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Zinc acetylacetonate (Zn(acac)₂, CAS No. 14024-63-6), also known as zinc(II) bis(acetylacetonate) or Zn(2,4-pentanedionate)₂, is a highly versatile coordination compound widely used in materials science, catalysis, and nanotechnology.
This comprehensive review covers its synthesis, structural properties, spectroscopic characterization, and diverse applications, including its role as a precursor in chemical vapor deposition (CVD), sol-gel processes, polymer stabilization, and biomedical applications.
Recent advances in its use for nanomaterials and environmental remediation are also discussed.
CAS No. 14024-63-6
Introduction
Zinc acetylacetonate (Zn(C₅H₇O₂)₂, CAS No. 14024-63-6), also referred to as zinc(II) 2,4-pentanedionate or zinc diketonate, is a coordination complex where zinc(II) is chelated by two acetylacetonate (acac) ligands.
Due to its excellent thermal stability, solubility in organic solvents, and volatility, it is extensively used as a precursor in materials science, particularly for the deposition of zinc oxide (ZnO) thin films.
This article provides an in-depth review of:
The molecular structure and coordination chemistry of Zn(acac)₂.
Various synthetic approaches, including conventional and advanced methods.
Key physicochemical properties influencing its industrial applications.
Cutting-edge uses in nanotechnology, catalysis, and biomedicine.
Chemical Structure and Bonding
Zn(acac)₂ typically exhibits a tetrahedral or octahedral geometry, depending on hydration state and solvent interactions. Key structural features include:
Chelation: The acac ligands bind to Zn²⁺ via oxygen atoms in a bidentate manner, forming stable six-membered rings.
Polymorphism: Exists in both monomeric (in nonpolar solvents) and polymeric forms (in solid state).
X-ray Crystallography Data:
Space group: P2₁/c
Unit cell parameters: a = 8.92 Å, b = 10.45 Å, c = 12.31 Å, β = 105.7°
Synthesis Methods
Direct Reaction of Zinc Salts with Acetylacetone
The most common synthesis involves reacting zinc chloride (ZnCl₂) or zinc acetate (Zn(OAc)₂) with acetylacetone (Hacac) in the presence of a base (e.g., NaOH or NH₃):
Yield: ~85–90%
Purity: ≥98% (recrystallization from ethanol improves purity).
Solvothermal and Microwave-Assisted Synthesis
Solvothermal Method: High-pressure, high-temperature reactions in autoclaves improve crystallinity.
Microwave Synthesis: Reduces reaction time from hours to minutes (~15 min at 150°C).
Alternative Synthetic Routes
Electrochemical Synthesis: Zinc anode oxidation in acetylacetone-containing electrolytes.
Solid-State Mechanochemical Synthesis: Grinding zinc oxide with Hacac in a ball mill.
Physicochemical Properties
Thermal Stability and Decomposition
Melting Point: ~138°C (with decomposition).
Thermogravimetric Analysis (TGA): Decomposes at 250–350°C to form ZnO.
Volatility: Sublimes at ~120°C under vacuum, making it suitable for CVD.
Solubility and Reactivity
Soluble in: Chloroform, THF, methanol, acetone.
Insoluble in: Water, hexane.
Hydrolysis: Slow decomposition in moist air.
Crystallographic Data
Density: 1.42 g/cm³
Refractive Index: 1.55
Spectroscopic Characterization
Infrared (IR) Spectroscopy
C=O stretch: ~1600 cm⁻¹ (strong).
Zn-O vibration: ~450 cm⁻¹.
NMR Spectroscopy
¹H NMR (CDCl₃): δ 5.5 ppm (CH), 2.0 ppm (CH₃).
¹³C NMR: δ 185 ppm (C=O), 100 ppm (CH).
X-ray Diffraction (XRD)
Confirms crystalline structure with characteristic peaks at 2θ = 10.5°, 15.8°.
Mass Spectrometry (MS)
Molecular ion peak: m/z 263 [Zn(acac)₂]⁺.
Applications
Thin Film Deposition (CVD/ALD)
Used to deposit ZnO films for solar cells, sensors, and transparent conductive oxides.
Catalysis
Henry reaction catalyst for C-C bond formation.
Polymerization initiator for polyesters.
Polymer Stabilizers
UV stabilizer in plastics (prevents degradation).
Biomedical Applications
Antimicrobial activity against bacteria and fungi.
Anticancer potential (under research).
Energy and Environment
Supercapacitors (ZnO-based electrodes).
Photocatalysis for pollutant degradation.
SAFETY INFORMATION ABOUT ZINC ACETYLACETONATE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off conSAFETYtaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
