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Charge-transfer excitations and phtophysical properties of molecular building blocks
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis reports a state-of-the-art theoretical study of photophysical properties of organic charge-transfer aromatic molecules. These molecules are building blocks of molecular functional materials used in modern photonics technology and play essential roles in chemistry and biology in general. A good understanding of these systems is thus important.

The theoretical results for permanent dipole moments of some substituted benzenes have been obtained using the coupled cluster singles and doubles (CCSD) method. The performance of density functional theory (DFT) for the geometry and electronic properties has been compared with that of traditional ab initio methods, such as Hartree-Fock, second-order Möller Plesset perturbation theory (MP2), CCSD and CCSD(T). Limitations of the DFT methods for charge transfer molecules have been demonstrated. The multi-configuration self-consistent field (MCSCF) method has been applied to understand properties of the triplet states of benzene derivatives by studying their phosphorescence with the inclusion of contributions from vibronic coupling. It has also been employed to calculate the photophysics of the thioxanthone molecule containing three benzene rings in combination with the CASPT2 method, resolving a long-standing problem concerning the possible stable conformations of the molecule.

With knowledge of the building blocks a series of porphyrin derivatives with exceptionally large two-photon absorption cross sections were designed, and proposed for use in bioimaging applications. The static and dynamic properties of a few zinc and platinum organometallic compounds, being possible candidates for optical limiting devices, have also investigated.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 43 p.
Series
Theses in philosophy from the Royal Institute of Technology, ISSN 1654-627X
Keyword [en]
Theoretical chemistry, Photophysical porperties, CCSD, CASSCF
Keyword [sv]
Teoretisk kemi
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-184ISBN: 91-7178-020-3 (print)OAI: oai:DiVA.org:kth-184DiVA: diva2:7844
Public defence
2005-05-12, FA32, Albanova centrum, 10:00
Opponent
Supervisors
Note
QC 20101011Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2011-11-23Bibliographically approved
List of papers
1. The permanent dipole moment of gas-phase para-amino benzoic acid revisited
Open this publication in new window or tab >>The permanent dipole moment of gas-phase para-amino benzoic acid revisited
2004 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, no 1, 157-161 p.Article in journal (Refereed) Published
Abstract [en]

A study of permanent dipole moment of para-amino benzoic acid (PABA) by using various computational methods, was carried out. The dipole meoments of PABA was computed at Hartree-Fock, second-order Mφller-Plesset perturbation (MP2), coupled cluster singles and doubles (CCSD), triple corrections CCSD(T) and hybrid density functional theory at B3LYP level with different basis sets. It was found that the electron density by B3LYP resulted in large charge separation in the charge transfer molecules. It was stated that the best dipole moments were obtained at CCSD and CCSD(T) levels experiments.

Keyword
Benzene, Carrier concentration, Charge transfer, Computational geometry, Optimization, Parameter estimation, Perturbation techniques, Probability density function, Separation
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5081 (URN)10.1063/1.1756862 (DOI)000222112100018 ()2-s2.0-3142688269 (Scopus ID)
Note
QC 20101004 QC 20111101. Tidigare titel: "The Permanent Dipole moment of gas phase p-aminobenzoic acid revisited".Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-05Bibliographically approved
2. Electronic Properties of Ground and Charge Transfer States of p-Substituted-Anilines
Open this publication in new window or tab >>Electronic Properties of Ground and Charge Transfer States of p-Substituted-Anilines
2005 (English)Article in journal (Other academic) Submitted
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-5082 (URN)
Note
QS 2010 QS 20120319Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2012-03-19Bibliographically approved
3. CASSCF calculations of triplet-state properties: Applications to benzene derivatives
Open this publication in new window or tab >>CASSCF calculations of triplet-state properties: Applications to benzene derivatives
Show others...
2003 (English)In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 101, no 13, 2103-2114 p.Article in journal (Refereed) Published
Abstract [en]

We illustrate the capability of the complete active space self-consistent field method by Roos and co-workers for calculations of triplet state properties. We report phosphorescence lifetimes, zero-field splitting parameters, and nuclear quadrupole coupling constants for the lowest triplet state of a variety of benzene derivatives.

