-(N-methyl-4-quinolinium)-a-cyano-4( 2,3,5,6-tetrafluoro)styryldicyanomethanide [CH3(4)Q3CNQF4] is a typical example. Synthetic modification of the donor moiety was also undertaken, resulting in a diverse range of pyridinium, quinolinium and benzothiazolium-based materials, which may have use in nonlinear optical research. For the quinolinium system an extensive range of both 2- and 4-substituted analogues have been prepared and their properties compared and contrasted. The solvatochromic behaviour of these zwitterions was investigated in detail by dissolution in a range of organic solvents and measurement of their longest wavelength charge-transfer absorption bands using UV/Visible spectroscopy, which revealed that the substituents have a marked effect upon their solvatochromic properties. Most of the adducts studied display highly negative solvatochromism as the solvent polarity increases, in which their absorption maxima are linearly related with the normalised ENT values for the Reichardt dye. However the fluorinated quinolinium and pyridinium derivatives exhibit an unusual aggregation-induced reverse solvatochromism effect. The negative halochromic behaviour of selected zwitterions has also been investigated, with a hypsochromic shift of the longest wavelength CT absorption band being observed upon addition of electrolytes. Increased polarisation within the fluorinated R(4)Q3CNQF4 and R(2)Q3CNQF4 adducts has been indicated by solution state dipole moment measurements indicating greater nonlinear optical potential. However this increased polarisation has also been shown to be a major cause of the limited stability of these materials to photo-oxidation. The behaviour of the R(4)Q3CNQF4 and R(2)Q3CNQF4 zwitterions on the subphase and their resultant Langmuir-Blodgett film forming ability was also studied. However unlike the TCNQ-based materials the fluorinated adducts have been shown to be poor LB film forming materials.

No description available.

No description available.

No description available.