A Diprotonated Porphyrin as an Electron Mediator in Photoinduced Electron Transfer in Hydrogen-Bonded Supramolecular Assemblies

Abstract

We have successfully constructed hydrogen-bonded supramolecular assemblies based on a diprotonated saddle-distorted porphyrin (H 4 DPP 2+ ) and redox-active molecules bearing a carboxylate group, such as a RuII polypyridyl complex (Ru II COO – ) that can act as an electron donor and a benzyl viologen derivative (BV 2+ COO – ) that can act as an electron acceptor. Formation of supramolecular assemblies of H 4 DPP 2+ with Ru II COO – (H 4 DPP 2+ (Ru II COO – ) 2 and H 4 DPP 2+ (Ru II COO – )­(Cl – )) and BV 2+ COO – (H 4 DPP 2+ (BV 2+ COO – ) 2 ) was confirmed in acetone by 1H NMR measurements, CSI-TOF-MS, and X-ray crystallographic analysis. The photodynamics of H 4 DPP 2+ (Ru II COO – ) 2 and H 4 DPP 2+ (BV 2+ COO – ) 2 was elucidated by femto-, pico-, and nanosecond time-resolved transient absorption spectroscopy. In H 4 DPP 2+ (Ru II COO – ) 2 , intrasupramolecular photoinduced electron transfer (ET) occurred from the RuII center to the singlet excited state of H 4 DPP 2+ to afford an ET state involving one-electron-reduced H 4 DPP •+ and the corresponding one-electron-oxidized RuIII complex with the lifetime of 150 ps. On the other hand, in the presence of an external electron donor, intermolecular photoinduced ET occurred from an electron donor to the triplet excited state of H 4 DPP 2+ (BV 2+ COO – ) 2 to afford H 4 DPP •+ , following intrasupramolecular thermal ET proceeded from H 4 DPP •+ to BV 2+ COO – to form H 4 DPP 2+ (BV •+ COO – )­(BV 2+ COO – ) with the lifetime of 1.1 ms. Thus, H 4 DPP 2+ can act as an electron mediator in hydrogen-bonded supramolecular assemblies. This is the first example of porphyrins as a photosensitizer and an electron mediator in hydrogen-bonded ET systems.

Panchromatic light funneling through the synergy in hexabenzocoronene–(metallo)porphyrin–fullerene assemblies to realize the separation of charges

“…Such an inactive participation seems reasonable, considering that the involvement of either C 60 -or porphyrin centered triplet excited states in charge recombination processes depends on their energy relative to the charge separated state. [67][68][69] Similar to Fig. 12, a global t of the transient absorption data of 2-Zn$3 in chlorobenzene yields good results using ve species (ESI, Fig.…”

Nonplanar porphyrins: synthesis, properties, and unique functionalities

“…53). 321 The photodynamics of photoinduced ET was elucidated using femto-second laser flash photolysis in acetone upon photoexcitation at 500 nm. )(BV + COO À )(BV 2+ COO À ) with the lifetime of 1.1 ms (Fig.…”

“…53). 321 The photodynamics of photoinduced ET was elucidated using femto-second laser flash photolysis in acetone upon photoexcitation at 500 nm. The energy diagram of the photoinduced ET in [H 4 72 2+ ][ Ru II COO − ] 2 is shown in Fig.…”

“…On the other hand, a viologen derivative having a carboxy group, 4-(benzyl)-4′-(4-carboxyphenyl)-bipyridine ( BV 2+ COOH ; 240 ) has been applied to form a supramolecular assembly, [H 4 72 2+ ][ BV 2+ COO − ] 2 . 321 Upon photoexcitation at 532 nm in the presence of Me 10 Fc as an electron donor, intermolecular photoinduced ET occurred from Me 10 Fc to the triplet excited state of [H 4 72 ] 2+ in [H 4 72 2+ ][ BV 2+ COO − ] 2 ( 3 [(H 4 72 2+ )( BV 2+ COO − ) 2 ]*) to afford (H 4 72 ˙ + )( BV 2+ COO − ) 2 . Subsequent intrasupramolecular thermal ET proceeded from H 4 72 ˙ + to BV 2+ COO − to form (H 4 72 2+ )( BV ˙ + COO − )( BV 2+ COO − ) with the lifetime of 1.1 ms (Fig.…”

Tandem C–S Coupling and Debrominative Cyclization Enables an Easy Access to β-Thiazole-Fused Porphyrins

“…The π-electronic organization in these conjugated-tetrapyrrolic macrocycles can be modulated by introducing π-spacers , and chromophores − at the porphyrin periphery. In the past several decades, the peripheral functionalization of porphyrins led to the generation of diverse β- / meso -substituted, β- / meso -fused, and β, meso -fused porphyrin systems with significance in a vast realm of biological and material applications. − Additionally, these macrocycles have potential applications in diverse areas such as dye-sensitized solar cells (DSSC), photodynamic therapy (PDT), , nonlinear optical devices, sensing, catalysis, , and supramolecular assemblies. , In recent years, the interest of researchers is inclined toward the construction of β-fused porphyrins which led to a high degree of perturbation in the π-electronic cloud of the porphyrin macrocycle. In this context, a variety of porphyrin analogues decorated with five- and six-membered heterocycles have been synthesized. − Some of these β-heterocycle-fused porphyrin architectures such as the β-triazole-fused porphyrins proved to be important building blocks in the construction of porphyrin oligomers with improved electronics .…”