Keyword
FIELD SPLITTING PARAMETERS, AB-INITIO CALCULATIONS, PHOSPHORESCENCE SPECTRA, PARA-DICHLOROBENZENE, RADIATIVE LIFETIMES, AROMATIC-AMINES, RESPONSE THEORY, ANILINE, SINGLET, TRANSITIONS
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5083 (URN)10.1080/0026897031000109248 (DOI)000184449300017 ()
Note
QC 20100902Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-05Bibliographically approved
4. Ab initio calculations of vibronic activity in phosphorescence microwave double resonance spectra of para-dichlorobenzene
Open this publication in new window or tab >>Ab initio calculations of vibronic activity in phosphorescence microwave double resonance spectra of para-dichlorobenzene
2005 (English)In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 113, no 1, 15-27 p.Article in journal (Refereed) Published
Abstract [en]

The phosphorescence spectrum of p-dichlorobenzene has been calculated using multiconfiguration self-consistent-field wave functions and the quadratic response technique. Attention has been paid to the intensity distribution of the singlet-triplet (B-3(1u)->(1)A(g)) transition through a number of vibronic subbands. The second order spin-orbit coupling (SOC) contribution to the spin splitting of the B-3(1u) ((3)pi pi*) state is found to be almost negligible, and the calculations therefore provide a good estimate for the zero-field splitting (ZFS) parameters based only on the electron spin-spin coupling expectation values. Nuclear quadrupole resonance constants for the different Cl isotopes are also calculated to accomplish the ZFS assignment. The electric dipole activity of the spin sublevels in the triplet singlet transitions to the ground-state vibrational levels is estimated by calculations of derivatives using distorted geometries which are shifted from the equilibrium position along different vibrational modes. A vibrational analysis of the phosphorescence spectrum, based on the SOC-induced mixing of the singlet and triplet states calculated along different vibrational modes, provides reasonable agreement with experimental data.

Keyword
phosphorescence microwave double resonance spectra; vibronic activity; p-dichlorobenzene; quadratic response methodology; zero-field splitting parameters
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5084 (URN)10.1007/s00214-004-0596-x (DOI)000227633400002 ()2-s2.0-14644440780 (Scopus ID)
Note
QC 20100825Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-05Bibliographically approved
5. A butterfly like motion as a clue to the photophysics of thioxanthone
Open this publication in new window or tab >>A butterfly like motion as a clue to the photophysics of thioxanthone
2006 (English)In: Journal of Photochemistry and Photobiology A: Chemistry, ISSN 1010-6030, E-ISSN 1873-2666, Vol. 179, no 3, 298-304 p.Article in journal (Refereed) Published
Abstract [en]

A theoretical, quantum-chemical study of the thioxanthone (TX) molecule has been performed at the MP2 and CASPT2 levels of theory. Geometries, absorption energies, and transition and state properties have been investigated. Two conformers have been found very close in energy with planar (P) and non-planar (NP) structures, the latter characterized by a dihedral angle theta = 173.3 degrees representing the bend of the side benzene rings and an out-of-plane angle theta=4 degrees of the C=O bond. Large changes in the relative positions and properties of the two low-lying electronic absorption bands, pi pi* and n pi*, are computed when changing the conformation. As a consequence of the analysis of the TX absorption spectrum it is suggested that TX should be viewed as dynamically changing its conformation between the planar and the non-planar conformations. We coined such behavior as a "butterfly like motion". This dynamic view of the TX structure enables a plausible explanation of the photophysical properties observed for the system.

