Este trabalho teve como objetivo propor e investigar a contribuição de uma sequência didática para aulas prático-laboratoriais no ensino superior em Química. A sequência didática proposta buscou desenvolver habilidades e competências relacionadas, principalmente, à análise e seleção de resultados experimentais e fundamentais para a formação do profissional químico, de acordo com as Diretrizes Curriculares para o Ensino Superior em Química (BRASIL, 2001). As atividades elaboradas nesta proposta buscaram promover habilidades cognitivas de alta ordem (HOCS - High ordem cognitive skills), para isso foram utilizadas estratégias que não são tradicionalmente empregadas em disciplinas experimentais no ensino superior, como a abordagem investigativa, por exemplo. A aplicação da proposta ocorreu no contexto de uma disciplina experimental obrigatória oferecida para estudantes do primeiro ano de cursos de Química (Licenciatura em Química e Bacharelado em Química - com ênfase em Química Ambiental) da Universidade de São Paulo (USP). O tema da proposta desenvolvida foi titulações ácido-base e o principal objeto de estudo foi a curva de titulação e sua interpretação. De forma geral, os estudantes, os docentes e os monitores da disciplina foram receptivos com a proposta e com os objetivos de estudo. Considerando que o trabalho desenvolvido no contexto da disciplina experimental foi pontual e a sequência didática elaborada neste estudo teve duração de apenas cinco aulas do programa, os resultados obtidos foram satisfatórios e responderam questões relacionadas à promoção das HOCS. Foi possível explorar as potencialidades de metodologias que não são tradicionalmente utilizadas no laboratório didático no ensino superior em Química. / This study aimed to propose and investigate the contribution of a didactic sequence for practical and laboratory classes in higher education in chemistry. The proposed didactic sequence sought to develop related skills and competences, especially the analysis and selection of experimental and fundamental results in the formation of the chemical professional, according to the Curriculum Guidelines for Higher Education in Chemistry (BRAZIL, 2001). The activities developed in this proposal sought to promote high order cognitive skills (HOCS), for it was used strategies that are not traditionally used in experimental disciplines in higher education, as the investigative activities, for example. The implementation of the proposal took place in the context of a mandatory experimental subject offered to students in the first year chemistry courses (Degree in Chemistry and Bachelor of Chemistry - with emphasis on Environmental Chemistry) from the University of São Paulo (USP). The theme of the proposal was developed acid-base titrations and the main object of study was the titration curve and its interpretation. In general, students, teachers and instructors of discipline were receptive to the proposal and the study objectives. Whereas the work undertaken in the context of experimental course was timely and the didactic sequence elaborated in this study lasted only five program classes, the results were satisfactory and answered questions related to the promotion of the HOCS. It was possible to exploit the potential of methodologies that are not traditionally used in teaching laboratory in higher education in chemistry.

Este trabalho teve como objetivo propor e investigar a contribuição de uma sequência didática para aulas prático-laboratoriais no ensino superior em Química. A sequência didática proposta buscou desenvolver habilidades e competências relacionadas, principalmente, à análise e seleção de resultados experimentais e fundamentais para a formação do profissional químico, de acordo com as Diretrizes Curriculares para o Ensino Superior em Química (BRASIL, 2001). As atividades elaboradas nesta proposta buscaram promover habilidades cognitivas de alta ordem (HOCS - High ordem cognitive skills), para isso foram utilizadas estratégias que não são tradicionalmente empregadas em disciplinas experimentais no ensino superior, como a abordagem investigativa, por exemplo. A aplicação da proposta ocorreu no contexto de uma disciplina experimental obrigatória oferecida para estudantes do primeiro ano de cursos de Química (Licenciatura em Química e Bacharelado em Química - com ênfase em Química Ambiental) da Universidade de São Paulo (USP). O tema da proposta desenvolvida foi titulações ácido-base e o principal objeto de estudo foi a curva de titulação e sua interpretação. De forma geral, os estudantes, os docentes e os monitores da disciplina foram receptivos com a proposta e com os objetivos de estudo. Considerando que o trabalho desenvolvido no contexto da disciplina experimental foi pontual e a sequência didática elaborada neste estudo teve duração de apenas cinco aulas do programa, os resultados obtidos foram satisfatórios e responderam questões relacionadas à promoção das HOCS. Foi possível explorar as potencialidades de metodologias que não são tradicionalmente utilizadas no laboratório didático no ensino superior em Química. / This study aimed to propose and investigate the contribution of a didactic sequence for practical and laboratory classes in higher education in chemistry. The proposed didactic sequence sought to develop related skills and competences, especially the analysis and selection of experimental and fundamental results in the formation of the chemical professional, according to the Curriculum Guidelines for Higher Education in Chemistry (BRAZIL, 2001). The activities developed in this proposal sought to promote high order cognitive skills (HOCS), for it was used strategies that are not traditionally used in experimental disciplines in higher education, as the investigative activities, for example. The implementation of the proposal took place in the context of a mandatory experimental subject offered to students in the first year chemistry courses (Degree in Chemistry and Bachelor of Chemistry - with emphasis on Environmental Chemistry) from the University of São Paulo (USP). The theme of the proposal was developed acid-base titrations and the main object of study was the titration curve and its interpretation. In general, students, teachers and instructors of discipline were receptive to the proposal and the study objectives. Whereas the work undertaken in the context of experimental course was timely and the didactic sequence elaborated in this study lasted only five program classes, the results were satisfactory and answered questions related to the promotion of the HOCS. It was possible to exploit the potential of methodologies that are not traditionally used in teaching laboratory in higher education in chemistry.

