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Theoretical study on nonlinearoptical properties of organicchromophores in solutions
KTH, School of Biotechnology (BIO), Theoretical Chemistry. (Theoretical Chemistry)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Inter-molecular interactions have significant influences on linear and nonlinear optical properties of molecules including one- and two-photon absorptions, emissions, and various high order nonlinear polarizations. The related investigation has become an active and challenging research area. The theoretical structure-to-property relationship obtained from quantum chemical calculations of single organic conjugated molecules often can not be directly applied to real materials in condensed phases. One has to consider the effect of environment, that is, inter-molecular interactions, where the model systems experience in real experiments or applications. The change of molecular conformations under all kinds of interactions and its effects on linear and nonlinear optical properties are the central issue of this thesis.

Special attentions have been paid to symmetrical diamino substituted distyrylbenzene chromophores with different torsional angles, two dipolar merocyanine dyes of various orientations, two isomers of a V-shaped 2-hydroxypyrimidine derivative and their various dimers, and the structural fluctuations of interacting polar chromophores in solutions. Quantum chemical methods in combination with molecular dynamics simulations have been employed to study molecular conformations and optical properties in solutions, in particular the solvent and aggregation effects on one- and two-photon absorption. More specifically, time-dependent density functional theory has been used for all electronic calculations, while the polarizable continuum model and supermolecule approach have also been employed to take into account solvent effects.

Moreover, the propagation of an ultrashort laser pulse through a one-dimensional asymmetric organic molecular medium which possesses large permanent dipole moments has been simulated by solving full Maxwell-Bloch equations using predictor-corrector finite-difference time-domain method. We have focused on the supercontinuum generation of spectra and the formation of attosecond pulses.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , p. 80
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2010:9
Keyword [en]
two-photon absorption, solvent effects, aggregation effects, molecular dynamics simulation
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-12748ISBN: 978-91-7415-630-0 (print)OAI: oai:DiVA.org:kth-12748DiVA, id: diva2:318542
Public defence
2010-06-07, FA 31, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100630Available from: 2010-05-12 Created: 2010-05-07 Last updated: 2011-01-21Bibliographically approved
List of papers
1. Solvent effects on two-photon absorption of dialkylamino substituted distyrylbenzene chromophore
Open this publication in new window or tab >>Solvent effects on two-photon absorption of dialkylamino substituted distyrylbenzene chromophore
Show others...
2007 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, no 20Article in journal (Refereed) Published
Abstract [en]

Solvent effects on the two-photon absorption of a symmetrical diamino substituted distyrylbenzene chromophore have been studied using the density functional response theory in combination with the polarizable continuum model. It is shown that the dielectric medium has a rather small effect both on the bond length alternation and on the one-photon absorption spectrum, but it affects significantly the two-photon absorption cross section. It is found that both one- and two-photon absorptions are extremely sensitive to the planarity of the molecule, and the absorption intensity can be dramatically reduced by the conformation distortion. It has led to the conclusion that the experimentally observed anomalous solvent effect on the two-photon absorption of dialkylamino substituted distyrylbenzene chromophores cannot be attributed to the intrinsic properties of a single molecule and its interaction with solvents.

Keyword
density-functional theory, polarizable continuum model, cross-sections, organic chromophores, electronic-structure, molecules, derivatives
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-13829 (URN)10.1063/1.2740641 (DOI)000246891700037 ()2-s2.0-34249864511 (Scopus ID)
Note
QC 20100630Available from: 2010-06-30 Created: 2010-06-30 Last updated: 2017-12-12Bibliographically approved
2. Molecular Dynamics and Quantum Chemistry Study on Conformations and Optical Properties of Hydrogen Bonded Dipolar Merocyanine Dyes
Open this publication in new window or tab >>Molecular Dynamics and Quantum Chemistry Study on Conformations and Optical Properties of Hydrogen Bonded Dipolar Merocyanine Dyes
2009 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 113, no 30, p. 10271-10276Article in journal (Refereed) Published
Abstract [en]

An earlier proposed strategy to orient two merocyanine dyes in the desirable head-to-tail parallel fashion through multiple hydrogen bonds has been examined by molecular dynamics simulations and quantum chemical calculations. Two different merocyanine dyes dissolved in chloroform solution under various conditions are simulated by molecular dynamics. It is found that two dipolar units can be well connected through various numbers of hydrogen bonds. Although the probability to form the desirable head-to-tail dimer is unfortunately small even under strong poling electric field and low temperature, the formation of unwanted antiparallel structure has been effectively reduced. Typical hydrogen bonded dimers obtained from molecular dynamics simulations have been studied by hybrid density functional calculations. It is found that only the most probable complex can lead to the optical absorption spectrum that is in close agreement with the corresponding experiments. Calculated results for dipole moments of ground and charge transfer states, as well as first hyperpolarizabilities, of three typical complexes have also been provided.

