Structural Effects of C₆Substitution in 6-(4-(Dimethylamino)phenyl)fulvenes

Abstract

The single-crystal X-ray structures of 6-(4-(dimethylamino)phenyl)-6-methylfulvene ( 2 ) and of two polymorphs of 6-(4-(dimethylamino)phenyl)-6-phenylfulvene ( 3 ( P 2 1 / c ) and 3 ( Pca 2 1 )) have been determined and the structures of a series of 6-arylfulvenes ( 1 − 8 ) have been optimized at the HF/6-31G level. Analysis of these structures reveals how resonance and crystal lattice effects influence the degree of coplanarity between the aryl and fulvene rings. The torsional angles at the aryl−fulvene bonds are significantly larger in the optimized structures than in the X-ray structures. Natural bond orbital π charges and dipole moments calculated for the X-ray and optimized structures show that the crystalline environment enhances molecular polarization. Qualitative responses for second harmonic generation in powder samples have been observed in 2, 3 ( Pca 2 1 ), and 5 . Compounds 2 and 3 ( Pca 2 1 ) have similar packing motifs despite packing in different space groups.