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One of the intriguing features of biological systems is the prevalence of highly selective and often very strong interactions among different cellular components. Such interactions play a variety of organizational, mechanical, and physiological roles at the cellular and organism levels. Antigen-antibody complexes are representative examples of highly selective and potent interactions involving proteins. The marked specificity of protein-antibody complexes have led to a wide range of applications in cellular and molecular biology related research. They have become an integral research tool in the present genomic and proteomic era. Unfortunately, the production of selective tools based on antigen-antibody interactions requires cumbersome protocols. The long term goal of this project explores the possibility of manipulating liposomes to serve as the chemical receptors ("artificial antibodies") against selected proteins. Cellular lipids (e.g., lipid rafts) are known to facilitate highly selective binding of proteins on cell membranes. The binding of proteins to cell membranes can be envisaged to be modulated via interactions between polar (charged) and non-polar head groups of lipids and the complementary amino acid residues of proteins. Their interaction is facilitated by a combination of van der Waals, electrostatic, hydrogen bonding and hydrophobic forces. A further interesting aspect of the above interaction is the "fluidity" of the membrane resident lipids, which can migrate from other regions to further enhance the complementary interactions of proteins on the initially "docked" membrane surface. With these features in mind, the end goal of this project is expected to deliver lipid-based chemical receptors "synthetically" designed against proteins to function as "artificial antibodies". Protein sensing will be accomplished with lipid receptors assembled in templated polymerized liposomes. The research presented here specifically focus on the analytical aspects of protein sensing via polymerized liposome vesicles. Lanthanide ions (Eu(III) and Tb(III)) are incorporated into polymerized liposome with the expectation to "report" quantitative and qualitative information on the interacting protein. Our proposition is to extract quantitative and qualitative information from the luminescence intensity and the luminescence lifetime of the lanthanide ion, respectively. A thorough investigation is presented regarding the analytical potential of these two parameters for protein sensing. Two chemometic approaches - namely partial least squares (PLS-1) and artificial neural networks (ANN) - are compared towards quantitative and qualitative analysis of proteins in binary mixtures.

One of the intriguing features of biological systems is the prevalence of highly selective and often very strong interactions among different cellular components. Such interactions play a variety of organizational, mechanical, and physiological roles at the cellular and organism levels. Antigen-antibody complexes are representative examples of highly selective and potent interactions involving proteins. The marked specificity of protein-antibody complexes have led to a wide range of applications in cellular and molecular biology related research. They have become an integral research tool in the present genomic and proteomic era. Unfortunately, the production of selective tools based on antigen-antibody interactions requires cumbersome protocols. The long term goal of this project explores the possibility of manipulating liposomes to serve as the chemical receptors ("artificial antibodies") against selected proteins. Cellular lipids (e.g., lipid rafts) are known to facilitate highly selective binding of proteins on cell membranes. The binding of proteins to cell membranes can be envisaged to be modulated via interactions between polar (charged) and non-polar head groups of lipids and the complementary amino acid residues of proteins. Their interaction is facilitated by a combination of van der Waals, electrostatic, hydrogen bonding and hydrophobic forces. A further interesting aspect of the above interaction is the "fluidity" of the membrane resident lipids, which can migrate from other regions to further enhance the complementary interactions of proteins on the initially "docked" membrane surface. With these features in mind, the end goal of this project is expected to deliver lipid-based chemical receptors "synthetically" designed against proteins to function as "artificial antibodies". Protein sensing will be accomplished with lipid receptors assembled in templated polymerized liposomes. The research presented here specifically focus on the analytical aspects of protein sensing via polymerized liposome vesicles. Lanthanide ions (Eu3+ and Tb3+) are incorporated into polymerized liposome with the expectation to "report" quantitative and qualitative information on the interacting protein. Our proposition is to extract quantitative and qualitative information from the luminescence intensity and the luminescence lifetime of the lanthanide ion, respectively. A thorough investigation is presented regarding the analytical potential of these two parameters for protein sensing. Two chemometic approaches - namely partial least squares (PLS-1) and artificial neural networks (ANN) - are compared towards quantitative and qualitative analysis of proteins in binary mixtures.

