Spectroscopic Demonstration of Exciton Dynamics and Excimer Formation in a Sterically Controlled Perylene Bisimide Dimer Aggregate

Although it is commonly known that H-type PBI aggregates give rise to a broad, red-shifted excimer fluorescence with considerably longer fluorescence lifetimes than observed for the monomers, the underlying mechanisms of excimer formation and other relevant exciton dynamics in such π-stacked systems are still far from being understood. In this context, we demonstrate a thorough spectroscopic investigation on the exciton relaxation pathways, including excimer formation, in a perylene-3,4:9,10-bis­(dicarboximide) (PBI) dimer aggregate <b>1</b> by using time-resolved fluorescence and transient absorption spectroscopy combined with excitation-power and polarization dependence. It was found that the excited dimer formation process followed by structural rearrangement is approximately two times faster than observed within larger PBI aggregates. Excitation-power-dependent transient absorption decay profiles revealed the fully delocalized nature of excitons in the dimer as opposed to larger stacks

Excited-State Vibrational Coherence in Perylene Bisimide Probed by Femtosecond Broadband Pump–Probe Spectroscopy

Broadband laser pulses with ultrashort duration are capable of triggering impulsive excitation of the superposition of vibrational eigenstates, giving rise to quantum beating signals originating from coherent wave packet motions along the potential energy surface. In this work, coherent vibrational wave packet dynamics of an <i>N</i>,<i>N</i>′-bis­(2,6-dimethylphenyl)­perylene bisimide (<b>DMP-PBI</b>) were investigated by femtosecond broadband pump–probe spectroscopy which features fast and balanced data acquisition with a wide spectral coverage of >200 nm. Clear modulations were observed in the envelope of the stimulated emission decay profiles of <b>DMP-PBI</b> with the oscillation frequencies of 140 and 275 cm^–1. Fast Fourier transform analysis of each oscillatory mode revealed characteristic phase jumps near the maxima of the steady-state fluorescence, indicating that the observed vibrational coherence originates from an excited-state wave packet motion. Quantum calculations of the normal modes at the low-frequency region suggest that low-frequency C–C (CC) stretching motions accompanied by deformation of the dimethylphenyl substituents are responsible for the manifestation of such coherent wave packet dynamics

Synthesis of Highly Twisted and Fully π‑Conjugated Porphyrinic Oligomers

Highly twisted π-conjugated molecules have been attractive but challenging targets. We report here an efficient synthesis of highly twisted diporphyrins with 126° and 136° twist angles that involves an oxidative fusion reaction of planar aminoporphyrin precursors at room temperature. Repeated amination–oxidative fusion sequences provide a unidirectionally twisted tetramer. The twisting angle of the tetramer is 298°

Additional file 1 of TLR7 activation by miR-21 promotes renal fibrosis by activating the pro-inflammatory signaling pathway in tubule epithelial cells

Additional file 1: Supplementary Table 1. Information of Antibodiesused in Western blotting. SupplementaryTable 2. Primer sequences for qPC

Nino otomi de frente, 2451

IIS-UNA