Solvent and temperature effects on the decay dynamics of [p-N,N-(dialkylamino)benzylidene]malononitriles

Safarzadeh–Amiri, Ali

doi:10.1016/0009-2614(86)80201-9

Cited by 20 publications

(22 citation statements)

References 23 publications

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“…Hence, we only show the timedependent fractional occupations of the S 0 and S 1 states in Figure 3. The results are rather stable toward the selection of the ASs because similar S 1 decay behavior is found in the simulations employing the following ASs: (12,10), (14,14), and (16,14). In these simulations, DMN is initially excited to the S 1 state.…”

Section: The Journal Of Physical Chemistry Asupporting

confidence: 61%

“…This is confirmed by the histogram of the θ d distribution of all hopping events that shows a maximum between 30 and 40° (Figure 4d), matching the pyramidalization angle at C8 in the optimized CI 01α structure (Figure 2a). We note again that the calculations with different ASs, namely, (12,10), (14,14), and (16,14), lead to the same conclusion; they all support nonadiabatic decay via CI 01α . This mechanism has also been favored by Allen et al, 1 Jee et al, 2 and the Maroncelli group.…”

Section: The Journal Of Physical Chemistry Asupporting

confidence: 53%

“…At the OM2/MRCI level, the S 0 minimum is almost planar (see Figure 2a and Supporting Information). OM2/MRCI optimizations with different ASs, that is, (12,10), (12,12), and (14,14), give similar bond lengths and angles. These OM2 results are consistent with recent ab initio and DFT calculations 3 in which the type of optimized S 0 structure (planar versus nonplanar) was found to depend on the level of theory and basis set; DFT methods gave planar geometries, while correlated ab initio methods yielded slight deviations from planarity (e.g., by 8°at the amino nitrogen atom in the RI-CC2/def2-TZVP optimized structure).…”

Section: Resultsmentioning

confidence: 56%

“…Two of them are characterized by twists around the C4−C7 single and C7C8 double bonds (τ c and τ b ), and the other two are characterized , τ c (c), and θ d (d) at the S 1 → S 0 hopping events, obtained with OM2/MRCI-SD employing different active spaces, (12,10), (12,12), (14,14), and (16,14). The numbers of hopping events are given in parentheses.…”

Section: Resultsmentioning

confidence: 99%

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Nonadiabatic Decay Dynamics of a Benzylidene Malononitrile

et al. 2012

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The photoinduced nonadiabatic decay dynamics of 2-[4-(dimethylamino)benzylidene]malononitrile (DMN) in the gas phase is investigated at the semiempirical OM2/MRCI level using surface hopping simulations. A lifetime of 1.2 ps is predicted for the S(1) state, in accordance with experimental observation. The dominant reaction coordinate is found to be the twisting around the C7═C8 double bond accompanied by pronounced pyramidalization at the C8 atom. Motion along this coordinate leads to the lowest-energy conical intersection (CI(01α)). Several other S(0)/S(1) conical intersections have also been located by full optimization but play no role in the dynamics. The time-resolved fluorescence spectrum of DMN is simulated by computing emission energies and oscillator strengths along the trajectories. It compares well with the experimental spectrum. The use of different active spaces in the OM2/MRCI calculations yields similar results and thus demonstrates their internal consistency.

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Section: The Journal Of Physical Chemistry Asupporting

confidence: 61%

Section: The Journal Of Physical Chemistry Asupporting

confidence: 53%

Section: Resultsmentioning

confidence: 56%

Section: Resultsmentioning

confidence: 99%

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Nonadiabatic Decay Dynamics of a Benzylidene Malononitrile

et al. 2012

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“…In the empirical derivation by Loutfy et al , the constant C depends on both the dye and the solvent, and the exponent x was experimentally determined [2] and found to be near 0.6 [1,7,10,17]. Some studies stipulate a temperature-dependent rate of TICT formation [1,3,18], where the relaxation rate through intramolecular rotation (i.e., TICT formation), k rot , follows an Arrhenius function (Equation 3),

k_{r o t} = k_{r o t}^{0} \cdot e x p true(- \frac{E_{A}}{k_{B} T} true)

where

k_{r o t}^{0}

is an intrinsic, dye-dependent reorientation rate, E A is an apparent activation energy, k B is Boltzmann's constant, and T the temperature. The quantum yield ϕ F is inversely proportional to k rot , and therefore, temperature can be assumed to havea significant direct effect on the fluorophore's quantum yield.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic and Extrinsic Temperature-Dependency of Viscosity-Sensitive Fluorescent Molecular Rotors

et al. 2011

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Molecular rotors are a group of environment-sensitive fluorescent probes whose quantum yield depends on the ability to form twisted intramolecular chargetransfer (TICT) states. TICT formation is dominantly governed by the solvent's microviscosity, but polarity and the ability of the solvent to form hydrogen bonds play an additional role. The relationship between quantum yield ϕF and viscosity η is widely accepted as a power-law, ϕF = C · ηx. In this study, we isolated the direct influence of the temperature on the TICT formation rate by examining several molecular rotors in protic and aprotic solvents over a range of temperatures. Each solvent's viscosity was determined as a function of temperature and used in the above power-law to determine how the proportionality constant C varies with temperature. We found that the power-law relationship fully explains the variations of the measured steady-state intensity by temperature-induced variations of the solvent viscosity, and C can be assumed to be temperature-independent. The exponent x, however, was found to be significantly higher in aprotic solvents than in protic solvents. We conclude that the ability of the solvent to form hydrogen bonds has a major influence on the relationship between viscosity and quantum yield. To use molecular rotors for the quantitative determination of viscosity or microviscosity, the exponent x needs to be determined for each dye-solvent combination.

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Pressure‐Induced Emission Enhancement of a Series of Dicyanovinyl‐Substituted Aromatics: Pressure Tuning of the Molecular Population with Different Conformations

Wang

et al. 2008

ChemPhysChem

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A series of dicyanovinyl-substituted aromatic compounds (Ar-DCV; Ar=9-anthracenyl, 1-naphthyl, 1-pyrenyl) with dual fluorescence are prepared, and their emission properties--when molecularly dispersed in a polymer medium--are investigated under pressure perturbation. The total emission intensity is enhanced drastically from ambient pressure up to 70 kbar. Emission 30-107 times more intense than that at ambient pressure is observed at higher pressure. In dual emission, the enhancement of the local excited state (LE state) is significantly different from that of the intramolecular charge-transfer state (ICT state). The intensity of the ICT emission increases faster (30-370 times) than that of the LE emission (less than 20 times). In accordance with spectroscopic data, emission dynamics at different pressures, and computational studies on the molecular conformations of these compounds, a kinetic model is proposed to explain the effect of pressure on the emissive properties of the Ar-DCV compounds from the point of view of pressure-dependent populations of the species in the ground state.

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Solvent and temperature effects on the decay dynamics of [p-N,N-(dialkylamino)benzylidene]malononitriles

Cited by 20 publications

References 23 publications

Nonadiabatic Decay Dynamics of a Benzylidene Malononitrile

Nonadiabatic Decay Dynamics of a Benzylidene Malononitrile

Intrinsic and Extrinsic Temperature-Dependency of Viscosity-Sensitive Fluorescent Molecular Rotors

Pressure‐Induced Emission Enhancement of a Series of Dicyanovinyl‐Substituted Aromatics: Pressure Tuning of the Molecular Population with Different Conformations

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