Title of article :
Crystal structures, syntheses, and spectroscopic and electrochemical measurements of two push–pull chromophores: 2-[4-(dimethylamino)benzylidene]-1H-indene-1,3(2H)-dione and (E)-2-{3-[4-(dimethylamino)phenyl]allylidene}-1H-indene-1,3(2H)-dione
Author/Authors :
Bogdanov, Georgii Department of Chemistry - New Mexico Highlands University, USA , Tillotson, John P. School of Chemistry and Biochemistry - Georgia Institute of Technology, Atlanta, USA , Timofeeva, Tatiana Department of Chemistry - New Mexico Highlands University, USA
Abstract :
The title pull–push chromophores, 2-[4-(dimethylamino)benzylidene]-1H-indene-1,3(2H)-dione, C18H15NO2 (ID[1]) and (E)-2-{3-[4-(dimethylamino)phenyl]allylidene}-1H-indene-1,3(2H)-dione, C20H17NO2 (ID[2]), have donor–π-bridge–acceptor structures. The molecule with the short π-bridge, ID[1], is almost planar while for the molecule with a longer bridge, ID[2], is less planar. The benzene ring is inclined to the mean plane of the 2,3-dihydro-1H-indene unit by 3.19 (4)° in ID[1] and 13.06 (8)° in ID[2]. The structures of three polymorphs of compound ID[1] have been reported: the α-polymorph [space group P21/c; Magomedova & Zvonkova (1978[Magomedova, N. S. & Zvonkova, Z. V. (1978). Kristallografiya, 23, 281-288.]). Kristallografiya, 23, 281–288], the β-polymorph [space group P21/c; Magomedova & Zvonkova (1980[Magomedova, N. S. & Zvonkova, Z. V. (1980). Kristallografiya, 25, 1183-1187.]). Kristallografiya, 25 1183–1187] and the γ-polymorph [space group Pna21; Magomedova, Neigauz, Zvonkova & Novakovskaya (1980[Magomedova, N. S., Neigauz, M. G., Zvonkova, Z. V. & Novakovskaya, L. A. (1980). Kristallografiya, 25, 400-402.]). Kristallografiya, 25, 400–402]. The molecular packing in ID[1] studied here is centrosymmetric (space group P21/c) and corresponds to the β-polymorph structure. The molecular packing in ID[2] is non-centrosymmetric (space group P21), which suggests potential NLO properties for this crystalline material. In both compounds, there is short intramolecular C—H⋯O contact present, enclosing an S(7) ring motif. In the crystal of ID[1], molecules are linked by C—H⋯O hydrogen bonds and C—H⋯π interactions, forming layers parallel to the bc plane. In the crystal of ID[2], molecules are liked by C—H⋯O hydrogen bonds to form 21 helices propagating along the b-axis direction. The molecules in the helix are linked by offset π–π interactions with, for example, a centroid–centroid distance of 3.9664 (13) Å (= b axis) separating the indene rings, and an offset of 1.869 Å. Spectroscopic and electrochemical measurements show the ability of these compounds to easily transfer electrons through the π-conjugated chain.
Keywords :
crystal structure , donor–π-bridge–acceptor , non-linear chromophores , indane derivatives , NLO
