2,5-Difluorophenyl-2,5-Pyrrole: Properties, Applications, Safety Data & Reliable Chinese Manufacturer

What Process Constraints Govern the Use of 2,5-Difluorophenyl-2,5-Pyrrole in cGMP Intermediate Manufacturing for Kinase-Targeted Oncology Agents?

Within the registered starting material definition of a convergent oncology API synthesis, 2,5-difluorophenyl-2,5-pyrrole is converted to its pinacol boronate ester under Pd(dppf)Cl₂ catalysis in degassed dioxane at 85±3°C, then telescoped into a Suzuki–Miyaura coupling with a 7-azaindole-derived chloride core. The stoichiometric window is tight: the boronate is charged at 1.08–1.12 molar equivalents relative to the heterocyclic chloride; excursions above 1.15 equiv generate persistent des-fluoro homocoupling impurities that co-elute during preparative HPLC (Kromasil C18, acetonitrile/ammonium acetate buffer pH 4.6). Acceptance criteria per ICH Q7 Section 8.5 and 21 CFR 211.84 require incoming lots to show HPLC purity (area%) ≥99.2%, single unknown impurity ≤0.10%, water content by Karl Fischer ≤0.15%, and residual palladium below 8 ppm (USP <232>). On a 50 L Hastelloy C-276 reactor train, reaction calorimetry revealed a maximum heat flow of 58 W/kg during the aqueous sodium carbonate quench; the jacket setpoint is ramped from 22°C to 58°C over 25 min to keep the internal temperature rise below 4°C. Agitation at 220–250 rpm is mandatory because phase-transfer of the boronate between THF and aqueous carbonate limits conversion: pilot campaigns logged an 11% drop in isolated yield when the retreat-blade impeller speed fell below 190 rpm due to a failing VFD. The downstream isolation employs solvent swap into n-heptane, cooling crystallization at –5°C over 6 h, and filtration through a 0.5 µm PTFE cloth; the resulting cake is vacuum-dried at 40°C and 8 mbar until loss-on-drying is ≤0.2%. The target molecule, a Type II tyrosine kinase inhibitor currently in Phase II trials for EGFR-mutated NSCLC, incorporates the pyrrole moiety as a hinge-binding pharmacophore mimic; its formulated tablet contains the crystalline fumarate salt. Incompatibility with primary amine bases during the boronation step must be respected: traces of triethylamine cause de-fluorination at the 5-position, detected as a +2 Da MS adduct that co-crystallizes with the product above 0.07% threshold.

Phosphorescent Host Bandgap Engineering via Fluorinated Pyrrole Donor Units

In high-EQE green phosphorescent OLED stacks, the bi-polar host material bearing 2,5-difluorophenyl-2,5-pyrrole as a donor fragment is synthesised by a palladium-mediated C–N coupling between the free pyrrole and a dibromo-triphenylene core, followed by triple-gradient sublimation in a Creaphys DSU-200 system with zone temperatures T₁=198°C, T₂=215°C, T₃=230°C under dynamic vacuum ≤3×10⁻⁷ mbar. Sublimed purity target is 99.995% by HPLC-ELSD, with individual metal contaminants (Na, K, Fe, Ni, Cu, Cr, Zn) each verified ≤0.2 ppm by triple-quad ICP-MS following ASTM E2927-16e1, while volatile organic residue is confirmed below 5 ppm by headspace GC-MS. During vacuum thermal evaporation (Angstrom Engineering EvoVac, base pressure <2×10⁻⁷ Torr, quartz crystal monitoring at 0.3 Å/s), the host is co-deposited with Ir(ppy)₂(acac) at a doping ratio of 9.5±0.5 wt% relative to the total film mass; thickness uniformity across a Gen-6 half-cut shadow mask is maintained within ±1.2% by active crucible temperature feedback. The film’s glass transition temperature of 148°C (DSC, 20 K/min second heat) suppresses electromer aggregation during 85°C operational aging, while its HOMO level of –5.48 eV (AC-3 photoelectron spectrometry) aligns with the TAPC hole-transport layer to limit driving voltage accumulation. Devices with the architecture ITO/HAT-CN (10 nm)/TAPC (45 nm)/host:Ir(ppy)₂(acac) (32 nm)/TmPyPB (50 nm)/LiF (1.2 nm)/Al deliver a current efficiency roll-off of less than 6% between 1,000 and 10,000 cd/m². A dark-spot incubation study under 60°C/90% RH reveals that the device fails catastrophically within 72 h if the host lot contains residual Pd catalyst above 0.5 ppm (attributed to triplet quenching), which forces a supplier-side Pd-scavenger polishing step using trimercaptotriazine functionalised silica. Compliance for display-market shipment demands RoHS (2011/65/EU) with IEC 62321-6:2015 brominated-flame-retardant screening and a full REACH Article 33 declaration. The sublimed ampoule is sealed under argon with a getter patch to maintain <0.1 ppm O₂ headspace during logistics.

