&lt;title&gt;Dynamics of self-organized porphyrin aggregates&lt;/title&gt;

Zenkevich, É. I.; Шульга, А. М.; Chernook, A. V.; Rempel, U.; Borczyskowski, Christian von

doi:10.1117/12.197430

Cited by 7 publications

(12 citation statements)

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“…In these aggregates Zn-porphyrin or Zn-chlorin dimers are coordinated at two points (i.e. both the Zn ions in the dimer subunits are coordinated simultaneously by the same free base) by the nitrogen atoms of two pyridyl substituents of tetrapyrrolic molecules [23][24][25]. Phenyl-bridged chemical dimers of Zn-porphyrins have been shown to facilitate the complex formation (complexation constants up to 5 × 10 7 M-~).…”

Section: Introductionmentioning

confidence: 99%

“…Recently we have applied a key-hole mechanism which is based on a modification of the abovementioned coordination method [22] and provides high complexation constants (= 107 M -l) for the construction of self-organized heterogeneous trimeric porphyrin assemblies [23][24][25]. In these aggregates Zn-porphyrin or Zn-chlorin dimers are coordinated at two points (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Formation and optical properties of self-organized pentameric porphyrin arrays

Chernook

Rempel

Borczyskowski

et al. 1996

Chemical Physics Letters

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Principles of formation, electronic absorption and fluorescence spectra are reported for self-organized pentameric arrays of tetrapyrrolic macrocycles. In these arrays two molecules of Zn-porphyrin dimers, Zn(II)l,4-bis [5-(10,15,20+tri-p-hexylphenylporphyrinyl)]-benzene ((ZnHTPP) 2) are bound via one molecule of a tetrapyridyl-substituted free base of porphyrin or tetrahydroporphyrin. The process of self-assembly is based on the twofold coordination of the central Zn ions !n the dimer with the nitrogen atoms of the pyridyl rings in the free base which is strong enough to make the complexes stable at room temperature. The formation of the complexes can be followed by changes in the absorption bands of (ZnHTPP) 2 characteristic of an axial extra-ligation of Zn-porphyrins with pyridine or pyridyl-substituted compounds. The spectral behavior of the free bases in the pentads is determined by a non-planar distortion of their macrocycle caused by the two-point binding with the dimers. The fluorescence intensity of the Zn-porphyrin dimer decreases essentially upon complexation with the tetrapyridyl-substituted free bases. This quenching effect is assigned to a singlet-silaglet energy transfer from the complexed Zn-porphyrin dimers to the free base subunit in the pentad.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Formation and optical properties of self-organized pentameric porphyrin arrays

Chernook

Rempel

Borczyskowski

et al. 1996

Chemical Physics Letters

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“…Chemical structures of the components used to form the arrays are given in [9, lo]. Synthesis, purification and identification of all monomeric and dimeric compounds as well as the procedure of calculation of thermodynamic parameters of the complexes (complexation constants, activation energy) will be published elsewhere [9,10]. All measurements were performed for the methylcyclohexane solutions (concentration ranged from 5.10m7 to 8 1 0e6 M) in the temperature range from 140 K to 360 K. When necessary small amounts (~10 % by volume) of dichloromethane were added to the stock solutions to dissolve some ligands.…”

Section: Methodsmentioning

confidence: 99%

“…Fluorescence lifetimes and time-resolved spectra were measured using photon-counting spectrofluorometer PRA 3000 and a laser fluorescent picosecond setup (the response time is down to 30 ps) [9].…”

Section: Methodsmentioning

confidence: 99%

“…Recently we have described some photophysical and thermodynamic properties of trimeric and pentameric porphyrin and chlorin complexes [9]. In order to interpret in details the photophysics of such systems it is necessary to analyze their spectral parameters taking into account a possible geometry of the systems and to compare experimental data with theoretical calculations using nowadays approaches.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopy of interchromophoric interactions in self-organized porphyrin and chlorin complexes

Borczyskowski¹,

Rempel²,

Zenkevich³

et al. 1995

Journal of Molecular Structure

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Spectral-luminescentproperties of multimolecular complexes (triads and pentads, complexation constants range from 5.106 to 5.107 M") formed by two-fold coordination of dipyridyl and tetra-pyridyl substituted porphyrin or related molecules with Zn-porphyrin and Zn-chlorin dimers having various spacers between macrocycles (-CH2-CHz-or phenyl ring) have been studied in methylcyclohexane solutions in a temperature range from 140 to 360 K. The red shift of Zn-dimer electronic Q-and B-bands (AK550 cm-') upon complexation with pyridyl containing ligands is explained in terms of extra-ligation which influences the relative position for HOMO's al, and azu according to the four-orbital model. The splitting of Zndimer B-bands (AE2600 cm-') as well as the significant transformation of these bands in trimeric and pentameric complexes (redistribution of the absorption band intensities in Soret region and appearance of complicated splitted spectral manifolds A&1900 cm-') is connected with excitonic interactions of strong B-transitions of n-conjugated macrocycles included in the complex. Observed experimental splittings are compared with theoretical values calculated using the point dipole approximation and a computer-simulated geometry of the complexes under investigation. It has been observed that mutual influence of rc-electronic macrocycles in the complexes leads to the red shift of porphyrin extra-ligand free base Qbands (A~120 cm-') and is accompanied by quenching a fluorescence of certain components.

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Formation Principles and Ligand Dynamics of Nanoassemblies of CdSe Quantum Dots and Functionalised Dye Molecules

et al. 2011

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Functional dye molecules, such as porphyrins, attached to CdSe quantum dots (QDs) through anchoring meso-pyridyl substituents, form quasi-stable nanoassemblies. This fact results in photoluminescence (PL) quenching of the QDs both due to Förster resonance energy transfer (FRET) and the formation of non-radiative surface states under conditions of quantum confinement (non-FRET). The formation process is in competition with the ligand dynamics. At least two timescales are found for the formation of the assemblies: 1) one faster than 60 s attributed to saturation of empty attachment sites and 2) one slower than 600 s, which is attributed to a reorganisation of the tri-n-octylphosphine oxide (TOPO) ligand shell. Finally, this process results in almost complete exchange of the TOPO shell by porphyrin dye molecules. Following a Stern-Volmer analysis, we established a microscopic description of PL quenching and assembly formation. Based on this formalism, we determined the equilibrium constant for assembly formation between QDs and the pyridyl-functionalised dye molecules to be K ≈ 10(5) - 10(7) M(-1), which is several orders of magnitude larger than that of the TOPO ligands. Our results give additional insights into the non-FRET PL quenching processes involved and show that the QD surface is inhomogeneous with respect to the involved attachment and detachment processes. In comparison with other methods, such as NMR spectroscopy, the advantage of our approach is that ligand dynamics can be investigated at extremely low ratios of dye molecules to QDs.

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<title>Dynamics of self-organized porphyrin aggregates</title>

Cited by 7 publications

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Formation and optical properties of self-organized pentameric porphyrin arrays

Formation and optical properties of self-organized pentameric porphyrin arrays

Spectroscopy of interchromophoric interactions in self-organized porphyrin and chlorin complexes

Formation Principles and Ligand Dynamics of Nanoassemblies of CdSe Quantum Dots and Functionalised Dye Molecules

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