Estudo teórico sobre o efeito de substituintes na interação cátion- em rutenofanos

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2013Estudou-se, através de métodos de química teórica, o efeito do substituinte na interação cátion-? em rutenofanos. Para isto investigou-se a estrutura eletrônica de uma série de nove complexos de fórmula geral [Ru(NH3)3(?6-C16H12R4)]2+: 1 (R1=R2=R3=R4=H), 2 (R1=R2=R3=R4=F), 3 (R1=R2=R3=R4=Cl), 4 (R1=R2=R3=R4=CN), 5 (R1=R2=R3=R4=CH3), 6 (R1=R4=NO2 e R2=R3=H), 7 (R1=R4=NH2 e R2=R3=H), 8 (R1=R4=OCH3 e R2=R3=H), 9 (R1=R2=R3=R4=H e carbono ipso protonado). A magnitude da interação cátion-? foi avaliada, bem como decomposta em suas diferentes componentes por meio da análise da decomposição de energia proposta por Su-Li no nível de teoria MP2/def2-TZVP. Observou-se que tais interações são principalmente covalentes em sua natureza, ao passo que a contribuição eletrostática é bastante significativa, sendo que os substituintes retiradores de elétrons enfraquecem a interação, já os doadores fortalecem as mesmas. Informações adicionais foram obtidas por meio de análises NBO, as quais revelam que as retrodoações, em especial aquelas do tipo 4d ? 2pz, são mais importantes sob uma perspectiva energética. Um estudo topológico sob a luz da teoria QTAIM sugere que as interações cátion-? nos rutenofanos estudados são consistentes com interações de camada fechada com propriedades que apontam para ligações coordenadas

Structures of interfaces and foam films of (poly)electrolyte / surfactant mixtures

Foam films are the building blocks of macroscopic foams and thus, crucial for their performance. The present thesis studies the interactions between surfactants (Ss) and (poly)electrolytes at interfaces and inside foam films. Mixtures of oppositely charged polyelectrolytes (Ps) and Ss are able to stabilize foam films depending on the ratio between the two components. Even though salt appears in many applications of P/ S mixtures, its impact on foam films formed by these mixtures is barely studied. To obtain a general understanding of foam films, their different components are studied in this thesis individually and in combination: from bulk solutions, over a single air / liquid interface to foam films. The first part of this thesis focuses on the air / liquid interface of two P/ S mixtures: PSS /C14TAB and sPSO2-220 /C14TAB. Tensiometry and neutron reflectometry are used to investigate their surface activity, interfacial composition, and interfacial structures. While PSS /C14TAB mixtures only form monolayers, sPSO2-220 /C14TAB mixtures form extended structures around the bulk stoichiometric mixing point (BSMP), which are suppressed with increasing ionic strength. The main driving force for the formation of extended structures is to maximize the gain of entropy by reaching an interfacial P/S ratio of 1. Increasing the flexibility of the P (via increasing the ionic strength or using the more flexible PSS) enables almost reaching this ratio within a monolayer structure. In the second part, foam fllms of sPSO2-220 /C14TAB mixtures and the effect of LiBr are studied using a Thin Film Pressure Balance (TFPB). Below the BSMP, unstable foam films form irrespective of cLiBr, while above the BSMP, the foam films are stable. A low amount of added LiBr destabilizes the foam films, whereas a high amount stabilizes them. The stabilization results from a steric repulsion of sPSO2-220 /C14TAB complexes inside the foam film bulk. The complexes contribute to the apparent surface potential between the interfaces. The foam film stability framework is extended, now including the bulk omplexes: a minimal charge of the P/ S complexes is necessary to stabilize foam films. Additionally, it is observed that the P/ S mixtures aren't equilibrated and phase separate on the time scale of months. The last part focuses on the foam films of the non-ionic S BrijO10 and the Keggin polyoxometalate H4SiW12O40. SiW12O404- adsorbs at the BrijO10 and charges the foam film interfaces. BrijO10 micelles trapped inside the foam film lead to an additional long-range steric stabilization. These micelles act as a reservoir for excess S in the subinterfacial region making the foam films more resistant to disturbances and thus, leading to stable foams