Gegenstand dieser Arbeit ist die Frage wie thermische und photochemische Gleichgewichte verbunden werden können und sich gegenseitig beeinflussen. Dazu wurden zwei Projekte bearbeitet, zum einen das Konzept der „säure-katalysierten Zykloreversion“ und zum anderen das Konzept der „licht-induzierten pKs Veränderung“. Im ersten Konzepte wurde eine extern steuerbare, thermische Rückreaktion genutzt, um die Zusammensetzung im photostationären Zustand zu kontrollieren. Durch Zugabe von katalytischen Mengen einer starken Säure wurde die Ringöffnung eines Diarylethens, welches mit einem Flurenol substituiert ist, eingeleitet. Der zugrundeliegende Prozess wurde kinetisch und thermodynamisch, sowohl durch Experimente als auch durch computergestützte Rechnungen beschrieben. Eine säure-induzierte Dehydratation öffnet einen neuen Reaktionspfad, wodurch die normalerweise sehr hohe Reaktionsbarriere der Ringöffnung umgangen werden kann. Die quantitative Umsetzung mit Säure führt zu einer kompletten Löschung der photochemischen Reaktivität. Dieses Konzept kann in der Speicherung von Lichtenergie in photochromen metastabilen Systemen genutzt werden. Durch die Nutzung von 3-H-Thiazol-2-on als Rest im Diarylethen konnte eine signifikante pKs Änderung von 2.8 Einheiten in wässriger Umgebung erreicht werden. Dabei wurden zwei Säure-Base Gleichgewichtssysteme miteinander gekoppelt, welche an der thermischen Umwandlung gehindert sind, jedoch photochemisch ineinander überführt werden können. Des Weiteren wurde eine hohe Abhängigkeit der Quantenausbeute von dem Protonierung festgestellt. Diese wurde genutzt um die Performance der Photoreaktion zu beeinflussen. Die Beeinflussung der Photoreaktion erfolgt nicht durch Veränderung der Energetik des Grundzustandes, sondern durch Veränderung der Potentialhyperfläche des angeregten Zustandes. Durch neue molekulare Designs konnte eine signifikante Verbesserung im Vergleich zu bekannter Molekülen und Konzepten in beiden Projekten erreicht werden. / Two projects are implemented in this work, which share the goal to interconnect acid-base equilibria with the photoreactions of diarylethene (DAE) photoswitches. This task can be divided into two logic questions: How can photochemical equilibria be controlled or rather influenced via an acidic or basic stimulus and how can a photoreaction induce control over an acid-base equilibrium? In the first project, “Acid-Catalyzed Cycloreversion”, an externally tunable thermal back reaction was designed to influence a photochemical equilibrium. Upon addition of catalytic amounts of acid, a closed DAE carrying a fluorenol moiety undergoes facile thermal ring opening. The underlying thermodynamics and kinetics of the entire system have been analyzed experimentally as well as computationally. Appling an excess of acid leads to a complete inhibition of the photoreaction through the introduction of a charge-transfer. My work suggests that acid catalysis provides a useful tool to bypass thermal barriers, potentially usable to efficiently trigger the release of light energy stored in photoswitches. In the second project, entitled “Light-induced pKa Modulation”, a significant pKa change of 2.8 units in an aqueous medium was achieved by connecting two different acid-base equilibria. These thermodynamic equilibria are separated by a high activation barrier, overcome by a photoreaction. The developed system which is based on the incorporation of a 3 H thiazol 2 one moiety into a DAE, shows a strong dependency of the quantum yield and hence, of the photoconversion on the protonation state. Adjusting the pH within the range of the pKa change, a substantial enhancement of the photoconversion is achievable as well as a distinct alteration of the performance of the photoreaction. This effect does not originate from different reaction paths on the ground state potential energy surface (PES), but results presumably from a protonated state dependent difference in the excited PES.