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Theoretical Design of Molecular Photonic Materials
KTH, School of Biotechnology (BIO).
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents a theoretical study on optical properties of molecular materials. Special emphasis has been put on the influence of solvent environment, nuclear vibrations, and aggregation effects on molecular properties like linear and nonlinear polarizabilities, one- and two-photon absorption probabilities. All calculations have been performed by means of time independent and dependent quantum chemical methods at the Hartree-Fock and density functional theory levels. Solvation models that include both long range and short range interactions have been employed for calculations of optical properties of molecules in solutions. Pure vibrational and zero-point vibrationally averaged contributions have been taken into account for linear and nonlinear polarizabilities. The linear coupling model is applied to simulate vibronic profiles of optical absorption spectra. The computational strategies described in this thesis are very useful for the design of efficient molecular photonic materials.

More specifically, the nonmonotonic behavior of the solvatochromic shifts and the first hyperpolarizability of para-nitroaniline (pNA) with respect to the polarity of the solvents have been theoretically confirmed for the first time. The significant contributions of the hydrogen bonding on the electronic structures of pNA are revealed. Vibrational contributions to the linear and nonlinear polarizabilities of methanol, ethanol and propanol have been calculated both at the static limit and in dynamic optical processes. The importance of vibrational contributions to certain nonlinear optical processes have been demonstrated. A series of end-capped triply branched dendritic chromophores have been studied with the result that their second order nonlinear optical properties are found strongly dependent on the mutual orientations of the three chromophores, numbers of caps and the conjugation length of the chromophores. Several possible mechanisms for the origin of the Q-band splitting of aluminum phthalocyanine chloride have been examined. Calculated vibronic one-photon absorption profiles of two molecular systems are found to be in very good agreement with the corresponding experiments, allowing to provide proper assignments for different spectral features. Furthermore, effects of vibronic coupling in the nonradiative decay processes have been considered which helps to understand the aggregation enhanced luminescence of silole molecules. The study of molecular aggregation effects on two-photon absorption cross sections of octupolar molecules has highlighted the need to use a hybrid method that combines density functional response theory and molecular dynamics simulations for the design of molecular materials.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , p. 52
Series
Trita-TEC-PHD, ISSN 1653-4468
Keywords [en]
Optical property, Molecular material, Solvent environment, Nuclear vibrations, Aggregation effect
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-4333ISBN: 978-91-7178-619-7 (print)OAI: oai:DiVA.org:kth-4333DiVA, id: diva2:11844
Public defence
2007-04-27, FA32, Roslagstullsbacken 21, AlbaNova University Center, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2010-08-20Bibliographically approved
List of papers
1. Solvent dependence of solvatochromic shifts and the first hyperpolarizability of para-nitroaniline: a nonmonotonic behaviour
Open this publication in new window or tab >>Solvent dependence of solvatochromic shifts and the first hyperpolarizability of para-nitroaniline: a nonmonotonic behaviour
2003 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 119, no 8, p. 4409-Article in journal (Refereed) Published
Abstract [en]

Solvent dependence of the electronic structure and nonlinear optical properties of the para-nitroaniline (pNA) molecule on the polarity of the solutions has been studied using the polarizable continuum model in combination with the hybrid density functional theory. With a supermolecular approach, specific hydrogen bonding effects have also been fully considered. Good agreement between theory and experiments are obtained for both solvatochromic shifts of the charge transfer state and the solvent-induced first hyperpolarizability of pNA.

