{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.pentalene","code":"thing-q3554979","url":"https://ver.cy/models/thing/q3554979/","name":"pentalene","alternateNames":[],"kind":"thing","status":"published","version":"0.1.0-research.1","language":"en","classifiers":{"family":"Thing Registry","category":"Physical world and living systems","entryKind":"thing","plane":"PHY","domain":["PHY.MAT"],"industry":[],"navPath":"","tags":[],"facets":{}},"whatItIs":"Pentalene is a bicyclic conjugated hydrocarbon, C8H6, consisting of two fused five-membered carbon rings whose eight π electrons give the neutral parent molecule antiaromatic character and high reactivity.","purpose":"Enable an agent to recognize parent pentalene, assess evidence for its presence and persistence, and decide which characterization or handling claims apply to the observed species.","scope":{"in":["Parent pentalene identity and its fused five-membered carbon-ring connectivity","Electronic structure and condition-specific evidence of antiaromaticity","Transient, matrix-isolated, or otherwise experimentally supported occurrences","Identification, abundance, purity, and contamination in the observed sample","Persistence, dimerization, and other demonstrated transformations","Parent-specific identifiers, physical-property evidence, and handling constraints"],"out":["Substituted pentalenes and benzannulated pentalene derivatives as independent substances","Pentalenide ions, their salts, and metal coordination complexes as independent substances","Dihydropentalenes, hydrogenated congeners, and pentalene dimers as independent substances","Synthetic apparatus and preparation processes beyond their relationship to a pentalene observation","Electronic devices and materials containing a pentalene-derived structural unit"],"boundaries":[]},"distinguishingFeatures":["Require C8H6 composition together with connectivity consisting of two five-membered carbon rings sharing one edge; formula alone does not distinguish structural isomers.","Require the unsubstituted parent skeleton; added substituents or annulated rings identify related substances rather than parent pentalene.","Require neutral charge for this entry; a pentalenide dianion or metal-bound ligand must not inherit the parent molecule's property record.","Distinguish evidence of the monomer from evidence of a dimer, precursor, or decomposition product in the same experiment.","Treat the neutral parent's eight-pi-electron antiaromatic framework as electronic context rather than a sufficient analytical identification."],"structure":{"bundles":[{"id":"parent-identity","name":"Parent identity","description":"Establish exactly which molecular species the pentalene record denotes.","layers":[{"id":"molecular-connectivity","name":"Molecular connectivity","description":"Resolve composition and the fused-ring molecular graph.","findings":[{"id":"parent-structure-test","name":"Parent structure test","description":"Identity requires the neutral C8H6 parent with two edge-fused five-membered carbon rings, rather than a formula match alone.","questions":[{"text":"Which structure representation establishes the fused five-membered-ring connectivity of the claimed pentalene?","id":"parent-structure-test-q01","kind":"definition"},{"text":"Does the represented species contain substituents, additional fused rings, extra hydrogen atoms, or a nonzero charge?","id":"parent-structure-test-q02","kind":"boundary"}]}]},{"id":"registry-and-neighbours","name":"Registry and neighbours","description":"Link identifiers and neighbouring species without merging their identities.","findings":[{"id":"structure-checked-cross-references","name":"Structure-checked cross-references","description":"External identifiers and synonyms need explicit structure checks before attachment to vr.tr.pentalene.","questions":[{"text":"Which authoritative records assign identifiers to neutral unsubstituted pentalene, and do their structures agree?","id":"structure-checked-cross-references-q01","kind":"provenance"},{"text":"Which records instead denote a pentalenide salt, coordinated ligand, substituted pentalene, or dimer?","id":"structure-checked-cross-references-q02","kind":"boundary"}]}]}]},{"id":"electronic-structure","name":"Electronic structure","description":"Represent pentalene's electronic framework and the evidence used to characterize it.","layers":[{"id":"neutral-pi-framework","name":"Neutral pi framework","description":"Connect the parent molecular graph to its electronic interpretation.","findings":[{"id":"antiaromaticity-evidence","name":"Antiaromaticity evidence","description":"Neutral pentalene is described as a coplanar eight-pi-electron Hückel antiaromatic hydrocarbon; the model must preserve the method and species behind more detailed claims. [Chemical Science research article](https://pubs.rsc.org/en/content/articlehtml/2025/sc/d4sc06439a).","questions":[{"text":"Which