Two-photon absorption in three-dimensional chromophores based on [2.2]-paracyclophane

GP Bartholomew, M Rumi, SJK Pond… - Journal of the …, 2004 - ACS Publications
GP Bartholomew, M Rumi, SJK Pond, JW Perry, S Tretiak, GC Bazan
Journal of the American Chemical Society, 2004ACS Publications
A series of α, ω-bis donor substituted oligophenylenevinylene dimers held together by the
[2.2] paracyclophane core were synthesized to probe how the number of repeat units and
through-space delocalization influence two-photon absorption cross sections. Specifically,
the paracyclophane molecules are tetra (4, 7, 12, 15)-(4 '-dihexylaminostyryl)[2.2]
paracyclophane (3R D), tetra (4, 7, 12, 15)-(4 ''-(4 '-dihexylaminostyryl) styryl)[2.2]
paracyclophane (5R D), and tetra (4, 7, 12, 15)-(4 '''-(4 ''-(4 '-dihexylaminostyryl) styryl) …
A series of α,ω-bis donor substituted oligophenylenevinylene dimers held together by the [2.2]paracyclophane core were synthesized to probe how the number of repeat units and through-space delocalization influence two-photon absorption cross sections. Specifically, the paracyclophane molecules are tetra(4,7,12,15)-(4‘-dihexylaminostyryl)[2.2]paracyclophane (3RD), tetra(4,7,12,15)-(4‘ ‘-(4‘-dihexylaminostyryl)styryl)[2.2]paracyclophane (5RD), and tetra(4,7,12,15)-(4‘ ‘‘-(4‘ ‘-(4‘-dihexylaminostyryl)styryl)styryl)[2.2]paracyclophane (7RD). The compounds bis(1,4)-(4‘-dihexylaminostyryl)benzene (3R) and bis(1,4)-(4‘ ‘-(4‘-dihexylaminostyryl)styryl)benzene (5R) were also synthesized to reveal the properties of the “monomeric” counterparts. The two-photon absorption cross sections were determined by the two-photon induced fluorescence method using both femtosecond and nanosecond pulsed lasers as excitation sources. While there is a red shift in the linear absorption spectra when going from the “monomer” chromophore to the paracyclophane “dimer” (i.e., 3R 3RD, 5R 5RD), there is no shift in the two-photon absorption maxima. A theoretical treatment of these trends and the dependence of transition dipole moments on molecular structure rely on calculations that interfaced time-dependent density functional theory (TDDFT) techniques with the collective electronic oscillator (CEO) program. These theoretical and experimental results indicate that intermolecular interactions can strongly affect Bu states but weakly perturb Ag states, due to the small dipole−dipole coupling between Ag states on the chromophores in the dimer.
ACS Publications
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