Research in the fields of molecular conductors and magnets over the past four decades has involved collaborative efforts of chemists and physicists whose common goal is to design useful materials composed of molecular building blocks. Of particular interest are materials whose properties can be tuned by electronic or steric changes in the molecular sub-units. The research on TCNQ derivatives described in this thesis was inspired by the observation that, although a vast amount of research has been directed at understanding binary M(TCNQ•-) materials, analogous compounds based on substituted TCNQ acceptors are surprisingly scarce. Single crystals of a new structure type for the M+(TCNQ)•- binary family were isolated from reactions of two dihalogenated TCNQ derivatives with Cu(I) ions, namely Cu(TCNQX2) (X = Cl, Br). The new 3-D compound Cu(TCNQCl2) exhibits the highest conductivity of the M+(TCNQ)•- series to date, despite the greater separation of TCNQCl2 units as compared to other derivatives. Compounds of lower dimensionality were also obtained, namely the 2-D Cu(TCNQBr2)(CH3CN) and 1-D Cu(TCNQI2)(CH3CN)2 phases. Several 2p-3d heterospin molecular magnets were also synthesized. For example a “magnetic sponge” material based on a 2-D hexagonal framework of composition {[Mn2(TCNQF4)(CH3OH)7.5(H2O)0.5]-(TCNQF4)2•7.5CH3OH}∞, as well as molecular magnets based on first row metal ions and TCNQF4 ligands of composition MII(TCNQF4)-•(TCNQF42-)0.5(CH3CN) (M = Mn, Co) were prepared. In addition, unprecedented isostructural 2-D frameworks based on combinations of first row metal ions with TCNQBr2 radicals of composition [M(TCNQBr2)2(H2O)2]∞ (M = Mn, Zn) were synthesized. Lanthanide chemistry is also described in this dissertation. A series of mononuclear Ln-TCNQF4 heterospin complexes of composition {MIII[TCNQF4]2[H2O]x}(TCNQF4)(3H2O) (M = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er and Yb) was also obtained which exhibit remarkable properties. In this family of compounds there exists an unprecedented subtle interplay between single molecule magnetic behavior and phonon bottleneck effect behavior for the Tb analogue. Magnetic ordering was observed for the Sm analogue. A homologous series of 1-D materials based on alternating lanthanide ions and hexacyanometallates of formula {[Ln(tptz)(H2O)4Fe(CN)6]•8H2O}∞ (Ln = Pr, Nd, Sm, Eu, Gd, Tb) was obtained and a detailed magnetic study provided incontrovertible evidence that the SmIII-[FeIII(CN)6]3- compound exhibits ferromagnetic and not antiferromagnetic coupling as had been reported for related 1-D chains.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-05-13T14:09:47Z No. of bitstreams: 1 arquivo total.pdf: 4037386 bytes, checksum: 2733330d803024eb0abfbac341b0b0da (MD5) / Made available in DSpace on 2016-05-13T14:09:47Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 4037386 bytes, checksum: 2733330d803024eb0abfbac341b0b0da (MD5) Previous issue date: 2014-08-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In the present work, it has been investigated the influence of the position of electron-donor substituents in aromatic carboxylate ligands on the photoluminescent properties of Tb3+ and Eu3+complexes. It was synthesized complexes of general formula [Ln (R-2-Bz)3fen] and [Ln (4-R-Bz)3fen] with Ln = Eu3+, Gd3+ and Tb3+; R =-NH2,-NH (CO) CH3,-OH,-O (CO) CH3,-O (C4H9); phen = 1,10-phenanthroline, which were characterized by complexometric titration, elemental analysis, absorption IR spectra and diffuse reflectance. The phosphorescence spectra of the complexes [Gd (2-R-Bz)3fen] and [Gd (4-R-Bz)3fen] showed that the energies of the triplet states of the ligands are coordinated above and in a good resonance condition with the emitting states of both ions Eu3+ and Tb3+ and it is favorable to the efficient process of ligand-metal energy transfer. Such states are localized on the 1,10-phenanthroline ligands in all complexes. For the complexes of the Tb3+ ion, it