Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Neste trabalho à apresentada a sÃntese, caracterizaÃÃo e o estudo da liberaÃÃo fotoquÃmica de Ãxido nÃtrico pelos nitrosilo complexos trans-[Fe(cyclam)(NO+)Cl]Cl2 e trans-[Ru(NH3)4L(NO)]Cl3, onde L=Imidazol, Benzoimidazol, CafeÃna e Teofileno, bem como pelo novo composto [cyclam(NO)4]. AtravÃs de uma nova rota sintÃtica, obteve-se o composto trans-[Fe(cyclam)(NO+)Cl]Cl2, o qual apresenta o ligante Ãxido nÃtrico coordenado ao Ãtomo de ferro na sua forma linear (NO+), νNO=1888 cm-1, com um Ãngulo de ligaÃÃo Fe-NO igual a 177,40. O estudo do comportamento fotoquÃmico deste nitrosilo complexo evidenciou a liberaÃÃo de Ãxido nÃtrico e formaÃÃo do aqua complexo de FeIII quando o composto à irradiado em meio aquoso pH=3,4, com luz de λirradiaÃÃo=310 nm. Entretanto, quando o mesmo à irradiado em meio aquoso pH=7,04, observa-se ocorrer apenas a reaÃÃo de fotorreduÃÃo do Ãxido nÃtrico com φ=0,4Â0,05 mol/einstein, gerando a espÃcie trans-[Fe(cyclam)(NO0)Cl]+. O composto [cyclam(NO)4] foi obtido atravÃs da reaÃÃo de nitrosilaÃÃo do macrocÃclico cyclam. A troca dos hidrogÃnios do cyclam por molÃculas de NO, foi evidenciada pela anÃlise do espectro vibracional na regiÃo do IV do composto [cyclam(NO)4], o qual apresenta duas bandas caracterÃsticas em 1454 e 1139 cm-1, atribuÃdas a νNO e νNN, respectivamente. ApÃs fotÃlise com luz branca, observa-se a diminuiÃÃo da intensidade destas bandas e o aparecimento de uma nova absorÃÃo em 2228 cm-1 atribuÃda a νNO+, indicando que o composto comporta-se como um doador de Ãxido nÃtrico nestas condiÃÃes, atravÃs da clivagem heterolÃtica da ligaÃÃo N-NO. Os compostos do tipo trans-[Ru(NH3)4L(NO)]Cl3, onde L=Imidazol, Benzoimidazol, CafeÃna e Teofileno, coordenados atravÃs do Ãtomo de carbono do anel imidazÃlico, foram sintetizados de acordo com a literatura e caracterizados por ressonÃncia magnÃtica nuclear e espectroscopia vibracional na regiÃo do infravermelho. Estudos mostraram que a irradiaÃÃo desses compostos com luz de λirradiaÃÃo=330, 410 e 440 nm para L= Imidazol, CafeÃna e Teofileno e λirradiaÃÃo=330 nm para L=Benzoimidazol em meio de NaCl 1 mol.L-1, leva exclusivamente à formaÃÃo do Ãon complexo trans-[Ru(NH3)4L(Cl)]2+ apÃs liberaÃÃo do ligante NO0. Os valores de φNO para tal fotorreaÃÃo sÃo dependentes / In the present work, a new route was developed for preparing the compound trans-[Fe(cyclam)(NO+)Cl]Cl2, where the nitric oxide is bonding of the iron in the form linear (NO+) with a bond angle Fe-NO at 177,40. The complex was characterized by uv-visible, infrared and electronic paramagnetic resonances spectroscopies, electrochemical techniques and crystal structure determination were undertaken. The study of the photochemical behavior this nitrosyl complex showed the nitric oxide release and appearance of trans-[Fe(cyclam)(H2O)2]3+ species where the compound is irradiated in the λirr=330 nm in aqueous solution pH=3,4. However, when the compound was irradiated in aqueous solution pH=7,04, was observed the reaction of photoreduction and the production of specie trans-[Fe(cyclam)(NO0)Cl]+ (φ=0,4Â0,05 mol/einstein). The study of the photochemical behavior of the trans-[Ru(NH3)4L(NO)]Cl3 complexes, where L=ImK2, BzImK2, Caf and Teo showed the nitric oxide production and appearance of trans-[Ru(NH3)4L(Cl)]2+ species, as product of the photolysis in KCl aqueous solution, in the 330-440 nm region when L= ImK2, Caf and Teo and in the λirr=330 nm when L=BzImK2 . The quantum yields (φNO) for this reaction is sensitive to the nature of L, λirr and pH. The lowest quantum yields are found for L=BzImK2 (φNO=0,005Â0,0005 mol/einstein) and the higher was observed for the L=Teo (0,68Â0,05 mol/einstein). The absence of observable photochemical reaction when these complexes were irradiated on 410-440nm is explained on basis of the changes in character of the lowest energy MLCT band on function of the ligand L. The incorporation of NO in the composition of many molecules is of interest to study the chemical and enzymatic mechanisms of NO release and the pharmacological aspects and biomedical applications of these compounds. Assuming that the N-nitroso compounds belong to a class of NO donors by transferring nitrosyl homolytically or heterolytically to another species, we have performed the nitrosilation reaction of the cyclam species aiming to study the reactivity of a new N-nitrosamine system toward the release of nitric oxide species. The infrared spectrum of [cyclam(NO)4] displays two characteristic bands at 1454 and 1139 cm-1 assigned to the νNO and νNN modes, respectively. The peaks of νN-H observed in the range 3400-3190 cm-1 in the spectrum of thecyclam starting material disappear in the spectrum of [cyclam(NO)4]. Upon white light photolysis of the compound dispersed in KBr, is observed the decrease of the νNO and νNN and of the appearance of a new band at 2228 cm-1, assigned to the νNO+ stretching mode. This indicates that the [cyclam(NO)4] compound under this photolysis conditions behaves as a nitrosyl donor through an heterolytic cleavage of N-NO bond.
| Identifer | oai:union.ndltd.org:IBICT/oai:www.teses.ufc.br:1203 |
| Date | 02 May 2006 |
| Creators | Alda Karine Medeiros Holanda |
| Contributors | Luiz Gonzaga de FranÃa Lopes, Severino Alves JÃnior, Zenis Novais da Rocha, Ãcaro de Sousa Moreira, Idalina Maria Moreira de Carvalho |
| Publisher | Universidade Federal do CearÃ, Programa de PÃs-GraduaÃÃo em QuÃmica InorgÃnica, UFC, BR |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UFC, instname:Universidade Federal do Ceará, instacron:UFC |
| Rights | info:eu-repo/semantics/openAccess |
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