Design of a conductive metal–organic framework based on a TTF-inspired Ligand
Bibliographic record
Abstract
This thesis presents the design of novel sulphur-metal linked conductive metal-organic frameworks (c-MOFs) based on a tetrathiafulvalene (TTF)-inspired ligand, 2,4,6-tris(4,5-disulfanyl-1,3-dithiol-2-ylidene)-1,3,5-cyclohexanetrione (TDCT). TDCT was chosen due to its planar π-conjugated structure, reversible redox activity, narrow electrochemical bandgap (1.27 eV), non-integer oxidation state, and the precedence of high conductivity in related TTF and dithiolene systems. The combination of conductivity and porosity in c-MOF enables various applications, such as electrocatalysis, energy storage and sensing.To verify the feasibility of the synthesis of c-MOF based on TDCT ligands, we first synthesized molecular complexes modelling the structure of the target c-MOFs, [Ni(4Bu-TDCT)₂]2-(Bu4N+)2 and [Zn(4Bu-TDCT)₂]2–(Bu4N+)2. Cyanoethyl protecting groups were introduced onto the ligand molecules to obtain air-stable derivatives. Following in-situ deprotection and coordination with metal ions, the resulting complexes were obtained as dark orange and dark green solids. Their structures were established via NMR spectroscopy and mass spectrometry. The ¹³C NMR spectrum of the Ni complex showed no signals for carbon atoms located in proximity (within eight bonds) of the metal center. This is attributed to paramagnetic broadening owed to the presence of the oxidized radical anion species [Ni(4Bu-TDCT)₂]•-. Integration of the S–CH₂ and N–CH₂ proton signals confirmed the presence of a mixed-valence state in the nickel complex, showing its non-stoichiometric nature as [Ni(4Bu-TDCT)₂]1.37–(Bu4N+)1.37. In contrast, the Zn complex revealed the expected stoichiometric ratio [Zn(4Bu-TDCT)₂]2–(Bu4N+)2 and did not show any paramagnetic broadening in its NMR.The Ni complex in CDCl3 solution also exhibited a strong Electron Paramagnetic Resonance (EPR) signal, while the Zn complex was EPR silent. Cyclic voltammetry (CV) revealed a highly electron-rich nature of [Ni(4Bu-TDCT)₂], which undergoes a reversible oxidation at a very low potential E1/2 = –0.69 V vs. Fc/Fc⁺, suggesting facile oxidation by oxygen in the air. In contrast, the oxidation potential of Zn complex was higher (E1/2 = -0.21 V vs. Fc/Fc⁺), explaining its greater air stability.Both complexes also showed reversible two-electron reduction waves (one electron per ligand). The electrochemically determined HOMO-LUMO gaps (1.27 eV and 1.76eV) are very close to their optical gaps, Eg =1.28 eV for Ni and 1.76 eV for Zn. Guided by these results, we explored the synthesis of a two-dimensional c-MOF, Ni₃(TDCT)₂, via a similar deprotection strategy from hexa(2-cyanoethyl)-TDCT precursor. The reaction is limited by the oxidative instability of the hexaanionic TDCT intermediate, and we explored several strategies to minimize the oxidative side reactions. We have the preliminary investigations showing partial crystallinity observed in the WAXS of the c-MOF. The electrical conductivity of 10-3 S/cm was measured in compressed pellets by a two-probe technique. This work establishes a new TTF-derived platform of ligand for conductive framework development and underscores the importance as well as the challenges of redox-active linkers in the design of c-MOFs
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".