Singlet and Triplet Excited States and Intersystem Crossing in Free‐Base Porphyrin: TDDFT and DFT/MRCI Study

Perun, Serhiy; Tatchen, Jörg; Marian, Christel M.

doi:10.1002/cphc.200700509

Cited by 121 publications

(132 citation statements)

References 40 publications

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“…It is worth mentioning that the electronic SOC terms computed here may largely increase if vibrational effects are considered, particularly those corresponding to outof-plane modes, as proven by the calculations of Marian and co-workers [40,41] on ISC rates in systems of similar size. The electronic values obtained here are, however, adequate for the present purpose of identifying the regions of the hypersurface simultaneously displaying small singlet-triplet gaps and large SOC terms.…”

mentioning

confidence: 68%

Ultrafast Decay of the Excited Singlet States of Thioxanthone by Internal Conversion and Intersystem Crossing

et al. 2010

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The experimental ultrafast photophysics of thioxanthone in several aprotic organic solvents at room temperature is presented, measured using femtosecond transient absorption together with high‐level ab initio CASPT2 calculations of the singlet‐ and triplet‐state manifolds in the gas phase, including computed state minima and conical intersections, transition energies, oscillator strengths, and spin–orbit coupling terms. The initially populated singlet ππ* state is shown to decay through internal conversion and intersystem crossing processes via intermediate nπ* singlet and triplet states, respectively. Two easily accessible conical intersections explain the favorable internal conversion rates and low fluorescence quantum yields in nonpolar media. The presence of a singlet–triplet crossing near the singlet ππ* minimum and the large spin–orbit coupling terms also rationalize the high intersystem crossing rates. A phenomenological kinetic scheme is proposed that accounts for the decrease in internal conversion and intersystem crossing (i.e. the very large experimental crescendo of the fluorescence quantum yield) with the increase of solvent polarity.

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confidence: 68%

Ultrafast Decay of the Excited Singlet States of Thioxanthone by Internal Conversion and Intersystem Crossing

et al. 2010

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“…[24] An analogous expansion has also been predicted by calculations for Pr in the S 1 and T 1 electronic states. [65] We have optimized the transition-state structure for the ground-state trans-cis conversion in 1. The calculated cistrans energy difference is 3.90 kcal mol À1 (3.55 kcal mol…”

Section: Discussionmentioning

confidence: 99%

Bridging the Gap between Porphyrins and Porphycenes: Substituent‐Position‐Sensitive Tautomerism and Photophysics in meso‐Diphenyloctaethylporphyrins

Gawinkowski¹,

Orzanowska²,

Izdebska³

et al. 2011

Chemistry A European J

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2,3,7,8,12,13,17,18-Octaethyl-5,15-diphenylporphyrin (1) is characterized by an inner cavity with a rectangular shape and small NH⋅⋅⋅N distances. It resembles porphycene, which is a constitutional isomer of porphyrin known for its strong intramolecular hydrogen bonds and rapid tautomerization. Such distortion of the porphyrin cavity leads to tautomeric properties of 1 that are intermediate between those of porphyrin and porphycene. In particular, a tautomerization in the lowest excited singlet state of 1 has been discovered, occurring with a rate three orders of magnitude lower than that in porphycene, but three to four orders of magnitude higher than that in porphyrin. An isomer of 1, 2,3,7,8,12,13,17,18-octaethyl-5,10-diphenylporphyrin (2), exhibits a different kind of geometry distortion. This molecule is nonplanar, but the inner cavity shape and dimensions are similar to those of the parent porphyrin. The same hydrogen-bonding strength as that in porphyrin is observed for 2. In contrast, the nonplanarity of 2 significantly influences the photophysics, leading to a decrease in fluorescence quantum yield and lifetime. Absorption, magnetic circular dichroism, and fluorescence spectra are similar for 1 and 2 and resemble those of parent porphyrin. This is a consequence of comparable energy splittings of the frontier orbitals, ΔHOMO≈ΔLUMO. The results demonstrate that judicious selection of substituents and their position enables a controlled modification of geometry, hydrogen-bonding strength, tautomerization rate, and photophysical and spectral parameters of porphyrinoids.