magnetic, geometric, energetic, or spectroscopic evidence supports the antiaromaticity assignment for the parent?","id":"antiaromaticity-evidence-q01","kind":"provenance"},{"text":"What geometry and bond-length alternation are reported, and are they measured or calculated?","id":"antiaromaticity-evidence-q02","kind":"measurement"}]}]},{"id":"state-dependent-properties","name":"State-dependent properties","description":"Keep electronic-state assignments attached to their measurements or calculations.","findings":[{"id":"charge-spin-and-excitation","name":"Charge, spin, and excitation","description":"Properties assigned to an ion, excited state, or coordinated species cannot automatically describe neutral ground-state pentalene.","questions":[{"text":"Which charge, multiplicity, and excitation state were used for each reported spectrum or calculated property?","id":"charge-spin-and-excitation-q01","kind":"definition"},{"text":"Does the evidence concern free neutral pentalene or an electronically altered neighbouring species?","id":"charge-spin-and-excitation-q02","kind":"boundary"}]}]}]},{"id":"occurrence-and-identification","name":"Occurrence and identification","description":"Describe where pentalene was observed and how its presence was established.","layers":[{"id":"experimental-occurrence","name":"Experimental occurrence","description":"Record the environment and history of each claimed parent observation.","findings":[{"id":"condition-bound-presence","name":"Condition-bound presence","description":"An occurrence record should couple the detected parent to its preparation, environment, temperature, and elapsed time.","questions":[{"text":"Was pentalene observed in a matrix, gas phase, solution, or another environment, and under what temperature and pressure?","id":"condition-bound-presence-q01","kind":"measurement"},{"text":"Which precursor and preparation event produced the observed species, and when was the identifying measurement taken?","id":"condition-bound-presence-q02","kind":"provenance"}]}]},{"id":"analytical-assignment","name":"Analytical assignment","description":"Assess whether the signal identifies parent pentalene within the actual mixture.","findings":[{"id":"monomer-specific-signals","name":"Monomer-specific signals","description":"Assignments must distinguish the parent from precursor residues, dimers, isomers, and host-environment signals.","questions":[{"text":"Which measured bands or other signals identify the parent, with what uncertainty and supporting comparison?","id":"monomer-specific-signals-q01","kind":"measurement"},{"text":"How were precursor, dimer, and alternative-isomer assignments excluded or bounded?","id":"monomer-specific-signals-q02","kind":"boundary"},{"text":"What monomer abundance or detection limit supports the claim of presence?","id":"monomer-specific-signals-q03","kind":"measurement"}]}]}]},{"id":"persistence-and-transformations","name":"Persistence and transformations","description":"Track how the parent survives or changes during an observation.","layers":[{"id":"monomer-loss","name":"Monomer loss","description":"Represent demonstrated pathways that remove parent pentalene.","findings":[{"id":"dimerization-and-competing-pathways","name":"Dimerization and competing pathways","description":"Dimerization is a specific pathway to investigate; its products and kinetics must be established for the parent under the stated conditions.","questions":[{"text":"Which products are experimentally assigned when parent pentalene disappears?","id":"dimerization-and-competing-pathways-q01","kind":"provenance"},{"text":"How do temperature, concentration, and isolation environment affect observed monomer loss?","id":"dimerization-and-competing-pathways-q02","kind":"measurement"}]}]},{"id":"usable-observation-window","name":"Usable observation window","description":"Translate persistence evidence into limits on a proposed characterization.","findings":[{"id":"time-and-condition-validity","name":"Time and condition validity","description":"An observation window should be justified by measured persistence rather than an assumed universal stability threshold.","questions":[{"text":"Over what interval does the parent remain detectable or sufficiently abundant under the proposed measurement conditions?","id":"time-and-condition-validity-q01","kind":"measurement"},{"text":"What evidence supports continuing, repeating, or ending characterization after a temperature or irradiation change?","id":"time-and-condition-validity-q02","kind":"action"}]}]}]},{"id":"property-and-handling-evidence","name":"Property and handling evidence","description":"Qualify physical constants and handling information for the actual parent species and experimental preparation.","layers":[{"id":"physical-constants","name":"Physical constants","description":"Determine which conventional material properties are supported for