Photophysical Properties of Oligophenylene Ethynylenes Modified by Donor and/or Acceptor Groups
Bibliographic record
Abstract
To create highly fluorescent organic compounds in longer wavelength regions, and to gain physical chemistry insight into the photophysical characteristics, we investigated photophysical properties (Phi(f), lambda(em), tau, lambda(abs), epsilon, k(r), and k(d)) and their controlling factor dependence of the following pi-conjugated molecular rods consisting of p-phenyleneethynylene units modified by donor (OMe) and/or acceptor (CN): (1) side-donor modification systems (SD systems), (2) side-acceptor modification systems (SA systems), and (3) systems consisting of donor block and acceptor block (BL systems). As a result, very high Phi(f) values (>0.95) were obtained for BL systems. Bathochromic shifts of lambd(em) in the same pi conjugation length were largest for BL systems. Thus we succeeded in the creation of highly efficient light emitters in the longer wavelength region by block modification (e.g., Phi(f) = 0.97, lambda(em) = 464 nm for BL-9), contrary to expectation from energy gap law. Considerably intense solid emission (Phi(f) approximately 0.5) in the longer wavelength region (500-560 nm) was also found for BL systems, presumably because of molecular orientation that hinders the self-quenching of fluorescence in solids. From (1) a Lippert-Mataga plot, (2) density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, and (3) the positive linear relationship between the optical transition energy (nu(em)) and the difference between the highest occupied molecular orbital of the donor and the lowest unoccupied molecular orbital of the acceptor (HOMO(D)-LUMO(A) difference), it is elucidated that the excited singlet (S1) state of BL systems has a high charge transfer nature. The number (n) of energetically equivalent dipolar structure (EEDS) units in the oligoarylene ethynylenes is shown to be a measure of the effective pi conjugation length in the S1 state. The S1 state planarity increases with n values of EEDS units and by the introduction of donor and/or acceptor groups. It is worth noting that the Phi(f) values increase linearly with the n values of EEDS units.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".