Dichloridobis(4-fluoroaniline-κN)zinc

In the title compound, [ZnCl2(C6H6FN)2], the ZnII atom has a slightly distorted tetrahedral geometry, being coordinated by the N atoms of two 4-fluoroaniline molecules and the two Cl− anions. The two benzene rings are almost perpendicular to one another, making a dihedral angle of 89.96 (13)°. In the crystal, molecules are linked via pairs of N—H⋯Cl hydrogen bonds, forming chains propagating along the b axis. These chains are in turn linked via a second pair of N—H⋯Cl hydrogen bonds, forming a two-dimensional network parallel to the ab plane. The title compound crystallizes in the space group Pca21 and exhibits weak second harmonic generation (SHG) properties.

In the title compound, [ZnCl 2 (C 6 H 6 FN) 2 ], the Zn II atom has a slightly distorted tetrahedral geometry, being coordinated by the N atoms of two 4-fluoroaniline molecules and the two Cl À anions. The two benzene rings are almost perpendicular to one another, making a dihedral angle of 89.96 (13) . In the crystal, molecules are linked via pairs of N-HÁ Á ÁCl hydrogen bonds, forming chains propagating along the b axis. These chains are in turn linked via a second pair of N-HÁ Á ÁCl hydrogen bonds, forming a two-dimensional network parallel to the ab plane. The title compound crystallizes in the space group Pca2 1 and exhibits weak second harmonic generation (SHG) properties.

Experimental
Crystal data [ZnCl 2 (C 6   In the title compound ( Fig. 1), the zinc atom has a slightly distorted tetrahedral geometry, being coordinated by the atoms N1 and N2 of two p-fluoroaniline molecules and the two Clanions. The two benzene rings (C1-C6 and C7-C12) are perpendicular to one another with a dihedral angle of 89.96 (13)°. In the p-chloroaniline and p-bromoaniline ZnCl 2 complexes mentioned above the same angles are 80.65 (16) and 80.0 (3)°, respectively.
In the crystal of the title compound, molecules are linked via a pair of N-H···Cl hydrogen bonds forming chains propagating along the b axis direction. These chains are in turn linked via a second pair of N-H···Cl hydrogen bonds to form a two-dimensional network lying parallel to the ab plane (Table 1 and Fig. 2). This contrasts with the packing in the crystals of the p-chloroaniline and p-bromoaniline ZnCl 2 complexes. There molecules are linked by four N-H···halogen bonds to form chains propagating along [010], with no significant interactions between the chains.
As the title compound crystallized in a noncentrosymmetric space group it was decided to measure the second harmonic generation (SHG) properties of all three compounds; dichloro-bis(p-fluoroaniline)zinc, dichloro-bis(p-chloroaniline)zinc and dichloro-bis(p-bromoaniline)zinc. The SHG conversion efficiency was determined by the powder technique developed by (Kurtz & Perry, 1968). The crystals were powdered and the fine powdered samples were inserted in a micro-capillary tube and then subjected to a Q-switched Nd: YAG laser emitting 1064 nm radiation with 3.9 mJ/pulse.
The frequency doubling was confirmed by the emission of green radiation of wavelength 532 nm collected by a monochromator after separating the 1064 nm pump beam with an IR-blocking filter. A detector connected to a power meter was used to detect the second harmonic intensity.
The output beam voltage produced by dichloro-bis(p-fluoroaniline)zinc, dichloro-bis(p-chloroaniline)zinc and dichlorobis(p-bromoaniline)zinc derivatives were 15, 3 and 10 mV, respectively. The same quantity of crystalline KDP (potassium dihydrogen phosphate) powder, used as a reference material, produced 140 mV as output beam voltage. Hence the three samples exhibits SHG efficiency of only ca 0.11, 0.02 and 0.07 times that of the KDP.

Experimental
The title compound was prepared by the condensation reaction of p-fluoroaniline with ZnCl 2 in a 1:1 molar ratio. The reaction mixture was dissolved in methanol and heated under reflux for 6 h. The resulting solution was filtered and allowed to evaporate. Colourless rod-like crystals of the title compound, suitable for X-ray diffraction analysis, were obtained in a period of ca 7 days. The same method was used for the preparation of the p-chloroaniline and p-bromo- aniline ZnCl 2 complexes.

Refinement
All the H atoms could be located in a difference Fourier map. In the final cycles of refinement they were included in calculated positions and treated as riding atoms: N-H = 0.92 Å and C-H = 0.95 Å with U iso (H) = 1.2U eq (N or C).    Table 1 for details).