1-Ethyl-3,3-dimethylspiro[indoline-2,8′-phenaleno[1,9-fg]chromene]

Both molecules in the asymmetric unit of the title compound are twisted. In the crystal, weak C—H⋯π interactions link the molecules into a three-dimensional network.

The title pyrene-fused spiropyran derivative, C 30 H 25 NO, crystallizes with two molecules in the asymmetric unit with dihedral angles between their fused-ring sub units of 76.20 (8) and 89.38 (9) � .In the crystal, weak C-H� � �� interactions link the molecules into a three-dimensional network.

Structure description
As a photochromic material, spiropyran has emerged as a platform for developing new types of dynamic materials, which can respond with reversible isomerization to different stimuli such as solvents, metal ions, acids and bases and temperature (Klajn, 2014;Kozlenko et al., 2023).Many interesting strategies have been applied over the past decades to construct a spiropyran-based probe with particular purposes (Das et al., 2023;He et al., 2021).As a classical polycyclic aromatic hydrocarbon and promising chromophore, pyrene is often adapted to build or extend fluorescent materials (Yao et al., 2018;Zhou et al., 2011).Herein, we describe the synthesis and structure of the title compound, which is new derivative of spiropyran featuring pyrene substitution.
The title compound crystallizes in the uncommon space group Fdd2 with two molecules (A containing C1 and B containing C31) in the asymmetric unit (Fig. 1).In each molecule, the phenyl group of the indole moiety is nearly perpendicular to the chromene moiety [dihedral angles for molecules A and B are 76.20 (8)  In the extended structure of the title compound, C-H� � �� interactions (Table 1) link the molecules into a three-dimensional network, which features wave-like chains of molecules propagating along the [010] direction (Fig. 2).

Synthesis and crystallization
The synthesis of 2-hydroxy-1-pyrenecarbaldehyde followed the previously reported procedure (Luong et al., 2020).Then, 2-hydroxy-1-pyrenecarbaldehyde and 2,3,3-trimethyl-1-ethylindole were added to 20 ml of acetonitrile in a Schlenk tube.After heating for 12 h at 85 � C, the mixture was cooled to room temperature and the precipitate was recovered by filtration.
Single crystals of the title compound were obtained as paleyellow plates by slow diffusion of hexane into its chloroform solution at room temperature.A suitable crystal for data collection was chosen under an optical microscope and quickly coated with high vacuum grease (Dow Corning Corporation) to prevent decomposition.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen-bond geometry (A ˚, � ).

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.

Figure 1
Figure 1The molecular structure of the title compound showing 50% displacement ellipsoids.H atoms omitted for clarity.

Table 2
Experimental details.