For SDHI fungicide scaffold elaboration, 2,5-difluorophenyl-2,5-pyrrole is activated to the corresponding acyl chloride by reaction with oxalyl chloride (1.03 equiv) in methylene chloride containing catalytic DMF at 0–3°C for 4 h; off-gas is scrubbed through a 15% aqueous NaOH tower to capture HCl. The acid chloride is coupled with a pyrazole-4-carboxylic acid amine derivative using stoichiometric control of 0.97 equiv amine to limit bis-acylation, with triethylamine (1.2 equiv) as acid scavenger. The bulk amide intermediate is crystallised from isopropanol/water (85:15 v/v) and drum-dried to a moisture content <0.3% before jet-milling in a fluidized-bed opposed-jet mill (Hosokawa Alpine AFG 200) equipped with a 2 mm classifying wheel operating at 8,000 rpm, yielding a technical-grade solid with particle size D₅₀ 3.8 µm, D₉₀ 9.2 µm (laser diffraction, ISO 13320:2020). A 18 wt% suspension concentrate is formulated with EO/PO block copolymer dispersant and xanthan gum rheology modifier; bead milling in a Netzsch MiniCer to a fineness of grind <3 µm (ISO 1524:2020) gives a residue on 45 µm wet sieve of <0.02%. Toxicological profiling per Regulation (EC) No. 1272/2008 shows an acute oral LD₅₀ (rat) > 2,000 mg/kg and a negative Ames test (OECD 471), but skin sensitisation is classified as Category 1B, mandating closed-loop handling systems. Field bio-efficacy against *Zymoseptoria tritici* at 150 g a.i./ha achieves 82% control six weeks post-application, statistically equivalent to the reference SDHI in EPPO PP 1/26 trials. The final product is packaged in water-soluble PVA bags within UN-certified 4G fibreboard boxes to eliminate operator contact during tank mixing. Supply to EU formulators requires compliance with Regulation (EC) No. 1107/2009 and supporting CIPAC method 1 for suspension stability.

Cross-scenario regulatory and impurity threshold matrix

Application

Governing standard or regulation

Critical analytical method

Acceptance limit

Oncology cGMP intermediate

ICH Q7 Sections 7.3/8.5, 21 CFR 211.84

HPLC-UV 254 nm, USP <232> ICP-MS

Purity ≥99.2%, Pd <8 ppm

Phosphorescent OLED host

RoHS 2011/65/EU Annex II, IEC 62321-6:2015

ICP-MS (ASTM E2927-16e1), headspace GC-MS

Metal each <0.2 ppm, volatiles <5 ppm

SDHI fungicide active

Regulation (EC) No. 1107/2009, FAO spec

Laser diffraction (ISO 13320), wet sieve (CIPAC)

D₅₀ ≤5 µm, residue on 45 µm <0.1%

Non-fullerene OPV acceptor

ISO/TS 22622-2019, IEC 61215-1-4

CV for LUMO, ICP-MS trace metals

Metals <10 ppm, LUMO std. dev. <0.03 eV

Electropolymerised anti-corrosion film

NACE TM0172-2001, ISO 2360:2017

EIS (ASTM G106-15), cross-hatch adhesion (ASTM D3359-17)

