Nucleobase Recognition by Artificial Receptors Possessing a Ferrocene Skeleton as a Novel Modular Unit for Hydrogen Bonding and Stacking Interactions

Synthetic strategies have been devised that allow the rational design and isolation of highly coloured boron dipyrromethene (BODIPY) dyes that absorb across much of the visible region. Each dye has an aryl polycycle (usually pyrene or perylene) connected to the central BODIPY core through a conjugated tether at the 3,5-positions. Both mono- and difunctionalised derivatives are accessible, in certain cases containing both pyrene and perylene residues. For all new compounds, the photophysical properties have been recorded in solution at ambient temperature and in a glassy matrix at 77 K. The presence of the aryl polycycle(s) affects the absorption and emission maxima of the BODIPY nucleus, thereby confirming that these units are coupled electronically. Indeed, the band maxima and oscillator strengths depend on the conjugation length of the entire molecule, whereas there is no sign of fluorescence from the polycycle. As a consequence, the radiative rate constant tends to increase with each added appendage. The nature of the linkage (styryl, ethenyl, or ethynyl) also exerts an effect on the photophysical properties and, in particular, the absorption spectrum is perturbed in the region of the aryl polycycle. The perylene-containing BODIPY derivatives absorb over a wide spectral range and emit in the far-red region in almost quantitative yield. A notable exception to this generic behaviour is provided by the anthracenyl derivative, which exhibits charge-transfer absorption and emission spectra in weakly polar media at ambient temperature. Regular BODIPY-like behaviour is restored in a glassy matrix at 77 K. Overall, these new dyes represent an important addition to the range of strongly absorbing and emitting reagents that could be used as solar concentrators.

Section: Resultsmentioning

confidence: 99%

Quasi‐One‐Dimensional Electronic Systems Formed from Boron Dipyrromethene (BODIPY) Dyes

Ziessel

Rihn

Harriman

2010

“…Synthesis of the alkynylpyrenes: Most alkynylpyrenes (pyrene À CC À R), where R is pyridyl, [15] bipyridyl, [15] terpyridyl, [15] quinolyl, [16] thienyl, [17] ferrocenyl, [18] or some other group, [19][20][21] have been synthesized by Sonogashira coupling reactions.…”

Section: Resultsmentioning

confidence: 99%

“…Tetrakis(tertbutylethynyl)pyrene 6 and (arylethynyl)pyrenes 7-9 were synthesized in a similar manner by using the corresponding acetylene derivatives. Unsymmetrical dialkynylpyrene 10, designed as a water-soluble alkynylpyrene, was prepared in a stepwise manner via monosubstituted 20 starting from 1,6-diiodopyrene (18) and the hydrophilic acetylene 19. Alkynylpyrenes 11-13 for biomolecular probes were each prepared from 1-bromopyrene (14).…”

Section: Resultsmentioning

confidence: 99%

Alkynylpyrenes as Improved Pyrene‐Based Biomolecular Probes with the Advantages of High Fluorescence Quantum Yields and Long Absorption/Emission Wavelengths

Maeda

Mizuno

et al. 2006

Self Cite

227

144

The photochemical properties of various alkynylpyrene derivatives have been investigated in detail with a view to developing a new class of pyrene-based biomolecular probes. The absorption maxima of the alkynylpyrenes were seen to be shifted to longer wavelengths compared with those of the unsubstituted parent pyrene. Fluorescence quantum yields of the alkynylpyrenes dramatically increased up to 0.99 in ethanol, and only slight quenching of the fluorescence occurred even under aerated conditions. The alkynylpyrenes have been successfully introduced into representative biomolecules such as peptides, proteins, and DNAs. The detectabilities of the labeled biomolecules were significantly improved, with the unique photochemical characteristics of the pyrene nucleus being maintained.

“…This pstacking also obtains in solution. [14,15] Aromatic p-p stacking occurs at distances of 3.30 to 3.50 . [16] This distance span is slightly greater than the interplanar Cp-Cp separation (3.298 ), nonetheless, p-p stacking of 1,1'-diaryl ferrocenes is almost universally observed.…”

Section: Resultsmentioning

confidence: 99%

Protonmotive Force: Development of Electrostatic Drivers for Synthetic Molecular Motors

Crowley

Steele

Bosnich

2006

Ferrocene has been investigated as a platform for developing protonmotive electrostatic drivers for molecular motors. When two 3-pyridine groups are substituted to the (rapidly rotating) cyclopentadienyl (Cp) rings of ferrocene, one on each Cp, it is shown that the (Cp) eclipsed, pi-stacked rotameric conformation is preferred both in solution and in the solid state. Upon quaternization of both of the pyridines substituents, either by protonation or by alkylation, it is shown that the preferred rotameric conformation is one where the pyridinium groups are rotated away from the fully pi-stacked conformation. Electrostatic calculations indicate that the rotation is caused by the electrostatic repulsion between the charges. Consistently, when the pi-stacking energy is increased pi-stacked population increases, and conversely when the electrostatic repulsion is increased pi-stacked population is decreased. This work serves to provide an approximate estimate of the amount of torque that the electrostatically driven ferrocene platform can generate when incorporated into a molecular motor. The overall conclusion is that the electrostatic interaction energy between dicationic ferrocene dipyridyl systems is similar to the pi-stacking interaction energy and, consequently, at least tricationic systems are required to fully uncouple the pi-stacked pyridine substituents.