N-Methacryloyl-4-(piperidin-1-yl)-1,8-naphthalimide

In the title compound, C21H20N2O3, the naphthalimide unit is almost planar (r.m.s. deviation for the 15 non-H atoms = 0.059 Å). The carboximide N atom and the five C atoms of the 2-methylprop-2-enoyl substituent also lie in a plane (r.m.s. deviation = 0.009 Å), which subtends an angle of 84.34 (7)° to the naphthalamide plane. This orients the =CH2 group of the vinyl fragment towards the naphthalimide rings, giving the molecule an extended configuration. The piperidine ring adopts a chair conformation and there is evidence for some delocalization between the naphthalene and piperidine units, the C—Npip bond length being 1.404 (4) Å. In the crystal structure, π–π contacts with centroid–centroid distances of 3.5351 (18) and 3.7794 (18) Å supported by C—H⋯O hydrogen bonds link adjacent molecules in a head-to-tail fashion, forming dimers. These are further stabilized by other C—H⋯O contacts of varying strength, which stack the molecules down the b axis.

In the title compound, C 21 H 20 N 2 O 3 , the naphthalimide unit is almost planar (r.m.s. deviation for the 15 non-H atoms = 0.059 Å ). The carboximide N atom and the five C atoms of the 2-methylprop-2-enoyl substituent also lie in a plane (r.m.s. deviation = 0.009 Å ), which subtends an angle of 84.34 (7) to the naphthalamide plane. This orients the CH 2 group of the vinyl fragment towards the naphthalimide rings, giving the molecule an extended configuration. The piperidine ring adopts a chair conformation and there is evidence for some delocalization between the naphthalene and piperidine units, the C-N pip bond length being 1.404 (4) Å . In the crystal structure,contacts with centroid-centroid distances of 3.5351 (18) and 3.7794 (18) Å supported by C-HÁ Á ÁO hydrogen bonds link adjacent molecules in a head-to-tail fashion, forming dimers. These are further stabilized by other C-HÁ Á ÁO contacts of varying strength, which stack the molecules down the b axis.

Comment
We have recently been interested in naphthalimide derivatives as components of donor-acceptor arrays because, as good acceptors, they often exhibit strong fluorescence together with redox triggered LMCT transitions in the near-IR (McAdam et al. 2003(McAdam et al. , 2010Flood et al. 2007). We have also incorporated fluorescent naphthalimides into polymer systems (Dana et al., 2007;Munro et al., 2008). Methacrylate derivatives are polymer precursors and the title compound, I, Fig 1, was synthesised to further scope the possibilities of incorporating fluorescent naphthalimide derivatives into polymers.
The title compound comprises a 1,8-naphthalimide ring system with a piperidino ring at the C4 position of the naphthalene ring and a 2-methyl-prop-2-en-1-one substituent on the N1 atom of the dicarboxamide ring. The naphthalimide unit is planar with an rms deviation from the best fit meanplane through all 15 non-hydrogen atoms of 0.0494 Å. The C13 atom of the propenone headgroup and the N2 atom of the piperidine ring are both displaced slightly from this plane with deviations 0.170 (4) and 0.004 (3) Å respectively both in the same direction. Bond lengths within the dicarboxamide ring are normal (Allen et al., 1987) and consistent with a degree of delocalisation in the naphthalimide system. In keeping with previous observations (Easton et al., 1992;Batchelor et al., 1997;Tagg et al., 2008) the N1-C13 bond is relatively long, 1.486 (4) Å, suggesting that there is a node at the N1 atom. In contrast the C4-N2 bond is short, 1.404 (4)  The N1, C13, (O1), C14, C15, C16 segment of the propenone is also planar (rms deviation 0.0920 Å) and subtends an angle of 84.44 (7)° to the naphthalimide plane. This orients the =C15H 2 of the vinyl fragment towards the naphthalimide rings.

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.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.