Fluorescence excitation spectroscopy of [2.2]paracyclophane in supersonic jets

Shen, T. L.; Jackson, James E.; Yeh, Jing-Yue; Nocera, Daniel G.; Leroi, G. E.

doi:10.1016/0009-2614(92)85384-m

Cited by 20 publications

(46 citation statements)

References 26 publications

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“…The parent compound [2.2]paracyclophane (PC) has been investigated in detail by gas phase spectroscopy. [14][15][16] Our groups recently studied pseudo-ortho-dihydroxy [2.2]paracyclophane (o-DHPC), also termed 4,12-dihydroxy [2.2]paracyclophane by resonance-enhanced multi-photon ionization (REMPI) in a free jet. 17 The experimental results were interpreted on the basis of ab initio calculations using the spin-component-scaled variants of the second-order Møller-Plesset perturbation method (SCS-MP2) and the approximate coupled cluster second-order method (SCS-CC2).…”

Section: Introductionmentioning

confidence: 99%

Paracyclophanes as model compounds for strongly interacting π-systems. Part 2: mono-hydroxy[2.2]paracyclophane

Schon

Roth

Fischer

et al. 2011

Phys. Chem. Chem. Phys.

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The structure of the electronic ground- and first excited state of mono-hydroxy [2.2]paracyclophane (MHPC) and the S(1)← S(0) electronic transition have been investigated by resonance-enhanced multiphoton ionisation (REMPI) and by quantum chemical spin-component-scaled-approximate coupled cluster second order (SCS-CC2) computations. The origin of the S(1)← S(0) transition was located at 30,772 cm(-1) (3.815 eV) in the REMPI spectrum. The value has to be compared with a computed excitation energy of 3.79 eV. The vibrational structure of the spectrum confirms a significant geometry change upon excitation along the coordinates corresponding to twist- and shift-motions in the molecule. It gives rise to an experimentally observed progression with a fundamental of +30 cm(-1) and an inverse anharmonicity. From the experimental data a shallow potential along the twist coordinate was derived for the S(1) state. For the shift vibration a wavenumber of +91 cm(-1) was observed, while +85 cm(-1) was computed. The ionisation energy of MHPC was determined to be 7.63 ± 0.05 eV using synchrotron radiation. When compared to earlier results on the parent compound [2.2]paracyclophane and pseudo-ortho-dihydroxy[2.2]paracyclophane it can be seen that already small variations in the substitution pattern have a significant impact on the shapes of the involved potential energy surfaces leading to strong variations in ground and excited state geometries and opto-electronic properties governing the exciton transfer processes.

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Section: Introductionmentioning

confidence: 99%

Paracyclophanes as model compounds for strongly interacting π-systems. Part 2: mono-hydroxy[2.2]paracyclophane

Schon

Roth

Fischer

et al. 2011

Phys. Chem. Chem. Phys.

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“…The unique properties of paracyclophanes motivated a large number of investigations 14 but so far the parent [2,2]paracyclophane (PC) represents the only paracyclophane that has been investigated by gas phase spectroscopy. [15][16][17] Since such studies provide detailed information we applied resonance-enhanced multi-photon-ionization (REMPI) in a free jet to investigate pseudo-ortho-dihydroxy [2.2]paracyclophane (o-DHPC). The molecule is also termed 4,12-dihydroxy [2.2] paracyclophane.…”

Section: Introductionmentioning

confidence: 99%

Paracyclophanes as model compounds for strongly interacting π-systems. Part 1. Pseudo-ortho-dihydroxy[2.2]paracyclophane

Schon

Roth

Fischer

et al. 2010

Phys. Chem. Chem. Phys.

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In this work we describe a study of the ground and first excited state structures and energetics of a dihydroxy-derivative of [2.2]paracyclophane (PC), the pseudo-ortho-dihydroxy[2.2]paracyclophane (o-DHPC), also termed 4,12-dihydroxy[2.2]paracyclophane. In order to understand the electronic interactions between the two pi-systems, the molecule is investigated by REMPI spectroscopy in a free jet and by quantum chemical calculations. REMPI-spectra of the cluster with one water molecule were also obtained and aid in the interpretation. The origin of the S(1) <-- S(0) transition lies at 31,483 cm(-1) (3.903 eV) for o-DHPC and 31,263 cm(-1) (3.876 eV) for the o-DHPC x H(2)O cluster. An adiabatic excitation energy of 3.87 eV was computed for the S(1) <-- S(0) transition in o-DHPC. The SCS-CC2 calculations deviate by less than 0.1 eV for the adiabatic excitation energies of PC, o-DHPC and the related aromatic molecules benzene and phenol. Considerable activity in a breathing vibration of 190 cm(-1) is found in the S(1) state of o-DHPC and o-DHPC x H(2)O, in agreement with the computed SCS-CC2 value of 185 cm(-1). Further vibrations appear at +11 cm(-1) and +54 cm(-1) in o-DHPC. The computations and the available experimental data of the parent PC show that both PC and o-DHPC are rather flexible with respect to motions of the benzene moieties.While PC has a double minimum potential energy with respect to the torsional motion, a single-minimum structure is found for the ground state of o-DHPC. The geometry change upon excitation is less pronounced in o-DHPC as compared to PC. Two of the three possible rotational conformers of the OH groups were found to have similar energies, but spectral hole burning shows that the spectra are dominated by a single rotamer.

