Porphyrin‐Appended Europium(III) Bis(phthalocyaninato) Complexes: Synthesis, Characterization, and Photophysical Properties

Abstract

Mixed cyclization of 3-mono-, 4-mono-, or 4,5-di(porphyrinated) phthalonitrile compounds 2, 3, or 6 and unsubstituted phthalonitrile with the half-sandwich complex [EuIII(acac)(Pc)] (Pc=phthalocyaninate, acac=acetylacetonate) as the template in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in n-pentanol afforded novel porphyrin-appended europium(III) bis(phthalocyaninato) complexes 7-9 in 30-40% yield. These mixed tetrapyrrole triads and tetrad were spectroscopically and electrochemically characterized and their photophysical properties were also investigated with steady-state and transient spectroscopic methods. It has been found that the fluorescence of the porphyrin moiety is quenched effectively by the double-decker unit through an intramolecular photoinduced electron-transfer process, which takes place in several hundred femtoseconds, while the recombination of the charge-separated state occurs in several picoseconds. By using different phthalocyanines containing different numbers of porphyrin substituents at the peripheral or nonperipheral position(s) of the ligand, while the other unsubstituted phthalocyanine remains unchanged in these double-deckers, the effects of the number and the position of the porphyrin substituents on these photophysical processes were also examined.

Historic overview and new developments in synthetic methods for preparation of the rare-earth tetrapyrrolic complexes

“…Such a hypothesis agrees well with the reported UV-vis spectrum of 158 (Figure 19), which has a split Q-band characteristic for the metal-free Pcs. An interesting set of Por-substituted rare-earth double-decker complexes 163-165 was prepared using the synthetic approaches outlined in Scheme 32 [284]. In this case, 4hydroxyphenyl-substituted Pors were introduced in the reaction with nitro-substituted PNs or 4,5-dichlorophthalonitrile to form PN-containing Pors.…”

“…In this case, 4hydroxyphenyl-substituted Pors were introduced in the reaction with nitro-substituted PNs or 4,5-dichlorophthalonitrile to form PN-containing Pors. Further reaction of such PN-containing Pors with unsubstituted PN and europium PcEu(acac) precursor leads to the formation of Porsubstituted europium double-decker complexes 163-165 in 31-40% yields [284]. In a separate study, the rare-earth double-decker Pcs were linked to a fullerene using an esterification reaction 52 between a double-decker hydroxymethyl Pc and a fullerene derivatized with a carboxylic acid functional group to form dyads 166 (Scheme 33) [285].…”

Photochemical Transformations Involving Porphyrins and Phthalocyanines

“…The porphyrin fluorescence was effectively quenched by the double-decker unit through an intramolecular photoinduced electron transfer process. Both the photoinduced electron transfer and recombination of the charge-separated state depended on the number and position of the porphyrin units attached to phthalocyanines (Bian et al 2007). Many systems were prepared and detailed photophysical analyses were carried out for zinc tetrapyrrole systems (Senge and Sergeeva 2006).…”

Perylene diimide-appended mixed (phthalocyaninato)(porphyrinato) europium(III) double-decker complex: Synthesis, spectroscopy and electrochemical properties

“…Covalently linked electron donoreacceptor systems involving sandwich-type bis(porphyrinate) metal unit were first reported in 1996 with a quinine [40,41] or a pyromellitic imide [40] chromophore as the electron-acceptor partner. In 2007, the photophysical properties for a series of porphyrin-appended bis(phthalocyaninato) europium complexes having different number of porphyrin-substituents at the peripheral or non-peripheral position(s) of the phthalocyanine ligand were examined for the first time by this group [42]. A rapid and efficient photoinduced electron-transfer process from the porphyrin unit(s) to [Eu(Pc) 2 ] core was revealed.…”