Keywords
Charge transfer; Composition effects; Electronic structure; Hydrogen bonds; Mathematical models; Nonlinear optics; Polarization; Probability density function; Solvents; Supramolecular chemistry; Hybrid density functional theory; Hyperpolarizability; Nonmonotonic behavior; Paranitroaniline; Polarizable continuum model; Solvatochromic shifts; Solvent dependence; Nitrogen compounds
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6970 (URN)10.1063/1.1594181 (DOI)000184675600036 ()
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved
2. Vibrational contributions to nonlinear optical properties of methanol, ethanol and propanol
Open this publication in new window or tab >>Vibrational contributions to nonlinear optical properties of methanol, ethanol and propanol
2005 (English)In: Journal of Molecular Structure: THEOCHEM, ISSN 0166-1280, Vol. 717, no 1-3, p. 223-230Article in journal (Refereed) Published
Abstract [en]

Static and dynamic vibrational contributions to the linear polarizability and the first and second nonlinear hyperpolarizabilities of methanol, ethanol and propanol have been calculated. Both the pure vibrational contribution and the zero-point vibrational averaging contribution have been determined by adopting the perturbation treatment of Bishop and Kirtman at the Hartree-Fock level. The pure vibrational contribution is quite important at the static limit, while in the optical region it varies for different nonlinear optical processes. The zero-point vibrational averaging contribution is a quite large correction to the electronic nonlinear optical (NLO) properties, especially for the second hyperpolarizability at finite fundamental frequencies. Vibrational analysis shows that the swinging modes at around 300 cm(-1) and the C-H stretching modes at around 3160 cm(-1) often give large contributions.

Keywords
Nonlinear optical properties; Vibrational contributions; alcohol; carbon; hydrogen; methanol; propanol; article; calculation; frequency analysis; mathematical model; nonlinear system; optics; polarization; vibration
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6971 (URN)10.1016/j.theochem.2004.12.023 (DOI)000228024900030 ()2-s2.0-14844337490 (Scopus ID)
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved
3. Three-branched dendritic dipolar nonlinear optical chromophores, more than three times a single-strand chromophore?
Open this publication in new window or tab >>Three-branched dendritic dipolar nonlinear optical chromophores, more than three times a single-strand chromophore?
Show others...
2008 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, no 47, p. 14751-14761Article in journal (Refereed) Published
Abstract [en]

To elucidate the dependence of the nonlinear optical (NLO) response on the conformation of triply branched derivatives, a new series of D-pi-A dendrimers has been synthesized. A combined approach of experiments (UV-vis and EOA measurements) and computational predictions (semiempirical and ab initio) was applied both on the dendrimers and on the corresponding single-strand chromophores. It has been shown that depending on the surrounding media the NLO activity of a flexible dendrimer can be very different. Two limiting cases are proposed: (i) the dendrimer resembles a solution of the corresponding single-strand chromophores with about 3-fold concentration, where the hyperpolarizability is the sum of the effect of three noninteracting single-strand subunits ("independent chromophores" limit); (ii) the dendrimers show nearly parallel or helical alignments of the single-strand subunits. Because of this change of conformation the NLO activity can be enhanced up to nine times the value of the "independent chromophores" limit and, thus, are more than a single strand chromophore. Conformers of dendrimers with interacting single-strand chromophores have been identified experimentally in nonpolar solutions by the EOA spectroscopy and possible structures have been revealed by numerical calculations, which could moreover show the tendency of the effects on the hyperpolarizability due to structural changes of the flexible dendritic architecture. Implications for future research developments are given to implement the "more than three times" concept.

Keywords
Dendrimers; Numerical analysis; Ab initio; Computational predictions; Dendritic architectures; Future researches; Hyperpolarizability; Limiting cases; New series; Nlo activities; Nonlinear optical chromophores; Nonlinear optical responses; Nonpolar solutions; Numerical calculations; Semiempirical; Structural changes; Chromophores
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6972 (URN)10.1021/jp802369c (DOI)000261056400010 ()2-s2.0-57449109538 (Scopus ID)
Note
QC 20100820. Tidigare titel: Three-branched dendritic NLOphores, more than three times a single-strand chromophore? Titel ändrad och uppdaterad från Submitted till Published 20100820.Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved
4. Hyperpolarizabilities of end-capped triply branched dendrimers: a theoretical study
Open this publication in new window or tab >>Hyperpolarizabilities of end-capped triply branched dendrimers: a theoretical study
Show others...
(English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690Article in journal (Other academic) Submitted
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-7958 (URN)
Note
QS 20120328Available from: 2008-02-05 Created: 2008-02-05 Last updated: 2017-12-14Bibliographically approved
5. Origin of the Q-band splitting in the absorption spectra of aluminum phthalocyanine chloride
Open this publication in new window or tab >>Origin of the Q-band splitting in the absorption spectra of aluminum phthalocyanine chloride
2007 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 438, no 1-3, p. 36-40Article in journal (Refereed) Published
Abstract [en]

