Femtosecond Spectroscopic Studies of the One- and Two-Photon Excited-State Dynamics of 2,2,17,17-Tetramethyloctadeca-5,9,13-trien-3,7,11,15-tetrayne:  A Trimeric Oligodiacetylene

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A new series of pure and highly soluble oligodiacetylenes (ODAs) was synthesized in high yield and on a multi-milligram scale by a sequence of Sonogashira reactions with a strongly reduced level of homocoupling. The lambda max and epsilon max of these ODAs show an increase with both chain elongation and solvent polarity. A plot of lambda max absorption versus 1/CL (CL=conjugation length) was shown to be linear. The lambda max converges to 435 nm for the longest members of the series at micromolar concentration. This reveals that the longest wavelength absorption observed for PDA chains (lambda max up to 700 nm) is due to aggregation effects. The fluorescence quantum yield increased from monomer to trimer and decreased for longer ODAs. A similar trend is found for the lifetime of fluorescence with a maximum of 600 ps for the trimer. The observed linearity of the rotational correlation time with the oligomer length implies that the ODA chains in solution lack significant geometrical changes. This implies that the ODAs in solution are fully stretched molecular rods of up to 4 nm in length.

Section: Steady-state Optical Absorption In Solutionsupporting

confidence: 78%

Section: -N (Cl)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis and Optical Properties of all‐trans‐Oligodiacetylenes

Pilzak

Lagen

Hendrikx

et al. 2008

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“…[11b, 12,15,19,20] The dominant solvent effect is the polarization shift, which is attributed to the difference in solvent refractive index. [21] A bathochromic effect is observed upon changing the solvent from n-hexane (refractive index, n r = 1.375; empirical solvent polarity parameter, E T (30) = 31.0) to DCE (n r = 1.445; E T (30) = 41.3).…”

Section: Steady-state Absorption In Solutionmentioning

confidence: 99%

“…This tendency is analogous to the trends shown for long oligodiacetylene oligomers 2-n [15] and the trimeric oligodiacetylenes investigated previously. [12,20,29] The rotation correlation times t R for HODAs recorded in n-hexane are listed in Table 5. Because longer oligomers display a marginal emission the experimental error for these measurements was relatively high.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

Synthesis and Optoelectronic Properties of Nanometer‐Sized and Highly Soluble Homocoupled Oligodiacetylenes

Pilzak¹,

Baggerman²,

Lagen³

et al. 2009

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A new series of pure, nanometer-sized and highly-soluble homocoupled oligodiacetylenes (HODA) consisting of two symmetrical oligodiacetylene units was synthesized with high yield and on a multi-milligram scale under mild, catalytic Sonogashira conditions. The lambda(max) and the epsilon(max) of absorption for these HODAs show an increase with the chain elongation. The lambda(max) converges to 450 nm for the longest members of the series at micromolar concentration and to 462 nm for thin drop-casted films. An additional red-shifted absorption is observed in the solid state and in solution at low temperatures, which is caused by aggregation. The lambda(max) of the fluorescence emission increases with the chain length and reaches 492 nm for the longest oligomer. The fluorescence quantum yield has its maximum for the shortest oligomer and decreases rapidly for the longer ones. A similar trend is found for the fluorescence lifetime with a maximum of 100 ps for the homocoupled monomer. The rotational correlation time shows a linear increase with the oligomer length. This reveals a significant persistence length and indicates that the HODA molecules are fully stretched molecular rods (up to 8.2 nm).

Hybrid Conjugated Organic Oligomers Consisting of Oligodiacetylene and Thiophene Units: Synthesis and Optical Properties

Pilzak

Gruijthuijsen

Doorn

et al. 2009

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Novel and highly soluble hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units have been synthesized in high purity through iterative and divergent approaches based on a sequence of Sonogashira reactions. The series of thiophene-containing oligodiacetylenes (ThODAs) and homocoupled ThODAs (HThODAs) show--both in solution and in the solid state--a strong optical absorption, which is progressively red shifted with increasing chain length. The linear correlation of the absorption maximum (lambda(A)(max)) with the inverse of conjugation length (CL = number of double and triple bonds) shows that the effective conjugation length of this system is extended up to at least CL = 20. Furthermore, absorption measurements of dropcast thin films display not only a bathochromic shift of the absorption maxima but also a higher wavelength absorption, which is attributed to increased pi-pi interactions. The wavelength of the maximum fluorescence emission (lambda(E)(max)) also increases with CL, and emission is maximal for oligomers with CL=7-12 (fluorescence quantum yield Phi(F) = approximately 0.2). Both longer and shorter oligomers display marginal emission. The calculated Stokes shifts of these planar materials are relatively large (0.4 eV) for all oligomers, and likely due to excitation to the S(2) state, thus suggesting that the presence of enyne moieties dominates the ordering of the lowest excited states. The fluorescence lifetimes (tau(F)) are short (tau(F,max) =<<1 ns) and closely follow the tendency obtained for the fluorescence quantum yield. The anisotropy lifetimes show a near-linear increase with CL, in line with highly rigid oligomers.