The conditions required for a formal biradical to exist in a zwitterionic form in the ground state are discussed following the recent experimental observation of zwitterionic structure in the ground state of a quinoid molecule (di-tert-butyl derivative of 2,5-diamino-1,4-benzoquinonediimine, I). A unique characteristic of molecules of this class is the fact that they may be considered as being ...

The mol-ecule of the title compound, C(23)H(18)Cl(2)N(4)O, assumes a non-planar conformation in which the pyrazolone ring forms dihedral angles of 32.61 (19), 76.73 (14) and 52.57 (19)° with the three benzene rings. The secondary amino group is involved in an intra-molecular N-H⋯O hydrogen bond. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers. An...

The title compound, C(31)H(25)NO(6), has a structure related to other 3,4-diaryl-substituted maleic anhydride derivatives which have been shown to be useful as photochromic materials. The dihedral angles between the maleimide ring system and the benzene rings bonded to it are 44.48 (3) and 17.89 (3)°, while the angles between each of the latter rings and the corresponding ether bridging connect...

The title compound, C19H20O6, consists of a tetra-substituted benzene ring with one substituent being an α,β-unsaturated cinnamoyl group, which forms an extended conjugated system in the mol-ecule. In addition, two meth-oxy-meth-oxy and one hy-droxy group are bonded to the central benzene ring. The dihedral angle between eh rings is 10.22 (10)°. An intra-molecular hydrogen bond is observed betw...

In the title mol-ecule, C(16)H(12)F(2)N(2)O, the pyrazole ring adopts a slight envelope conformation with the methyl-ene C atom deviating by 0.114 (3) Å from the mean plane of the other four atoms [maximum deviation = 0.021 (3) Å]. The dihedral angles between the four essentially planar atoms of the pyrazole ring and the fluoro-substituted benzene rings are 2.6 (2) and 82.2 (2)°. The dihedral a...

In the title mol-ecule, C14H10ClNO3, the amide C=O bond is anti to the o-carb-oxy substituent in the adjacent benzene ring, a conformation that facilitates the formation of an intra-molecular amide-N-H⋯O(carbon-yl) hydrogen bond that closes an S(6) loop. The central amide segment is twisted away from the carb-oxy- and chloro-substituted benzene rings by 13.93 (17) and 15.26 (15)°, respectively....

In the title mol-ecule, C(21)H(19)N(3)O(2), the central pyridine ring makes dihedral angles of 14.46 (9) and 34.67 (8)° with the 4-amino- and 4-eth-oxy-substituted benzene rings, respectively. The eth-oxy group is essentially coplanar with the attached benzene ring [C-O-C-C torsion angle = 178.70 (16)°] as is the meth-oxy group with the pyridine ring [C-O-C-N torsion angle = -3.0 (3)°]. In the ...

In the title compound, C(15)H(10)BrClO, the dihedral angle between the mean planes of the benzene rings in the ortho-bromo- and para-chloro-substituted rings is 70.5 (6)°. The dihedral angles between the mean plane of the prop-2-en-1-one group and the mean planes of the benzene rings in the 4-chloro-phenyl and 2-bromo-phenyl rings are 14.9 (3) and 63.3 (8)°, respectively. In the crystal, invers...

In the crystal structure of the title substituted ferrocene complex, [Fe(C₁₉H₁₈O₂P)₂], the Fe(II) atom lies on a twofold rotation axis, giving an eclipsed cyclo-penta-dienyl conformation with a ring centroid separation of 3.292 (7) Å and an Fe-C bond-length range of 2.0239 (15)-2.0521 (15) Å. In the ligand, the cyclo-penta-dienyl ring forms dihedral angles of 60.36 (6) and 82.93 (6)° with the t...

In the title mol-ecule, C(16)H(15)FN(4)O, the dihedral angle between the fluoro-substituted benzene ring and the pyrimidinone ring is 52.34 (7)°, while the dihedral angle between the fused benzene ring and the pyrimidinone ring is 3.30 (6)°. An intra-molecular N-H⋯N hydrogen bond may, in part, influence the conformation of the mol-ecule. In the crystal structure, inter-molecular N-H⋯N hydrogen ...