parent pentalene.","findings":[{"id":"measurable-parent-properties","name":"Measurable parent properties","description":"Melting point, boiling point, density, and similar entries require evidence that the measurement concerns the parent and remains meaningful before transformation.","questions":[{"text":"Which physical constants have been measured for the parent, with units, conditions, and uncertainty?","id":"measurable-parent-properties-q01","kind":"measurement"},{"text":"Does each proposed constant describe an equilibrium property, a calculation, or a reaction-limited observation?","id":"measurable-parent-properties-q02","kind":"boundary"}]}]},{"id":"handling-applicability","name":"Handling applicability","description":"Separate parent-specific information from hazards and controls associated with the full experimental system.","findings":[{"id":"parent-versus-preparation-controls","name":"Parent versus preparation controls","description":"Hazard classifications, exposure limits, and handling decisions require applicable evidence; missing parent data must remain explicitly unresolved.","questions":[{"text":"Which hazard classifications or exposure limits, if any, are documented specifically for neutral parent pentalene?","id":"parent-versus-preparation-controls-q01","kind":"provenance"},{"text":"Which handling constraints arise from pentalene itself, and which arise from the precursor, solvent, matrix, irradiation, or cryogenic apparatus?","id":"parent-versus-preparation-controls-q02","kind":"boundary"},{"text":"What documented experimental guidance supports the proposed storage, transfer, or disposal of this particular preparation?","id":"parent-versus-preparation-controls-q03","kind":"action"}]}]}]},{"id":"evidence-and-external-alignment","name":"Evidence and external alignment","description":"What the world already says about this thing, gathered so the model can be checked against it.","layers":[{"id":"reported-evidence","name":"Reported evidence","description":"Findings from the breadth pass, kept separate from the structural claims.","findings":[{"id":"evidence-confidence-notes","name":"Check these first","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these check these first hold for the sense of pentalene this model covers, and on what evidence?","id":"evidence-confidence-notes-q01","kind":"provenance"}]},{"id":"evidence-identifiers","name":"Identifiers and schemes","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these identifiers and schemes hold for the sense of pentalene this model covers, and on what evidence?","id":"evidence-identifiers-q01","kind":"provenance"}]},{"id":"evidence-real-world-use","name":"Real-world use","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these real-world use hold for the sense of pentalene this model covers, and on what evidence?","id":"evidence-real-world-use-q01","kind":"provenance"}]},{"id":"evidence-measurements","name":"Typical measurements","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these typical measurements hold for the sense of pentalene this model covers, and on what evidence?","id":"evidence-measurements-q01","kind":"provenance"}]},{"id":"evidence-failure-modes-and-hazards","name":"Failure modes and hazards","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these failure modes and hazards hold for the sense of pentalene this model covers, and on what evidence?","id":"evidence-failure-modes-and-hazards-q01","kind":"provenance"}]},{"id":"evidence-neighbours","name":"Neighbouring kinds and how to tell them apart","description":"Recalled without web access and unsourced; every item is a lead to verify.","questions":[{"text":"Which of these neighbouring kinds and how to tell them apart hold for the sense of pentalene this model covers, and on what evidence?","id":"evidence-neighbours-q01","kind":"provenance"}]}]}]}]},"agentConduct":{"may":["Describe pentalene's structure, antiaromaticity and reactivity from published chemistry.","Distinguish the unstable parent molecule from its stabilised substituted derivatives in a record."],"mustNot":["Present the parent pentalene as a stable, bottled reagent that can be ordered or stored.","Merge data for substituted pentalenes or the dimer into the record of the parent molecule.","Invent spectra, properties or yields that have not been reported."],"requiresHuman":["Approving any laboratory work that generates reactive intermediates of this kind."]