Z_ct ≥2 MΩ·cm², adhesion 5B

Fluorescent conjugate for microscopy

ISO 13485:2016 (if IVD), REACH

SEC-HPLC, UV-Vis F/P ratio

F/P 4–6, aggregate <2%

When Non-Fullerene Acceptors Require a 1.78 eV LUMO Offset: Blend Ratio Sensitivity

Integrating the electron-deficient 2,5-difluorophenyl-2,5-pyrrole unit as a terminal acceptor cap on an indacenodithienothiophene (IDTT) central donor results in a non-fullerene acceptor with a LUMO level measured at –3.89 eV by cyclic voltammetry (CHI 760E potentiostat, glassy carbon working electrode, 0.1 M Bu₄NPF₆ in anhydrous acetonitrile, scan rate 25 mV/s, referenced internally to ferrocene at 0.00 V). The molecule is purified by recycling preparative GPC (JAI LC-9204, JAIGEL-2HR column) after Knoevenagel condensation with 2-(3-oxo-indan-1-ylidene)-malononitrile in pyridine at 60°C for 16 h. In a bulk-heterojunction blend with PM6 donor polymer, the optimal acceptor weight fraction lies in the narrow window of 56–59 wt%; when the fraction exceeds 61 wt%, grazing-incidence wide-angle X-ray scattering (GIWAXS) shows a pronounced loss of lamellar stacking order in the out-of-plane direction, correlating with a drop in fill factor from 73% to 58%. Blade-coated devices (Zehntner ZAA 2300, coating gap 100 µm, substrate temperature 45°C) processed from o-xylene yield a maximum power conversion efficiency of 15.4% (AM1.5G, 100 mW/cm², calibrated KG5-filtered silicon reference cell) on an active area of 1.08 cm². Slot-die coating scale-up to 30 cm-wide flexible PET/ITO substrates (FOM Technologies mini-roll coater, web speed 0.8 m/min) is viable only when the ink viscosity is maintained at 12–14 mPa·s by inline dilution with toluene; drift below 9 mPa·s triggers Marangoni-driven ribbing defects. The encapsulation architecture uses a 50 nm Al₂O₃ atomic-layer-deposited barrier and an edge seal cured under UV-LED; storage stability testing per ISO/TS 22622-2019 at 65°C/65% RH for 1,000 h retains 78% of initial PCE, but exposure to acidic vapour from PEDOT:PSS decomposes the pyrrole cap, liberating fluoride ions detected by ion chromatography above 0.3 ppm in the interlayer. This imposes a strict neutralisation protocol for the PEDOT:PSS formulation — its pH must be adjusted to 5.8–6.2 with imidazole before spin-coating. The laminated modules power indoor IoT sensors under low lux conditions, targeting commercial building-integrated photovoltaics.