The Q-band of aluminum phthalocyanine chloride (AlPcCl) shows experimentally distinct splitting in the aqueous solution. Time-dependent density functional theory calculations with inclusion of polarizable continuum model have been performed to reveal the origin of this splitting. It is found that the spectral splitting caused by the formation of dimers and interaction with two water molecules are much smaller than what was predicted by previous semi-empirical study. Our calculations indicate that the experimentally observed large Q-band splitting can be explained by considering the geometrical distortions that are associated with changes of bonds between carbon and nitrogen atoms.

Keywords
Carbon; Chemical bonds; Dimers; Molecular dynamics; Nitrogen; Quantum theory; Spectrum analysis; Aluminum phthalocyanine chloride; Nitrogen atoms; Q-band splitting; Water molecules; Aluminum compounds
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6974 (URN)10.1016/j.cplett.2007.02.048 (DOI)000245776300007 ()2-s2.0-84962429310 (Scopus ID)
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved
6. Solvent effects on the vibronic one-photon absorption profiles of dioxaborine heterocycles
Open this publication in new window or tab >>Solvent effects on the vibronic one-photon absorption profiles of dioxaborine heterocycles
Show others...
2005 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 123, no 19, p. 194311-1-194311-7Article in journal (Refereed) Published
Abstract [en]

The vibronic profiles of one-photon absorption spectra of dioxaborine heterocycles in gas phase and solution have been calculated at the Hartree-Fock and density-functional-theory levels. The polarizable continuum model has been applied to simulate the solvent effect, while the linear coupling model is used to compute the Franck-Condon and Herzberg-Teller contributions. It is found that a good agreement between theory and experiment can be achieved when the solvent effect and electron correlation are taken into account simultaneously. For the first excited charge-transfer state, the maximum of its Herzberg-Teller profile is blueshifted from that of the Franck-Condon profile. The shifted energy is found to be around 0.2 eV, which agrees well with the measured energy difference between two- and one-photon absorptions of the first excited state.

Keywords
Charge transfer; Energy absorption; Mathematical models; Molecular vibrations; Organic solvents; Probability density function; Dioxaborine; Hartree-Fock levels; Photon absorption; Solvent effects; Boron compounds
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6975 (URN)10.1063/1.2121590 (DOI)000233353200023 ()2-s2.0-27744587300 (Scopus ID)
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved
7. Density functional theory study of vibronic structure of the first absorption Qx band in free-base porphin
Open this publication in new window or tab >>Density functional theory study of vibronic structure of the first absorption Qx band in free-base porphin
Show others...
2006 (English)In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 65, no 2, p. 308-323Article in journal (Refereed) Published
Abstract [en]

Harmonic vibrational frequencies and vibronic intensities in the first S-0 -> S-1 (pi pi*) absorption band of free-base porphin (H2P) are investigated by hybrid density functional theory (DFT) with the standard B3LYP functional. The S-0-S-1 transition probability is calculated using time-dependent DFT with account of Franck-Condon (FC) and Herzberg-Teller (HT) contributions to the electric-dipole transition moments including displacements along all 108 vibrational modes. Two weak wide bands observed in the gas phase absorption spectra of the H2P molecule at 626 and 576 nm are interpreted as the 0-0 band of the X(1)A(g)-> B-3u transition and the 0-1 band with largest contributions from the nu(10)(a(g)) = 1610 cm(-1) and nu(19)(b(1g)) = 1600 cm(-1) modes, respectively, in agreement with previous tentative assignments. Both bands are induced by the HT mechanism, while the FC contributions are negligible. A number of fine structure bands, including combination of two vibrational quanta, are obtained and compared with available spectra from supersonic jet and Shpolskij matrices. Both absorption and fluorescence spectra are interpreted on ground of the linear coupling model and a good fulfillment of the mirror-symmetry rule.

