Search results for "Fluid solution"
showing 5 items of 5 documents
Counterion-Mediated Crossing of the Cyanine Limit in Crystals and Fluid Solution: Bond Length Alternation and Spectral Broadening Unveiled by Quantum…
2020
Absorption spectra of cyanine⊕·Br⊖ salts show a remarkable solvent dependence in non/polar solvents, exhibiting narrow, sharp band shapes in dichloromethane but broad features in toluene; this chan...
Autonomous artificial nanomotor powered by sunlight
2006
Light excitation powers the reversible shuttling movement of the ring component of a rotaxane between two stations located at a 1.3-nm distance on its dumbbell-shaped component. The photoinduced shuttling movement, which occurs in solution, is based on a “four-stroke” synchronized sequence of electronic and nuclear processes. At room temperature the deactivation time of the high-energy charge-transfer state obtained by light excitation is ≈10 μs, and the time period required for the ring-displacement process is on the order of 100 μs. The rotaxane behaves as an autonomous linear motor and operates with a quantum efficiency up to ≈12%. The investigated system is a unique example of an artif…
Inverted energy gap law for the nonradiative decay in fluorescent floppy molecules: larger fluorescence quantum yields for smaller energy gaps
2019
A data survey on experimental fluorescence quantum yields of (multi)substituted dicyano-distyrylbenzenes in fluid solution evidences that non-radiative decay increases with the Franck-Condon energy (E-FC), being opposite to the conventional energy gap law. Quantum-chemistry indicates that this is controlled by access to the conical intersection (CI) following the Bell-Evans-Polanyi principle as a first-step approximation for this family of molecules; the variations in E-FC among the different compounds are found to be decisive, while those of E-CI are estimated to be weaker or even enhancing the effect. The current findings may have significant consequences for the design of molecules for o…
Two-Photon Transitions in CW-ENDOR Spectra of Radicals in Fluid Solution
2002
The radical anion of duroquinone (2,3,5,6-tetramethyl-1,4-benzoquinone) was used as a model compound to describe the low-frequency (LF) ENDOR lines observed in many radical systems. These LF lines ...
Origin of the temperature dependence of the rate of singlet energy transfer in a three-component truxene-bridged dyads
2014
We report a truxene-based dyad built upon one donor (tri-meso-phenylzinc(II)porphyrin) and two acceptors (octa-β-alkylporphyrin free base) in which the donor exhibits free rotation around a Ctruxene-Cmeso single bond at 298 K in fluid solution but not at 77 K in a glass matrix, whereas the acceptors have very limited motion as they are blocked by β-methyl groups. This case is interesting because all the structural and spectroscopic parameters affecting the rate for singlet energy transfer according to a Förster Resonance Energy Transfer are only weakly temperature dependent, leaving only the Dexter mechanism explaining the larger variation in rate of energy transfers with the temperature h…