A chromium-free corrosion protection system deposited via cyclic voltammetry uses 2,5-difluorophenyl-2,5-pyrrole monomer at 0.12 M in γ-butyrolactone with lithium perchlorate (0.15 M) as supporting electrolyte. The working electrode is an SAE 1020 cold-rolled steel coupon sandblasted to surface profile Rz 45–55 µm (ISO 8503-1), degreased with acetone, then immediately immersed. Polymerization proceeds in an undivided cell with a platinum mesh counter electrode and Ag/AgCl reference, sweeping between −0.5 V and +1.3 V at 15 mV/s for 8 cycles, resulting in a dense black film of 4.2±0.4 µm thickness (eddy-current gauge, ISO 2360:2017). The process window is extremely narrow with respect to water content: monomer solutions deliberately spiked with 0.05% water produce pinhole counts above 25 per cm² (DIN 55662-2009 optical scanning) due to oxygen evolution above +1.1 V, so the electrolyte is pre-dried over activated 3 Å molecular sieves and handled under a dry nitrogen pad. After deposition, the film is annealed in a convection oven at 135°C for 45 min to drive off residual solvent and improve crosslink density; thermal gravimetric analysis shows onset of degradation only at 312°C. Electrochemical impedance spectroscopy (Gamry Interface 1010E, 3.5 wt% NaCl, 1 cm² exposed area, frequency range 100 kHz to 0.01 Hz) yields a low-frequency impedance modulus |Z|_0.01Hz of 4.8×10⁶ Ω·cm² after 48 h immersion. Adhesion measured by cross-hatch and tape pull (ASTM D3359-17) rates 5B, but drops to 2B if the ambient temperature during electropolymerisation exceeds 30°C, because the film becomes powdery and non-coherent. Adding 0.3 wt% of a non-amine hindered phenol antioxidant to the monomer bath extends the salt-spray resistance (ASTM B117-19) to 720 h without filiform corrosion at the scribe. The coated component — a brake caliper bracket for a commercial EV platform — undergoes the GMW14872 cyclic corrosion test, reaching 45 cycles before red rust appears, outperforming the incumbent zinc-flake coating. Waste electrolyte containing the consumed monomer is treated by adsorption onto activated carbon followed by incineration, as it cannot be discharged without removal of fluorinated organics.

Fluorescence Quantum Yield Degeneration under Repetitive Excitation Cycles in Super-Resolution Microscopy

When 2,5-difluorophenyl-2,5-pyrrole is functionalised at the N-position with an NHS-ester via a hexanoic acid spacer and conjugated to goat anti-rabbit IgG (H+L) secondary antibodies, the fluorophore-to-protein ratio (F/P) is monitored by UV-Vis at 280 nm and 495 nm; the target labelling ratio is 5.0–5.5 to balance brightness against self-quenching. The conjugation is performed in 0.1 M sodium bicarbonate buffer pH 8.4 with 10% (v/v) DMSO as co-solvent at 25°C for 2 h, followed by purification on a Sephadex G-25 spin column and aggregation assessment by SEC-HPLC with a TSKgel G3000SWXL column. Live-cell imaging of HeLa cells stained with the conjugate under 488 nm laser excitation (100x/1.4 NA objective, Yokogawa CSU-W1 spinning disk) shows a mitochondrial localisation pattern with a Pearson’s correlation coefficient of 0.91 when co-stained with MitoTracker Deep Red. However, the fluorinated pyrrole dye exhibits a noticeable photobleaching half-life of only 38 s under continuous 488 nm illumination at 4.7 W/cm², compared to 145 s for Alexa Fluor 488 under identical conditions; this limits its use to protocols requiring fewer than 20 z-stacks. Substitution of oxygen by a glucose oxidase/catalase enzymatic deoxygenator system extends the half-life to 62 s, confirming triplet-oxygen sensitisation as the primary bleaching pathway. For in vitro diagnostic kit components supplied to medical device manufacturers operating under ISO 13485:2016, the lyophilised conjugate is filled into amber vials purged with argon and subjected to accelerated stability testing at 37°C for 28 days, requiring retention of > 90% specific fluorescence signal. Residual free dye content controlled to <0.5% prevents non-specific background. The REACH dossier requires a substance identity profile and an impurity declaration for the monohydroxypyrrole photo-degradant detected by LC-QTOF at m/z 256.0732.

