Primary photoinduced processes of organic chromophores studied by various fluorescence techniques [Elektronische Ressource] / vorgelegt von Ciprian R. Roman

Informations

• Publié par: friedrich-alexander-universitat_erlangen-nurnberg
• Publié le: 01 janvier 2006
• Nombre de lectures: 16
• Langue: Deutsch
• Poids de l'ouvrage: 2 Mo

Extrait

Primary photoinduced processes of organic chromophores
studied by various fluorescence techniques
Den Naturwissenschaftlichen Fakulta¨ten
der Friedrich-Alexander-Universita¨t Erlangen-Nu¨rnberg
zur
Erlangung des Doktorgrades
vorgelegt von
Ciprian R. Roman
aus Cluj Napoca, RomaniaAls Dissertation genehmigt
von den Naturwissenschaftlichen Fakulta¨ten
der Universita¨t Erlangen-Nu¨rnberg
Tag der mu¨ndlichen Pru¨fung: 8. Dezember 2005
Vorsitzender der
Promotionskommission: Professor Dr. D.-P. Ha¨der
Erstberichterstatter: Professor Dr. S. Schneider
Zweitberichterstatter: Professor Dr. G. GramppMeiner FamilieMein besonderer Dank gilt:
Herrn Prof. Dr. S. Schneider
fu¨r die Mo¨glichkeit an seinem Lehrstuhl zu promovieren. Sein Interesse und Engagement
haben sehr zum Gelingen der Arbeit beigetragen. Ich vergesse nie sein Versta¨ndnis, seine
Geduld und seine zahlreichen Ratschla¨ge bei verschiedenen Problemen.
Herrn Dipl. Phys. D.-Th. Marian
fu¨r seine praktischen Ratschla¨ge bei der experimentellen Durchfu¨hrung und fu¨r seine
unermu¨dliche Mitarbeit und Diskussionsbereitschaft.
Frau Dr. N. Acar und Herrn Dr. M.O. Schmitt
fu¨r ihre Hilfe bei der Probenvorbereitung und die wertvollen Diskussionen aus dem
chemischen und biologischen Bereich.
¨Den Mitarbeitern den Institutwerkstaten (insbesondere dem Herrn Wallner und
dem Herrn Wo¨lfel)
fu¨r ihren Einsatz und ihr gutes und sorgfa¨ltiges Arbeiten.
Den weiteren Mitarbeitern und Mitarbeiterinnen des Lehrstuhls
fu¨r die kollegiale Zusammenarbeit und das angenehme freundliche Arbeitsklima.Contents
Introduction 3
1 Theory, methods and instruments 5
1.1 Definitions and instruments for steady-state measurements . . . . . . . . . . 5
1.2 Time-resolved fluorescence anisotropy . . . . . . . . . . . . . . . . . . . . . 9
1.2.1 Theory and block scheme of the aparatus employed . . . . . . . . . . 9
1.2.2 Differences between the “classical” and the new alternative method . 15
1.3 The rotating table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.4 Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
1.4.1 Analysis of the anisotropy decays . . . . . . . . . . . . . . . . . . . 22
1.4.2 Obtaining , and r from examining I (t) and I (t) . . . . . . . . . 310 k ⊥
1.5 The high-pressure equipment . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1.5.1 Steady-state fluorescence measurements under high-pressure . . . . . 35
1.5.2 Effect of pressure on the photo-physical properties . . . . . . . . . . 36
2 Bonding between tetracycline derivates and TetR protein 39
2.1 Spectroscopy of sancycline and 10-propoxysancycline . . . . . . . . . . . . 41
2.1.1 Steady-state absorption spectroscopy . . . . . . . . . . . . . . . . . 44
2.1.2 Steady-state fluorescence spectroscopy . . . . . . . . . . . . . . . . 48
2.1.3 Time-resolved fluorescence spectroscopy . . . . . . . . . . . . . . . 57
2.2 Time-resolved fluorescence anisotropy measurements . . . . . . . . . . . . . 62
2.2.1 Anisotropy of sancycline . . . . . . . . . . . . . . . . . . . . . . . . 62
2.2.2 Anisotropy decays of TetR protein . . . . . . . . . . . . . . . . . . . 63
qt2
2.2.3 Anisotropy of a fluorophor-labelled DNA sequence . . . . . . . . . . 65
2.2.4 Observations related to the rotational correlation time . . . . . . . . 69
3 Applications of Stern-Volmer equation 71
3.1 Complex formation between pyrene derivatives and pyridine . . . . . . . . . 71
3.2 Complex formation between cyanopyrene and triethylamine . . . . . . . . . 79
3.2.1 Excimer formation of cyanopyrene . . . . . . . . . . . . . . . . . . . 81
3.2.2 Exciplex formation between cyanopyrene and triethylamine . . . . . 84
3.3 Cyanopyrene/ triethylamine exciplex under pressure . . . . . . . . . . . . . . 95
3.3.1 Free cyanopyrene under high-pressure . . . . . . . . . . . . . . . . . 96
3.3.2 Time-resolved measurements of cyanopyrene/ triethylamine
system under high-pressure . . . . . . . . . . . . . . . . . . . . . . . 98
3.3.3 Kinetic parameters at high-pressure . . . . . . . . . . . . . . . . . . 102
3.3.4 Diffusion-controlled reaction and electron-transfer rate constants . . . 104
3.3.5 The dependence of diffusion constant k on viscosity . . . . . . . 106di f f
3.4 Phenothiazine-Pyrene dyad under pressure . . . . . . . . . . . . . . . . . . . 108