Keyword
ABSORPTION CROSS-SECTIONS, PARTICLE MESH EWALD, 2-PHOTON ABSORPTION, ELECTRIC-FIELD, 1ST HYPERPOLARIZABILITY, OCTUPOLAR MOLECULES, ORGANIC-MOLECULES, DESIGN, CHROMOPHORES, SIMULATIONS
Identifiers
urn:nbn:se:kth:diva-13826 (URN)10.1021/jp900864b (DOI)000268231000032 ()2-s2.0-67651213781 (Scopus ID)
Note
QC20100630Available from: 2010-06-30 Created: 2010-06-29 Last updated: 2017-12-12Bibliographically approved
3. Effects of Co-existing Isomers on Two-PhotonAbsorption of Organic Molecules in Solutions
Open this publication in new window or tab >>Effects of Co-existing Isomers on Two-PhotonAbsorption of Organic Molecules in Solutions
2010 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 41, p. 13167-13172Article in journal (Refereed) Published
Abstract [en]

Isomer-dependent two-photon absorption spectra Of organic molecules in solutions have been identified by time-dependent density functional theory calculations. Experimentally observed enhancements in two-photon absorptions of V-shaped hydroxypyrimidine derivatives are not due to the formation of molecular chillers but to mainly the co-occurrence of geometrical isomers. Solvent effects on both one- and two-photon absorption spectra have been carefully examined by using a supermolecular approach in combination with a polarizable continuum model. Special attention has been paid to understand the effects of hydrogen bonds on electronic structure and absorption spectra of these chromophores. Our calculated results are very helpful for understanding the corresponding experimental observations.

Identifiers
urn:nbn:se:kth:diva-13830 (URN)10.1021/jp103527q (DOI)000282855100018 ()2-s2.0-77958064867 (Scopus ID)
Note
Uppdaterad från submitted till published 20101123 QC20100630Available from: 2010-06-30 Created: 2010-06-30 Last updated: 2017-12-12Bibliographically approved
4. Effects of Structural Fluctuations on Two-Photon Absorption Activity of Interacting Dipolar Chromophores
Open this publication in new window or tab >>Effects of Structural Fluctuations on Two-Photon Absorption Activity of Interacting Dipolar Chromophores
2010 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 33, p. 10814-10820Article in journal (Refereed) Published
Abstract [en]

One- and two-photon absorption properties of organic chromophores consisting of interacting dipolar branches have been studied using density functional response theory in combination with molecular dynamics simulation. Effects of dipole interaction on optical absorptions have been examined. The importance of solvent effects on optical properties of charge-transfer states is explored by means of polarizable continuum model. It is found that for the interacting dipolar molecule with flexible conformations in solutions, the structural fluctuations can result in new spectral features or significant broadening of one-photon absorption spectrum. Our study highlights again the usefulness of the combined quantum chemical and molecular dynamics approach for modeling two-photon absorption materials in solutions.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-26846 (URN)10.1021/jp103791s (DOI)000280962100015 ()2-s2.0-77955893521 (Scopus ID)
Note
QC 20101206 Uppdaterad från submitted till published.Available from: 2010-12-06 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved
5. Modulation of supercontinuum generation and formation of an attosecond pulse from a generalized two-level medium
Open this publication in new window or tab >>Modulation of supercontinuum generation and formation of an attosecond pulse from a generalized two-level medium
2007 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 40, p. 1523-1534Article in journal (Refereed) Published
Abstract [en]

The propagation of ultrashort pulses in a generalized two- level system, consisting of permanent dipole moments, is simulated by solving the full Maxwell - Bloch equations. Special attention has been paid to the supercontinuum generation of spectra and the formation of attosecond ( as) pulses. It is found that the supercontinuum generation is strongly modulated by both area and width of the pulse, resulting from the interference between the splitting pulses in the time domain and the implication of the time - energy uncertainty relation. The effect of the permanent dipole moment on the supercontinuum generation is discussed in detail. Calculations show that a well- shaped 132 as pulse can be generated from a 2 fs incoming pulse under the condition where the permanent dipole moment difference between two levels is equal to the transition dipole moment between them. Influences of carrier- envelope phase and time- dependent ionization on the spectral and temporal evolution of the ultrashort pulses are also discussed at length.

Keyword
femtosecond optical pulses, laser-pulses, ionization
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-11458 (URN)10.1088/0953-4075/40/8/006 (DOI)000246010300007 ()2-s2.0-34247138000 (Scopus ID)
Note
QC 20100630Available from: 2009-11-11 Created: 2009-11-11 Last updated: 2017-12-12Bibliographically approved

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