A convenient and selective route to a <i>trans</i>-difunctionalized macrocyclic hexadentate N<sub>4</sub>O<sub>2</sub> ligand
Bibliographic record
Abstract
The synthesis and characterization of a novel difunctionalized tetraaza macrocycle, 1,8-bis(2-hydroxybenzyl)-1,4,8,11-tetraazacyclotetradecane (abbreviated H2bcyclamb), is described. The diprotic hexadentate ligand N4O2 was conveniently synthesized in two steps by the cyclic condensation reaction of 1,4,8,11-tetraazacyclotetradecane (abbreviated cyclam) and salicylaldehyde, followed by NaBH4 reduction of the cyclic hexahydropyrimidine condensate. The difunctionalization was selective and is the first procedure of trans-difunctionalization of a tetraazamacrocycle, without generating mono-, tri-, or tetra-functionalized products, with only 1,8-difunctionalized product being isolated, and with the convenience of the functionalization occurring as a result of deprotection. The trans-arrangement of the two functional groups in H2bcyclamb was verified by X-ray crystallographic studies of the copper(II) complex [Cu(H2bcyclamb)](OAc)2·2H2O. The crystal is monoclinic, P21/c, with a = 10.0931(2), b = 13.8820(1), c = 10.8752(1) Å, β = 106.332(1)°, V = 1462.26(3) Å3. The structure of [Cu(H2bcyclamb)](OAc)2·2H2O also shows the metal ion in an elongated octahedral geometry.Key words: 1,8-difunctionalized, cyclam, copper(II) complex.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.002 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".