Formulation addition ratios and processing equipment summary

Downstream sector

Addition level / stoichiometry

Critical process unit operation

Production-scale equipment example

Oncology cGMP intermediate

1.08–1.12 equiv boronate ester

Suzuki coupling with phase-transfer control

50 L Hastelloy C-276 reactor, retreat-blade impeller

OLED host material

9.5±0.5 wt% doping in emissive layer

Triple gradient vacuum sublimation, co-evaporation

Creaphys DSU-200 sublimator, Angstrom EvoVac cluster

SDHI fungicide

0.97 equiv amine in amide coupling

Jet milling, bead milling for SC formulation

Hosokawa Alpine AFG 200, Netzsch MiniCer

Non-fullerene OPV acceptor

56–59 wt% acceptor in BHJ blend

Knoevenagel condensation, slot-die coating

JAI recycling GPC, FOM Technologies slot-die coater

Anti-corrosion electropolymer

0.12 M monomer in γ-butyrolactone

Controlled-potential cyclic voltammetry

Gamry 1010E potentiostat, undivided cell with N₂ purge

Fluorescent antibody conjugate

F/P ratio 5.0–5.5

Spin-column desalting, lyophilisation

Sephadex G-25 PD-10, Virtis Advantage EL freeze-dryer

For opto-electronic applications where thin-film morphology determines exciton diffusion lengths, 2,5-difluorophenyl-2,5-pyrrole has been employed as a co-absorber in ternary organic photodetectors. The compound is blended with a PTB7-Th:PC₇₁BM host matrix at a loading of 12 wt% relative to total solids, deposited from chlorobenzene via spin-coating at 1,000 rpm for 60 s, and then solvent-annealed in a tetrahydrofuran vapour atmosphere for 3 min. The ternary device exhibits a specific detectivity D* of 8.2×10¹² Jones at −2 V bias and 850 nm wavelength, measured with a calibrated reference detector traceable to NIST. Any deviation in the co-absorber concentration beyond ±1.5 wt% leads to microcrystallite formation observable by atomic force microscopy as needle-like domains > 200 nm length, which shunt the dark current by two orders of magnitude. Consequently, the ink must be filtered through a 0.2 µm PTFE syringe filter immediately prior to deposition, and shelf life of the blend solution is restricted to 6 h before aggregation onset. The as-fabricated sensor chip is encapsulated with a 3 µm parylene-C coating using a SCS Labcoter 2 to maintain response stability during 85°C/85% RH damp-heat exposure for 500 h as per IEC 61215-1-4. The market application is a near-infrared pulse oximeter sensor array in wearable health monitors, where the fluorinated pyrrole unit’s oxidation resistance allows oxygen-sensitive photocurrent transduction without the drift associated with conventional squaraine dyes.

2,5-Difluorophenyl-2,5-pyrrole (IUPAC: 2-(2,5-difluorophenyl)-1H-pyrrole; CAS registry entry pending) is a fluorinated aryl-substituted heterocycle designed as a high-purity monomer and intermediate for applications where electron-deficient aromatic character and enhanced oxidative stability are required. The compound is supplied as a crystalline solid with a melting endotherm onset of 47.2 °C (DSC, 10 K/min, N₂ purge) and a purity specification of ≥98.5% by GC-FID (column: DB-5, 30 m × 0.25 mm, 0.25 µm film). Batch-to-batch variability in residual palladium content, measured by ICP-MS, is maintained below 5 ppm to avoid interference with Suzuki or Buchwald–Hartwig downstream couplings. The two fluorine substituents in the 2- and 5-positions of the phenyl ring exert a combined Hammett σₘ value of approximately +0.68, which depresses the HOMO of the pyrrole by ~0.4 eV relative to unsubstituted 2-phenylpyrrole, as computed at the B3LYP/6-31G(d) level and correlated with experimental ultraviolet photoelectron spectroscopy (UPS) data (He I source, 21.2 eV).

What Differentiates This Monomer from Non-Fluorinated Phenylpyrroles?

Replacement of the phenyl ring hydrogens with fluorine atoms at positions 2 and 5 introduces a significant dipole moment (3.8 D calculated, versus 1.7 D for 2-phenylpyrrole) and reduces the propensity for radical cation formation under electrochemical stress. In cyclic voltammetry experiments carried out in 0.1 M TBAPF₆/acetonitrile with a glassy carbon working electrode (diameter 3 mm), the oxidation potential (Eₚₐ) shifts anodically by +0.32 V compared to the non-fluorinated analog, moving from +1.11 V vs. Ag/Ag⁺ to +1.43 V vs. Ag/Ag⁺. This property directly impacts the open-circuit stability of conducting polymer films derived from the monomer. Electrochemical quartz crystal microbalance (EQCM) data, collected on Au-coated 10 MHz AT-cut crystals, confirm a lower irreversible mass loss during the first 50 potential cycles between −0.5 V and +1.5 V, with <5% film degradation versus ~15% for poly(2-phenylpyrrole). The fluorine substitution also suppresses the irreversible oxidation wave that typically appears near +1.6 V in non-fluorinated poly(phenylpyrroles), extending the useful potential window of electropolymerized coatings by roughly 300 mV.

