Assignment of the 6,6′-Dioxo-3,3′-biverdazyl Ground State by Using Broken Symmetry and Spectroscopy Oriented Configuration Interaction Techniques
Bibliographic record
Abstract
The singlet-triplet energy differences (DeltaE(ST)) and the Heisenberg-Dirac-van-Vleck exchange parameter (J) of 6,6'-dioxo-3,3'-biverdazyl (BVD) have been studied by hybrid density functional (HDF), broken symmetry (BS), and spectroscopy oriented configuration interaction (SORCI) methods. Energy surface scans as a function of the dihedral angle between the two verdazyl rings (phi(N2C3C3'N2')) have been performed. The BS computations predict an antiferromagnetic ground state. However, the diradical index (R(BS)) ranges from 97.5 to 99.9%, implying that the interactions between the two unpaired electrons are very weak. To calculate J and DeltaE(ST), the multireference character introduced by these weak spin-spin interactions must be taken into account. Consequently, multireference difference dedicated configuration interaction (MRDDCI) methods, as implemented in the SORCI procedure, are used. The in-plane pi (IPpi), out-of-plane pi (OPpi), and sigma configurations are included in the CI expansions in a balanced fashion. The OPpi-OPpi and OPpi-IPpi overlaps are the predominant factors that influence the J and DeltaE(ST) as a function of phi(N2C3C3'N2') and cause them to peak around 40 and 140 degrees. In these regions, the antiferromagnetic interactions are minimal, and the MRDDCI methods predict a triplet ground state. At phi(N2C3C3'N2') = 0, DeltaE(ST)[MRDDCI3(14,12)] is in excellent agreement with that of 1,1',5,5'-tetramethyl-6,6'-dioxo-3,3'-biverdazyl determined experimentally from electron paramagnetic resonance (EPR) spectroscopy and differs only by 2.3%. Furthermore, DeltaE(ST)[MRDDCI3(14,12)] is consistently smaller than J(Y) as the verdazyl rings rotate with respect to each other. This corroborates the theory that the HDF-BS technique increases the singlet-triplet energy gap and favors the singlet state. Because the SORCI method is specifically designed for large molecules, the present very good results open the way for the computation of the magnetic properties of larger molecules by the SORCI method. To the best of our knowledge, this is the first time that DeltaE(ST) has been computed by the MRDDCI3 method by utilizing such a large CI reference space for a molecule of this size.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".