Synthesis and Characterization of Novel Pyrene-Dendronized Porphyrins Exhibiting Efficient Fluorescence Resonance Energy Transfer: Optical and Photophysical Properties

Abstract

A novel series of pyrene dendronized porphyrins bearing two and four pyrenyl groups (Py(2)-TMEG1 and Py(4)-TMEG2) were successfully synthesized. First and second generation Fréchet type dendrons (Py(2)-G1OH and Py(4)-G2OH) were prepared from 1-pyrenylbutanol and 3,5-dihydroxybenzyl alcohol. These compounds were further linked to a trimesitylphenylporphyrin containing a butyric acid spacer via an esterification reaction to obtain the desired products. Dendrons and dendronized porphyrins were fully characterized by FTIR and (1)H NMR spectroscopy and their molecular weights were determined by matrix-assisted laser desorption ionization time of flight mass spectrometry. Their optical and photophysical properties were studied by absorption and fluorescence spectroscopies. The formation of dynamic excimers was detected in the pyrene-labeled dendrons, with more excimer being produced in the higher generation dendron. The fluorescence spectra of the pyrene dendronized porphyrins exhibited a significant decrease in the amount of pyrene monomer and excimer emission, jointly with the appearance of a new emission band at 661 nm characteristic of porphyrin emission, an indication that fluorescence resonance energy transfer (FRET) occurred from one of the excited pyrene species to the porphyrin. The FRET efficiency was found to be almost quantitative ranging between 97% and 99% depending on the construct. Model Free analysis of the fluorescence decays acquired with the pyrene monomer, excimer, and porphyrin core established that only residual pyrene excimer formation in the dendrons could occur before FRET from the excited pyrene monomer to the ground-state porphyrin core.

Synthesis, characterization and photophysical studies of novel pyrene labeled ruthenium (II) trisbipyridine complex cored dendrimers

“…[38] The synthesis of the compounds 2 and 3 was previously reported by our research group. [35] All other reagents were purchased and used as received. Synthetic procedures were carried out in dry solvents under argon atmosphere unless otherwise specified.…”

“…[33,34] In our research group, we have introduced pyrene at the periphery of dendrimers in order to observe resonance energy transfer to a porphyrine moiety. [35,36] In this work we have introduced a Ru(II) trisbipyridine at the core of our dendrimer. We have studied the photophysical properties of bipyridine-cored dendrons, the efficient energy transfer from pyrene to ruthenium bipyridine complex through antenna effect, as well as the protection from oxygen quenching of the fluorescence emission by the dendritic shell.…”

Materials for FRET Analysis: Beyond Traditional Dye–Dye Combinations

“…This precise structural control has made dendrimers interesting synthetic platforms in which to mimic Nature's light-harvesting structures, reviewed in Ref. [124], and in the development of new photovoltaic materials [125]. Of the many types of dendrimers reported, the poly(amidoamine) (PAMAM)-based materials are the most utilized because the many primary amines enable facile functionalization [122,123].…”

Synthesis, characterization and optical properties of novel oligothiophenes bearing pyrene units attached via well defined oligo(ethylene glycol) spacers

“…We studied the effect of the internal stacking in the optical and photophysical properties [19][20][21][22]. Very recently, we carried out the incorporation of pyrene units into dendritic molecules bearing porphyrin and fullerene moieties in order to study the fluorescence energy transfer phenomenon (FRET) as a function of the distance between the donor (pyrene) and the acceptor group (porphyrin or fullerene) [23][24][25]. We reported also a series of polythiophenes containing pyrene groups attached via alkyl chains.…”