Keyword
thioxanthone, absorption spectrum, CASPT2, ground state structure
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-5085 (URN)10.1016/j.jphotochem.2005.08.033 (DOI)000236722300009 ()2-s2.0-33644857241 (Scopus ID)
Note
Tidigare titel: A butterfly effect as a clue to the unique photophysics of thioxanthone Uppdaterad från submitted till published: 20101011. QC 20101011Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-05Bibliographically approved
6. Charge-transfer Zn-porphyrin derivatives with very large two-photon absorption cross sections at the fundamental wavelengths of 1.3-1.5 mu m fundamental wavelengths
Open this publication in new window or tab >>Charge-transfer Zn-porphyrin derivatives with very large two-photon absorption cross sections at the fundamental wavelengths of 1.3-1.5 mu m fundamental wavelengths
2005 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, no 9, 096101- p.Article in journal (Refereed) Published
Abstract [en]

 A series of charge-transfer Zn-porphyrin derivatives with large two-photon absorption cross sections at 1.3-1.5 mum fundamental wavelengths are designed using time-dependent hybrid density functional theory. The fluorescence of these chromospheres is expected to be in the region of 700-900 nm. These unique features make them suitable for a variety of biophotonic and telecommunication applications.

Keyword
Absorption, Charge transfer, Derivatives, Photons, Telecommunication
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5086 (URN)10.1063/1.1858864 (DOI)000227483300087 ()2-s2.0-22944463327 (Scopus ID)
Note
QC 20100903Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-05Bibliographically approved
7. Effects of Conjugation Length, Electron Donor and Acceptor Strengths on Two-Photon Absorption Cross Sections of Asymmetric Zinc-Porphyrin Derivatives
Open this publication in new window or tab >>Effects of Conjugation Length, Electron Donor and Acceptor Strengths on Two-Photon Absorption Cross Sections of Asymmetric Zinc-Porphyrin Derivatives
2006 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, no 9, 094310- p.Article in journal (Refereed) Published
Abstract [en]

 Exceptionally large two-photon absorption cross sections at the infrared region have been revealed by time-dependent density functional theory calculations for asymmetric charge-transfer conjugated zinc-porphyrin derivatives. The largest two-photon cross section is found to be more than one order of magnitude larger than for the conventional two-photon active organic molecules. The calculations show that the formation of strong charge-transfer states depends on the length of the conjugation bridge between the zinc-porphyrin core and the electron donor/acceptor. The two-photon absorption cross section can be greatly enhanced by increasing the strengths of the electron donor/acceptor.

Keyword
MULTIPHOTON MICROSCOPY, CHROMOPHORES, MOLECULES, DESIGN, LASER
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-5087 (URN)10.1063/1.2178790 (DOI)000235828300024 ()2-s2.0-34547926404 (Scopus ID)
Note
QC 20100910. Uppdaterad från In press till Published (20100910)Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-05Bibliographically approved
8. Optical limiting properties of Zinc- and Platinum-based organometallic compounds
Open this publication in new window or tab >>Optical limiting properties of Zinc- and Platinum-based organometallic compounds
2004 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 108, no 36, 7406-7416 p.Article in journal (Refereed) Published
Abstract [en]

Optical power limiting is theoretically studied using an approach that combines quantum electronic structure calculations of multiphoton excitations and classical calculations of dynamical wave propagation. We illustrate the capability of such a combined approach by presenting results for a couple of organometallic compounds; basic metal-base porphyrins, vinylphenylamine porhyrin, and the so-called type IVc platinum compound. A comparative analysis of their electronic properties related to nonlinear absorption of electromagnetic radiation and their optical limiting capability has been performed based on dynamical simulations of the nonlinear pulse propagation taking account of resonant as well as off-resonant effects. Several key features and rate-limiting steps in the transmission have been examined in relation to various characteristics of the pulse. It is found that the resonant vs off-resonant conditions, the saturation conditions and the dephasing play critical roles for the nonlinear transmission. The saturation effects are sensitive to the pulse duration, the inter-system crossing rate and the quenching of the higher triplet state. The inter-system crossing rate has to be comparable with the inverse pulse duration in order to boost the stepwise two-photon channel associated with singlet-singlet followed by triplet-triplet transitions. It is illustrated that structure-to-property relations of the rate-limiting steps serve as important criteria for choices of compounds suitable for the application of interest.

Keyword
Activation energy, Electromagnetic wave propagation, Optical properties, Optical pumping, Optical resolving power, Photolysis, Raman spectroscopy, Saturation (materials composition)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-5088 (URN)10.1021/jp040078s (DOI)000223703600010 ()2-s2.0-4544279724 (Scopus ID)
Note
QC 20100924 QC 20110916Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-05Bibliographically approved

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