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“…Thus we concluded that including electron correlation and polarization functions in the theoretical chemistry more correctly models the minimum energy conformation than prior Hartree-Fock calculations. 7,8 (2) The reference provided by a reviewer of HH's comment discusses integration grid problems for B3LYP in calculations on the pseudorotation of tetrahydrofuran. 9 Implications that this same problem is present in our calculations are total speculation.…”

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confidence: 99%

Reply to Comment on “Distinctive Normal Harmonic Vibrations of [2.2]Paracyclophane”

Walden

Glatzhofer

1999

J. Phys. Chem. A

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Regarding calculations of the equilibrium structure of [2.2]-paracyclophane, the primary complaint of the commentors seems to lie ultimately in who calculated a D 2 minimum structure first. Henseler and Hohlneicher take exception first with the level of agreement with experiment which we reported and secondly with our reported energy difference between the D 2 and D 2h conformers. Henseler and Hohlneicher (HH) continue with the claim that a paper reporting MP2 energies for the benzene dimer 2 supports their allegation that the MP2 method they used to calculate energies for [2.2]paracyclophane is superior to the B3LYP hybrid Hartree-Fock/density functional method which we used. 3 In regards to HH's first point, our reported agreement with experiment: (1) HH object to our definition of the twist angle and our comparison with the angle derived from experiment. The angle we chose to represent the twist has been used in other publications 4,5 and is more straightforward to visualize and to extract from the data. We regret, and appreciate their observation, that we were actually comparing with a "half-twist" angle. Reanalysis of our data shows the calculated half-twist angle, as defined by the crystallographers, 6 to be 1.2°, in comparison with the experimental value of 3.2°. Within the limits of compational methods, this is still excellent agreement for a very low-energy torsion, especially when comparing to a solid state structure.(2) Neither here nor in the original paper do we claim that the calculated twist angle is the exact twist angle for the equilibrium conformation of [2.2]paracyclophane. We simply claimed to have the best calculated angle in the literature to that date. (3) Overall, we asserted and still maintain that this method provides "very good" agreement with the X-ray crystallographic structure.In regards to HH's second point, our reported energy difference for D 2 and D 2h conformers: (1) We are fully aware of the uncertainty of the very small energy difference between the two conformers. We state in the paper in question that, "This energy difference is so near the limitations of the method as to be inconclusive regarding the equilibrium structure." Agreement with experiment on as many data points as possible is a much better test. Our calculated vibrational frequencies and intensities for the D 2 structure are in excellent overall agreement with the experimental IR spectrum. This agreement was much better than that from vibrations of the D 2h structure. Thus we concluded that including electron correlation and polarization functions in the theoretical chemistry more correctly models the minimum energy conformation than prior Hartree-Fock calculations. 7,8 (2) The reference provided by a reviewer of HH's comment discusses integration grid problems for B3LYP in calculations on the pseudorotation of tetrahydrofuran. 9 Implications that this same problem is present in our calculations are total speculation. Without a dedicated multinode supercomputer with gigabytes of memory, the calculations which wer...

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Fluorescence excitation spectroscopy of [2.2]paracyclophane in supersonic jets

Cited by 20 publications

References 26 publications

Paracyclophanes as model compounds for strongly interacting π-systems. Part 2: mono-hydroxy[2.2]paracyclophane

Paracyclophanes as model compounds for strongly interacting π-systems. Part 2: mono-hydroxy[2.2]paracyclophane

Paracyclophanes as model compounds for strongly interacting π-systems. Part 1. Pseudo-ortho-dihydroxy[2.2]paracyclophane

Reply to Comment on “Distinctive Normal Harmonic Vibrations of [2.2]Paracyclophane”

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