was found that acetylation of both substituents N or O-donors caused an increase in the lifetimes for most compounds, which is much higher at ambient temperature than at low temperature. For the Eu3+ complex it was observed a strong dependence of the intensity parameters Ω2 and quantum efficiency of luminescence with the nature and position of the electron-donors substituents, which could be rationalized on the basis of electronic and steric effects. Such effects exerted strong influence on the LMCT charge transfer states, directly contributing to the dependence of the quantum efficiency of luminescence with the position of the electron-donor substituents the carboxylate ligands. Steric interactions promoted conjugation breakage due to the removal of the aromatic ring from the conjugation plane of the carboxylate group, reducing the ability of the electron-donating oxygen atoms and consequently increasing the LMCT energy states. It was demonstrated, for the first time, that the loss of conjugation by steric interaction may eliminate or reduce the effect of LMCT states as a suppression channel of luminescence in Eu3+ complexes. / No presente trabalho, investigou-se a influência da posição de substituintes elétron-doadores em ligantes carboxilatos aromáticos sobre as propriedades fotoluminescentes de complexos dos íons Tb3+ e Eu3+. Foram sintetizados complexos de fórmula geral [Ln(2-R-Bz)3fen] e [Ln(4-R-Bz)3fen] , com Ln = Eu3+, Gd3+ e Tb3+; R = -NH2, -NH(CO)CH3, -OH, -O(CO)CH3, -O(C4H9); fen = 1,10-fenantrolina, que foram caracterizados por titulação complexométrica, análise elementar, espectroscopia de absorção na região do infravermelho e de reflectância difusa. Os espectros de fosforescência dos complexos [Gd(2-R-Bz)3fen] e [Gd(4-R-Bz)3fen] revelaram que as energias dos estados tripleto dos ligantes coordenados encontram-se acima e em boa condição de ressonância com os estados emissores de ambos os íons Eu3+ e Tb3+, o que favorece o processo eficiente de transferência de energia ligante-metal, sendo tais estados localizados sobre os ligantes 1,10-fenantrolina em todos os complexos. Para os complexos do íon Tb3+, observou-se que a acetilação de ambos os substituintes N ou O-doadores causou elevação dos tempos de vida para a maioria dos compostos, sendo bem maiores a temperatura ambiente que a baixa temperatura. Para os complexos do íon Eu3+ observou-se uma forte dependência dos parâmetros de intensidade Ω2 e da eficiência quântica de luminescência com a natureza e a posição dos substituintes elétron-doadores, que puderam ser racionalizados a partir dos efeitos eletrônicos e estéricos, atuando de forma antagônica. Tais efeitos, exerceram forte influência sobre os estados de transferência de carga LMCT, contribuindo diretamente para a dependência da eficiência quântica de luminescência com a posição dos substituintes elétron-doadores dos ligantes carboxilatos. Interações estéricas promoveram a quebra de conjugação devido à retirada do anel aromático do plano de conjugação do grupo carboxilato, reduzindo a capacidade elétron-doadora dos oxigênios e, consequentemente, elevando a energia dos estados LMCT. Foi demonstrado, pela primeira vez, que a quebra de conjugação mediante interação estérica pode eliminar ou reduzir o efeito dos estados LMCT como um canal de supressão da luminescência em complexos do íon Eu3+.

Submitted by ELAINE CRISTINA MUNIZ null (elainecris7@yahoo.com.br) on 2016-03-11T12:09:12Z No. of bitstreams: 1 ELAINE CRISTINA MUNIZ-tese.pdf: 10917322 bytes, checksum: bd6553f5a382221f4d18db6600416bcb (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-03-14T18:09:48Z (GMT) No. of bitstreams: 1 muniz_ec_dr_araiq_par.pdf: 726928 bytes, checksum: c405502c64aca6bda28f96dbbfbca30f (MD5) / Made available in DSpace on 2016-03-14T18:09:48Z (GMT). No. of bitstreams: 1 muniz_ec_dr_araiq_par.pdf: 726928 bytes, checksum: c405502c64aca6bda28f96dbbfbca30f (MD5) Previous issue date: 2016-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Materiais