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Stereochemical Effects on Platinum Acetylide Two-Photon Chromophores
journal contribution
posted on 2019-10-17, 19:34 authored by Abigail
H. Shelton, Silvano R. Valandro, Randi S. Price, Galyna G. Dubinina, Khalil A. Abboud, Geoffrey Wicks, Aleksander Rebane, Muhammad Younus, Kirk S. SchanzeA series
of cis-platinum(II) acetylide complexes
containing two-photon-absorbing chromophores have been synthesized
and characterized to explore the effects of stereochemistry on the
nonlinear absorption properties. The molecules feature 4-(phenylethynyl)phenylethynylene
(PE2), diphenylaminofluorene (DPAF), and benzothiazolylfluorene (BTF)
ligands. The photophysical properties were investigated under one-
and two-photon conditions and compared to the known trans analogues via UV–visible absorption, photoluminescence, femtosecond
and nanosecond transient absorption (TA), nanosecond z-scan, and femtosecond
two-photon absorption (2PA). The bent cis complexes
exhibit blue shifts in the absorption, emission, femtosecond, and
nanosecond TA spectra along with lower molar extinction coefficients
and lower phosphorescence yields relative to the trans complexes suggesting less efficient Pt-induced spin–orbit
coupling and intersystem crossing in the cis configuration.
The cis chromophores are noncentrosymmetric and therefore
show dipolar behavior with a pronounced 2PA in the 0–0 transition
of the S0 → S1 band, while the trans complexes show quadrupolar behavior with a forbidden
0–0 transition. In the S0 → Sn region, both cis and trans complexes show intense two-photon-absorption bands (up to 3700 GM
by the peak cross section for cis-BTF) which contain
a significant contribution from the excited state absorption (S1 → Sn). All six complexes
exhibit comparable nonlinear absorption response with a significant
contribution from triplet–triplet absorption that slightly
favors trans complexes but is more strongly dependent
upon the structure of the π-conjugated chromophore.
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chromophoreshow dipolar behaviorGMPlatinum Acetylide Two-Photon Chromophorescis complexes exhibittrans complexesPAPEnonlinear absorption propertiesUVBTFfemtosecondnonlinear absorption responsemolar extinction coefficientstrans complexes showtrans complexes show quadrupolar behaviornanosecond TA spectraDPAF
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