C004 — Bisoctrizole (Methylene Bis-Benzotriazolyl Tetramethylbutylphenol / Tinosorb M / MBBT)
Section 1: Identity
| Property | Value | Confidence |
|---|---|---|
| INCI | Methylene Bis-Benzotriazolyl Tetramethylbutylphenol | C1 |
| USAN/proposed | Bisoctrizole | C1 |
| Common abbreviation | MBBT | C1 |
| IUPAC | 2,2'-Methylenebis[6-(2H-1,2,3-benzotriazol-2-yl)-4-(2,4,4-trimethylpentan-2-yl)phenol] | C1 |
| Trade names | Tinosorb M (BASF; aqueous dispersion); Parsol Max (DSM); Eversorb M (Everlight); Milestab 360 (MPI); UV-360 | C1 |
| CAS | 103597-45-1 | C1 |
| Molecular formula | C₄₁H₅₀N₆O₂ | C1 |
| Molecular weight | 658.88 g/mol | C1 |
| Appearance / form | Pure: yellow-cream powder, mp 195.7 °C. Commercial: 50% w/w aqueous dispersion (Tinosorb M) of microfine particles <200 nm stabilized by decyl glucoside + xanthan gum + propylene glycol | C1 |
| Particle nature | Organomineral / particulate organic UV filter — molecular substance but used as suspended particles (200 nm range) | C1 |
This particulate nature is unique: MBBT is insoluble in cosmetic oils and water but is delivered as a stable nanodispersion. It therefore acts as a hybrid organic–particulate filter, combining molecular absorption with particle-level scattering.
Regulatory status
| Region | Status | Max concentration |
|---|---|---|
| USA (FDA) | Not approved as sunscreen active. BASF submitted TEA 2002–2009; FDA Sept 3, 2014 feedback letter requested clarifications. As of 2026 still pending GRASE determination. | (TEA pending) |
| EU (Annex VI, entry 23) | Approved (both nano and non-nano forms) | 10% |
| Australia (TGA) | Approved | 10% |
| Japan | Approved | 10% |
| South Korea, ASEAN, Mercosur, China, Canada | Approved | 10% |
EU SCCS opinion SCCS/1546/15 (rev. 25 June 2015), reconfirmed January 2018: nano-MBBT at up to 10% in dermally applied cosmetics on healthy intact skin does not pose a risk. C1.
Typical use concentration
- 1–10% in EU/AU/JP products; 2–6% common
- Almost always combined with other filters for synergistic broad-spectrum coverage
- Particularly common in "mineral-feel" hybrid formulations and in combination with avobenzone (which it strongly stabilizes)
Section 2: UV Absorption Spectrum
MBBT is a broad-spectrum filter covering UVB and UVA (~280–400 nm) with two characteristic absorption bands. Spectrum differs between dissolved (rare/unrealistic for cosmetics) and dispersed/particulate forms.
In solution (e.g., chloroform, THF — for spectroscopic characterization)
| Band | λmax (nm) | Assignment | Confidence |
|---|---|---|---|
| Short-wavelength | 305 | Local π→π* of benzotriazole moiety | C2 |
| Long-wavelength | 350 | π→π* charge transfer (CT) state involving the phenol-benzotriazole donor-acceptor system | C2 |
In aqueous particulate dispersion (Tinosorb M, 200-nm particles — actual cosmetic state)
| Band | λmax (nm) | Notes | Confidence |
|---|---|---|---|
| Short-wavelength | 305 | Roughly preserved | C2 |
| Long-wavelength (red-shifted) | 360 | Bathochromic shift from 350 → 360 due to aggregation | C2 |
| Shoulder | ~380 | Particle-induced extension (aggregation effect — H- or J-aggregate spectroscopy) | C2 |
Molar absorption coefficient
| Quantity | Value | Solvent | Confidence |
|---|---|---|---|
| ε at 305 nm | ~52,000 M⁻¹cm⁻¹ | Chloroform/THF (solution) | C2 (cited in BASF material; comparative literature on MBBT) |
| ε at 350 nm | ~46,000 M⁻¹cm⁻¹ | Solution | C2 |
| Effective ε in aqueous dispersion | Similar magnitude per chromophore but spectrum broadened | aq dispersion | C2 |
| E(1%, 1cm) | computed ≈ 700–790 at 350 nm using ε=46,000, MW=658.88 → E1% ≈ 698 | calc | C3 |
Bandwidth / spectral coverage
- Effective from ~280 to 400 nm (full UVB + UVA)
- Critical wavelength reported ~388 nm
- UVA/UVB ratio ~1:1 (balanced broad-spectrum)
- Particle-form absorption supplemented by light scattering: contributes 5–10% to attenuation in formulations, especially at higher concentrations
- Some absorption extends marginally into visible/blue light (~400–410 nm) — relevant for HEV protection claims
References: SCCS/1546/15; BASF Tinosorb M technical info PRD 30482916; reviews in Cosmetics MDPI 10(4):101 (2023); ChemicalBook entry 3283802.
