Cis-trans isomerism in the pyridyl analogs of azobenzene. Kinetic and molecular orbital analysis

Brown, Ellis V.; Granneman, G. Richard

doi:10.1021/ja00836a025

Cited by 243 publications

(165 citation statements)

References 2 publications

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“…The trans to cis potential energy barriers for systems A and B are 1.060 eV and 1.433 eV, respectively. These features are similar to the azobenzene molecule in the gas phase where its trans isomer is experimentally reported to be more stable than the cis counterpart by 0.6 eV and the potential energy barrier from the trans to the cis counterpart is 1.0 eV [34].…”

Section: Resultssupporting

confidence: 64%

Silicon-based molecular switch junctions

Nozaki

Cuniberti

2009

Nano Res.

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In contrast to the static operations of conventional semiconductor devices, the dynamic conformational freedom in molecular devices opens up the possibility of using individual molecules as new types of devices such as a molecular conformational switch or for molecular data storage. Bistable molecules such as those having two stable cis and trans isomeric confi gurations could provide, once clamped between two electrodes, a switching phenomenon in the non-equilibrium current response. Here, we model molecular switch junctions formed at silicon contacts and demonstrate the potential of such tunable molecular switches in electrode/molecule/ electrode confi gurations. Using the non-equilibrium Green function (NEGF) approach implemented with the density-functional-based tight-binding (DFTB) theory, a series of properties such as electron transmissions, current voltage characteristics in the different isomer conformations, and potential energy surfaces (PESs) as a function of the reaction coordinates along the trans to cis transition were calculated for two azobenzene-based model compounds. Furthermore, in order to investigate the stability of molecular switches under ambient conditions, molecular dynamics (MD) simulations at room temperature were performed and time-dependent fl uctuations of the conductance along the MD pathways were calculated. Our numerical results show that the transmission spectra of the cis isomers are more conductive than trans counterparts inside the bias window for both model compounds. The current voltage characteristics consequently show the same trends. Additionally, calculations of the time-dependent transmission fluctuations along the MD pathways have shown that the transmission in the cis isomers is always signifi cantly larger than that in their trans counterparts, showing that molecular switches can be expected to work as robust molecular switching components.

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Section: Resultssupporting

confidence: 64%

Silicon-based molecular switch junctions

Nozaki

Cuniberti

2009

Nano Res.

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“…This may render the torsional coordinate the more important for the thermal isomerization. In this respect, it is worth noting that the preexponential factor for thermal isomerization is about 10 11 s )1 [2,36], definitely lower than the typical frequency factor kT/h for adiabatic reactions. We calculated the optimized geometries for the Z and E isomers.…”

Section: Ground Statementioning

confidence: 90%

“…The Z and E isomers are separated by potential-energy barriers along both the torsional coordinate, along which the N=N bond is partially broken, and the in-plane inversion path, because the N hybridization changes from sp 2 to sp. Experimentally [2,36], it is found that thermal Z-E isomerization is associated with a barrier of 22-23 kcal mol )1 , i.e., the transition-state energy is about 35 kcal mol )1 above the E isomer. Obviously, this value pertains to the energy of the lower of the two barriers, but experiments do not specify with which path it is associated.…”

Section: Ground Statementioning

confidence: 99%

A theoretical study of the lowest electronic states of azobenzene: the role of torsion coordinate in the cis–trans photoisomerization

et al. 2003

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Abstract. In the present paper we report the results of a multiconfigurational computational study on potentialenergy curves of azobenzene along the NN twisting to clarify the role of this coordinate in the decay of the S 2 (pp*) and S 1 (np*) states. We have found that there is a singlet state, S 3 at the trans geometry, on the basis of the doubly excited configuration n 2 p* 2 , that has a deep minimum at about 90°of twisting, where it is the lowest excited singlet state. The existence of this state provides an explanation for the short lifetime of S 2 (pp*) and for the wavelength-dependence of azobenzene photochemistry. We have characterized the S 1 (np*) state by calculating its vibrational frequencies, which are found to correspond to the recently observed transient Raman spectrum. We have also computed the potential-energy curve for the triplet T 1 (np*) at the density functional theory B3LYP level, which indicates that in this state the isomerization occurs along the twisting coordinate.

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“…The experimental barrier heights, which are estimated by kinetic measurements, are 176 kJ/mol for stilbene [16], 92 kJ/mol for azobenzene [17] and 70 kJ/mol for NBA [18]. Thus, the thermal barrier between the two isomers of NBA is the lowest and the ground state relaxation from the Z form to the E form is quite rapid, with a rate parameter ca.…”

mentioning

confidence: 96%

Ab initio DFT study of Z–E isomerization pathways of N–benzylideneaniline

et al. 2007

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The ground state properties and absorption spectra of N -benzylideneaniline (NBA) have been studied at the density functional (DFT) and at the time-dependent density functional (TD-DFT) level of the theory. The equilibrium geometries of the E and Z isomers in the ground state and their vibrational frequencies have been computed. Furthermore, the excitation energies of the lowest excited singlet and triplet states and the potential energy curves along the torsion and the inversion isomerization coordinates were evaluated. The results are discussed in light of the available experimental data.

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Cis-trans isomerism in the pyridyl analogs of azobenzene. Kinetic and molecular orbital analysis

Cited by 243 publications

References 2 publications

Silicon-based molecular switch junctions

Silicon-based molecular switch junctions

A theoretical study of the lowest electronic states of azobenzene: the role of torsion coordinate in the cis–trans photoisomerization

Ab initio DFT study of Z–E isomerization pathways of N–benzylideneaniline

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