3.4.1 Photo-induced charge-transfer . . . . . . . . . . . . . . . . . . . . . 109
3.4.2 Fluorescence measurements of phenothiazine-pyrene dyad
under high-pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.4.3 Determination of the dipole moment of the exciplex . . . . . . . . . 113
3.4.4 Time-resolved measurements of phenothiazine-pyrene dyad . . . . . 115
Summary 119
Zusammenfassung 123
A Appendix 127
A.1 Controlling of the rotating table . . . . . . . . . . . . . . . . . . . . . . . . 127
A.2 Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Bibliography 133
qSolange Du nicht zu steigen aufho¨rst,
ho¨ren die Stufen nicht auf,
unter Deinen steigenden Fu¨ssen,
wachsen sie aufwa¨rts.
Franz Kafka
Introduction
Research and experimental development consists of creative work undertaken on a systematic
basis in order to increase knowledge, including knowledge of humanity, culture and society,
and the use of this stock of knowledge to develop new applications. Science is the study and
theoretical explanation of natural phenomena in an orderly way. Physics are the sciences,
which study the properties of matter and movements using experimental techniques or theore-
tical analyses. Chemistry is the science that studies the structure and properties of substances
and their reactions. The present work is, of course, in the domain of physics and chemistry but
because of the fact that in chapter 2, the samples are proteins, DNA sequences and tetracycline
derivates, we have to remember the importance of biology too. An interdisciplinary study is
necessary today in many projects. Here, for example, the biologists have to analyze the effect
of antibiotics against bacteria. Therefore, the chemists can study the chemical interactions
and bonding between these compounds and the analysis can be made very well with methods
from experimental physics. Hence, physical chemistry is a branch of science applying physical
methods and theory to the study of chemical systems. Such methods are found in spectroscopy,
which is that part of physics that deals with the theory and interpretation of interactions be-
tween matter and radiation. In spectroscopy science, an important role in physical chemistry is
the study of fluorescence spectra. Fluorescence is the most important of the keywords in this
work and means the emission of electromagnetic radiation, especially of visible light, stimu-
lated in a substance by the absorption of incident radiation. Fluorescence and time-resolved
fluorescence are primarily research tools in biochemistry and biophysics, but these can be also
applied successfully in other branches (see chapter 3). More, fluorescence anisotropy mea-4
surements provide an interesting method for monitoring molecular reorientational motions in
solutions.
In this work, chapter 1 presents the principle of fluorescence, theory and some definitions
from this domain and the instruments used. The measurements of time-resolved fluorescence
anisotropy are new in our group. Others perform such measurements using a lot of methods.
In this work, in chapter 1, a new and alternative method comparing to the classical one is
described. Our method needs new equipment, a rotating table with optical components that is
also described in chapter 1. More details about controlling of this table, the necessary software
and hardware are described in appendix A1. Therefore, besides the science domains mentioned
above, this work combines ideas from branches like automatics, electronics and programming.
Next chapters present the experimental results using the described methods. Hence, chap-
ter 2 analyses the bonding between tetracycline derivates and TetR proteins. First, many
steady-state spectra and time-resolved measurements for samples based on sancycline and 10-
propoxy-sancycline resolve the longstanding quarrel about the properties of hydroxyl group
O10H from tetracycline. At the end of this chapter, the most interesting of my anisotropy
measurements are presented.
Last chapter presents numerous fluorescence measurements for different samples based on
pyrene derivates. Due to the long lifetime in the excited states and a strong fluorescence
of these substances, they have many applications in development of solar cells with organic
substances, in studies of photosynthesis by plants and other technologies. Chapter 3 will
present measurements to analyse the fluorescence quenching of pyrene derivates with different
quenchers, formation of the exciplexes and their properties under high-pressure. The work
ends with a study about the photo-induced electron transfer in phenothiazine-pyrene dyad and
its behavior under high-pressure.