The neutral diradical 5,5<i>'</i>-bis(1,3,2,4-dithiadiazolyl) [-], the first main group radical to exhibit a dramatic increase in paramagnetism on mechanical grinding
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Bibliographic record
Abstract
Reduction of [([Formula: see text]) 2 ][As 6 ] 2 with triphenylantimony and tetrabutylammonium chloride produced the diradical 5,5'-bis(1,3,2,4-dithiadiazolyl) [[Formula: see text]-[Formula: see text]] in high yield as a black solid with widely ranging magnetic susceptibilities (e.g., 0.6 to 2.6 μ B ), which on oxidation with AsF 5 regenerated [([Formula: see text]) 2 ][AsF 6 ] 2 . The identity of [[Formula: see text]-[Formula: see text]] was established from EPR, vibrational, and mass spectra. Ab initio molecular orbital [MPW1PW91/6-311G(2df)] calculations show the lowest energy structure to consist of two coplanar rings separated by a CC single bond (1.444 Å), reflected in the comparison of the vibrational spectra of the diradical with that of [([Formula: see text]) 2 ][AsF 6 ] 2 and the calculated spectra. Confidence in the calculated [MPW1PW91/6-311G(2df)] structure of the diradical is supported by the excellent agreement between the calculated and X-ray single crystal structure geometries of [[Formula: see text]] 2 and [([Formula: see text]) 2 ] 2+ in [([Formula: see text]) 2 ][AsF 6 ] 2 . The molecular orbitals indicate the diradical is essentially disjoint, confirmed by a very small (0.07 kJ mol 1 ) GVB-PP(TC-SCF)/6-311G* calculated singlettriplet energy gap. Accordingly, the EPR spectrum of the diradical (in tetrahydrofuran, 293 K) shows a simple 3-line pattern (g = 2.0043, a( 14 N) = 1.11 mT) with no observable exchange coupling between the two radical centers. Mechanical grinding of the diradical results in a large increase in paramagnetism (e.g., from 1.03 to 2.55 μ B ) that is unprecedented in main group chemistry. The X-ray diffraction data of the ground and unground powder are consistent with a second order phase change on grinding. Attempts to obtain crystals of the diradical by sublimation led instead to numerous decomposition and rearrangement products, including 4-cyano-1,2,3,5-dithiadiazolyl [NC-[Formula: see text]], monoclinic space group C2/c, a = 9.46(2) Å, b = 7.625(5) Å, c = 13.17(2) Å, β = 107.94(4)°, Z = 8. The structure consists of axially symmetric, co-facial, cis dimers linked to form strands through two sets of C[Formula: see text]N δ ···S δ+ contacts. More efficient and larger scale preparations of [SNS][AsF 6 ] and [([Formula: see text]) 2 ][AsF 6 ] 2 are reported. Key words: 5,5'-bis(1,3,2,4-dithiadiazolyl), diradical, paramagnetism, mechanical grinding, second order phase change, 4-cyano-1,2,3,5-dithiadiazolyl.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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 it