luminescentes despertam grande interesse nas pesquisas devido à variedade de aplicações, podendo ser empregados em displays eletrônicos, lâmpadas fluorescentes e diodos emissores de luz, por exemplo. Neste contexto, os íons lantanídeos trivalentes são destaque pois apresentam propriedades luminescentes únicas como alta pureza de cor, tempo de vida de nano a milissegundos e linhas de emissão definidas e estreitas provenientes de transições intraconfiguracionais 4f-4f. No entanto, devida à natureza proibida dessas transições, os íons lantanídeos apresentam baixa absortividade molar. Para suprir essa deficiência, pode ser realizada a coordenação destes íons com bons grupos cromóforos capazes de transferir energia para os níveis 4f dos lantanídeos. Outra estratégia para melhorar as propriedades luminescentes de materiais é através da combinação e/ou dopagem utilizando diferentes lantanídeos, o que pode resultar na emissão de ambos os íons ou na emissão preferencial de um deles por meio de processos de transferência de energia. Espécies bimetálicas heteronucleares e polímeros de coordenação porosos (Metal Organic Frameworks, MOFs) se destacam neste cenário. Neste trabalho foram estudadas quatro séries de compostos bimetálicos heteronucleares utilizando succinato de sódio e ácido 3,5-dicarbóxipirazolico como ligantes e variando a razão entre dois íons lantanídeos distintos, Gd3+:Eu3+, Gd3+:Tb3+, Dy3+:Eu3+ e Eu3+:Tb3+. Os compostos obtidos foram caracterizados por difração de raios X de monocristal e de pó, espectroscopia na região do IV, análise térmica, espectroscopia de reflectância difusa, espectroscopia de fotoluminescência com excitação UV, luminescência com excitação por raios X e microscopia eletrônica de varredura associada à espectroscopia por energia dispersiva. Os complexos apresentaram interessantes propriedades luminescentes. Para as séries de compostos contendo íons Gd3+, quanto maior a quantidade de Gd3+, maior a intensidade da banda relativa à transferência de carga do ligante para o metal, indicando que os íons Gd3+ possuem um papel importante no mecanismo de transferência de energia do ligante para os lantanídeos emissores. Foram calculados os parâmetros de intensidade, as taxas de decaimento radiativo e não-radiativo e a eficiência quântica para a série Gd3+:Eu3+, que apresentaram baixa eficiência quântica, devido principalmente à supressão da luminescência pelas moléculas de água presente na estrutura. Os compostos da série Dy3+:Eu3+ não apresentam transferência de energia entre os lantanídeos e só foi possível observar a emissão dos dois íons ao mesmo tempo quando a excitação é realizada no ligante ou quando se utilizou raios X para a excitação. Já na série Eu3+:Tb3+, observou-se transferência de energia apenas dos íons Tb3+ para os íons Eu3+. O oposto não foi verificado. Os espectros de emissão dessa série registrados em diferentes temperaturas mostram que os compostos Eu3+:Tb3+ possuem potencialidade para aplicação como termômetro molecular na faixa de temperatura entre -80 e 25°C. Foram realizadas três sínteses diferentes para preparação dos MOFs. Os compostos obtidos apresentam intensidade de emissão e eficiência quântica elevadas. Além disso, a estabilidade térmica dos compostos é evidência de que os compostos obtidos podem ser de fato MOFs. / Luminescent materials attract interest in research due to the diversity of applications. These materials can be used at electronic displays, fluorescent lamps and light emitting diodes, for example. In this context, trivalent lanthanide ions are interesting because of their unique luminescent properties like high color purity, nano to milliseconds lifetime and narrow emission lines from 4f-4f transitions. However, because of the nature of forbidden 4f-4f transitions, lanthanide ions have low molar absorptivity. To supply this deficiency, the lanthanide ions can be coordinated to chromophore groups, capable of transfer energy to