Noncovalent interactions in acid–porphyrin complexes

Webb, Matthew J.; Bampos, Nick

doi:10.1039/c2sc20271a

Cited by 34 publications

(25 citation statements)

References 134 publications

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“…1) undergoes protonation at one or both of the pyrrole nitrogen atoms, which results in formation of either a monocation or dication, respectively [6][7][8][9][10][11][12][13][14][15][16][17][18]. Although the existence of the mono-protonated cation was reported elsewhere, the diprotonated porphyrin form was practically the only stable product found in acidic media [9][10][11][12][13][14][15][16][17]. The dication, H 4 Por 2?…”

Section: Introductionmentioning

confidence: 88%

“…Hence, the pK a or pK b quantities reported elsewhere are occasionally referred to as ''relative acidity constant'' [9] and/or ''apparent pK a '' [10]. With this in mind, we have demonstrated a simple alternative approach to assess the porphyrin's susceptibility to form a diprotonated chromophore system (bis-TFA adduct), based on direct correlation analysis applied to raw experimental data.…”

Section: Coomentioning

confidence: 99%

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meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

et al. 2015

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Susceptibility to interact with trifluoroacetic acid (TFA) of selected freebase porphyrins, including a novel lipophilic 3-n-pentadecyl(phenoxy)-ethoxyphenyl-substituted porphyrin, and photostability of their diprotonated compounds was explored in benzene and N,N-dimethylformamide (DMF). Results have been discussed in terms of the commonly applied pK a -based procedure and confronted with a simple approach derived from experimentally-determined correlations reflecting the porphyrins affinity for TFA. Density functional theory (DFT) has proved the porphyrin moiety creates stable diprotonated species involving two TFA molecules, in which the fluorine atoms effectively contribute to the overall interaction of the acid with the porphyrin macrocycle. The relevance of the mesosubstituent and ambient medium to the reactivity and photostability of diverse porphyrin derivatives was emphasized and referred to structural features of the investigated diprotonated porphyrins.

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Section: Introductionmentioning

confidence: 88%

Section: Coomentioning

confidence: 99%

meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

et al. 2015

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“…Webb and Bampos investigated the dynamics and the complexation behavior of porphyrin diacids in solution and offered insight into the mechanisms of both porphyrin protonation and acid-accelerated metallation. [93] They also showed the effects of varying both the acid and the porphyrin on proton transfer and anion recognition and put an emphasis on the role of macrocyclic conformational control in intramolecular proton transfer.Inaddition, the effects of saddling, meso-phenyl twisting,a nd different hydrogen-bonded counterions on the optical properties of [H 4 TPP 2+ ][X À ] 2 (where X À = F À ,C l À ,B r À ,I À )w ere elaborated theoretically via density functional theory (DFT) and time-dependent density functional theory (TDDFT) by Rosa and co-workers. [94] Next to this fundamental research, ab road landscape of applications emphasizing the H-bonding and anion-binding properties of porphyrin dications exists:T he diprotonated form of octaalkylporphyrin 59 acted as ab romide-selective sensor in the system 59-Et 4 NBr-HClO 4 -CH 3 CN ( Figure 16).…”

Section: Porphyrin (Di)cationsmentioning

confidence: 99%

Molecular Engineering of Free‐Base Porphyrins as Ligands—The N−H⋅⋅⋅X Binding Motif in Tetrapyrroles

Kielmann

Senge

2018

Angew Chem Int Ed

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The core N-H units of planar porphyrins are often inaccessible to forming hydrogen-bonding complexes with acceptor molecules. This is due to the fact that the amine moieties are "shielded" by the macrocyclic system, impeding the formation of intermolecular H-bonds. However, methods exist to modulate the tetrapyrrole conformations and to reshape the vector of N-H orientation outwards, thus increasing their availability and reactivity. Strategies include the use of porpho(di)methenes and phlorins (calixphyrins), as well as saddle-distorted porphyrins. The former form cavities due to interruption of the aromatic system. The latter are highly basic systems and capable of binding anions and neutral molecules via N-H⋅⋅⋅X-type H-bonds. This Review discusses the role of porphyrin(oid) ligands in various coordination-type complexes, means to access the core for hydrogen bonding, the concept of conformational control, and emerging applications, such as organocatalysis and sensors.

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“…For example, the first reductionp otential of tetraphenylporphyrin (H 2 TPP) shifts from À1.19 V( vs. SCE) to À0.44 Vu pon formationo ft he diprotonated form (H 4 TPP 2 + )i nC H 2 Cl 2 . [37][38][39][40][41][42][43][44][45] Actually,i na protics olvents such as benzonitrile, protonation of saddle-distorted dodecaphenylporphyrin (H 2 DPP) proceeds easily in one step to give ad iprotonated species (H 4 DPP 2 + )u sing hydrochloric acid (HCl) and much weaker acids such as carboxylic acids (RCOOH) as proton sources. Thep rotonation affords saddle-distorted diprotonated porphyrins (H 4 P 2 + )u nder strongly acidic conditions as shown in Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics and Photodynamics of a Monoprotonated Porphyrin Directly Stabilized by Hydrogen Bonding with Polar Protic Solvents

Suzuki

Kotani

Ishizuka

et al. 2017

Chemistry A European J

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Addition of 1 equiv of TFA to an acetone solution containing dodecaphenylporphyrin (H DPP) in the presence of 10 % MeOH (v/v) resulted in selective formation of a monoprotonated form (H DPP ), in sharp contrast to protonation of H DPP directly affording a diprotonated form (H DPP ) in acetone in the absence of MeOH. The crucial role of MeOH for selective H DPP formation was interpreted as hydrogen-bonding stabilization of H DPP , since a MeOH molecule was found to form hydrogen bonds with an NH proton of H DPP in the crystal. The selectivity of H DPP formation was evaluated by the formation yield of H DPP , which increased when elevating the portion of MeOH (0-10 %) in acetone with saturation behavior, suggesting that H DPP is stabilized by hydrogen bonding with MeOH even in solution, together with the thermodynamic parameters determined from a van't Hoff plot based on the spectroscopic titration. Femto- and nanosecond laser flash photolysis allowed us to elucidate the photodynamics of H DPP in intermolecular photoinduced electron transfer (ET) from ferrocene derivatives as one-electron donors to the triplet excited state of H DPP as an electron acceptor. The second-order rate constants of the ET reactions were evaluated in light of the Marcus theory of ET. The reorganization energy of ET was determined to be 1.87 eV, which is slightly larger than that of H DPP in acetonitrile (1.69 eV), due to larger structural change upon ET than that of H DPP .

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Noncovalent interactions in acid–porphyrin complexes

Cited by 34 publications

References 134 publications

meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

Molecular Engineering of Free‐Base Porphyrins as Ligands—The N−H⋅⋅⋅X Binding Motif in Tetrapyrroles

Thermodynamics and Photodynamics of a Monoprotonated Porphyrin Directly Stabilized by Hydrogen Bonding with Polar Protic Solvents

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