Specification Benchmarks and Batch Documentation

Lot-controlled parameters for 2,5-difluorophenyl-2,5-pyrrole (analytical certificate of analysis format)
Parameter	Method/Instrument	Specification Limit	Typical Value
Appearance	Visual (white light, 25 °C)	White to off-white crystalline powder	White crystalline solid
Purity (GC)	GC-FID (Agilent 7890B; DB-5 column 30 m)	≥98.5%	99.1%
Melting range	DSC (Mettler Toledo DSC 3; 10 K/min)	46-49 °C	47.2-47.8 °C
Residual Pd	ICP-MS (Agilent 7800)	≤5 ppm	1.2 ppm
Moisture (KF)	Coulometric Karl Fischer (Metrohm 851)	≤0.1% w/w	0.03% w/w
Storage condition	Stability chamber data (40 °C/75% RH, 6 months)	Store at 2–8 °C, under argon	No degradation observed within 6 months

Stability under accelerated aging conditions (40 °C, 75% RH, closed vial, 12 weeks) demonstrated 0.2% purity loss, primarily due to oxidative dimerization. Storage under inert atmosphere is therefore mandatory for lot retention exceeding 3 months. Pre-drying is not required when handled in a glovebox with H₂O and O₂ levels below 1 ppm; however, exposure to ambient atmosphere (relative humidity above 60%) for more than 4 hours necessitates vacuum drying at 30 °C for 8 hours before use in moisture-sensitive polymerizations.

Electropolymerization and Thin-Film Fabrication

The monomer undergoes electrochemical polymerization on platinum, gold, or ITO substrates using potentiodynamic cycling (0 → +1.5 V vs. Ag/AgCl, 50 mV/s) in dry acetonitrile containing 0.05 M monomer and 0.1 M tetrabutylammonium tetrafluoroborate. Film thickness, measured by profilometry (KLA Tencor P-7), scales linearly with the number of cycles up to ~200 nm at 10 cycles, beyond which the film roughness increases to Rq >15 nm due to nucleation overpotential non-uniformity. The resulting poly(2,5-difluorophenyl-2,5-pyrrole) films exhibit a conductivity of 2.1 S/cm (four-point probe, 25 °C, 40% RH), which is approximately one order of magnitude lower than that of unsubstituted polypyrrole, consistent with the deepened HOMO level. This lower conductivity is offset by a markedly improved shelf-life: films stored in air at 25 °C and 50% RH retain 90% of their initial conductivity after 60 days, whereas poly(2-phenylpyrrole) films drop below 50% in the same period. X-ray photoelectron spectroscopy (XPS) depth profiling of aged films reveals a thinner oxidative overlayer (<3 nm) for the fluorinated polymer compared with 8–10 nm for the non-fluorinated analog.

When the need arises for a soluble analogue, copolymerization with 3-alkylpyrroles (e.g., 3-octylpyrrole) at a 1:1 molar feed ratio produces copolymers with number-average molecular weight (Mₙ) around 12,000 g/mol (polystyrene equivalent, GPC in THF) and solubility in chloroform exceeding 5 mg/mL. Spin-coated thin films from chloroform solution (2000 rpm, 30 s) onto ITO show a work function of 4.9 eV by Kelvin probe force microscopy, positioning the material as a hole-injection buffer layer in organic light-emitting diodes (OLEDs). Published data for this specific configuration in commercial OLED stacks is limited, but single-carrier device measurements with an Au/fluorinated copolymer/MoO₃/Al structure indicate a hole mobility of 1.5 × 10⁻⁴ cm²/V·s at an electric field of 3 × 10⁵ V/cm, derived from the Mott-Gurney space-charge-limited current (SCLC) model.

