Joining High Coloration and Fast Color Fading with Photochromic Fused‐Naphthopyrans

Abstract

An easy synthesis of photochromic naphthopyrans with a lactone ring linking the naphthalene core to the pyran double bond is described. UV irradiation (or exposure to sunlight) of these uncolored compounds provide a single photoisomer with an intense orange coloration that returns completely to the initial uncolored state much faster than common naphthopyrans used in commercial photochromic ophthalmic lenses. A polymeric uncolored material doped with one of these lactone‐fused naphthopyrans develops an intense orange coloration (ΔAbs = 0.73) when exposed to the UV light for 30 s, at room temperature, and returns to the uncolored state in just 1 min. The use of these photochromic compounds allows a faster adaptation of the material's coloration to the surrounding UV‐light intensity, without compromising the color intensity, an important feature to create high performance photochromic ophthalmic lenses.

Highly transparent photochromic films with a tunable and fast solution-like response

“…The first approach consists in the synthesis of new photochromic molecules with minimal conformational changes along the photochromic interconversion to minimize the matrix effect. This has been mainly achieved with imidazole-based molecules, [21][22][23][24][25][26][27][28][29][30][31][32][33] prepared by Abe et al, or preventing the formation of the naphthopyrans (transoid-trans) [34][35][36][37][38][39][40][41][42][43] /spirooxazines (trans-merocyanines) 44,45 long-lived isomeric open form, responsible for the slowdown of the ring-closure reaction (oxazines, substituted…”

Synthesis of Vinylnaphthofurans and NMR Analysis of their Photoswitching

“…General mechanism for the photochromic behavior of vinylnaphthofuran 3 a. 7.30 ppm, and OH at 5.07 ppm confirm the phenolic group attached to the carbon C-2. P 3 is then identified as the 4'phenyl-[1,2'-binaphthalen]-2-ol (Figure S28).…”

“…For instance, the reaction of methyl 4-hydroxy-6-methoxy-2-naphthoate with 1,1-diphenylbut-2-yne-1,4-diol, at room temperature, under acid catalysis, gives directly a naphthopyran with a fused lactone ring (Scheme 3). [7,8] Contrary to common thermally reversible photochromic naphthopyrans used in the ophthalmic lenses industry, which generate two colored species, with different thermal stability, under sunlight, these lactone-fused naphthopyrans can only form a single colored photoisomer and thus exhibit a faster color decay in the dark. [9,10] However, we observed that the ester group in the meta position of the naphthol is essential for the formation of the pyranic ring.…”

Reversible Photochromic Properties of Ti2O3(H2O)2(C2O4) ⋅ H2O Material

“…[2] Unlike P-type compounds, T-type compounds have faster discoloration and fading rates. These materials include azo copolymers, [3] fusednaphthopyrans, [4] monomer-polymer heterostructures, [5] polyurethane cement composites, [6] WO 3 nanoparticle [7] and so on. It is typically used in aerospace, optical lens, other scientific and technological fields.…”