Differences of proton tautomerism in substituted porphyrins

Kümmerl, L.; Kliesch, H.; Wöhrle, Dieter; Haarer, D.

doi:10.1016/0009-2614(94)00830-2

Cited by 18 publications

(7 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar values have been reported for Chl* in glassy ( T m = 50 K) or crystalline benzophenone host ( T m = 30−45 K) . The Pc 3 Nc* ( T m = 115−117 K) is slightly less stable than the broad holes burned in the parent phthalocyanine and its substituted derivatives in PMMA matrix ( T m = 124−126 K) . The deuterated Pc 3 Nc* is as stable thermally as the spectral holes burned in the S 1 band of meso -tetrapropylporphine in PMMA matrix ( T m = 152 K) …”

Section: Resultssupporting

confidence: 78%

“…The Pc 3 Nc* ( T m = 115−117 K) is slightly less stable than the broad holes burned in the parent phthalocyanine and its substituted derivatives in PMMA matrix ( T m = 124−126 K) . The deuterated Pc 3 Nc* is as stable thermally as the spectral holes burned in the S 1 band of meso -tetrapropylporphine in PMMA matrix ( T m = 152 K) 4 Thermal Decay of the Photoaccumulated Product: The Half-Decay Temperature ( T m ) and FWHM (Δ T ) of the Gaussian Barrier Distribution Function a pigmentmatrix b T m (K)Δ T (K) Pc 3 NcPEld11727 PVB11530 Pc 3 Nc−D 2 PVB15356 chlorinPVB5128 chlorin−D 2 PVB6147 a FWHM, full-width at half-maximum.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Phthalonaphthalocyanines: New Far-Red Dyes for Spectral Hole Burning

Renge¹,

Wolleb²,

Spahni³

et al. 1997

J. Phys. Chem. A

View full text Add to dashboard Cite

Mixed phthalocyanines carrying one anthracene (Pc3An) or substituted naphthalene nucleus (Pc3NcR2, R = H, OCH3, or SC12H25) are proposed as low-temperature photochroms for spectral hole burning. Solubility of these compounds in polymers was greatly enhanced by introducing the 2,4-dimethyl-3-pentoxy substituent to the remaining three benzopyrrolic fragments. The wavelengths and intensities of the Q transitions (S1 and S2) were measured for two prototropic tautomers having different position of the pair of inner protons. The average energy of the two lowest transitions is very similar in both tautomers, although the S1−S2 splitting is much smaller in the less stable form. The relative equilibrium concentration of the tautomers at room temperature depends on the electron releasing properties of the substituents. This allows one to predict the positions of protons in each form. Absorption dichroism of stretched polyethylene films was used in order to establish the direction of the S1 and S2 transition dipole moments in the molecular framework. The tautomers can be completely converted into each other at 10 K by light with quantum yields of (1−2) × 10-3 and (5−8) × 10-3, respectively, depending on the direction of the process. Most probably the phototransformation occurs in the vibrationally relaxed triplet state via the tunneling of a single proton which results in an intermediate state with cis-configuration of protons. The photochemically accumulated less stable form decays at higher temperatures (T) as a result of a thermally activated tunneling process at characteristic T of 115 and 153 K for protonated and deuterated Pc3Nc, respectively. The strength of linear electron−photon coupling (EPC), which is crucial from the point of view of spectral hole burning, is characterized by Debye−Waller factors (DWFs) about 0.6−0.75, depending on the compound and the polymer matrix. The T dependence of quasihomogeneous hole width (Γqh) obeys a power law with coefficients 2.5 ± 0.5 (between 6 and 30−45 K). In different polymer hosts, the DWF increases and the hole width decreases in the following order: polystyrene > poly(vinyl butyral) > polyethylene. The strength of EPC for the lowest transitions is similar in both tautomeric forms. A slight enhancement of the EPC strength in the series of dyes Pc3Nc(OCH3)2 ∼ Pc3Nc < Pc3Nc(SC12H25)2 < Pc3An is correlated with the increase of electron-withdrawing power of substituents, plausibly, as a result of the increase of dipole moment change upon electronic excitation. Spectroscopic properties, phototautomerization quantum yields, and the EPC strength of mixed phthalocyanines were compared with those of chlorin and porphyrins.

show abstract

Section: Resultssupporting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Phthalonaphthalocyanines: New Far-Red Dyes for Spectral Hole Burning

Renge¹,

Wolleb²,

Spahni³

et al. 1997

J. Phys. Chem. A

View full text Add to dashboard Cite

show abstract

“…The IP monomer and oligomers have one hydrogen atom inside each of the isoporphyrin rings. Hydrogen migration that has been studied extensively in free-base porphyrinoids using experimental and theoretical methods [75][76][77][78][79][80][81][82][83][84][85][86] is likely to occur in free-base isoporphyrin as well. Therefore, we consider only one constitutional isomer of the free-base isoporphyrin oligomers in this work.…”

Section: Molecular Structures and Nomenclaturementioning

confidence: 99%

Calculations of current densities and aromatic pathways in cyclic porphyrin and isoporphyrin arrays

Franzke

Sundholm

Weigend

2017

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Magnetically induced current density susceptibilities have been studied for a number of cyclic ethyne- and butadiyne-bridged porphyrin and isoporphyrin arrays. The current density susceptibilities have been calculated using the gauge-including magnetically induced current (GIMIC) method, which is interfaced to the TURBOMOLE quantum chemistry code. Aromatic properties and current pathways have been analyzed and discussed by numerical integration of the current density susceptibilities passing selected chemical bonds yielding current strength susceptibilities. Despite the interrupted π-framework, zinc(ii) isoporphyrin sustains a ring current of ca. 10 nA T. Porphyrin and isoporphyrin dimers sustain a significant current strength at the linker, whereas the larger porphyrinoid arrays sustain mainly local ring currents. Isoporphyrin dimers with saturated meso carbons have strong net diatropic ring-current strengths of 20 nA T fulfilling Hückels aromaticity rule. Porphyrin trimers and tetramers exhibit almost no current strength at the linker. The porphyrin moieties maintain their strong net diatropic ring current.

show abstract

“…The backward reaction of hole burning processes or large changes of microscopic environments of the dye molecules can induce the hole filling phenomenon. Because the thermally induced hydrogen tautomerization of TPP does not occur below PERSISTENT SPECTRAL HOLE BURNING STUDY 100 K, 12 the decrease in hole area below 100 K in the present study reflects large changes of microscopic environments caused by some relaxation of matrix polymers. In addition, two free-base porphyrins, which have quite different substituents (namely, TPP and protoporphyrin IX), have shown quite similar excursion-temperature dependence of hole broadening.…”

Section: Resultsmentioning

confidence: 91%