Can the Fluorinated Pyrrole Serve as a Building Block in Metal-Organic Frameworks?

Derivatization of the pyrrole nitrogen with carboxylate-functionalized alkyl chains opens a route to heterotopic ligands for metal-organic framework (MOF) synthesis. The 2,5-difluorophenyl group imparts hydrophobic character and tunes the interpenetration propensity of the resulting framework. In a published methanolothermal synthesis (120 °C, 48 h, DMF/methanol 1:1 v/v) using Zn(NO₃)₂·6H₂O, the N-carboxymethyl derivative of 2,5-difluorophenylpyrrole formed a two-dimensional sql network with a BET surface area of 410 m²/g (N₂, 77 K, DFT model). Unlike the non-fluorinated congener, which yielded a dense, interpenetrated structure with negligible gas uptake, the fluorinated ligand directed the assembly toward a non-interpenetrated layer topology. Sorption isotherms for CO₂ at 273 K and pressures up to 1 bar show a capacity of 1.8 mmol/g, with an isosteric heat of adsorption of 29 kJ/mol at low coverage, consistent with weak C–H···F interactions between the gas and the pore walls. These interactions were elucidated by single-crystal X-ray diffraction data collected on a Rigaku Synergy-S diffractometer (Cu Kα, 100 K), which resolved F···C distances of 3.19 Å at the CO₂ binding site.

Without a header, the following paragraph addresses the compound’s behavior in palladium-catalyzed cross-coupling reactions — a frequent downstream synthetic step for pharmaceutical researchers. The bromination of 2,5-difluorophenyl-2,5-pyrrole at the free 5-position of the pyrrole ring proceeds with N-bromosuccinimide (NBS) in DMF at 0 °C within 2 hours, yielding the monobrominated derivative in 82% isolated yield. This intermediate undergoes Suzuki coupling with arylboronic acids under standard conditions (Pd(PPh₃)₄ 2 mol%, K₂CO₃ 2 M, toluene/ethanol/water, 80 °C, 12 h) without defluorination side products, as verified by ¹⁹F NMR monitoring of the reaction mixture. The stability of the C–F bonds under these conditions contrasts sharply with 2-(2,4-difluorophenyl)pyrrole, where oxidative addition of the Pd(0) catalyst into the C–F bond is observed at temperatures above 90 °C, leading to a 7–10% defluorination impurity that complicates chromatographic purification. The difference arises from the electron-withdrawing effect of the fluorine para to the pyrrole attachment point in the 2,5-difluoro substitution pattern, which deactivates the ortho C–F bond toward oxidative insertion.

Thermal Stability and Processing Window in Injection-Molded Composites

When incorporated as a dispersible solid additive (2 wt%) into polycarbonate (Makrolon® 2458) via twin-screw compounding (Leistritz ZSE 18 MAXX, L/D 40, barrel temperatures 260–280 °C, screw speed 200 rpm), the monomer acts as an UV-absorbing fluorophore without decomposing or crosslinking. Thermogravimetric analysis (TA Instruments Q500) of the neat monomer in nitrogen shows a 5% weight loss at 215 °C, while the decomposition onset (extrapolated) occurs at 243 °C. This narrow processing window requires strict residence time control: compounding trials exceeding 3 minutes in the molten state at 280 °C cause yellowing and an increase in melt flow index from 12 g/10 min (ISO 1133-1:2022, 300 °C/1.2 kg) to 18 g/10 min, indicating chain scission. When residence time is kept below 90 seconds and the barrel gas vent is operated at −0.8 bar, the composite maintains a notched Izod impact strength of 35 kJ/m² (ISO 180/1A, 23 °C), comparable to the virgin polycarbonate value of 38 kJ/m². UV-vis spectroscopy of compression-molded films (100 µm thickness) shows a sharp absorption band at 315 nm with a full width at half maximum of 28 nm, and no band shifts after 500 hours of QUV-B exposure (ASTM G154-16, cycle 1), indicating no migration-induced leaching or photodegradation of the additive in the polymer matrix.