Keywords
Absorption; Electronic structure; Fluorescence; Harmonic analysis; Lattice vibrations; Mathematical models; Probability density function; Electric-dipole transition moments; Harmonic vibrational frequencies; Porphin; Vibronic coupling; Aromatic compounds; porphine; porphyrin; article; chemical model; chemical structure; chemistry; computer assisted emission tomography; fluorescence; infrared spectrophotometry; infrared spectroscopy; light; luminescence; mathematics; physical chemistry; quantum theory; Raman spectrometry; spectroscopy; ultraviolet spectrophotometry; vibration; Chemistry, Physical; Fluorescence; Light; Luminescent Measurements; Mathematics; Models, Chemical; Models, Molecular; Porphyrins; Quantum Theory; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Spectrum Analysis; Spectrum Analysis, Raman; Tomography, Emission-Computed; Vibration
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6976 (URN)10.1016/j.saa.2005.10.047 (DOI)000240692400010 ()2-s2.0-33747880113 (Scopus ID)
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved
8. Aggregation effects on two-photon absorption spectra of octupolar molecules
Open this publication in new window or tab >>Aggregation effects on two-photon absorption spectra of octupolar molecules
Show others...
2007 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 2, p. 026101-Article in journal (Refereed) Published
Abstract [en]

Aggregation effects on two-photon absorption cross sections of an octupolar molecule, 1,3,5-triamino-2,4,6-trinitrobenzene, have been examined by means of density functional theory calculations in combination with molecular dynamic simulations. It is shown that this octupolar molecule becomes polar in solution and forms aggregates due to the presence of hydrogen bonding between molecules, which can induce a strong redshift of the charge-transfer state and significantly alter the TPA cross section.

Keywords
Absorption spectra; Agglomeration; Charge transfer; Computer simulation; Density functional theory; Hydrogen bonds; Molecular dynamics; Photons; Cross sections; Octupolar molecules; Redshift; Nitrogen compounds
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-7956 (URN)10.1063/1.2751190 (DOI)000248020000038 ()2-s2.0-34547152716 (Scopus ID)
Note
QC 20100820Available from: 2008-02-05 Created: 2008-02-05 Last updated: 2017-12-14Bibliographically approved
9. Aggregation-enhanced luminescence and vibronic coupling of silole molecules from first principles
Open this publication in new window or tab >>Aggregation-enhanced luminescence and vibronic coupling of silole molecules from first principles
Show others...
2006 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 73, no 20, p. 205409-Article in journal (Refereed) Published
Abstract [en]

Aggregate formation in molecular solids usually quenches the luminescence, a piece of bad news for molecular electronic devices. However, siloles present extremely high luminescent efficiency in solid state as well as in aggregation, but have almost no luminescence in solution. By employing a first-principles calculation to study excited states and vibronic couplings, we find that it is the low-frequency twisting motions of side rings which enhance the nonradiative decay. These motions can be suppressed either by solid-state packing, by aggregation formation in polar solvents, or by increasing the solvent viscosity; thereby, the radiative decay becomes dominant, resulting in peculiar aggregate-induced emission phenomena in siloles.

Keywords
RESTRICTED INTRAMOLECULAR ROTATION; LIGHT-EMITTING-DIODES; THERMAL-STABILITY; INDUCED EMISSION; 2, 3, 4, 5-TETRAPHENYLSILOLES; PHOTOLUMINESCENCE; POLYMERS; STATES
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6978 (URN)10.1103/PhysRevB.73.205409 (DOI)000237950500092 ()2-s2.0-33646570891 (Scopus ID)
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved

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