Two-Photon Absorption And Two-Photon Circular Dichroism Of A Hexahelicene Derivative With A Terminal Donor-Phenyl-Acceptor Motif

Abstract

Herein, we report on the theoretical-experimental analysis of the two photon absorption and circular dichroism spectra of 1-(2-pyridyl)-4-methoxy-carbo[6]helicene derivative (P6). The primary outcomes of our investigation on this particular helicene derivative with a donor-acceptor motif on one end led to two important conclusions: (1) the lengthening of the π-electron delocalization within the helical core of P6 predominantly increases the contribution of the magnetic dipole transition moment to the two-photon circular dichroism (TPCD) signal; and (2) the electric quadrupole transition moment contribution to the TPCD signal is enhanced by the intramolecular charge transfer (ICT) produced by the donor-acceptor combination on one end of the molecule. To corroborate our results, we performed a comparative theoretical analysis of the effect of the energy gap and ICT on TPCD on a series of P6-like helicenes with different donor-acceptor combinations. Two-photon absorption and TPCD spectra were obtained using the double L-scan technique over a broad spectral range (400-900 nm) using 90 fs pulses at a low repetition rate (2-50 Hz) produced by an amplified femtosecond system. The theoretical simulations were calculated using time dependent density functional theory at the CAM-B3LYP/6-311++G(d,p) level of theory.

Publication Date

4-5-2018

Publication Title

Journal of Physical Chemistry A

Volume

122

Issue

13

Number of Pages

3365-3373

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1021/acs.jpca.8b00347

Socpus ID

85045059476 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85045059476

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