},"ethics":{"considerations":["Honest reporting of reactive species protects researchers who build on the record."],"affectedParties":["Researchers relying on the record","Students learning aromaticity"]},"owners":{"steward":"Nobody owns the compound; the research groups who report it answer for their data.","roles":[],"masterSystems":[]},"relations":[{"target":"Q11173","type":"parent","note":"registry parent class"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.pentalene","Wikidata: Q3554979 (https://www.wikidata.org/wiki/Q3554979)"]},"properties":{"applicability":"required","items":["Molecular identity: C8H6; neutral, unsubstituted fused five-membered bicyclic carbon skeleton","Identifier mapping: Verified structure-linked CAS, PubChem, EC, InChI, or SMILES records; unresolved where unverified","Electronic state: Charge, spin multiplicity, ground or excited state, and experimental or computational assignment","Observation environment: Matrix identity, solvent or gas environment, pressure, irradiation history, and isolation method","Temperature and elapsed time: K and s, with uncertainty and preparation or observation reference time","Monomer abundance: mol/L, mole fraction, or calibrated signal-derived population with method and detection limit","Spectroscopic signature: IR bands in cm^-1, electronic absorption wavelengths in nm, or other supported analytical observables","Persistence and conversion: Observed lifetime in s; conversion fraction; rate constants with reaction-order-dependent units","Physical-property evidence status: Measured for parent; calculated; inferred from analogue; unavailable; inaccessible before reaction"]},"recognition":{"applicability":"required","items":["The parent molecule is not observed as a bulk material at room temperature; it is detected only transiently or under matrix isolation.","Isolable pentalenes carry bulky substituents and are usually strongly coloured solids."]},"capabilities":{"applicability":"required","items":["Resolve whether a named record describes parent pentalene or a related chemical species.","Compare an observed spectrum with condition-matched evidence for the parent monomer.","Track pentalene formation and disappearance alongside precursor and product populations.","Assess whether a proposed observation window fits a demonstrated persistence range.","Compare calculated and experimental properties while preserving their different evidential status.","Identify missing parent-specific evidence before assigning physical constants or handling classifications."]},"hazards":{"applicability":"required","items":["The parent molecule dimerises rapidly, so samples labelled as pentalene are likely something else.","Confusing derivatives with the parent leads to wrong property data in databases."]},"interfaces":{"applicability":"required","items":["The Globally Harmonized System of Classification and Labelling of Chemicals, issued by the United Nations, provides the framework for evaluating and communicating chemical hazards where adopted into applicable rules."]},"context":{"applicability":"required","items":["Parent pentalene is encountered in specialist chemical research on antiaromaticity, molecular structure and reactive species.","It is studied to understand how its fused ring system affects electronic behavior and chemical persistence.","Findings about substituted derivatives or metal complexes require separate interpretation before being applied to the neutral parent molecule."]}},"sources":[{"title":"Wikidata item Q3554979: pentalene","url":"https://www.wikidata.org/wiki/Q3554979","note":"identity and sense of the item"},{"title":"Wikipedia: Pentalene","url":"https://en.wikipedia.org/wiki/Pentalene","note":"general description of the item"}],"openQuestions":["Which CAS, PubChem, and EC records can be verified against the neutral unsubstituted parent structure?","Which primary experiments provide the strongest parent-pentalene identification, and what spectra and detection limits do they report?","What parent-specific persistence and dimerization data exist across matrices, gas-phase conditions, and any demonstrated solution environments?","Which conventional physical constants are experimentally accessible for the parent rather than calculated, borrowed from derivatives, or precluded by transformation?","What parent-specific hazard and regulatory information exists, and what handling questions remain supported only by preparation-specific evidence?"],"resources":{"spec":"/models/things/publications/thing-q3554979/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q3554979/spec.json"],"providers":["Codex"],"researchStatus":"unreviewed","generatedAt":"2026-09-12T11:59:15Z","builder":"tools/build_cards.py@1.0.0"},"completeness":{"sections":{"classifiers":"filled","whatItIs":"filled","purpose":"filled","distinguishingFeatures":"filled","structure":"filled","agentConduct":"filled","ethics":"filled","owners":"filled","relations":"filled","interaction.identity":"filled","interaction.properties":"filled","interaction.recognition":"filled","interaction.capabilities":"filled","interaction.hazards":"filled","interaction.interfaces":"filled","interaction.context":"filled","sources":"filled"},"notes":{"_gate":"Published through the thing publication gate 1.0 on 2026-10-07T10:10:30+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass"},"score":1.0}}