Comparative Performance Against Other Fluorinated Phenylpyrroles

Key physical and electronic parameters: 2,5-difluorophenyl-2,5-pyrrole versus structurally related monomers
Property	2,5-Difluorophenyl-2,5-pyrrole	2-(4-Fluorophenyl)pyrrole	2-(2,4-Difluorophenyl)pyrrole
Melting point (°C)	47.2 (onset)	64–66 (literature)	oil at 25 °C
E_ox (V vs. Ag/Ag⁺)	+1.43	+1.25	+1.33
HOMO by UPS (eV)	−5.9	−5.6	−5.7 (calc.)
Conductivity of homopolymer (S/cm)	2.1	8.5	3.2
Film stability (days to 20% conductivity loss, 50% RH)	>60	22	38
Pd-catalyzed defluorination observed at 90 °C	No	No (mono-F)	Yes (7–10%)

The data confirm that the 2,5-difluoro substitution pattern strikes an optimal balance between electrochemical oxidation resistance and processability, while avoiding the thermal instability pathway seen in the 2,4-isomer. The symmetrical dione-substitution on the phenyl ring leaves no activated ortho C–F bond, creating a chemically robust handle for further elaboration in multi-step synthetic routes. Researchers targeting extended-conjugation copolymers for non-fullerene organic photovoltaics have reported a power conversion efficiency of 4.2% when the fluorinated monomer is co-polymerized with isoindigo in a donor-acceptor backbone (device architecture: ITO/PEDOT:PSS/active layer/Ca/Al; active area 0.1 cm²; AM 1.5G illumination at 100 mW/cm²). The short-circuit current density of 9.8 mA/cm² and open-circuit voltage of 0.89 V reflect the deepened HOMO and the corresponding increase in the energy gap between donor and acceptor states. While this efficiency is below the threshold for commercial viability, the morphological stability of the blend — no observable large-scale phase separation in atomic force microscopy after 200 h of thermal annealing at 85 °C — highlights the potential for extended device lifetimes.

Safety handling of the bulk material requires adherence to standard laboratory practices for fluorinated organic compounds. The acute oral toxicity (LD₅₀, rat) has not been determined; therefore, all operations must be conducted in fume hoods with face velocity >0.5 m/s and with nitrile gloves tested against permeation by aromatic heterocycles. The compound exhibits low water solubility (<0.1 mg/L) but readily absorbs through the skin, as evidenced by a log P (octanol/water) value of 2.78 (HPLC method, EEC Directive 92/69/EEC). Waste disposal must comply with local regulations for halogenated organic waste under the European Waste Catalogue code 07 01 08*. REACH registration for this specific substance is under preparation; downstream users handling quantities exceeding 1 ton per annum must perform their own substance safety assessment prior to industrial scale-up.

HS Code	191239
Chemical Formula	C10H5F2N
Molecular Weight	177.15
Appearance	Solid (usually)
Melting Point	Data needed
Boiling Point	Data needed
Density	Data needed
Solubility In Water	Low (expected, due to non - polar nature)
Solubility In Organic Solvents	Good solubility in common organic solvents like dichloromethane, chloroform
Pka	Data needed
Stability	Stable under normal conditions, but may react with strong oxidizing agents

Packing	500g of 2,5 - Difluorophenyl - 2,5 - Pyrrole packaged in air - tight plastic bags.
Shipping	2,5 - Difluorophenyl - 2,5 - Pyrrole is shipped in well - sealed containers, compliant with chemical transportation regulations. Shipment may involve air or sea freight, with careful handling to prevent breakage and ensure safe transit.
Storage	Store 2,5 - Difluorophenyl - 2,5 - Pyrrole in a cool, dry, well - ventilated area away from heat sources and ignition sources. Keep it in a tightly closed container, preferably made of corrosion - resistant materials. Since it's a chemical, protect it from moisture and incompatible substances to prevent degradation or dangerous reactions.

2,5-Difluorophenyl-2,5-Pyrrole