title: 2-Cyano-5-({4-[N-methyl-N-(2-hy-droxy-eth-yl)amino] phen-yl}diazen-yl)pyridine.
abstract: In the title compound, C(15)H(15)N(5)O, the benzene and pyridine rings make a dihedral angle of 30.86 (7)°. In the crystal, chains of mol-ecules are wrapped around the screw axes into compressed helices, through hydrogen bonding between the hy-droxy and cyano groups. The chains are linked by weak C-H⋯N and C-H⋯O inter-actions. The π conjugated unit of the mol-ecule is almost perpendicular to the helix axis, and the formation of the helix is allowed by a gauche-type torsion angle in the hy-droxy-ethyl tail. In this way, consecutive chromophore units along the chain are placed in a strict anti-parallel arrangement, and this is energetically favoured because of the high dipole moment of the mol-ecule.
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Napoli 'Federico II', Complesso di Monte S. Angelo, Via Cinthia, 80126 Napoli,  Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Centore
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Piccialli