Dirhodium(II,II)-porphyrin-based multiredox systems were easily prepared by combining the versatile reactivity, both axial and equatorial, of the [Rh2(form)2 (O2CCF3)2(H2O)2] (form = N,N′-di-p-tolylformamidinate) complex and the well-known coordination capability of meso-substituted phenylporphyrins. In this way, redox systems featured by porphyrins axially or equatorially coordinated to the dirhodium subunits were obtained. Electrochemical and luminescence properties of the new assemblies were also investigated. Porphyrin-dirhodium(II,II) multiredox assemblies were synthesized by exploiting both the classical axial and the peculiar equatorial reactivity of the complex [Rh2(form)2 (O2CCF3)2(H2O)2] (1) (form = N,N′-di-p-tolylformamidinate). The species [Rh2(form)2(PCOO)2] (2), featuring two bridged (carboxyphenyl)porphyrins in the equatorial positions, was prepared by metathetical reaction of 1 with the sodium salt of meso-5-(4-carboxyphenyl)-5,10,15-triphenylporphyrin (PCOO). Conversely, redox systems in which porphyrins are axially ligated to dirhodium were obtained by treating 1 with a variety of functionalized meso-pyridylporphyrins. Depending on the number and position of the peripheral pyridyl substituents, assemblies with different nuclearity, both in terms of metal and porphyrin subunits, were isolated. The 1:2 dirhodium/porphyrin adduct, [Rh2(form)2 (O2CCF3)2(PYP)2] (3) was obtained by treatment of 1 with triphenyl(pyridyl)porphyrin (PyP). By combination of 1 with the cis-5,10diphenyl-15,20-dipyridylporphyrin (cis-DPyP) the molecular square box, [Rh2(form)2 (CF3CO2)2(cis-DPyP)]4 (4) was isolated in good yield. The reaction of 1 with 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TPyP) is dependent on the experimental conditions and led to two different products: the grid polymer [{Rh2(form)2 (CF3CO2)2}2(TPyP)]n (5) and the symmetric tetramer [{Rh2(form)2 (CF3CO2)2}4(TPyP)] (6), respectively. All the products were characterized by conventional spectroscopic methods. Proton NMR spectroscopy resulted particularly useful for the characterization of dirhodiumphenyl(pyridyl)porphyrin aggregates. The 2,6-pyridyl proton resonances are highly affected by coordination and experience significantly upfield shifts with respect to the corresponding unbound porphyrin. Systems 2, 3, 4, and 6 underwent many redox processes in the potential window under investigation (+2; -1.4 V), each one of them can be assigned to the specific subunits of the molecular arrays. The emission studies performed on the same aggregates revealed that the porphyrin-based emission was significantly quenched by, most likely, reductive electron transfer from dirhodium subunits to the excited porphyrin chromophores. Such a process appears to be larger in the pyridylporphyrin-dirhodium systems with respect to the (carboxyphenyl)porphyrin ones.

Synthesis and characterization of Dirhodium(II,II)-porphyrin-based multiredox systems

LO SCHIAVO, Sandra;SERRONI, Scolastica;PUNTORIERO, Fausto;TRESOLDI, Giuseppe;PIRAINO, Pasquale
2002-01-01

Abstract

Dirhodium(II,II)-porphyrin-based multiredox systems were easily prepared by combining the versatile reactivity, both axial and equatorial, of the [Rh2(form)2 (O2CCF3)2(H2O)2] (form = N,N′-di-p-tolylformamidinate) complex and the well-known coordination capability of meso-substituted phenylporphyrins. In this way, redox systems featured by porphyrins axially or equatorially coordinated to the dirhodium subunits were obtained. Electrochemical and luminescence properties of the new assemblies were also investigated. Porphyrin-dirhodium(II,II) multiredox assemblies were synthesized by exploiting both the classical axial and the peculiar equatorial reactivity of the complex [Rh2(form)2 (O2CCF3)2(H2O)2] (1) (form = N,N′-di-p-tolylformamidinate). The species [Rh2(form)2(PCOO)2] (2), featuring two bridged (carboxyphenyl)porphyrins in the equatorial positions, was prepared by metathetical reaction of 1 with the sodium salt of meso-5-(4-carboxyphenyl)-5,10,15-triphenylporphyrin (PCOO). Conversely, redox systems in which porphyrins are axially ligated to dirhodium were obtained by treating 1 with a variety of functionalized meso-pyridylporphyrins. Depending on the number and position of the peripheral pyridyl substituents, assemblies with different nuclearity, both in terms of metal and porphyrin subunits, were isolated. The 1:2 dirhodium/porphyrin adduct, [Rh2(form)2 (O2CCF3)2(PYP)2] (3) was obtained by treatment of 1 with triphenyl(pyridyl)porphyrin (PyP). By combination of 1 with the cis-5,10diphenyl-15,20-dipyridylporphyrin (cis-DPyP) the molecular square box, [Rh2(form)2 (CF3CO2)2(cis-DPyP)]4 (4) was isolated in good yield. The reaction of 1 with 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TPyP) is dependent on the experimental conditions and led to two different products: the grid polymer [{Rh2(form)2 (CF3CO2)2}2(TPyP)]n (5) and the symmetric tetramer [{Rh2(form)2 (CF3CO2)2}4(TPyP)] (6), respectively. All the products were characterized by conventional spectroscopic methods. Proton NMR spectroscopy resulted particularly useful for the characterization of dirhodiumphenyl(pyridyl)porphyrin aggregates. The 2,6-pyridyl proton resonances are highly affected by coordination and experience significantly upfield shifts with respect to the corresponding unbound porphyrin. Systems 2, 3, 4, and 6 underwent many redox processes in the potential window under investigation (+2; -1.4 V), each one of them can be assigned to the specific subunits of the molecular arrays. The emission studies performed on the same aggregates revealed that the porphyrin-based emission was significantly quenched by, most likely, reductive electron transfer from dirhodium subunits to the excited porphyrin chromophores. Such a process appears to be larger in the pyridylporphyrin-dirhodium systems with respect to the (carboxyphenyl)porphyrin ones.
2002
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/1597739
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 14
  • ???jsp.display-item.citation.isi??? 13
social impact