Polarisation-dependent two-photon spectra of triptycene

Kundu, Tapanendu; Nath, Dilip C.; Samanta, Anunay; Chowdhury, Mihir

doi:10.1016/0009-2614(87)80068-4

Cited by 10 publications

(5 citation statements)

References 20 publications

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“…Actually, the absolute value of the disagreement between the two models increases when comparing higher frequency modes, as exemplified by a RMS deviation of 33 cm-' for the difference between AM1 and ab initio frequencies in the 50-500 cm-' range (vI-vII) as compared with 84 cm-' in the 500-900 cm-' (~1 2 -~2 3 ) , However, the relative value of the disagreement remains practically the same along the ~1 -~2 3 series as the lower root-mean-square values correspond to low-frequency vibrations. A detailed examination of the nature of AM1 modes exhibiting the largest deviations from ab initio frequencies (vI, u7, v22) did not reveal that they systematically originate from a certain type of nuclear motion.…”

Section: 2mentioning

confidence: 79%

“…In the first excited state, triptycene exhibits an interesting excitonic coupling of the three constituent o-xylene S, electronic states. [2][3][4] In fact, our recent investigation of the Jahn-Teller (JT) effect in the first electronically excited S, ( ') state of this system11 was one of the motivations for analyzing the low-frequency ground-state modes. In the S, «-S0 electronic spectrum, the S, state vibronic coupling leads to the appearance of a very low-frequency e' vibrational mode and irregular level structure.…”

Section: Introductionmentioning

confidence: 99%

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The low-frequency vibrations of triptycene

Furlan¹,

Fischer²,

Fluekiger³

et al. 1992

J. Phys. Chem.

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The ground-state vibrational spectra of triptycene (9,10-dihydro-9,10[ 1',2']benzenoanthracene) were studied by fluorescence emission and IR and Raman spectroscopies, as well as by semiempirical (AMI) and ab initio (HartreeFock) quantum chemical calculations. Comparison of experimental vibrational frequencies and intensities in the range 60-1oOO cm-l with the semiempirical and the ab initio values is made. Excellent agreement is found between experiment and ab initio calculation with respect to vibrational frequencies. Agreement with the frequencies predicted by the semiempirical AM1 calculation is less satisfactory. The interpretation and assignment of the lowest frequency vibrational modes is also discussed in terms of a vibrational excimer model in a basis of symmetry-adapted combinations of local benzene ring coordinates. The two lowest frequency modes at 64 and 21 1 cm-' are identified by shape and symmetry (e' and a i , respectively), which is very important for the understanding of the Jahn-Teller effect in the first excited state 'E' of triptycene.

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Section: 2mentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

The low-frequency vibrations of triptycene

Furlan¹,

Fischer²,

Fluekiger³

et al. 1992

J. Phys. Chem.

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“…The molecules investigated here differ considerably from the BODIPY derivatives discussed just above for at least two reasons: (1) the BODIPY chromophore acts here as electron donor, and (2) these are DABS, whereas the above-mentioned molecules are directly linked DA pairs. Indeed, triptycene has been shown to be equivalent to three weakly coupled o -xylene molecules. − Thus, the benzene ring of the triptycenyl moiety directly connected to the chromophore can be considered as a bridge, whereas the nitrobenzene moieties can be regarded as two independent electron acceptors.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, triptycene has been shown to be equivalent to three weakly coupled o-xylene molecules. [46][47][48] Thus, the benzene ring of the triptycenyl moiety directly connected to the chromophore can be considered as a bridge, whereas the nitrobenzene moieties can be regarded as two independent electron acceptors.…”

Section: Introductionmentioning

confidence: 99%

Excited-State Dynamics of Donor−Acceptor Bridged Systems Containing a Boron−Dipyrromethene Chromophore: Interplay between Charge Separation and Reorientational Motion

2007

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The excited-state dynamics of a series of electron donor-acceptor bridged systems (DABS) consisting of a boron-dipyrromethene chromophore covalently linked to a dinitro-substituted triptycene has been investigated using femtosecond time-resolved spectroscopy. The chromophores differ by the number of bromine atom substituents. The fluorescence lifetime of the DABS without any bromine atom is strongly reduced when going from toluene to polar solvents, this shortening being already present in chloroform. This effect is about 10 times weaker with a single bromine atom and negligible with two bromine atoms on the chromophore. The excited-state lifetime shortening is ascribed to a charge transfer from the excited chromophore to a nitrobenzene moiety, the driving force of this process depending on the number of bromine substituents. The occurrence of this process is further confirmed by the investigation of the excited-state dynamics of the chromophore alone in pure nitrobenzene. Surprisingly, no correlation between the charge separation time constant and the dielectric properties of the solvents could be observed. However, a good correlation between the charge separation time constant and the diffusional reorientation time of the chromophore alone, measured by fluorescence anisotropy, was found. Quantum chemistry calculations suggest that quasi-free rotation about the single bond linking the chromophore to the triptycene moiety permits a sufficient coupling of the donor and the acceptor to ensure efficient charge separation. The charge separation dynamics in these molecules is thus controlled by the reorientational motion of the donor relative to the acceptor.

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“…The broad band has been ascribed by us to the A'~ --. A] transition (Kundu et al 1987). However, the 0-0 origin of the band is debatable.…”

mentioning

confidence: 99%

One- and two-photon spectra of some selected molecules: A comparative study

Chowdhury

Chakraborty

Kundu

et al. 1991

Proc. Indian Acad. Sci. (Chem. Sci.)

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The complementarity of one-and two-photon spectroscopy has been utilised for throwing light on the following problems of chemical interest: (1) Weak interaction between identical chromophores separated by insulating bridges gives rise to split states of different symmetries. Two-photon spectroscopy (TPA), in conjunction with one-photon absorption (OPA), has been used to identify the states and hence to estimate the magnitude of interaction in bimolecules and trimolecules. From the shifts between the one-and the two-photon spectra, the splittings have been estimated. Calculations confirm that the dominant interaction is the through-bond one. (2) The second type of problem is the identification of g and u vibrations in molecules. We have initiated studies on three molecules in jet-cooled conditions: 9,10-dihydro-anthracene (DHA). 9,10-dihydro-phenanthrene (DHP) and octa-fluoronaphthalene (OFN). Only the one-photon fluorescence excitation spectra have so far been obtained by us and the TPA spectra are under investigation. (3) The third class of molecules discussed here are the Ln 3 + complexes where f"~ f" transitions are intrinsically two-photon allowed. We have studied two GD 3 + single crystals. The CF-splittings, observed clearly in TPA, have been fitted with a parametric model. Some of our observations on the variations of TPA intensity patterns from crystal to crystal, such as circular:linear polarisation ratios, relative intensities of transitions to different J-states, do not quite fit in with the Axe-Judd-Downer model. The discrepancies call for a reappraisal of the role of ligand in the TPA process.

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Polarisation-dependent two-photon spectra of triptycene

Cited by 10 publications

References 20 publications

The low-frequency vibrations of triptycene

The low-frequency vibrations of triptycene

Excited-State Dynamics of Donor−Acceptor Bridged Systems Containing a Boron−Dipyrromethene Chromophore: Interplay between Charge Separation and Reorientational Motion

One- and two-photon spectra of some selected molecules: A comparative study

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