Nararak Leesakul

Photoactive azoimine dyes: 4-(2-Pyridylazo)-N,N-diethylaniline and 4-(2-pyridylazo)-N,N-dimethylaniline: Computational and experimental investigation

4-(2-Pyridylazo)-N,N-dimethylaniline and 4-(2-pyridylazo)-N,N-diethylaniline, two photoactive azoimine dyes, were prepared from the reaction of 2-aminopyridine with N,N-dialkyl-1,4-nitrosoaniline at room temperature. Structural characterizations of these dyes using single crystal X-ray diffraction, (1)H NMR, elemental analysis, mass spectroscopy and IR spectroscopy have been carried out. The X-ray structure indicates a trans configuration around the azo group. The photochemical behavior of these compounds differs from that of 2-phenylazopyridine, the non-dialkylamino substituent compound. The synthesized compounds show emission spectra at room temperature while 2-phenylazopyridine does not. The excitation spectra of these compounds differ from their absorption spectra which can be explained on the basis of the trans to cis photoisomerization which is supported by the TD-PBE0/6-31G(d,p) calculations. Both oxidation of the dialkylamino substituents (-NR(2); R=-CH(3) and -C(2)H(5)) and reduction of -N=N-/-N=N-(-) and -N=N-(-)/-N=N-(2-) were observed in the cyclic voltammogram indicating a π-acidity of both dyes.

N,N-Dimethyl-4-[(2-pyrid­yl)diazen­yl]aniline

The title compound, C13H14N4, adopts a trans configuration about the azo bond. There is a dihedral angle of 12.18 (7)° between the pyridine and benzene rings and the mean plane of the dimethylamino substituent is twisted by 6.1 (2)° relative to the benzene ring. In the crystal, weak intermolecular C—H⋯N hydrogen bonds result in a zigzag arrangement along [010].

2-{2-[4-(Dimethyl­amino)­phen­yl]diazen-1-ium-1-yl}pyridinium tetra­chlorido­zincate

The title compound, (C13H16N4)[ZnCl4], consists of a tetrahedral [ZnCl4]2− anion and a 2-{2-[4-(dimethylamino)phenyl]diazen-1-ium-1-yl}pyridinium dication. The pyridinium-N atom is syn to the azo bond which allows for the formation of an intramolecular N—H⋯N hydrogen bond. In the crystal, the cation and anion are held together by N—H⋯Cl hydrogen-bond interactions involving the pyridinium and diazen-1-ium N atoms. π–π stacking interactions occur between the pyridine and benzene rings of adjacent cations [centroid–centroid distances = 3.6270 (18) and 3.8685 (18) Å]; the stacks are parallel to the a axis.

Dichloridobis{N,N-diethyl-4-[(pyridin-2-yl-κN)diazen­yl]aniline}zinc

In the title complex, [ZnCl2(C15H18N4)2], the ZnII cation is coordinated by two N atoms from the pyridine rings of two unidentate N,N-diethyl-4-[(pyridin-2-yl)diazenyl]aniline ligands and two Cl atoms, resulting in a distorted tetrahedral geometry. The ligands are mutually transoid with respect to the metal atom. Weak intermolecular C—H⋯Cl hydrogen bonds and π–π interactions, with centroid–centroid distances of 3.8452 (14) and 3.9932 (14) Å, are found in the crystal packing.

Crystal structure of di-chlorido-bis-[2-(phenyl-diazen-yl)pyridine-κN (1)]zinc.

The structure of the title complex, [ZnCl2(C11H9N3)2], comprises two 2-(phenyldiazenyl)pyridine ligands coordinating to a central ZnII dichloride unit via the pyridyl N-atom donors, resulting in a slightly distorted tetrahedral geometry. The complex exhibits twofold rotation symmetry, with the rotation axis bisecting the zinc cation. The structure is stabilized by weak intermolecular C—H⋯Cl interactions [C⋯Cl = 3.411 (2) and 3.675 (2) Å], connecting neighbouring molecules into layers perpendicular to the c axis.

2-Amino-5-bromo­pyridin-1-ium (2-amino-5-bromo­pyridine-κN1)trichloridozincate

The structure of the title salt, (C5H6BrN2)[ZnCl3(C5H5BrN2)], consists of discrete 2-amino-5-bromopyridin-1-ium cations and distorted tetrahedral (2-amino-5-bromopyridine)trichloridozincate anions. In the crystal, the complex anions and cations are linked via N—H⋯Cl hydrogen bonds into layers parallel to (101). Short Br⋯Cl contacts of 3.4239 (11) and 3.4503 (12) Å are observed, as well as π–π stacking interactions between the pyridine and pyridinium rings, with alternating centroid-to-centroid distances of 3.653 (2) and 3.845 (2) Å.

Bis[5-chloro-2-(phenyl­diazenyl-κN2)pyridine-κN]bis­(thio­cyanato-κN)iron(II)

In the title complex, [Fe(NCS)2(C11H8ClN3)2], the FeII atom is coordinated by two N atoms from the thiocyanate ligands and four N atoms from two chelating 5-chloro-2-(phenyldiazenyl)pyridine ligands, generating a fairly regular FeN6 octahedral coordination geometry. The thiocyanate ions are in a cis disposition and the pyridine N atoms are in a trans orientation. In the crystal, a short intermolecular Cl⋯S contact [3.366 (3) Å] is observed.