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“…2.4-fold stronger emission relative to that of NCP-MOF-525, suggesting the N-methylation partially suppressed the nonradiative decay process by the proton-transfer reaction inside the macrocycle ( Figure S10). 13 In summary, novel zirconium-based metalorganic frameworks, NCP-MOF-525 and MeNCP-MOF-525, have been synthesized under the aforementioned reaction conditions using N-confused porphyrin carboxylic acid derivatives. The PXRD pattern analysis with Rietveld refinement proved that the compounds have a face-centered cubic ftw topology.…”

Section: ¹1mentioning

confidence: 99%

Zirconium-based Metal–Organic Frameworks with N-Confused Porphyrins: Synthesis, Structures, and Optical Properties

et al. 2017

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Metalorganic frameworks (MOFs) composed of zirconium (Zr 6 ) and N-confused porphyrins (NCPs) were synthesized. The cubic structures with ftw topology were determined by powder X-ray diffraction and microscopic analyses. These complexes represent high chemical stability toward various pH ranges and NIR absorption/emission derived from the NCP moieties.Keywords: Metal-organic frameworks | Porphyrin analogues | Near-IR propertiesZirconium-based metalorganic frameworks (Zr-MOFs), a class of porous coordination polymers consisting of multinuclear Zr-cluster ions and functional organic molecules, have attracted increasing attention due to their intrinsic chemical and thermal stability.1 These Zr-MOF materials are applicable toward catalysis (driven by light, acids, oxidants, etc.), gas storage/ separation, molecular sensing, drug delivery, etc.Among various organic building blocks for MOFs, porphyrin compounds have been extensively utilized due to their large π-conjugated backbone that can provide unique π-space and functionality for various applications. With their inherent large absorption coefficients in the visible to near-infrared (NIR) energy regions, 2 use of porphyrin ligands is advantageous for developing potential NIR-responsive materials. In addition, coordination of a large variety of metals in the porphyrinic core leads to the various metal-dependent heterogeneous catalysts.3 Stable MOF materials with efficient NIR light harvesting property have been demanded for photocatalytic systems as well. 4 To achieve the stable and robust porphyrinic MOF materials with specific functions (e.g., catalysts, sensors, etc.), synthesis of porphyrin-containing Zr-MOFs in a topologically pure phase is necessary. However, due to the flexible coordination modes of the high-valent zirconium(IV) clusters and the slow exchange reactions of the Zr IV -cation and carboxylate ligands, the rational synthesis of topology-controlled Zr-MOF remains challenging. Recently, Zhou et al. have reported the synthesis of various porphyrinic Zr-MOFs (e.g., a series of PCN-221225).5 The change in the synthetic conditions like substrate ratio, zirconium salt, temperature, reaction time, or solvent, brought a huge diversity in the resulting MOF topology. 6 The structures of porphyrinic linkers also affected the crystalline topology by changing the dihedral angles of the meso-aryl groups.7 Yaghi et al. have independently reported the synthesis of Zr-MOFs (e.g., MOF-525) with porphyrins under different conditions, resulting in the formation of an ftw-type cubic structure with a 4,12-coordinated Zr 6 cluster. 8 It is quite similar to PCN-221 5a containing 4,12-coordinated Zr 8 blocks. Thus, the topology of porphyrin-based MOFs largely relies on the reaction conditions.In this study, we have synthesized novel "N-confused" porphyrinic MOFs containing the most-substituted ftw topological Zr 6 clusters under the appropriate conditions (Scheme 1). The Zr 6 node (i.e., Zr 6 O 4 (OH) 4 (COO) 12 ) being targeted in this study has the highest connectiv...

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Singlet and Triplet Excited States and Intersystem Crossing in Free‐Base Porphyrin: TDDFT and DFT/MRCI Study

Cited by 121 publications

References 40 publications

Ultrafast Decay of the Excited Singlet States of Thioxanthone by Internal Conversion and Intersystem Crossing

Ultrafast Decay of the Excited Singlet States of Thioxanthone by Internal Conversion and Intersystem Crossing

Bridging the Gap between Porphyrins and Porphycenes: Substituent‐Position‐Sensitive Tautomerism and Photophysics in meso‐Diphenyloctaethylporphyrins

Zirconium-based Metal–Organic Frameworks with N-Confused Porphyrins: Synthesis, Structures, and Optical Properties

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