Section 3: Photodegradation Kinetics
MBBT/Tinosorb M is one of the most photostable UV filters known — typically cited as >95–99% remaining after extended UV exposure that would deplete avobenzone by 30–80%.
Photoprotection mechanism
The benzotriazole-phenol scaffold dissipates absorbed UV through excited-state intramolecular proton transfer (ESIPT), similar to bemotrizinol/DHHB family:
- Ground-state enol stabilized by intramolecular H-bond (phenol-OH to benzotriazole N)
- UV absorption → S₁ enol*
- Sub-ps proton transfer → S₁ keto*
- Internal conversion → S₀ keto
- Reverse H-transfer → S₀ enol (closed cycle)
Quantum yield of photochemical reaction: very small (estimated <10⁻⁴), making the filter effectively a catalyst converting UV to heat.
Quantitative data
| Parameter | Value | Conditions | Source / Confidence |
|---|---|---|---|
| % remaining after 25 MED in formulation | >95–98% | typical sunscreen emulsion | BASF / SCCS dossier — C1/C2 |
| % remaining after extended UV (Sayre-type 40 mJ/cm²) | ~99% | aq dispersion | BASF — C2 |
| Triplet yield Φ_T | Very low | aq dispersion | C2 (inferred from ESIPT dominance) |
| Singlet oxygen yield Φ_Δ | Negligible (<0.02) | C3 |
Particle aspects
- Particle size <200 nm: stable on cosmetic shelf life and in emulsions
- Particles do not penetrate intact skin (SCCS conclusion based on skin penetration studies)
- Photostability of particle is excellent; no measurable degradation under typical sunscreen testing regimens
Photoproducts
No significant photoproducts identified in the cosmetic-relevant UV dose range. Under harsh photolysis (deep UV / prolonged irradiation), trace amounts of: - Aldehydes from oxidation at the methylene bridge - Are not detected at cosmetic doses
Section 4: Photostabilization
MBBT not only requires no stabilization but stabilizes other filters, particularly avobenzone:
MBBT as a stabilizer
| Pair | Effect | Mechanism |
|---|---|---|
| MBBT + avobenzone | Increased avobenzone retention to >85–90% after 25 MED | Triplet energy transfer (MBBT particles act as triplet sink) + direct competition for UV absorption |
| MBBT + octinoxate | Compatible; reduced cinnamate degradation | Particulate UV competition |
| MBBT + DHHB | Compatible; both ESIPT-based, same protective mechanism class | |
| MBBT + Tinosorb S (bemotrizinol) | Compatible; complementary peaks at 305/360 vs 310/340 | |
| MBBT + zinc oxide / titanium dioxide | Compatible; pure mineral + organic-particulate combination |
Negative interactions
- None reported in peer-reviewed literature
- MBBT is also among the most reef-safe organic filters in available studies (no measurable coral toxicity at relevant concentrations)
- Lack of skin penetration of nano-MBBT was the basis of EU 2018 reconfirmation
Confidence summary
- §1 Identity: C1
- §2 Spectrum: dual peaks 305/360 in dispersion C1; ε values C2; E(1%,1cm) C3
- §3 Photodegradation: %remaining C2; ESIPT mechanism C2
- §4 Stabilization synergies: C2
Key references
- SCCS Opinion SCCS/1546/15 (rev. 25 June 2015) — "Methylene Bis-Benzotriazolyl Tetramethylbutylphenol (nano)" — health.ec.europa.eu
- SCCS reconfirmation, January 2018
- BASF Technical Information Tinosorb M PRD 30482916 (2019)
- EU Regulation (EC) 1223/2009 Annex VI entry 23
- BASF press release July 2018 — EU approval of nano UV filter
- Cosmetics (MDPI) 10(4):101 (2023) — UV filters review
- ChemicalBook entry 3283802 (CAS 103597-45-1) — physical properties