the 4f levels of lanthanides. It is also possible to improve the luminescent properties of materials by combining different lanthanides, which can result in the emission of both ions or in the preferential emission of one of them by energy transfer processes. Bimetallic heteronuclear complexes and metal organic frameworks (MOFs) are interesting in this context. In this work, four bimetallic heteronuclear compounds series with sodium succinate and 3,5- dicarboxypyrazolate ligands were prepared with different lanthanides ratio, Gd3+:Eu3+ , Gd3+:Tb3+, Dy3+:Eu3+ e Eu3+:Tb3+ . The compounds were characterized by single crystal and powder X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis, UV-Vis spectroscopy, photoluminescence spectroscopy, X-ray excited optical luminescence and field emission gun-scanning electron microscopy, with energy dispersive X-ray spectroscopy. The complexes present interesting luminescent properties. In Gd3+ compounds series, by increasing the amount of Gd3+ ions in the sample, the intensity of the relative charge transfer band also increases, indicating that the Gd3+ ions play an important role in the energy transfer mechanism from ligands to the lanthanides. The intensity parameters, the radiative and non-radiative decay rates and the quantum efficiency were calculated to Gd3+:Eu3+ series, which showed low quantum efficiency due to luminescence quenching by water molecules in the structure. The Dy3+:Eu3+ compounds does not show energy transfer between the lanthanides ions and the emission from both ions was observed simultaneously only under excitation at the ligand absorption or under X-rays excitation. In the Eu3+:Tb3+ series, the energy transfer was observed only from Tb3+ ions to the Eu3+ ions. The opposite was not verified. The emission spectra of the Eu3+:Tb3+ compound recorded at different temperatures show that this series compounds present potential to be applied as molecular thermometer in the range of -80 to 25 °C. Three different syntheses were performed to prepare MOFs. The obtained compounds exhibit high emission intensity and good quantum efficiency. Furthermore, the thermal stability of the compounds is evidence to propose that the obtained compounds is indeed MOFs. / CNPq: 141262/2012-5

Με σκοπό τη μελέτη της χημείας ένταξης του υποκαταστάτη δι-2,6-(2-πυριδυλοκαρβονυλο) πυριδίνη (dpcp) με μέταλλα μετάπτωσης 3d, παρασκευάστηκαν οι τετραπυρηνικές πλειάδες [Cu4(N3)2{pyCO(OMe)pyCO(OMe)py}2(MeOH)2](ClO4)∙2MeOH (1∙2MeOH) και [Co4(N3)2(NO3)2{pyCO(OMe)pyCO(OMe)py}2]∙0.5MeOH (2∙0.5MeOH), η εξαπυρηνική πλειάδα [Ni6(CO3)(N3)6{pyCOpyC(O)(OMe)py}3(MeOH)2(H2O)][Ni6(CO3)(N3)6 {pyCOpyC(O)(OMe)py}3(MeOH)3](ClO4)2 (3∙1.8MeOH) και η διπυρηνική πλειάδα [Fe2{pyCO(OMe)py(Η)CO(OMe)py}2(MeO)2](ClO4)2∙(4∙MeOH). Στην συνέχεια μελετήθηκε η χημεία ένταξης του ίδιου υποκαταστάτη με μέταλλα 3d και 4f και παρασκευάστηκαν τα ετερομεταλλικά διπυρηνικά σύμπλοκα [ΜIILnIII{pyCOH(OEt)pyCOH(OEt)py}3](ClO4)2∙EtOH (5-16∙EtOH) με ΜΙΙ = CuΙΙ, CoΙΙ, NiΙΙ, ZnΙΙ, MnΙΙ, FeΙΙ [LnΙΙΙ = GdΙΙΙ (5 - 10), TbΙΙΙ (11 – 16) αντίστοιχα]. Όλα τα σύμπλοκα χαρακτηρίστηκαν κρυσταλλογραφικά, τα σύμπλοκα 4, 10 και 16 χαρακτηρίστηκαν με φασματοσκοπία Mössbauer ενώ τα σύμπλοκα 1 – 10 χαρακτηρίστηκαν μαγνητικά. Πιο συγκεκριμένα, οι μαγνητικές μελέτες των συμπλόκων 1 – 3, 5 και 10 έδειξαν σιδηρομαγνητικές αλληλεπιδράσεις ενώ εκείνες των συμπλόκων 4, 6, 7 και 9 έδειξαν αντισιδηρομαγνητικές αλληλεπιδράσεις. Προκειμένου να μελετηθεί σε βάθος η οικογένεια των βασικών καρβοξυλικών αλάτων του σιδήρου [Fe3O(O2CR)6(H2O)3]A, παρασκευάστηκαν δύο σειρές αυτών των συμπλόκων με R = CCl3, CHBr2, CH2F, CH2Cl, C(OH)Ph2, H, Ph, (CH2)3Cl, Me, CHMe2, Et και CMe3. Στην πρώτη σειρά συμπλόκων (17 - 28) το αντισταθμιστικό ιόν (Α) είναι ClO4-, ενώ στη δεύτερη (29 - 40) είναι NO3-. Η προσπάθεια απομόνωσης του ανάλογου με R = CF3 ήταν άκαρπη και για τα δύο αντισταθμιστικά ιόντα και οδήγησε σε ένα τετραπυρηνικό σύμπλοκο [Fe4O2(O2CCF3)8(H2O)6] (41) με δομή τύπου «πεταλούδας». Πραγματοποιήθηκαν μετρήσεις Mössbauer σε στερεά δείγματα και για τις δύο σειρές και οι ισομερείς μετατοπίσεις και οι τετραπολικές αλληλεπιδράσεις διαφέρουν μεταξύ 0.51 – 0.54 mms-1 και 0.36 – 0.76 mms-1 αντίστοιχα. Μετρήσεις Mössbauer και σε διαλύματα αυτών έδειξαν τη σταθερότητά τους και σε διάλυμα, με εξαίρεση το σύμπλοκο 29 (R = Cl3C, Α = NO3-) που οδήγησε σε σύμπλοκο τύπου «πεταλούδας». Το υψηλής συμμετρίας σύμπλοκο [Fe3O(O2CPh)6(py)3](ClO4)∙py (42) έχει μελετηθεί στο παρελθόν κρυσταλλογραφικά αλλά και με μετρήσεις ανελαστικής σκέδασης νετρονίων IINS και είχε προταθεί ύπαρξη του μαγνητικού φαινομένου Jahn-Teller σε πολύ χαμηλές θερμοκρασίες. Θέλοντας να εξακριβωθεί εάν η μαγνητική συμμετρία σχετίζεται με την πραγματική, πραγματοποιήθηκαν κρυσταλλογραφικές μετρήσεις μεταβλητής θερμοκρασίας στο εργαστήριο ΒΜ01Α του ESRF. Τα αποτελέσματα των πειραματικών μετρήσεων έδειξαν ότι η πραγματική συμμετρία παραμένει ίδια. Στη συνέχεια από μετρήσεις μαγνητικής επιδεκτικότητας ac, παρατηρήθηκε η ύπαρξη μαγνητικών φαινομένων χαλάρωσης υπό την επίδραση ασθενών μαγνητικών πεδίων. / Seeking to study the coordination chemistry of the ligand di-2, 6-(2-pyridylcarbonyl) pyridine (dpcp) with 3d transition metal ions, the tetranuclear complexes [Cu4(N3)2{pyCO(OMe)pyCO(OMe)py}2(MeOH)2](ClO4)∙2MeOH (1∙2MeOH) and [Co4(N3)2(NO3)2{pyCO(OMe)pyCO(OMe)py}2]∙0.5MeOH (2∙0.5MeOH), the hexanuclear complex [Ni6(CO3)(N3)6{pyCOpyC(O)(OMe)py}3(MeOH)2(H2O)][Ni6(CO3)(N3)6{pyCOpyC(O) (OMe)py}3(MeOH)3](ClO4)2 (3∙1.8MeOH) and the dinuclear complex [Fe2{pyCO(OMe)py(Η)CO(OMe)py}2(MeO)2](ClO4)2∙(4∙MeOH) were synthesized. In addition, in order to study the coordination chemistry of the same ligand with mixed 3d transition metal ions and 4f lanthanide ions, the heterometallic dinuclear complexes [ΜIILnIII{pyCOH(OEt)pyCOH(OEt)py}3] (ClO4)2∙EtOH (5-16∙EtOH) were synthesized, with ΜΙΙ = CuΙΙ, CoΙΙ, NiΙΙ, ZnΙΙ, MnΙΙ, FeΙΙ [LnΙΙΙ = GdΙΙΙ (5 - 10), TbΙΙΙ (11 – 16) respectively]. All complexes were structurally characterized and complexes 4, 10 and 16 were characterized by Mössbauer spectroscopy. Magnetic properties measurements of complexes 1-3, 5 and 10 indicated the existence of ferromagnetic interactions, while those of 4, 6, 7 and 9 indicated the existence of antiferromagnetic interactions. For the in depth study of the family of basic iron (III) carboxylates [Fe3O(O2CR)6(H2O)3]A, two series of complexes were prepared with R = Cl3C, CHBr2, CH2F, CH2Cl, C(OH)Ph2, H, Ph, Cl(CH2)3, Me, CHMe2, Et and Me3C. For the former series (17 - 28) the counteranion (A-) is ClO4- and for the latter (29 - 40) is NO3-. Attempts to prepare the respective trifluoroacetate (R = CF3) complexes were unsuccessful and the reaction system lead to the tetranuclear “butterfly” complex [Fe4O2(O2CCF3)8(H2O)6] (41), irrespective of whether perchlorates or nitrates were used as counteranions. Mössbauer studies revealed very similar isomer shifts for all complexes in the region of 0.51 – 0.54 mms-1, and variable quadrupole splittings, ranging from 0.36 to 0.76 mms-1. Mössbauer studies of the complexes were carried out in frozen MeCN solutions in order to assess their stability in solution and they proved to be stable in MeCN solutions, except complex 29 (R = Cl3C, Α = NO3-), which dissociated to a butterfly-type complex. The high-symmetry cluster [Fe3O(O2CPh)6(py)3](ClO4)∙py (42) has been structurally characterized and its Inelastic Incoherent Neutron Scattering studies have been reported. These studies suggested the existence of a magnetic Jahn-Teller effect at lower temperatures. Seeking to study if there is any correlation between magnetic and structural symmetry, we undertook variable-temperature crystallographic studies on ESRF BM01A beamline. With the results of these data we concluded that the symmetry of the crystal remained. Moreover, we have discovered that this complex exhibits magnetic relaxation phenomena under weak magnetic fields, observed by ac magnetic susceptometry.