The effects of π-acceptor and π-donor substitution in cross-conjugated enynes

Zhao, Yuming; Ciulei, Sorin C.; Tykwinski, Rik R.

doi:10.1016/s0040-4039(01)01659-8

Cited by 24 publications

(17 citation statements)

References 17 publications

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“…Multiple conduction pathways in different dimensions are accessible by using cross-conjugated compounds 20–22,29,30. Electron-donor and -acceptor moieties are frequently incorporated into cross-conjugated structures to improve the dimensionality of electronic communication 4,5,10,22,27,36–40. Judicial placement of the donor and acceptor groups allows spatial separation of the HOMO and LUMO, as revealed by quantum-mechanical calculations.…”

Section: Introductionmentioning

confidence: 99%

Controlling the Conformational Changes in Donor–Acceptor [4]‐Dendralenes through Intramolecular Charge‐Transfer Processes

Kanibolotsky

Forgie

McEntee

et al. 2009

Chemistry A European J

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The synthesis of two [4]-dendralene compounds incorporating thiophene-(p-nitrophenyl) donor–acceptor units is presented. The dendralenes adopt two different conformers in solution and solid state and the transformation between the structures can be controlled by light and heat. The electron-donating components of the dendralenes are represented by bromothienyl (in 13) and ethylenedioxythiophene(EDOT)-thienyl (in 15) end-groups. The most facile transformation involves the isomerisation of donor–acceptor conjugated systems (a conformers) into structures in which only the thiophenes are conjugated (b conformers), and this process is driven by ambient light. The structures of the two conformers of compound 13 are confirmed by single-crystal X-ray diffraction studies and the structural changes in both compounds have been monitored by 1H NMR spectroscopy and absorption studies. The transformations were found to be first-order processes with rate constants of k = 0.0027 s−1 and k = 0.00022 s−1 for 13 and 15, respectively. Density functional theory calculations at the B3LYP/6-31G∗ level give credence to the proposed mechanism for the a→b conversion, which involves photoinduced intramolecular charge transfer (ICT) as the key step. The EDOT derivative (15) can be polymerised by electrochemical oxidation and a combination of cyclic voltammetry and UV/Vis spectroelectrochemical experiments indicate that the a conformer can be trapped and stabilised in the solid state.

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Section: Introductionmentioning

confidence: 99%

Controlling the Conformational Changes in Donor–Acceptor [4]‐Dendralenes through Intramolecular Charge‐Transfer Processes

Kanibolotsky

Forgie

McEntee

et al. 2009

Chemistry A European J

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“…[24][25][26][27][28][29][30] However, systematic investigations of the synthesis and optoelectronic properties of monoA C H T U N G T R E N N U N G disperse all-trans-oligodiacetylenes (or trans-oligo-A C H T U N G T R E N N U N G enynes) still remain very scarce. This is remarkable considering that polydiacetylenes (PDAs) figure prominently in current research on electronically conducting polymers (> 1500 publications since 1990 [31] ) and are of interest as nonlinear optical materials.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Optical Properties of all‐trans‐Oligodiacetylenes

Pilzak

Lagen

Hendrikx

et al. 2008

Chemistry A European J

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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.

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“…The difference between the peripheral groups (cyclohexylidene vs. isopropylidene) is negligible as shown by comparison of the UV/VIS spectra of iso-PTA dimers containing the two types of peripheral groups [11]. UV/VIS and structural data [1] strongly indicate the absence of cross-conjugation in the parent, nonexpanded dendralenes.…”

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confidence: 99%

Synthesis and Characterization of Multinanometer-Sized Expanded Dendralenes with an iso-Poly(triacetylene) Backbone

Burri¹,

Diederich²,

Nielsen

2002

HCA

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A series of [n]dendralenes (n 3, 4, 8, 3b ± d (Fig. 1)) expanded with buta-1,3-diynediyl moieties between the CC bonds were prepared by repetitive acetylenic scaffolding of 3-(cyclohexylidene)penta-1,4-diyne building blocks (Scheme). These remarkably unstable iso-poly(triacetylene) (iso-PTA) oligomers were characterized by 1 H-and 13 CÀNMR ( Fig. 3 and Table 1), IR, and UV/VIS (Figs. 4 and 6 and Table 2) spectroscopy, as well as mass spectrometry (Fig. 2). The expanded [8]dendralene contains 40 C(sp)-and C(sp 2 )-atoms in the backbone and represents the longest iso-PTA oligomer prepared to date. HOMO-LUMO Gap energies were determined as a function of oligomeric length ( Fig. 5 and Table 3), providing insight into the degree of p-electron delocalization in these cross-conjugated chromophores. A continous drop in the HOMO-LUMO gap with increasing number of monomeric repeating units provides evidence that cross-conjugation along the oligomeric backbone is effective to some extent. The limiting HOMO-LUMO gap energy for an infinitely long, buta-1,3-diynediyl-expanded dendralene was extrapolated to about 3.3 ± 3.5 eV. The conformational preferences of the expanded dendralenes were analyzed in semi-empirical calculations, revealing energetic preferences for planar or slightly twisted s-cis and −U-shaped× geometries.1. Introduction. ± Dendralenes are polyene hydrocarbons in which CC bonds are aligned in a cross-conjugated arrangement [1a]. This requires the presence of at least three CC bonds, and the simplest dendralene, therefore, is 3-(methylidene)penta-1,4-diene (a [3]dendralene). Novel synthetic approaches to dendralenes are currently being developed [1d,e], and these chromophores are increasingly investigated for their structural, electronic, and advanced materials properties [1]. Upon insertion of one or more acetylene units between the CC bonds, series of expanded dendralenes are obtained (Fig. 1). Diederich and co-workers [2] reported in 1995 the synthesis of the iso-poly(triacetylene)s 1a ± d by acetylenic scaffolding starting from appropriate tetraethynylethene (TEE, 3,hex-3-ene-1,5-diyne) precursors. Compounds 1c and 1d in this series are the first examples of expanded dendralenes, with buta-1,3-diynediyl bridges inserted between the CC bonds. More recently, Tykwinski and coworkers [3] introduced a new class of expanded dendralenes 2c ± i with the isopoly(diacetylene) backbone, featuring ethynediyl spacers between the CC bonds (the names iso-poly(diacetylene) (iso-PDA) and iso-poly(triacetylene) (iso-PTA) were introduced by Tykwinski and co-workers [3b]). In addition to compounds 2a ± i, with peripheral isopropylidene moieties, derivatives with peripheral cyclohexylidene and adamantylidene fragments were also reported [3d].

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The effects of π-acceptor and π-donor substitution in cross-conjugated enynes

Cited by 24 publications

References 17 publications

Controlling the Conformational Changes in Donor–Acceptor [4]‐Dendralenes through Intramolecular Charge‐Transfer Processes

Controlling the Conformational Changes in Donor–Acceptor [4]‐Dendralenes through Intramolecular Charge‐Transfer Processes

Synthesis and Optical Properties of all‐trans‐Oligodiacetylenes

Synthesis and Characterization of Multinanometer-Sized Expanded Dendralenes with an iso-Poly(triacetylene) Backbone

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